MStower V6
User’s Manual Engineering Systems
COPYRIGHT NOTICE (C) Copyright Engineering Systems (EEC) Limited 1997-2008. All rights are reserved. The copyright applies to this manual and to the corresponding software (together referred to herein as the “licensed material”). DISCLAIMER Subject to limitations imposed by law, Engineering Systems (EEC) Limited makes no warranty of any kind in connection with the licensed material. Engineering Systems (EEC) Limited shall not be liable for any errors contained in the licensed material nor for any incidental or consequential damages resulting from the use of the licensed material. Engineering Systems (EEC) Limited is not engaging in the provision of consulting services in supplying the licensed material. Users of the licensed material are advised that output from computer software should be subjected to independent checks. Engineering Systems (EEC) Limited reserves the right to revise and otherwise change the licensed material from time to time without notification, or provision of revised material. SOFTWARE LICENCE The software is supplied to the user under licence. It may be installed on as many computers as required but the number of concurrent users must not exceed the number of licences held. For network licences, use is permitted only in the country for which the licence was supplied. The software may not be sub-licensed, rented, or leased to another party. The licence can only be transferred to another party at the discretion of Engineering Systems (EEC) Limited.
Engineering Systems (EEC) Limited Systems House 27 Highclere Drive Hemel Hempstead HERTS HP3 8BY England Tel: +44 (0) 144 226 2647 E-mail:
[email protected] Web: www.mstower.com April, 2008
Crystal Palace Tower, London This is Britain’s tallest unguyed steel tower. It was checked for structural adequacy using MStower.
Preface MStower is a software package for the analysis and design of towers, masts, and poles. This software incorporates the very latest in Windows technology to make it easier to use and improve your productivity. “1:Introduction” provides an overview of the capabilities of MStower. Whether you are installing MStower for the first time or updating an existing system, you will find all the necessary information in “2:Getting Started”. “3:Menus & Toolbars” provides a summary of the commands available and other chapters provide reference and technical information. This manual is available to the MStower user on-line, together with “pop-up” help for toolbar buttons and dialog boxes. The on-line Help system provides a synchronized table of contents and powerful methods of searching for topics. If the file Readme.txt is present in the MStower program folder after installation, you should read it for information that became available after the manual was printed. The file is automatically displayed during installation but it may be displayed in Notepad at any time by double-clicking the file in Windows Explorer.
Contents 1:Introduction
1
General...................................................................................................................................... 1 Responsibility ........................................................................................................................... 4 Acknowledgement .................................................................................................................... 5 Enhancement Record ................................................................................................................ 5
2:Getting Started
9
Installing MStower ................................................................................................................... 9 Hardware Lock ......................................................................................................................... 9 Folders .................................................................................................................................... 10 Starting MStower.................................................................................................................... 11 Commands .............................................................................................................................. 12 Right-Clicking Away from Any Part of the Tower ................................................................ 12 How to Make a Shortcut on the Desktop ................................................................................ 13 Launch with Double-Click...................................................................................................... 13 Configuration.......................................................................................................................... 14 Printing in MStower ............................................................................................................... 15 Print and Print Preview Commands.......................................................................... 15 The Windows Print Dialog Box ............................................................................... 15 The Page Setup Dialog Box ..................................................................................... 16 Configurable User Graphic....................................................................................... 18 Steel Section Libraries ............................................................................................................ 18 Data from Earlier Versions ..................................................................................................... 19 Technical Support................................................................................................................... 19 Web Update ............................................................................................................................ 20
3:Menus & Toolbars
21
Layout..................................................................................................................................... 21 File Menu Commands............................................................................................................. 22 View Menu Commands .......................................................................................................... 23 Tower Menu Commands ........................................................................................................ 24 Member Checking Menu Commands ..................................................................................... 24 Structure Menu Commands .................................................................................................... 25 Analyse Menu Commands...................................................................................................... 26 Results Menu Commands ....................................................................................................... 27 Reports Menu Commands ...................................................................................................... 27 Show Menu Commands.......................................................................................................... 28 MSTower V6
Contents • i
Query Menu Commands .........................................................................................................29 Window Menu Commands......................................................................................................30 Help Menu Commands............................................................................................................31 Main Toolbar Commands........................................................................................................31 View Toolbar Commands .......................................................................................................32 Display Toolbar Commands....................................................................................................33 Help Toolbar Commands ........................................................................................................33 Draw Toolbar Commands .......................................................................................................34 Attributes Toolbar Commands ................................................................................................34 Results Toolbar Commands ....................................................................................................35 OK/Cancel Toolbar Commands ..............................................................................................35 Extra Buttons Toolbar Commands ..........................................................................................36 Selecting Which Toolbars Are Displayed ...............................................................................36 Customizing Toolbars .............................................................................................................37 The Ouput Window.................................................................................................................37
4:Operation
39
Data Files ................................................................................................................................39 Units..........................................................................................................................40 Coordinate Systems ..................................................................................................40 Sections.....................................................................................................................41 Member Checking.....................................................................................................41 Export to Microstran Archive File ............................................................................41 Errors.......................................................................................................................................41
5:Tower Data
43
General ....................................................................................................................................43 The Tower Data (TD) File ......................................................................................................44 Title Block ................................................................................................................45 Component Block .....................................................................................................45 Profile Block .............................................................................................................46 Supports Block..........................................................................................................53 Guys Block ...............................................................................................................54 Sections Block ..........................................................................................................55 Material Block ..........................................................................................................58 Bolt Data Block ........................................................................................................58 Guy Library.............................................................................................................................61 Steel Poles ...............................................................................................................................62 TD File Examples ...................................................................................................................65 Example 1 .................................................................................................................65 Example 2 .................................................................................................................66 Example 3 .................................................................................................................67 Example 4 .................................................................................................................68 Example 5 (Plan Bracing) .........................................................................................70
6:Standard Panels
71
General ....................................................................................................................................71 ii • Contents
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Index – Face Panels ................................................................................................................ 72 Index – Plan Bracing .............................................................................................................. 76 Index – Hip Bracing & Cross-Arms ....................................................................................... 77 D & V Face Panels ................................................................................................................. 78 X Face Panels ......................................................................................................................... 79 K Face Panels ......................................................................................................................... 84 M Face Panels......................................................................................................................... 94 W Face Panels......................................................................................................................... 96 XMA Face Panel..................................................................................................................... 98 XDMA Face Panel.................................................................................................................. 99 DM, DM2 Face Panel ........................................................................................................... 100 DMH, DMH2 Face Panel ..................................................................................................... 101 DLM, DLM2 Face Panel ...................................................................................................... 102 KXM, KXM2 Face Panel ..................................................................................................... 103 SH3, SH4 .............................................................................................................................. 104 Plan Bracing ......................................................................................................................... 105 Hip Bracing........................................................................................................................... 112 Cross-Arms ........................................................................................................................... 115
7:User-Defined Panels
117
General.................................................................................................................................. 117 The UDP File........................................................................................................................ 118 Making A UDP Using Graphics Input.................................................................................. 122 UDPs for Poles ..................................................................................................................... 122 Modifying An Existing UDP ................................................................................................ 123 Towers With Unequal Length Legs...................................................................................... 123 Creating a UDP from a Microstran Job ................................................................................ 124 UDP File Names ................................................................................................................... 125
8:Graphics Input for UDPs
127
General.................................................................................................................................. 127 Basic Drawing ...................................................................................................................... 128 The Drawing Snap Mode...................................................................................................... 130 The Drawing Plane ............................................................................................................... 131 Automatic Removal of Duplicate Nodes and Members ....................................................... 131 Cursors.................................................................................................................................. 132 Shortcut Keys ....................................................................................................................... 133 Selecting Nodes and Members ............................................................................................. 133 Right-Clicking on Nodes and Members ............................................................................... 134 The Node Properties Dialog Box.......................................................................................... 135 The Member Properties Dialog Box ..................................................................................... 135 Properties Dialog Boxes with Multiple Selection................................................................. 136 Extrusion............................................................................................................................... 136 Interrupting Commands ........................................................................................................ 136 The Stretch Command .......................................................................................................... 137 The Limit Command............................................................................................................. 138 Removing an Intermediate Node .......................................................................................... 139 UDP Graphical Example ...................................................................................................... 140 MSTower V6
Contents • iii
Step 1 – Create Data File for a Small Tower ..........................................................140 Step 2 – Build Tower ..............................................................................................142 Step 3 – Isolate UDP Members...............................................................................142 Step 4 – Add Members to UDP ..............................................................................143 Step 5 – Define Attributes of New Members..........................................................144 Step 6 – Copy New Members to Other Faces .........................................................144 Step 7 – Set Reference Nodes for New Members ...................................................145 Step 8 – Check UDP ...............................................................................................145 Step 9 – Convert Graphics to UDP File ..................................................................145
9:Tower Loading
147
General ..................................................................................................................................147 The Tower Loading (TWR) File ...........................................................................................148 Parameters Block ....................................................................................................148 Damping .................................................................................................................152 Basic Velocity.........................................................................................................152 Terrain Block ..........................................................................................................153 Velocity Profile Block ............................................................................................159 Named Node Block.................................................................................................160 Guy List Block........................................................................................................161 External Factor Block .............................................................................................162 Loads Block ............................................................................................................162 Wind Load Cases ....................................................................................................163 Cross-arms and Similar Members External to the Main Tower Body ....................165 Guyed Mast Patch Loadings ...................................................................................165 Dead Loads .............................................................................................................166 Ice Loads.................................................................................................................166 Miscellaneous Loads...............................................................................................167 Additional Node Loads ...........................................................................................167 Additional Member Temperatures ..........................................................................167 Eathquake Load Cases ............................................................................................168 Combination Load Cases ........................................................................................170 Panel Block .............................................................................................................170 Ancillary Block.......................................................................................................171 Output....................................................................................................................................178 Computation of Wind Resistance..........................................................................................179 BS 8100 ..................................................................................................................179 AS 3995 ..................................................................................................................180 AS 1170 ..................................................................................................................180 Malaysian Electricity Supply Regulations 1990 .....................................................180 EIA/TIA-222-F .......................................................................................................181 TIA-222-G ..............................................................................................................181 Computation of Deflections ..................................................................................................182 BS 8100 ..................................................................................................................182 Other Codes ............................................................................................................182 Dynamic Amplification of Wind Loads ................................................................................183 BS 8100 ..................................................................................................................183 AS 3995 ..................................................................................................................183 AS 1170 ..................................................................................................................184 iv • Contents
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EIA-222-F .............................................................................................................. 184 TIA-222-G.............................................................................................................. 184 ASCE 7................................................................................................................... 184 IS 875 ..................................................................................................................... 185 BNBC ..................................................................................................................... 185 ILE TR7.................................................................................................................. 185 Ancillary Libraries................................................................................................................ 186 Large Ancillary Library.......................................................................................... 186 Linear Ancillary Library......................................................................................... 188 Drag Coefficients ................................................................................................... 189
10:CAD Interface
191
General.................................................................................................................................. 191 Exporting a CAD DXF ......................................................................................................... 191 Exporting a Steel Detailing Neutral File............................................................................... 192 Section Alias File.................................................................................................................. 193 Windows Clipboard Operations............................................................................................ 193
11:Analysis
195
General.................................................................................................................................. 195 Method ................................................................................................................... 196 Consistency Check ................................................................................................. 196 Accuracy................................................................................................................. 196 Linear Elastic Analysis ......................................................................................................... 197 Non-Linear Analysis............................................................................................................. 197 Second-Order Effects ............................................................................................. 198 Running a Non-Linear Analysis ............................................................................. 200 Troubleshooting Non-Linear Analysis ................................................................... 203 Elastic Critical Load Analysis .............................................................................................. 204 Selecting Load Cases for ECL Analysis................................................................. 205 Analysis Control Parameters .................................................................................. 205 Why ECL Analysis May Give High k Factors ....................................................... 206 Dynamic Analysis................................................................................................................. 207 Analysis Control Parameters .................................................................................. 207 Dynamic Modes ..................................................................................................... 208 Response Spectrum Analysis................................................................................................ 209 Defining Load Cases .............................................................................................. 209 Running a Response Spectrum Analysis ................................................................ 209 Response Spectrum Curves .................................................................................... 212 Errors .................................................................................................................................... 213
12:Member Checking
215
General.................................................................................................................................. 215 Operation .............................................................................................................................. 216 Loading Parameters .............................................................................................................. 216 BS 8100 Part 3........................................................................................................ 216 BS 449 .................................................................................................................... 216 MSTower V6
Contents • v
ASCE 10-90, ASCE 10-97, ASCE Manual 72 .....................................................217 EIA-222-F...............................................................................................................217 TIA-222-G ..............................................................................................................217 AS 3995 ..................................................................................................................217 IS 802......................................................................................................................217 ILE TR7 ..................................................................................................................217 BS 5950 ..................................................................................................................218 AS 4100 ..................................................................................................................218 Design Loads.........................................................................................................................218 Member Checks to BS 8100 Part 3 .......................................................................................219 Member Checks to BS 449....................................................................................................220 Member Checks to AS 3995 .................................................................................................221 Member Checks to ASCE 10-90 1991 & ASCE 10-97 1991................................................222 Member Checks to EIA-222-F 1998 .....................................................................................223 Member Checks to TIA-222-G 2005 ....................................................................................225 Member Checks to IS 802.....................................................................................................226 Member Checking to ILE Technical Report 7 ......................................................................226 Member Checking to BS 5950 ..............................................................................................227 Member Checking to AS 4100..............................................................................................227 Member Checking to ASCE Manual 72................................................................................227 Obtaining Design Results......................................................................................................228 Steel Detailing.......................................................................................................................228 Editing Ancillary & Guy Libraries........................................................................................228
13:Editing the Section Library
229
General ..................................................................................................................................229 Section Library......................................................................................................................229 Section Library Manager.......................................................................................................233 Compiling a Library..............................................................................................................236 Editing a Library with a Text Editor .....................................................................................236 Library Viewer ......................................................................................................................237
14:Reports
239
Report Types .........................................................................................................................239 Display and Printing of Files.................................................................................................240 Input/Analysis Report ...........................................................................................................240 Error Report ..........................................................................................................................241 Static Log ..............................................................................................................................241 Dynamic Log.........................................................................................................................241 Design Summary...................................................................................................................241 Detailed Design Report .........................................................................................................242 Reaction Report.....................................................................................................................242 Rotation Report .....................................................................................................................242
15:Examples
243
General ..................................................................................................................................243 TWEX1 .................................................................................................................................246 vi • Contents
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15:Ancillary Programs
253
CTIDATA............................................................................................................................. 253
Index
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255
Contents • vii
1:Introduction
General MStower is a specialized program that assists in the analysis and checking of latticed steel communication and power transmission towers and guyed masts and steel monopoles. MStower contains options for defining the geometry, loading, analysis, plotting of input, results, and member checking. Loading may be computed in accordance with: •
BS 8100 Part 1 1986
•
BS 8100 Part 4 1995
•
AS 3995-1994
•
AS/NZS 1170.2:2002
•
Malaysian Electricity Supply Regulations 1990
•
EIA/TIA-222-F-1996.
•
TIA-222-G-2005.
•
Institution of Lighting Engineers Technical Report No. 7 – High Masts for Lighting and CCTV – 2000 Edition.
•
IS 875 (Part 3):1987
•
BNBC 93 – Bangladesh National Building Code
•
ANSI/ASCE 7-95
•
NSCP C101-01 – Philippines National Building Code
Member capacities may be checked against the requirements of:
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•
BS 8100 Part 3
•
BS 449
•
AS 3995-1994
•
ASCE 10-90, ASCE 10-97
•
EIA/TIA-222-F-1996
•
TIA-222-G-2005. 1:Introduction • 1
•
Institution of Lighting Engineers Technical Report No. 7 – High Masts for Lighting and CCTV – 2000 Edition.
•
BS 5950-1:2000 (for tubular poles)
•
IS 802 (Part 1 / Sec. 2):1992
Towers, which may be of three or four sides or a single cantilevered tubular pole, are assembled by combining a series of standard face, plan, hip, and cross-arm panels. The tower profile is defined by giving the height of individual panels and the width at “bend” points. All other widths are obtained by interpolation. The range of standard panels is being regularly increased with over 100 different panel types available at present. A number of the standard panels are parameterised so that the user may readily modify the configuration. If a suitable standard panel is not available the system accepts “userdefined panels” (UDP). While these require much more data than a standard panel, they allow the system to be used for virtually any tower configuration. A UDP may consist of anything from a few members that make up half a face panel to a full three-dimensional section of the tower. The result of the tower building process is a complete MStower data file, Job.mst, where “Job” is the MStower job name. The loading module of MStower computes loads due to self-weight, ice, and wind on the tower. As well as computing wind loads on the bare tower the program is able to take account of a wide range of ancillary items found on communication towers. Ancillaries are classified into the following categories: •
Linear ancillaries, normally within the body of the tower and consisting of items such as ladders, feeders and wave-guides.
•
Face ancillaries, attached to the face of the tower and consisting of small items such as minor antennae, gusset plates and platforms.
•
Large ancillaries, mounted out from the face of the tower and consisting of large dishes whose wind resistance is significant compared with that of the structural members of the tower.
•
Resistance. A group of ancillaries may be described by their wind resistance over a height range of the tower.
•
Insulators, located between the segments of multi-segment guys.
Ancillary libraries containing data describing the physical and drag characteristics of a wide range of antennae types are provided with MStower. The libraries are plain text files and may be easily added to by users. For a dish antenna the library would typically include its diameter, mass, location of center of gravity, surface area that may be coated with
2 • 1:Introduction
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ice, and its projected area and a drag coefficients for a range of angles of incidence. Six aerodynamic coefficients are specified for each angle of incidence to enable antenna forces and moments to be computed automatically. The use of ancillary libraries simplifies the preparation of the data needed to compute the loads on the tower. To fully describe an antenna its library reference, its location on the tower, and its bearing are required. MStower will extract all other data from the library, compute the forces acting on the antenna (dead load, ice-load, and wind loads) and transfer them into the tower as a set of statically equivalent forces. To assist in checking of input data MStower displays the tower and all linear and large ancillaries. As well as the visual display, any ancillary may be queried by “picking” with the graphics cursor to obtain its identification, location, library reference, and other pertinent data. The strength of members may be checked against the rules of the codes listed above, with the results available as a summary report giving the critical load case and condition or a larger detailed report suitable for checking the computations for each member. The results of the member check may be shown as a graphical display with the color in which a member is displayed depending on its maximum load/capacity ratio. Foundation reactions and ancillary rotations may also be reported.
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1:Introduction • 3
Responsibility MStower is intended to assist designers in performing the necessary calculations for checking and designing towers, guyed masts, and steel monopoles. Users must have an understanding of these structures and a good knowledge of the codes of practice to which they are working. MStower cannot replace sound and responsible engineering judgement and practice. The interpretation of the output from MStower and the application of this data is solely the responsibility of the user. Good engineering practice requires fully triangulated bracing systems in towers. Tower design codes do not check for bending stresses in members or their bending stiffness, so members in bending should not be used to restrain compression members. Features to check for include: •
Plan bracing must be fully triangulated to provide restraint and maintain the plan shape of the tower.
•
Hip bracing must be fully triangulated and connected to the plan bracing system within a panel to resist twisting of the whole leg/hip bracing assembly.
•
Bend points in K brace arrangements must have the knee fully braced in two directions.
•
The ends of K brace members must be restrained and coincide with plan bracing members at the top of the panel.
•
Leg bend points must be fully braced in two directions.
•
Where leg members join in towers with staggered face bracing, restraint should be provided in the unbraced face by plan bracing or a similar system.
MStower is not able to detect automatically the lack of restraint in nontriangulated arrangements. If non-triangulated bracing is used, additional manual checks to the relevant design code must be made to ensure that there is sufficient strength and stiffness to provide adequate restraint to other members. Designers should consider the safety of any temporary arrangements during construction.
4 • 1:Introduction
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Acknowledgement Initial development of sections of MStower was done under contracts with the Independent Broadcasting Authority, Eastern Electricity, British Telecom, and the British Broadcasting Corporation. Particular recognition is due to Mr M J Lambert of the Independent Broadcasting Authority who initiated this work.
Enhancement Record Version 3.1 New menu introduced. TWR file format revised. Terrain blocks introduced. Linear and large ancillary libraries introduced. 32 bit version of programs introduced. Additional standard panels introduced. GUST and MEAN keywords added to TWR file. Graphical input of UDPs introduced. Version 3.15 Screen querying of linear ancillary, large ancillary, and ancillary groups introduced with graphical representation of larger ancillaries. Ancillary libraries extended to include Andrew information. HP LaserJet printers now supported for plotting. PostScript format available for output files. Ancillary deflections and rotations calculated. Foundation reactions calculated. CROSS and BARE keywords added. Total mass and additional mass of ancillaries in TWR file. XIP, plan bracing at intersection point of face bracing. Optional Velocity Profile. Version 4 Masts including catenary cables to BS 8100 Part 4 and AS 3995. Additional standard panels. Named node block introduced. Supports block. MSTower V6
1:Introduction • 5
Version 4.1 EIA/TIA-222-F-1996. ASCE 10-90 1991 (Manual 52). Bolt checking to DD133/BS5950. Deflections/rotations. Version 4.15 Manual re-set in Microsoft Word. Examples revised. Partial safety factors for materials now applied at member checking stage. Database utilities added. Bolt data file included. Version 4.20 Shade factor introduced for linear and large ancillaries. Job.out file enhanced for results checking. Version 4.21 Tension-only members now available in UDPs; non-linear analysis module required. Version 5 New 32-bit Windows version. Ancillary display improved; split view with ancillary labelling. Database recognition and automatic loading from CSV files. Enhanced metafile export of views. Non-linear analysis convergence parameters added. Smear loading for wind on guys. UDP input completely revised. Support for DOS discontinued. Generation of TD and TWR files. Multi-segment guys and guy insulators supported. Asymmetrical ice loading added. Bolt checking to AS 3995, EIA-222, and ASCE 10-90 added. Version 6 Rectangular towers may be generated directly from standard panels. Different bracing patterns and sizes may be generated on X and Y faces of four sided towers using standard panels. Loading to AS/NZS 1170.2:2002, IS 875, BNBC, ASCE 7-95, Philippines NBC. Earthquake loading. 6 • 1:Introduction
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Greater user control over the manner in which ancillary resistance is used. Generation, loading, and checking of steel monopoles. Virtual reality graphics. Gust response factor calculations for dynamically sensitive towers for some codes. Member checking to ASCE 10-97, IS 802. Member checking to BS 8100 Part 4 replaces DD133-1986. Panels may have one or two sets of plan bracing. UDP member classes specified directly. Section Library Manager. Web downloads. TIA-222-G-2005 implemented.
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1:Introduction • 7
8 • 1:Introduction
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2:Getting Started
Installing MStower The Setup program will install MStower on your computer. Usually, Setup will begin when you insert the CD. If Setup does not begin automatically you must perform these steps: •
Click on the Windows Start button and select Run.
•
Browse to the Setup program on the distribution CD.
•
Execute the Setup program.
Setup will guide you through the installation process, prompting you for a name for the program folder (the default is C:\Mstower), and then copying the required files to the hard disk. Necessary fonts will be installed.
Hardware Lock MStower is normally supplied with a USB hardware lock that must be attached to the computer before you can start the program. Additional set-up procedures are required for systems with a network lock. These are described on a separate data sheet.
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2:Getting Started • 9
Folders The Setup program will establish a number of folders under the specified MStower folder. If you use the default name the folders as displayed in Windows Explorer will look like this:
MSTOWER FOLDERS
Folder Name
Comment
Mstower
MStower folder – you can choose this name during installation. “Mstower” is the default.
.....Data
Default data folder – you can open MStower files in other folders if you wish.
.....Examples
Example files – useful for testing and learning.
.....PDF
Contains documentation in PDF format, including full user manual.
.....Program
All MStower program files, library files, and Help files.
.....Service
For network version only, this folder contains network support and documentation files.
Library File Folder You may use the File > Configure > General > Library File Folder command to specify a folder for library files anywhere on the computer or in the Network Neighborhood. Files in this folder will be accessed when you refer to a library file with the “L:” prefix. Using the “P:” prefix will cause MStower to look in the Program folder for library files. Library file references that do not have a prefix cause MStower to look in the data folder for library files.
10 • 2:Getting Started
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Temporary File Folder By default, MStower writes intermediate data to the Windows temporary file folder. This is usually most satisfactory for all types of installation. You may, however, use the File > Configure > General > Temporary File Folder command to specify a different folder anywhere on the computer or in the Network Neighborhood.
Starting MStower The Setup program creates an MStower item on the Windows Programs menu (click Start, then Programs). Click on this item to start MStower. If you have not previously used MStower you should start with some of the examples supplied with MStower to familiarize yourself with the operation of the principal menu and toolbar items (see Chapter 15:Examples on page 243). To run an example, use the File > Open command and click on the required file in the dialog box. You may open any existing MStower job with the File > Open command. To start a new job based on an old job, open the old job and save a copy with another name using the File > Save Copy As command. You may now close the old job and open the new copy by selecting its name from the most recently used list on the File menu. Note the following powerful Help features, which make it easier for you to use MStower: •
There are tooltips on all toolbar buttons. Move the mouse cursor over the button for a moment and a little pop-up window displays the function of the button.
•
There is a prompt displayed on the left side of the status bar (at the bottom of the MStower window) whenever the cursor is positioned over a toolbar button or a menu item. Look here for prompts while you are performing input operations.
•
Context-sensitive help is available for all toolbar buttons by clicking the button. Once you have clicked this button, move the new cursor to any item and click.
•
Context-sensitive (pop-up) help is available in dialog boxes. Some items in dialog boxes also have tooltips.
Use the Help > MStower Help Topics command to display the Help Topics dialog box. With this, you can browse the table of contents, look through an index, or search all Help topic keywords.
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2:Getting Started • 11
Commands MStower commands are available from: •
The main menu.
•
Toolbar buttons.
•
The context menu.
Generally, all the commands are available on the main menu, while, for convenience, some of them are also available on toolbar buttons or the context menu. Commands selected from the main menu are referred to in this manual as shown in this example: View > Zoom > Window Commands selected by clicking a toolbar button are referred to by the name of the button, as shown in the tooltip.
Right-Clicking Away from Any Part of the Tower When you right-click in the main window, away from any node or member, the pop-up menu below appears.
MAIN CONTEXT MENU
This provides a very convenient alternative to the main menu for many commands. In effect, you can perform some operations in three different ways. For example, you can display the section number on all members by clicking a button on the Display toolbar, by selecting the View > Display Options command, or by right-clicking and then selecting Section Numbers. 12 • 2:Getting Started
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How to Make a Shortcut on the Desktop To make a shortcut to MStower on your desktop (the background that is visible when no programs are running), drag the MStower icon from the Start > Programs menu while holding down the Ctrl key.
Launch with Double-Click MStower job files (Job.mst, where “Job” is the job name) should be identified in Explorer with a distinctive icon. It is convenient to be able to double-click on one of these files in Explorer to start MStower with the job. To do this, the MST file type must be associated with MStower. The association between MStower and the MST file type may be established when MStower is installed. You may also establish the association with the procedure set out below. Here are the steps necessary to make MStower launch with a doubleclick: •
In Explorer select the View > Folder Options or View > Options command.
•
Select the File Types tab.
•
In the list box search for the MStower job file type, which may be shown as “MST File” or “MStower Document”. If found, select this file type and click the Remove button. Close the dialog box.
•
In Explorer browse to the MStower data folder and double-click on any MStower job file (if the file name extension “mst” is not visible you may see it by right-clicking and checking the properties of the file).
•
The Open With dialog box appears. Click on the Other button and browse to Mst.exe in the MStower program folder.
•
In the Description box type “MStower Job File” and click OK.
•
In Explorer select the View > Folder Options or View > Options command.
•
Select the File Types tab, then select “MStower Job File” in the list box and click the Edit button.
•
Click the Change Icon button and then select the second icon.
•
Click OK to close the Edit File Type dialog box.
•
Click OK to close the Folder Options dialog box.
Now, check that you have successfully set up your system by browsing to an MStower job file and double-clicking.
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2:Getting Started • 13
Configuration The first time you start MStower it will run in a partial screen window. Maximize the Window (use the button next to the X button at the top right of the MStower window) and the system will thereafter start in a fullscreen window. Toolbars may be activated or de-activated using the View > Toolbars command and they may also be floated or moved to different locations on the main window if desired (“docked”). Toolbar buttons may be dragged from one toolbar to another while the Alt key is held down. Chapter 3 contains more information on how you can customize the toolbars. The File > Configure command allows you to set program parameters such as colors, default library files and design codes, and maximum job size. The default settings for maximum job size will be sufficient for the majority of jobs. Increasing limits unnecessarily can result in slightly reduced operating speed.
FILE > CONFIGURE
14 • 2:Getting Started
MSTower V6
Printing in MStower Print and Print Preview Commands MStower differs from many standard Windows application in that there is a requirement to print both files (reports) and pictures. As in a standard Windows application, MStower has a Print command on the File menu (File > Print File). This is for printing files and reports. Also, there is a Print command on the View menu (View > Print View) and this is used for printing pictures of the structure. The File menu is shown in “File Menu Commands” on page 22 and the View menu is shown in “ View Menu Commands” on page 23. In addition to Print commands on the File and View menus, MStower has Print Preview commands on each of these menus. The print preview shows an exact image on the screen of the printed page. File > Print Preview shows you how a report will be printed while View > Print Preview is for MStower graphics. The main toolbar, usually located right under the menu, contains a Print button, , and a Preview button, . These buttons are for MStower graphics, not files or reports. Thus, they correspond to the Print and Preview commands on the View menu – notice that the tooltip for the Print button is “Print View”. The main toolbar is shown in “Main Toolbar Commands” on page 31.
The Windows Print Dialog Box While the Preview button acts exactly the same way as the corresponding menu command, the Print button does not. The View > Print View command displays the Windows Print dialog box so you can change the target printer, the number of copies, or printer settings with the Properties button. When you click OK in this dialog box the selected printer becomes the current printer. The File > Print File command also displays the Windows Print dialog box before printing. Clicking the print button on the main toolbar, however, initiates a graphics print without the display of the Windows Print dialog box. The view is printed immediately to the current printer.
WINDOWS PRINT DIALOG BOX MSTower V6
2:Getting Started • 15
Preview commands, File > Print Preview, View > Print Preview, and the Preview button, all do not display the Windows Print dialog box. The preview is always for the current printer. When you see a print preview on the screen, you will notice a Print button at the top left of the preview window. Clicking this will initiate printing on the current printer. If you want to change the target printer after seeing a preview, close the preview window and then select the Print command on either the File or the View menu. When previewing a multi-page report file, the Print button prints the whole file. If you want to print less than the full report use the File > Print File command and select the pages to be printed in the Windows Print dialog box.
The Page Setup Dialog Box The Page Setup dialog box allows you to change settings affecting the layout of printed output, either graphical or reports. The current printer, shown in the Page Setup dialog box, is initially the Windows default printer and remains so until a different printer is selected. A new current printer may be selected in the Windows Print Setup dialog box that is shown when you click the Change button. You may also change the current printer in the Windows Print dialog box shown when you select either View > Print View or File > Print File.
MSTOWER PAGE SETUP DIALOG BOX
Text Size The text size, in points, for both reports and graphical output. There are 72 points to the inch. The default value is 8.
16 • 2:Getting Started
MSTower V6
Orientation Mstower does not use the orientation setting stored with the printer properties. These two settings, one for reports and one for graphics, are used instead. Margins Margins may be set independently for reports and graphics. Logo Check this box if you want MStower to print a logo at the top of each page of printed output. When the box is checked you may choose one of the available bitmap files from the adjacent combo box. See “Configurable User Graphic” on page 18. Report Style When the number of columns is greater than 1 MStower will print multicolumn reports, as long as there is room on the page. When there is insufficient room for the number of columns selected the number of columns is automatically reduced, as required. To increase the density of printing in a report you may increase the number of columns and reduce the text size and margins. Graphics Style
MSTower V6
No color
With the exception of the configurable user graphic, which is always printed in its own colors, printing is in black only, even if using a color printer.
Heavy lines
Structure geometry is shown with heavy lines. This is more suitable for high-resolution printers, which otherwise print a very fine line.
Legends
Color legends for sections and load cases may be shown. The section legend is only shown when section numbers are included on the plot. The load case legend is only shown for the load cases for which loads are plotted.
Scale
The scale at which structure geometry is shown. With a scale of 100, for example, 1 m on the structure is represented as 10 mm on the plot. When the scale is zero (default) the structure is plotted to fill the space available.
2:Getting Started • 17
Configurable User Graphic You may use this feature to place your company logo at the top of all printed output.
MStower allows you to have a small graphic at the top of each page of printed output. Any valid Windows bitmap file existing in the program folder may be selected in the Page Setup dialog box. With this option selected the graphic is printed on each page. If the option is not selected no graphic will be printed and no space will be allowed for it. On installation MStower is configured to use the graphic shown below. You can unselect the option in Page Setup if you do not want a graphic.
DEFAULT GRAPHIC
The specification of the bitmap is: •
Width – 1200 pixels
•
Height – 200 pixels
•
Colors – 256
Bitmaps that do not match these requirements are not shown in the Page Setup dialog box. MStower prints the graphic in a space 50.8 mm wide by 8.5 mm high. Note: The Windows drivers for some printers do not support the printing of bitmaps.
Steel Section Libraries A source file is supplied with each steel section library. The source file is a text file with the file name extension “asc” and the corresponding library file has a file name extension of “lib” (e.g. As.asc, As.lib). Section Library Manager may be used to edit existing section libraries and create new ones. The File > Configure > Section Library Manager command gives access to powerful facilities for editing an existing library or making a new library by merging sections from existing libraries – see “Chapter 13:Editing the Section Library” on page 229. When a library is saved it may be compiled into a library file accessible to MStower (see “Compiling a Library” on page 236). It is recommended that you do not modify the standard libraries supplied with MStower – it is preferable to copy the source file to a file with a different name and then modify that. Steel section libraries used with previous versions of MStower are compatible with those used by V6.
18 • 2:Getting Started
MSTower V6
Data from Earlier Versions All data files (TD, TWR, UDP) and section and ancillary libraries from previous versions and .mst files from V5 are compatible with MStower V6. To open a V3 or V4 job: Select File > New then navigate to the data area and enter the job name. Select Tower > Build Tower > Process Tower File. The job should now be displayed graphically. To open a V5 job: Select File > Open, and select the job. It should be displayed in the state in which it was last saved. Because the format of some work files has been changed to allow the addition of new capabilities, you must rebuild the tower if you wish to do anything more than view the structure.
Technical Support Click the Check Version button in the Help About MStower dialog box to determine whether your software needs updating.
Microstran technical support is available by telephone, fax, and e-mail. Use the Help > About MStower command to display the serial number, the version number, and licence details for your software. This information is required when you ask for technical support. The Help About dialog box contains links to the MStower website, where you may submit a support request or update your software.
HELP ABOUT MSTOWER
MSTower V6
2:Getting Started • 19
Web Update From time to time, minor updates are provided without charge on the MStower website. You may use the web update facility to determine when an update is required. While your computer is connected to the internet, clicking the Check Version button in the Help About dialog box displays the dialog box shown below. This shows the dates of your MStower software and dates of the current web downloads, making it very easy to see whether an update is required.
MSTOWER WEB UPDATE DIALOG BOX
You can connect to the MStower website by clicking the Downloads hot link in the Help About dialog box. Here, you will recognize the components you need to download. Each download is an executable file – run it to unpack the update files. If prompted for a password when this executable runs you must e-mail MStower Support to obtain it. A new CD may be purchased as an alternative to using the internet download facility. When new versions (or major upgrades) become available they are not available on the MStower website – they must be purchased on a CD.
20 • 2:Getting Started
MSTower V6
3:Menus & Toolbars
Layout The diagram below shows the layout of the MStower screen. Commands may be initiated from the main menu, any toolbar, or a context (pop-up) menu. The main menu comprises a menu bar, each item of which gives access to a drop-down menu. Some items on drop-down menus lead to sub-menus. Each toolbar button usually corresponds to a command accessible from the main menu. Context menus, which appear when you click the right mouse button, contain a selection of commands from the main menu. This chapter lists all the commands available on the main menu and all toolbars.
LAYOUT OF MSTOWER WINDOW MSTower V6
3:Menus & Toolbars • 21
File Menu Commands
FILE MENU
The File menu offers the following commands:
22 • 3:Menus & Toolbars
Command
Action
New
Creates a new job.
Open
Opens an existing job.
Close
Closes the current job.
Save
Saves the current job using the same file name.
Save As
Saves the current job to a specified file name and changes the name of the current job accordingly.
Save Copy As
Saves a copy of the current job to a specified file name.
Delete
Deletes job files, optionally keeping source files.
List/Edit File
Opens the selected file with the MsEdit text editor for viewing or editing.
Page Setup
Change the printing options.
Print Preview
Displays the selected file on the screen, as it would appear printed.
Print File
Prints the selected file.
Import
Reads data into MStower from a file (e.g. Microstran Archive file or CAD DXF). This command is only available when editing a UDP.
Export
Writes MStower data to a file. File types include MStower archive file, results file, CAD DXF, and SDNF detailing file.
Configure
Configuration of program capacity, section library, material library, colors, intermediate file folder, and timed backup interval. Also used for editing of section and material
MSTower V6
libraries and dynamic response spectra. Recent Job
Selects recently used job.
Exit
Exits MStower
View Menu Commands
VIEW MENU
The View menu offers the following commands:
MSTower V6
Command
Action
Toolbars
Shows or hides the toolbars.
Status Bar
Shows or hides the status bar.
Redraw
Redraws the current view.
Viewpoint
Change the orientation of the structure in the view by selecting a new viewpoint.
Zoom
Change the scale of the view or select a rectangular part of the view to fill the display window.
Pan
Displace the view by the selected distance.
Limit
Select a part of the structure by one of several available methods. Unselected parts are shown in light grey or hidden.
Full
Redraws the current view so that it fills the window.
Copy
Copy view to Windows clipboard in EMF format.
Print Preview
Displays the view as it would appear printed
Print View
Prints the view.
Display Options
Select options for displaying node numbers, member numbers, etc.
Ancillary Sort Order
Specify whether ancillaries will be sorted by serial number or height.
3:Menus & Toolbars • 23
Virtual Reality
Displays a rendered 3-D interactive view of the tower model. You must have a VRML “plug-in” installed in your browser to use this facility.
Tower Menu Commands
TOWER MENU
The Tower menu offers the following commands: Command
Action
Build Tower
Opens the tower data (TD) file for editing and processing. Includes graphical creation of user-defined panels.
Load Tower
Opens the tower loading (TWR) file for editing and processing.
Analyse
Analyses the tower.
Gust Factor
Applies BS 8100 gust factoring to wind forces in tower members.
Build/Load/Analyse
Runs all the previous items sequentially.
Member Checking Menu Commands
MEMBER CHECKING MENU
24 • 3:Menus & Toolbars
MSTower V6
The Member Checking menu offers the following commands: Command
Action
BS 8100 Part 3
Checks members to the rules of BS 8100 Part 3.
BS 449
Checks member to the rules of BS 449.
ASCE 10-90
Checks member to the rules of ASCE 10-90.
ASCE 10-97
Checks member to the rules of ASCE 10-97.
EIA-222-F
Checks member to the rules of EIA-222-F.
TIA-222-G
Checks member to the rules of TIA-222-G.
AS 3995
Checks member to the rules of AS 3995.
IS 802
Checks member to the rules of IS 802.
ILE Tech. Report 7
Checks poles to the rules of ILE Tech. Report.
ASCE Manual 72
Checks poles to the rules of ASCE Manual 72.
BS 5950
Checks poles to the rules of BS 5950.
AS 4100
Checks poles to the rules of AS 4100.
EIA-222-F
Checks poles to the rules of EIA-222-F.
TIA-222-G
Checks poles to the rules of TIA-222-G.
Structure Menu Commands
STRUCTURE MENU
The Structure menu becomes active only when graphically inputting a UDP. It offers the following commands:
MSTower V6
Command
Action
Draw Members
Draw members or input node coordinates.
Erase Members
Erase selected members.
Select All
Selects all members, including any that may not be visible.
Drawing Settings
Snap modes for drawing members, grid spacing etc. 3:Menus & Toolbars • 25
Attributes
Input attributes of the structure, such as restraints, section numbers, etc.
Move
Move a node, move members, rotate members, stretch nodes.
Copy
Linear copy, polar copy, reflect members.
Sub-divide
Sub-divide selected members into a number of equal parts.
Insert Node
Insert a new node in a member.
Intersect
Insert new node(s) at intersection of selected members.
Renumber
Renumber nodes and members (sort or compact).
Analyse Menu Commands
ANALYSE MENU
The Analyse menu offers the following commands:
26 • 3:Menus & Toolbars
Command
Action
Check Input
Check structure and load data (normally automatic).
Linear
Perform linear analysis (first-order).
Non-Linear
Perform non-linear analysis (second-order).
Elastic Critical Load
Determine frame buckling load factors and buckling mode shapes.
Dynamic
Determine natural frequencies and mode shapes.
Response Spectrum
Add response spectrum and static analysis results.
MSTower V6
Results Menu Commands
RESULTS MENU
The Results menu offers the following commands: Command
Action
Select Load Cases
Select load cases for display of loads or results.
Select Natural Modes
Select modes for display of vibration mode shapes.
Select Buckling Modes
Select modes for display of buckling mode shapes.
Undisplaced Shape
Display structure in undisplaced position.
Member Actions
Display bending moment, shear force, axial force, torque, or displaced shape.
Natural Modes
Display vibration mode shapes.
Animate Modes
Show each currently displayed mode (natural or buckling) in alternate extreme positions. Press the space bar to show the next mode, Esc to cancel.
Buckling Modes
Display buckling mode shapes.
Design Ratios
Display results of member design check with colors representing range of design ratios. The legend in the Output window shows the range of values represented by each color.
Reports Menu Commands
REPORTS MENU
The Reports menu offers the following commands:
MSTower V6
Command
Action
Input/Analysis
Create report on structure and current analysis results.
3:Menus & Toolbars • 27
Show Menu Commands
SHOW MENU
The Show menu offers the following commands:
28 • 3:Menus & Toolbars
Command
Action
Section
Highlight members with specified section number.
Material
Highlight members with specified material number.
Member Type
Highlight members of specified type (tension-only etc.).
Member Class
Highlight members of specified classes such as legs, braces, etc.
Members
Highlight specified members.
Panels
Highlight members in a panel.
Wind Panels
Highlight members to show how tower is sub-divided for wind load calculations.
Nodes
Highlight members connected to specified nodes.
Master Nodes
Show master nodes.
Slave Nodes
Show slave nodes.
Node Masses
Show all nodes with non-zero added mass.
Design Members
Show all defined design members.
Cancel
Cancel current “Show” selection.
MSTower V6
Query Menu Commands
QUERY MENU
The Query menu offers the following commands: Command
Action
Node Data
List data for selected node (coordinates etc.).
Node Displacements
List displacements for selected node.
Support Reactions
List reactions for selected (support) node.
Master Node
List slave nodes for selected master node.
Slave Node
List constraints for selected slave node.
Member Data
List member data for selected member.
Member Displacements
List displacements for selected member.
Member Forces
List member forces for selected member.
Node Loads
List loads for selected node.
Member Loads
List loads for selected member.
Design Member
Highlight design member containing selected member.
Linear Ancillary
List properties of linear ancillary.
Large Ancillary
List properties of large ancillary.
Ancillary Group
List properties of ancillary group.
Note: Query data is displayed in the Output window.
MSTower V6
3:Menus & Toolbars • 29
Window Menu Commands
WINDOW MENU
The Window menu offers the following commands, which enable you to arrange multiple views in the application window:
30 • 3:Menus & Toolbars
Command
Action
Cascade
Arranges windows in an overlapped fashion.
Tile Horizontally
Arranges windows side-by-side.
Tile Vertically
Arranges windows above and below.
Output Window
Show or hide the Output window.
Window
All open windows are listed. Clicking one of these will move the focus to the selected window.
MSTower V6
Help Menu Commands
HELP MENU
The Help menu offers the following commands: Command
Action
MStower Help Topics
Display the Help Topics dialog box. This has three tabs, Contents, Index, and Find, so you can easily find help topics.
What’s This?
Display help for clicked buttons, menus, and windows.
Tip of the Day
Show Tip of the Day.
About MStower
Display details about this copy of MStower and system resources. Also contains links to Internet.
Main Toolbar Commands
MAIN TOOLBAR
The Main toolbar offers the following commands:
MSTower V6
•
Open a new job.
•
Open an existing job. MStower displays the Open dialog box, in which you can locate and open the desired file. This command is for opening an existing job – one for which there is already a Job.mst file, where “Job” is the name of the job as it was saved.
•
Save the job with its current name.
•
Print the view; i.e. print a picture showing the current view of the structure. Use the File > Print command to print a file.
•
Print preview; i.e. display exactly how the graphics will be printed. Use the File > Preview command to preview a file.
3:Menus & Toolbars • 31
View Toolbar Commands
VIEW TOOLBAR
The View toolbar offers the following commands:
32 • 3:Menus & Toolbars
•
Display front view.
•
Display right view.
•
Display top view.
•
Display oblique view.
•
Move viewpoint to left.
•
Move viewpoint to right.
•
Move viewpoint up.
•
Move viewpoint down.
•
Zoom to extents/limits of structure. If the View > Limit command is in effect, clicking this button alternately displays the full structure and the limited part of the structure.
•
Zoom to selected window.
•
Zoom in.
•
Zoom out.
•
Dynamically zoom view.
•
Dynamically rotate view.
•
Pan.
•
Limit > Window command.
•
Full View command.
•
Show the Output window.
MSTower V6
Display Toolbar Commands
DISPLAY TOOLBAR
The Display toolbar offers the following commands: •
Display node symbols.
•
Display of node numbers.
•
Display member numbers.
•
Display section numbers.
•
Display supports.
•
Display pins.
•
Display rendered view of members.
•
Display annotation of loads.
•
Display annotation of member force or displacement diagrams.
•
Increase scale for plotting loads, member forces, or displaced shape.
•
Decrease scale for plotting loads, member forces, or displaced shape.
Help Toolbar Commands
HELP TOOLBAR
The Help toolbar offers the following commands:
MSTower V6
•
Help Topics. Starts HTML Help providing access to on-line help with display of User Manual contents, index, and search facility.
•
Help About MStower. MStower version and licence details – includes links to internet.
3:Menus & Toolbars • 33
Draw Toolbar Commands
DRAW TOOLBAR
The Draw toolbar is available during graphical input of UDPs only. It offers the following commands: •
Draw members.
•
Erase members.
•
Move members.
•
Copy members.
•
Reflect members.
•
Sub-divide members.
•
Rotate members.
•
Display grid points and set Grid snap mode.
•
Set Middle/End snap mode.
•
Set Intersection snap mode.
Attributes Toolbar Commands
ATTRIBUTES TOOLBAR
The Attributes toolbar offers the following commands:
34 • 3:Menus & Toolbars
•
Input section numbers.
•
Input member releases.
•
Input member orientation reference node/axis.
MSTower V6
Results Toolbar Commands
RESULTS TOOLBAR
The Results toolbar offers the following commands: •
Display undisplaced structure.
•
Select load cases for display.
•
Display applied loads.
•
Display member actions. You must turn on this “switch” before you are able to select member forces for display.
•
Display axial force, Fx.
•
Display shear force, Fy.
•
Display shear force, Fz.
•
Display torque, Mx.
•
Display bending moment, My.
•
Display bending moment, Mz.
•
Display displaced structure.
•
Display natural vibration modes.
•
Display buckling modes.
•
Display design ratios. Design ratios are displayed graphically with different colors representing distinct ranges of values for the percentage of code capacity. For example, members shown bright red are loaded in excess of 110% of the design code capacity.
•
Display member force envelope.
•
Animate modes (natural or buckling). Each mode is displayed in turn. Press the space bar to move to the next mode or Escape to exit mode animation.
OK/Cancel Toolbar Commands
OK/CANCEL TOOLBAR
The OK/Cancel toolbar is an alternative to the context menu for confirming or cancelling selections. Display or hide it with the View > Toolbars command. This toolbar is not displayed initially.
MSTower V6
3:Menus & Toolbars • 35
Extra Buttons Toolbar Commands
EXTRA BUTTONS TOOLBAR
The Extra Buttons toolbar contains a number of buttons that may be added to other toolbars during customization. It is not displayed initially. The buttons available are: •
Display back view.
•
Display left view.
•
Display y axis for all members.
•
Polar copy.
•
Intersect members.
•
Insert node.
•
Redraw (F5).
Selecting Which Toolbars Are Displayed You may easily determine the toolbars that are displayed with the View > Toolbars command. This displays the dialog box shown below. All checked toolbars are displayed.
TOOLBARS DIALOG BOX
Any toolbar that has been customized may be reset to the original configuration by selecting it and then clicking the Reset button.
36 • 3:Menus & Toolbars
MSTower V6
Customizing Toolbars As well as being dockable, toolbars in MStower are customizable in two ways. Firstly, while pressing the Alt key you may drag any button to any position on the same or another toolbar. If you drag a button to a new position not on a toolbar, it will disappear. Secondly, you may click the Customize button in the Toolbars dialog box (View > Toolbars command). This displays the Customize property sheet. Clicking the New button creates a new empty toolbar with any specified name. On the Commands tab you may now select any existing toolbar and drag its buttons onto the new toolbar (or any other toolbar).
CUSTOMIZING TOOLBARS
The Ouput Window The Output window, normally at the bottom of the main window, is dockable. You may click on any part of the edge of the Output window and drag it, so that it floats inside the main window or docks on any edge of the main window. You may double-click on the title bar of the floating Output window and it will return to its previous docked position. Click the Output Window button to hide or display the Output window.
MSTower V6
3:Menus & Toolbars • 37
38 • 3:Menus & Toolbars
MSTower V6
4:Operation
Data Files The tower is described in data files by the minimum number of key dimensions and a description of the types of panel in the tower. Panel types are described by mnemonics of one to four characters. Panels may be selected from a set of built-in face, plan, hip, and cross-arm patterns or may be defined by the user. The following data files are used: •
Job.td The tower data file.
•
Job.udp An optional file containing the description of non-standard or userdefined panels.
•
Job.twr The tower loading file.
When a job is saved the above files and others associated with the job are copied into the job.mst file. It may be convenient to copy the data files from an existing MStower job and edit these, rather than creating them from the beginning. This may be done by opening the existing job and selecting the File > Save Copy As command to create the new job. The data files are text files, usually created and edited with the built-in text editor, MsEdit. Data is set out in blocks identified by keywords. Blank lines may be used as required to improve the readability of the file. The “$” character may be used to introduce comments; the “$” character and all text following on that line are ignored as input data. Individual items of data may be separated by one or more blank spaces. Each line of data must be no longer than 80 characters.
MSTower V6
4:Operation • 39
The following conventions are used to describe the input data: Square brackets are used to indicate optional data items. A and B may be omitted in this example: ...[ A ] [ B ]...
Braces are used to indicate where a choice must be made from a list of items. Items may be shown vertically, or horizontally when separated by vertical bars. For example: ...{ item 1 }... { item 2 } { item 3 }
or ...{ item 1 | item 2 | item3 }...
One of the items must be chosen. An ellipsis, “…”, indicates that the data description in this manual is continued on the next line. Unless otherwise noted, the data in the file must be on one line. Two dots, “..”, are used to indicate that there is a range of values between those shown, or that a series continues. The “&” character at the end of a line indicates that the data continues on the next line. Note: Square brackets, braces, the vertical line symbol, and the ellipsis are used to specify input – these characters do not appear in MStower data files.
Units MStower accepts two sets of units: •
Metric – using meters, kilonewtons, tonnes, and degrees Celsius, with some data items being input and/or reported in the more customary units of mm and kg.
•
US – using feet, kips, kip.sec2/ft, and degrees Fahrenheit, with some data items being input and/or reported in the more customary units of inches and pounds.
Entries in the ancillary and guy libraries are required in metric units.
Coordinate Systems The vertical axis of the tower is parallel to the global Z axis. The X and Y axis of the tower lie in the horizontal plane and do not need to be aligned with the geographic north. The X axis is always normal (in plan) to one face of the tower. Each member in MStower has its own set of member or local axes. The local x axis is aligned along the member while the local y and z axes correspond to the rectangular section axes. The reference node or axis defines the plane of the local y axis. 40 • 4:Operation
MSTower V6
Sections All sections in the tower must be described in an MStower section library file. Dimensions and properties are automatically extracted to compute surface and projected areas when calculating ice and wind loads and for determining member capacities.
Member Checking You must ensure that wind velocities and other factors used to compute loads are consistent with the code method chosen to check member strengths. BS 8100 Part 3, AS 3995, ASCE10, TIA-222-G, and IS-802 are limit states codes, whereas EIA/TIA-222-F uses permissible stresses.
Export to Microstran Archive File The MStower model may be exported to a Microstran archive file. This permits running of the model in the Microstran frame analysis and design program.
Errors After assembly of the tower, MStower checks for the following conditions: Overlaid Members and Unconnected Nodes These occur when a node is coincident with a member but not connected to it. When this occurs it is usually at the junction between panels and happens either because a horizontal has not been deleted or because of an incompatibility between panels. For example if a PL1 plan brace is used with an X face brace the PB1 member will overlay the H1 member. The duplicated member will not be detected by the assembly process because of the mid-side node in PB1. A list of such members will be displayed. Floating Members These are members that are not connected to the structure. If not removed they will result in errors during analysis. They can result if members are deleted; for example if PL1 plan bracing is used with XO face bracing and the PB1 member is deleted, the internal plan bracing members will not be connected to the tower. A list of such members will be displayed. You may readily locate overlaid and floating members using MStower screen plots. Select the Show > Members command and then enter the list of offending members. The full tower will now be displayed with the listed members highlighted. You may zoom to inspect the members more closely and determine the reason for the error. The TD or UDP file should be modified as necessary. MSTower V6
4:Operation • 41
Section Checks The tower builder does a number of sensibility checks as the tower is assembled and reports on the following: •
Section usage – whether the section is used as a leg, brace, or other type of member.
•
Whether the connection code is appropriate to the section type.
•
Whether a bolt-hole width has been specified for bolted members. There are also preliminary range checks on the magnitude.
You may inspect the above reports by clicking the Build tab on the Output window.
42 • 4:Operation
MSTower V6
5:Tower Data
General Data describing the tower geometry is entered into a free-format text file called Job.td, where “Job” is the job name. A prototype tower data file may be generated by selecting the Tower > Build Tower > Make Tower Data File command. The dialog box shown below appears for you to enter the basic geometric parameters.
GEOMETRY PARAMETERS DIALOG BOX
You may then enter details for each panel in this dialog box.
PANEL DETAILS DIALOG BOX
The resulting tower data file is shown below. It must now be customized for the particular tower you are modelling. The file will be displayed in the MsEdit text editor when you select the File > List/Edit File command and then choose “TD”.
MSTower V6
5:Tower Data • 43
TITL1 Test tower TITL2 UNITS 1 PROFILE FACES 4 WBASE 4.0000 RLBAS 0.0000 PANEL 1 HT 1.000 TW 1.000 FACE X $ LEG ? BR1 ? H1 ? PANEL 2 HT 1.000 TW 1.000 FACE X $ LEG ? BR1 ? H1 ? PANEL 3 HT 1.000 TW 1.000 FACE X $ LEG ? BR1 ? H1 ? PANEL 4 HT 1.000 TW 1.000 FACE X $ LEG ? BR1 ? H1 ? END SECTIONS LIBR P:UK IFACT 0.1 1 EA200X200X16 2 EA150X150X10 3 EA100X100X8 4 EA70X70X6 END
$ 1.00
BOLTDATA $ TODO - bolt data goes here - format of bolt data: $ [ X x Y y Z z NSP nsp LJ lj ] END END PROTOTYPE TOWER DATA FILE
The Tower Data (TD) File The tower data file is organized into logical blocks:
44 • 5:Tower Data
1.
Title block.
2.
Component block.
3.
Profile block.
4.
Supports block.
5.
Guys block.
6.
Sections block.
7.
Material block.
8.
Bolts block.
MSTower V6
Each block commences with a keyword identifying the block and terminates with the keyword END. The keyword EOF is used to terminate the file. Each data block is described in this chapter.
Title Block TITL1 TITL2 UNITS
titl1 titl2 units
where: TITL1
Keyword.
titl1
First line of job title.
TITL2
Keyword.
titl2
Second line of job title.
UNITS
Keyword.
units
Integer value indicating system of units being used – 1 or 4. 1 = SI units. 4 = US units.
Component Block Although MStower provides a comprehensive range of panel types, there may be times when you wish to define additional panel types. This block allows you to reference a file containing panel data to be included in the tower. COMPONENT udp [file] .. END
where:
MSTower V6
udp
Name (1-8 characters) of a user-defined panel.
file
Name of file containing the user-defined panel. It must have the file name extension “udp”. The file must be specified only if the UDP file is not named after the job. UDP files may be referenced by multiple jobs but unless named after the job will not be saved in the MST file. The file may contain more than one user-defined panel.
5:Tower Data • 45
Profile Block This block provides the data used to generate the node coordinates and member connectivity of the tower. Panels are described in order, from the top of the tower. The block contains descriptions of the face bracing, plan bracing, hip bracing, and cross-arms. Section property numbers may be assigned to the various types of members in each panel; the property number for a member type need not be specified again unless there is a change. Panel widths need to be input only at the bend points; intermediate widths will then be interpolated automatically. PROFILE FACES WBASE DBASE RLBAS
nface wbase dbase rlbas
PANEL nn HT hpanl [TW bpanl] [scale] BOLT class nbolt [bolt_id] class nbolt [bolt_id]... [BOLTY class nbolt [bolt_id] class nbolt [bolt_id]..] FACE ftype [SPACE s1 .. ns@sm .. sn]... [F1 f1 F2 f2]... [NTR ntr] [ND nd] [NPL npl]... [D] [INV] [LEFT]... [LEG leg BR1 br1 BR2 br2 BR3 br3... H1 h1 H2 h2 R1 r1 .. R9 r9]... [LA la] [LB lb] [LC lc] [LD ld] [XDISC] [FACEY ftype [SPACE s1 .. ns@sm .. sn]... [F1 f1 F2 f2]... [NTR ntr] [ND nd] [NPL npl]... [D] [INV] [LEFT]... [LEG leg BR1 br1 BR2 br2 BR3 br3... H1 h1 H2 h2 R1 r1 .. R9 r9] [MCAP class c1 c2 c3] PLAN ptype [PB1 pb1 PB2 pb2 PB3 pb3 ..]... [F1 f1 F2 f2] [locn] [NORST list] HIP htype [NTR ntr] [ND nd] [HP1 hp1] [HP2 hp2]... [NORST list] CROSS ctype [X | Y] [SPAN span] | [SL sl | SR sr]... [RL rl] [RR rr] [CR1 cr1 CR2 cr2 ..] PANEL .. END
where:
46 • 5:Tower Data
FACES
Keyword.
nface
Number of faces in the tower, either 3 or 4.
WBASE
Keyword.
wbase
Base width of tower; i.e., the base width of the lowest panel.
DBASE
Keyword, optional, applicable to 4 sided towers only.
dbase
Base depth of tower; i.e., the distance between the legs at the bottom of the tower for the face normal to the Y axis. Used to generate rectangular towers.
RLBAS
Keyword.
MSTower V6
rlbas
RL at tower base with respect to the ground level at the site. The nodes at the bottom of the legs will have this value as their Z coordinate.
PANEL
Keyword.
nn
Panel number.
HT
Keyword.
hpanl
Panel height.
TW
Keyword.
tw
Width at top of panel, for the face normal to the X axis. If not given, this value will be interpolated.
TD
Keyword, optional, used for rectangular towers.
tw
Width of the top of the panel, for the face normal to the Y axis. If not given, it will be interpolated.
scale
Optional keyword pertaining to variable dimensions F1 and F2: FR F1 and F2 are factors; the actual dimensions are obtained by multiplying a length as shown on the panel diagram. LE F1 and F2 are lengths. If omitted, fractional scaling, FR is assumed.
BOLT
Keyword.
class
Member class, one of the following member types: LEG Leg members. BR BR1..BR4 Bracing in the face. H H1 H2 Horizontal in the face. R R1..R9 Face redundant. PB PB1..PB10 Plan bracing. HP HP1..HP10 Hip bracing. CR CR1..CR10 Cross-arm members. If a mnemonic without a numeric suffix is used, all members of the class will have the number of bolts specified.
nbolt
The number of bolts in the end connection of the member – zero for welded connections. You may use as many class/nbolt pairs as are necessary.
MSTower V6
5:Tower Data • 47
bolt_id
Optional character string, used to identify the bolt in the BOLTDATA table.
BOLTY
Keyword, optional. The data required for BOLTY is similar to that for BOLT. Used to describe the bolting on the faces of the tower normal to the Y axis if it differs from that on the faces normal to the X axis.
FACE
Keyword.
ftype
Face bracing pattern type. User-defined panels must have their names prefixed with the “@” character; e.g. @XYZ refers to a user-defined panel XYZ. UDPs may have names with a maximum of 8 characters and must have been referenced in the COMPONENT block.
SPACE
Keyword.
s1..sn
List of spacings for XM, DM, DLM, DRM, DMH, KXM, and XDM type face bracing.
ns@sm
Shorthand way of indicating that a multiple panel has a number of identical spacings: ns Number of identical spacings. @ Keyword. sm Value of identical spacing.
48 • 5:Tower Data
F1,F2
Keywords.
f1,f2
Factors used to locate nodes for some bracing types. The use of these factors is shown on the individual bracing diagrams.
NTR,ND
Keywords.
ntr,nd
Number of levels of triangle and diagonal braces, respectively, in some face and hip brace patterns.
NPL
Keyword.
npl
Bracing pattern in part of a portal or cranked K face.
D
Keyword – used with XDM bracing.
LEFT
Keyword – used with DM bracing.
INV
Keyword, used with KB, KBP, KM, KMA, KMG, KMGA, KMGD, KMH, KMHA, KMV, KVH3, and KVS3, indicating that the panel is to be inverted.
LEG
Keyword.
leg
Section property number for leg members.
BRn
Keyword.
brn
Section property number for brace members, type n, where n is a digit from 1 to 3.
Hn
Keyword. MSTower V6
hn
Section property number for horizontal members, type n, where n is a digit from 1 to 2.
Rn
Keyword.
rn
Section property number for redundant or secondary bracing members, type n, where n is a digit from 1 to 9. All property numbers for a particular member class may be set by using the keyword without a numeric suffix; e.g. BR will set BR1, BR2, and BR3.
LA,LB,LC, Keywords. LD la,lb,lc, Section property numbers for leg A, B, C, and D, respectively. ld Leg A is in the positive X-Y quadrant and the other legs are identified in sequence, anti-clockwise from leg A when viewed in plan. The properties of the leg members of the tower may be assigned individually if they are not symmetrical. In any case, a non-zero property must follow the LEG keyword. XDISC
Optional keyword indicating that the X bracing is discontinuous at the intersection point. Triangulated plan bracing or a horizontal member stiff enough to provide restraint must be provided.
FACEY
Optional keyword. The data required for FACEY is similar to that for FACE. It is used to describe the bracing on the faces of the tower normal to the Y axis if it differs from that on the faces normal to the X axis. FACEY may be omitted, in which case: Square towers will have the pattern defined in FACE on all faces. Rectangular tower will have no bracing on the Y face; the panel must be made into a UDP and the bracing added manually.
MCAP
Keyword.
class
Member class, as described above under BOLT.
c1,c2,c3
User defined member capacity, kN or kips. c1 Capacity of member in compression. c2 Capacity of member in tension. c3 Capacity of joint. All three capacities must be given. Code rules will be used to compute the capacity if any of “c1 c2 c3” is entered as zero. For monopoles, c1, c2 and c3 are the compressive, flexural and torsional capacities respectively. If members are to be checked to BS 8100 or ILETR7, a partial safety factor for material of unity should be used when determining user defined capacities.
MSTower V6
5:Tower Data • 49
PLAN
Keyword.
ptype
Plan bracing pattern type.
PBn
Keyword.
pbn
Section property number for plan bracing member, type n, where n is a value from 1 to 10. The property numbers for all plan braces will be set to this value if the numeric suffix is omitted from the keyword.
F1,F2
Keywords.
f1,f2
Factors used to locate nodes for some bracing types. The use of these factors is shown on the individual bracing diagrams.
locn
Optional character string indicating the vertical location of plan bracing in the current panel. If omitted, the plan bracing will be placed at the top of the face panel. Must be one of: TOP Top of the face panel. BTM Bottom of the face panel. This may be required with certain inverted face panels or type “M” face bracing. XIP The level of the intersection of cross-brace members in the face. MID The mid-height of the face.
50 • 5:Tower Data
NORST
Keyword.
list
List of integers, 1–10, giving the suffix number of members that are to be considered as providing no buckling restraint to main load carrying members they connect to. For example, if a plan bracing pattern such as PL3 is used, NORST 2, will indicate that the PB2 member is not to be considered as providing restraint to the peripheral member at the mid-side node.
HIP
Keyword.
htype
Hip bracing pattern type.
NTR, ND
Keywords.
ntr, nd
Number of levels of triangle and diagonal braces, respectively, in some hip brace patterns.
HPn
Keyword.
hpn
Property number for hip bracing, type n. The property numbers for all hip braces will be set to this value if the numeric suffix is omitted from the keyword.
NORST
Keyword.
list
List of integers, 1–10, giving the suffix number of members MSTower V6
that are to be considered as providing no buckling restraint to main load carrying members they connect to. CROSS
Keyword.
ctype
Cross-bracing pattern type.
X,Y
Keywords indicating that the cross-arms are to be attached to the X or Y faces of the tower. If not specified the cross-arms will be attached to the Y faces; i.e. they will project to the left and right when viewed from the direction of the X axis.
SPAN
Keyword.
span
Total span of symmetrical cross-arm. If the cross-arm is not symmetrical, separate left-hand and right-hand “half” spans must be specified.
SL
Keyword.
sl
Left-hand “half” span of the cross-arm. Viewed from the positive X axis direction if attached to the Y faces, or viewed from the positive Y axis direction if attached to the X faces.
SR
Keyword.
sr
Right-hand “half” span of the cross-arm.
RL
Keyword.
rl
Rise of left-hand “half” span of the cross-arm when viewed as described above.
RR
Keyword.
rr
Rise of right-hand “half” span of the cross-arm.
CRn
Keyword.
crn
Section property number for cross-arm member, type n, where n is a value from 1 to 10. The property numbers for all crossarm members will be set to this value if the numeric suffix is omitted from the keyword.
Each panel must have one set of face braces and optionally one set of hip bracing and one or two sets of plan and/or cross-arm braces. Redundant members are pin-ended. All other members are assumed to be rigidly connected. Any member assigned a property number of zero will be deleted. For example an “X” face panel with H1 = 0 is identical to an “X0” panel. You must ensure that the deletion of members does not result in an unstable structure. When inverting panels, it may be necessary to delete the horizontal member in either the inverted panel or the panel on which it is mounted, if the two horizontals are not sub-divided in identical fashion. “C” nodes (reference nodes), which define member orientation, are allocated in the plane of the face or hip for all members except H1 and H2 type members, where the “C” node is in the direction of the global MSTower V6
5:Tower Data • 51
“Z” axis; i.e. for face members apart from H1 and H2, and hip braces, the member “y” axis lies in the plane of the hip or face. Orientation keywords may be applied to the section definition (see “Sections Block”, below) if the section is to be rotated. If a member class mnemonic is used without a numeric suffix all members of the class will have the number of bolts (or member capacities) specified. For example, if all redundants in a panel use the same bolting, specify: BOLT R nbolt [bolt-id] Bracing patterns and the location of different member types are shown on the bracing diagrams. Some face panels, such as XTR and KTR, are shown with asymmetrical redundants. In these cases, the arrangement of redundants on the left-hand part of the diagram applies to the X faces of the tower while that on the right-hand side applies to the Y faces. Note: The number of bolts in the ends of members is used in strength checking modules to determine buckling curves or effective slenderness ratios. If the number of bolts is not specified MStower will assume that all members are single-bolted except for legs, face bracing, and horizontals that are assumed to have two or more bolts. Normally, the bolt specification will be entered in the first panel; it is only necessary to enter changes (if any) in subsequent panels. The bolts themselves will not be checked unless bolt_ids are defined in BOLT statements and bolt information is defined in a BOLTDATA block.
52 • 5:Tower Data
MSTower V6
Supports Block This block is optional and may be used to modify the default support conditions of full fixity for all supports except for masts where the legs join at a single pinned support point. SUPPORTS {COORD x y z | LEG abcd}... {PINNED|FIXED [BUT {releases|springs}]} .. END
where: COORD
Keyword.
x y z
Coordinates of a node that is to be restrained.
LEG
Keyword.
abcd
Leg number in the form of a compact list using the characters A, B, C, or D. Leg A is in the positive X-Y quadrant. The other legs are identified in sequence, anti-clockwise from leg A when viewed in plan; e.g. AC would indicate that the support conditions apply to legs A and C.
PINNED
Keyword indicating that the node is pinned; i.e., it is free to rotate but all translational degrees of freedom are restrained.
FIXED
Keyword indicating that the node is completely fixed; i.e., all degrees of freedom are restrained.
BUT
Keyword used with FIXED to indicate that some degrees of freedom are to be released or have spring restraints.
releases
List of degrees of freedom to be released. One or more of: FX FY FZ MX MY MZ
springs
List of degrees of freedom that are to be restrained by springs, with the corresponding spring constant. One or more of the following pairs: KFX kfx KMY kmy
MSTower V6
KFY kfy KMZ kmz
KFZ kfz
KMX kmx
5:Tower Data • 53
Guys Block This block pertains to guyed masts only and is used to specify the library containing the properties of guy wires and their arrangement on the mast. GUYS LIB lib XB xb YB yb ZB zb XT xt YT yt Zt zt NO no ANGL angl... TO to KT kt LIB guy_id END
where:
54 • 5:Tower Data
LIB
Keyword.
lib
Name of library containing guy data. It is assumed that the library is located in the data folder unless the name is prefixed with “P:” or “L:”. “P:” indicates that the library is in the program folder and “L:” indicates that it is in the library folder.
XB
Keyword.
xb
Global X coordinate of the lower end of the guy.
YB
Keyword.
yb
Global Y coordinate of the lower end of the guy.
ZB
Keyword.
zb
Global Z coordinate of the lower end of the guy.
XT
Keyword.
xb
Global X coordinate of the upper end of the guy.
YT
Keyword.
yb
Global Y coordinate of the upper end of the guy.
ZT
Keyword.
zb
Global Z coordinate of the upper end of the guy.
NO
Keyword.
no
Number of guys in this group.
ANGL
Keyword.
angl
Angle between successive guys in the group, in degrees.
TO
Keyword.
to
Initial guy tension, in kN or kips. The unstrained length of the guy will be adjusted so that when stretched between the undisplaced end nodes, the maximum tension in the guy will equal this value. The still air tension will be less than the initial tension due to the elastic shortening of the shaft of the mast. Some trial-and-error adjustments of TO values may be necessary to obtain the required still-air tensions.
KT
Keyword.
kt
Guy connection efficiency factor.
LIB
Keyword.
guy_id
Character string of 1 to 16 characters used to identify the guy in the guy library. The properties of the guy required for analysis MSTower V6
and design will be taken from the guy library.
The first guy in the group will span between (xb, yb, zb) and (xt, yt, zt), and if no is greater than 1, additional cables will be automatically generated at an angular increment of angl anti-clockwise about the vertical axis of the mast. Guys can be generated only where they are radially symmetrical about the vertical axis of the mast. For example, guys that have their anchor points at different levels because of a sloping site have to be input singly. Usually, guys are input as single members. A guy may also be input as a number of segments to accommodate changes in properties or to allow an insulator to be positioned along its length. In this case, you should input the segments of guy sequentially, commencing at the anchor point and working up to the mast shaft with the coordinates of the lower end of one segment being set equal to those of the upper end of the preceding segment. The segments of guy may be generated as described above.
Sections Block This block specifies the section library and nominates the section to be used for each section property number. SECTIONS LIBR libr IFACT fact n sname [X|Y] [CONNECT con] [BH bh] [FY fy] [FU fu] .. END
where: LIBR
Keyword.
libr
Name of library containing section data. It is assumed that the library is located in the data folder unless the name is prefixed with “P:” or “L:”. “P:” indicates that the library is in the program folder and “L:” indicates that it is in the library folder.
IFACT
Keyword.
fact
Factor by which the section Ixx and Iyy will be multiplied on extraction from the library. When you specify a low value the tower will approach the condition of a space truss with pinended members. This is convenient for analysing as a space frame, with sufficient continuity across the joints to avoid mathematical instabilities due to coplanar nodes, but without generating significant bending moments.
n
Section property number.
sname
Name of library section.
X Y
Keywords used to indicate the orientation of the section with respect to the member y axis: X The section XX axis is aligned with the member y axis. Y The section YY axis is aligned with the member y axis. Use of these keywords will allow you to correctly orient
MSTower V6
5:Tower Data • 55
asymmetrical sections. For example, if an unequal angle is used in the face of the tower, orientation Y will result in the long leg of the angle being parallel to the face, whereas orientation X will result in the long leg being normal to the face of the tower. Note that the member y axis is not altered by the use of an orientation keyword. See diagram below. CONNECT
Keyword.
con
Single-character mnemonic indicating the connected element of the section: C Concentrically connected (default). L Long leg of angle. S Short leg of angle. F Flange of I, H, or T section. W Web of I, H, or T section. The following codes are applicable to braces of solid rod or tubular section to allow K factors to be determined in accordance with BS 8100 Part 3 Table 3: SG The member is attached to a gusset plate that is not shared with other members. MG The member is attached to a gusset plate that is shared with other members. CR Continuous solid rod bent in the form of a “W” welded to the tower legs. It is important that you specify the connected element for each section. If omitted, MStower assumes the member is concentrically connected, giving a higher strength than it may actually have.
BH
Keyword.
bh
Effective width of bolt holes, in mm or inches, in the connected element, taking into account any staggering of holes,
FY
Keyword.
fy
Yield stress of the section. It may be either a numerical value, in N/mm2 (MPa) or Kips/in2, or, a single-character mnemonic indicating the yield strength to be taken from the section library: N Normal yield stress (default). H High yield stress. N and H yield strengths correspond to the “y1” and “y2” yield strengths in the MStower section libraries. In UK libraries, these will normally be based on Grade 275 and Grade 355 steel, respectively. Generally, it is recommended that you use explicit numerical values for “fy”.
56 • 5:Tower Data
FU
Keyword.
fu
Ultimate tensile strength. Derived from fy if not specified.
MSTower V6
Note: MStower models members as three-dimensional beam-columns. If the default, IFACT 1, is used the second moments of area computed from the dimensions of the section will be used to determine the flexural stiffness of a member. A lower value of IFACT may be used to reduce the bending stiffness of members so that the analysis approaches that of a space truss but without the necessity of adding dummy members or springs to stabilize unstable nodes. The typically small bending moments found in triangulated towers will be reduced and the behaviour of the model will more closely approximate that of a space truss. If flexural stiffness is important “IFACT 1” should be used. This applies to structures that are not fully triangulated or where a second-order analysis or an elastic critical load analysis is required. The orientation of the section is the cross-section axis (XX or YY) that is coincident with the member y axis (see diagram below).
ORIENTATION OF SECTION
MSTower V6
5:Tower Data • 57
Material Block This block is optional. It is used to change the default values of the material used for the tower or the shaft of a mast. MATERIAL E e PR pr END
DENS dens
ALPHA alpha
where: E
Keyword.
e
Young’s modulus (2.05×105 N/mm2 or 29000 kips/in2).
PR
Keyword.
pr
Poisson’s ratio (0.3).
DENS
Keyword.
dens
Mass density (7850 kg/m3 or 490 lb/ft3).
ALPHA
Keyword.
alpha
Coefficient of thermal expansion (12.0×10-6 per °C or 5.9×10-6 per °F).
The default material properties are shown above in brackets. Note: Material properties for guys are obtained from the specified guy library.
Bolt Data Block This block specifies bolt diameters, grades, and other data required in checking the capacity of bolted end connections. BOLTDATA bolt_id grade D d AS as FY fy FU fu FV fv... [FV_EIA fv_eia | FV_ASCE fv_asce | FV_TIA fv_tia]... [X x] [Y y] [Zz z] [NSP nsp] [LJ lj]... [FYP fyp FUP fup TP tp]... [TENS AT at FT ft PR pr] .. END
where:
58 • 5:Tower Data
bolt_id
String of 1 to 8 characters used to identify the bolt type in the BOLT statement in the PANEL data above.
grade
Bolt grade description, e.g. “GR8.8”. The string has no significance to the program.
D
Keyword.
d
Nominal bolt diameter, in mm or inches.
AS
Keyword. MSTower V6
MSTower V6
as
Cross-sectional area of the bolt effective in shear, in mm2 or in2.
FY
Keyword.
fy
Yield stress of bolt, in N/mm2 (MPa) or kips/in2.
FU
Keyword.
fu
Ultimate tensile stress of bolt, in N/mm2 (MPa) or kips/in2.
FV
Keyword.
fv
Shear strength of bolt, in N/mm2 (MPa) or kips/in2, used when checking bolts to AS 3995; capacities to this code are strength limit state.
FV_EIA
Keyword.
fv_eia
Shear strength of bolt, in N/mm2 (MPa) or kips/in2, used when checking the capacity of bolted joints to EIA-222-F; capacities to this code are based on working stress.
FV_ASCE
Keyword.
fv_asce
Shear strength of bolt, in N/mm2 (MPa) or kips/in2, used when checking the capacity of bolted joints to ASCE 10-90; capacities to this code are for the strength limit state.
FV_TIA
Keyword.
fv_tia
Shear strength of bolt. If defined, the shear capacity of the bolt is (φb fv_tia As), otherwise the capacity is computed as (φb 0.4 fu As), assuming threads included in the shear plane.
X
Keyword.
x
Distance between end of the member and first bolt parallel to the axis of the member, in mm or in. If omitted, the member checking program assumes that code requirements are met.
Y
Keyword.
y
Distance between line of bolts and edge of member at right angles to the axis of the member, in mm or in. If omitted, the member checking program assumes that code requirements are met.
Z
Keyword.
z
Spacing between bolts parallel to the axis of the member, in mm or in. If omitted, the member checking program assumes that code requirements are met..
NSP
Keyword.
nsp
Number of shear planes. This value needs to be specified only if the number of shear planes in the bolted joint differs from the default values used in the member checking modules. Bolts are assumed to have a single shear plane for all sections except compound sections, DAL, DAS, CBB, and QAN, where the bolts are in double shear.
LJ
Keyword.
lj
Length of the line of bolts in the joint, in mm or in. This value 5:Tower Data • 59
is required only for codes that reduce the strength of long joints. If omitted, the strength will not be reduced. FYP
Keyword.
fyp
Yield strength of plies to be used in checking bearing capacity of joint. If omitted, the yield strength of the member material will be used.
FUP
Keyword.
fup
UTS of plies to be used in checking joints. Derived from fy if not specified.
TP
Keyword.
tp
Thickness of plies to be used in checking bearing capacity of joint. If omitted, a thickness obtained from the member section dimensions will be used.
TENS
Keyword indicating that the joint is a flanged joint, where tensile forces are carried by direct tension in the bolts and compression by direct end bearing. If omitted, the joint will be checked as a shear type.
AT
Keyword.
at
Cross-sectional area of the bolt effective in tension, in mm2 or in2
FT
Keyword.
ft
Tensile strength of the bolt, in N/mm2 or kips/in2 to be used when checking the tensile capacity of the joint. If omitted, a code-dependent fraction of the ultimate tensile strength of the bolt will be used.
PR
Keyword.
pr
Prying factor to take account of the increase in the bolt tension caused by prying action in the joint. The nominal capacity of the bolt subject to prying is taken as (at × ft / pr). If omitted, a factor of 1.0 will be used, i.e. the joint is not subject to prying, requiring relatively thick flanges.
Bolted joint capacities can be checked only in conjunction with a member check. This has been implemented for all codes other than BS 449. Shear type joints are checked for shear on the bolts and bearing on bolts and plies. No checks are carried out on the strength of gusset plates, so these must be separately considered. In particular, it is important that the compression capacity of overlapped gusset plates or “eccentrically connected cleats” should be checked. These often occur where hollow section compression members are connected to a gusset plate. In tension joints the bolts are checked for the applied forces plus specified prying – flange plates and welds are not checked. A bolt data file called Bolts is included in the program folder. You may copy its contents to TD files using Copy and Paste commands in MsEdit. 60 • 5:Tower Data
MSTower V6
Guy Library The guy library is a text file containing data giving the dimensions and structural characteristics of wire ropes used as guys. The guy library supplied with MStower is MS_Guy.lib, which may be modified if required. The structure of the guy library file is: GUYS guy-id .. END
d
m
ac
e
alpha
fu
ntype
where: GUYS
Keyword.
guy-id
String of 1 to 16 characters used to identify the guy ropes.
d
Diameter of guy rope, mm.
m
Mass per unit length, kg/m.
ac
Effective cross-sectional area, mm2.
e
Modulus of elasticity, N/mm2.
alpha
Coefficient of thermal expansion, per °C.
fu
Ultimate tensile stress, N/mm2.
ntype
Guy type, based on Table 4.1 of BS 8100 Part 1: 1. T4.1(b) Circular sections and smooth wire. 2. T4.1(c) Fine strand cable. 3. T4.1(d) Thick strand cable.
Note: The guy library uses metric units.
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Steel Poles A steel pole may be input using the following menu command: Tower > Build Tower > Make Tower Data File > Steel Pole Data In the Steel Pole Data dialog box you may choose parameters to define the pole. Permitted shapes include circular, square, or polygonal sections with 8, 12, 16, or 20 sides. Each panel is assumed to be a single length of circular cylinder or a tapered tube made up of a single width of steel plate. These panels will be further sub-divided before output to the tower data file.
STEEL POLE DATA DIALOG BOX
Note: Not all pole shapes available in MStower are covered by the various codes that deal with poles. In the next dialog box, data is input for each panel starting at the top of the pole. You may change panel heights, plate thicknesses, and yield strengths. Diameters have to be entered for the top of the pole and at bend points only. All other diameters are interpolated by MStower.
STEEL POLE PANEL DATA DIALOG BOX
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Once the data has been accepted MStower generates a TD file complete with a SECTION block and a section library for the pole. The menu command: Tower > Build Tower > Edit Tower Data may be selected to inspect the generated data file. Note that for poles “FACES 1” is specified in the TD file. The TD file for a tapered pole made up of two 6m high pieces is shown below: TITL1 Pole Example TITL2 UNITS 1 PROFILE FACES 1 WBASE 0.600 RLBAS 0.000 PANEL 1 HT FACE SH1 LEG PANEL 2 HT FACE SH1 LEG PANEL 3 HT FACE SH1 LEG PANEL 4 HT FACE SH1 LEG PANEL 5 HT FACE SH1 LEG PANEL 6 HT FACE SH1 LEG PANEL 7 HT FACE SH1 LEG PANEL 8 HT FACE SH1 LEG PANEL 9 HT FACE SH1 LEG PANEL 10 HT FACE SH1 LEG PANEL 11 HT FACE SH1 LEG PANEL 12 HT FACE SH1 LEG PANEL 13 HT FACE SH1 LEG PANEL 14 HT FACE SH1 LEG PANEL 15 HT FACE SH1 LEG PANEL 16 HT FACE SH1 LEG PANEL 17 HT FACE SH1 LEG PANEL 18 HT FACE SH1 LEG PANEL 19 HT
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0.6000 1 R1 0.6000 2 R1 0.6000 3 R1 0.6000 4 R1 0.6000 5 R1 0.6000 6 R1 0.6000 7 R1 0.6000 8 R1 0.6000 9 R1 0.6000 10 R1 0.6000 11 R1 0.6000 12 R1 0.6000 13 R1 0.6000 14 R1 0.6000 15 R1 0.6000 16 R1 0.6000 17 R1 0.6000 18 R1 0.6000
TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW 22 TW
0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000 0.6000
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FACE SH1 LEG 19 R1 22 PANEL 20 HT 0.6000 TW 0.6000 FACE SH1 LEG 20 R1 22 PANEL 21 HT 0.0000 TW 0.6000 FACE SH1 LEG 21 R1 22 END SECTIONS LIB Ex_Pole 1 C1.600x12 FY 250.00 2 C2.600x12 FY 250.00 3 C3.600x12 FY 250.00 4 C4.600x12 FY 250.00 5 C5.600x12 FY 250.00 6 C6.600x12 FY 250.00 7 C7.600x12 FY 250.00 8 C8.600x12 FY 250.00 9 C9.600x12 FY 250.00 10 C10.600x12 FY 250.00 11 C11.600x12 FY 250.00 12 C12.600x12 FY 250.00 13 C13.600x12 FY 250.00 14 C14.600x12 FY 250.00 15 C15.600x12 FY 250.00 16 C16.600x12 FY 250.00 17 C17.600x12 FY 250.00 18 C18.600x12 FY 250.00 19 C19.600x12 FY 250.00 20 C20.600x12 FY 250.00 21 C21.600x12 FY 250.00 22 DUMMY FY 250.00 END SUPPORT COORD 0.0 0.0 0.0 FIXED END EOF TD FILE FOR STEEL POLE
Each segment is modelled as a FACE SH1 panel. The SH1 panel consists of an axial shaft (leg) member with three radial dummy members at the top that locate nodes on the surface of the pole. These nodes are rigidly connected to the node on the axis of the pole by masterslave constraints. The purpose of the surface nodes is to facilitate the attachment of ancillaries to the pole. A SECTIONS block has also been generated. Each segment of a tapered pole will be represented by a separate section. The name of each section gives an indication of its shape, location, and thickness. A section library is automatically generated and compiled. Step changes in pole diameter may be allowed for by inserting a conical member of small height in the panel data dialog box. This segment may subsequently be edited from the TD file.
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Poles may also be input directly with the text editor. There should be a large enough number of panels to accurately represent the wind load, which is modelled by node forces applied to the axial nodes.
TD File Examples Example 1 The example below shows the TD file statements required to generate a pyramidal face panel with two sets of cross-arms.
PANEL 1 FACE CROSS CROSS
HT X0 CT CT
1.372 TW 0 LEG 1 H1 0 BR1 0 SPAN 6 RISE 7 CR1 10 CR2 12 SPAN 8
PANEL 2 HT 3.13 TW 1.6 FACE XDM SPACE .788 .787 .788 .787 D LEG 1 H1 2 BR1 2 PANEL 3 HT 1.575 FACE XDM SPACE .788 .787 D CROSS CT1 SPAN 8.32 CR1 10 CR2 12 CR3 15 CR4 16 CROSS ARM EXAMPLE
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Example 2 A square tower with different bracing patterns on the X and Y faces is created in the example below. The legs of the tower are sub-divided automatically to suit the bracing. Only members at the front are rendered.
PROFILE FACES 4 WBASE 4.0 RLBAS 0.0 PANEL 1 HT 3.5 FACE K1 FACEY K2 END
TW
3
SQUARE TOWER EXAMPLE
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Example 3 This example shows a rectangular tower with different bracing patterns on the X and Y faces. Only members at the front are rendered.
PROFILE FACES 4 WBASE 4.0 DBASE 3.0 RLBAS 0.0 PANEL 1 HT 6 TW 3.5 TD 2.5 BOLT BR1 3 FACE XO LEG 1 BR1 2 BOLTY BR1 4 FACEY K1 H1 0 BR1 3 PLAN PL2 END RECTANGULAR TOWER EXAMPLE
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Example 4 The example below is a single circuit tower; the upper part of the tower is rectangular while the lower section is square. The upper panels do not have bracing defined for the Y faces and are thus incomplete. They must be converted to UDPs and edited graphically.
PROFILE FACES 4 WBASE 8.0 DBASE 8.0 RLBAS 0.0 PANEL 1 HT 3.0 TW 18.0 TD 0.0 FACE KMGD ND 2 F1 0.667 INV PANEL 2 HT 2.0 TW 14.0 TD 1.0 FACE SCBR F1 0.667 F2 0.667 CROSS CT1 SPAN 22.0 CR1 1 CR2 2 CR3 3 PANEL 3 HT 7.5 TW 14.0 TD 1.0 FACE KMGD ND 2 F1 0.667 PANEL 4 HT 6.5 FACE XM23 INV PANEL 5 HT 3.25 TW 4.0 TD 4 $ square below here FACE XTR F1 0.5 PLAN PL2A PANEL 6 HT 3.25 $ TW is interpolated FACE M1 PANEL 8 HT 3.25 FACE K1 END SINGLE CIRCUIT TOWER EXAMPLE 68 • 5:Tower Data
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Note: In computing the transverse wind load on the V section of single circuit towers MStower considers the solidity of the outside faces of the arms of the V; the bracing on the inside faces of the arms is considered “internal to the tower” and is not considered. You should assess any additional wind loads on this section of the tower and add them to the WL cases as NDLDs.
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Example 5 (Plan Bracing) Plan bracing is located as shown.
LOCATION OF PLAN BRACING
This example shows part of a tower with plan bracing at the top and at the level of the X bracing intersection points. Only the members forming the plan bracing are rendered.
PROFILE FACES 4 WBASE 4.0 DBASE 4.0 RLBAS 0.0 PANEL 1 HT 6 TW 3.5 TD 3.5 BOLT BR1 3 FACE XO LEG 1 BR1 2 BOLTY BR1 4 FACEY XO H1 0 BR1 3 PLAN PL2 TOP PLAN PLX XIP END PLAN BRACING EXAMPLE
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6:Standard Panels
General This chapter shows the standard panels available in MStower. Many of these have been included to assist in modelling existing towers or to give the starting geometry for making a UDP. The inclusion of any particular panel pattern should not be construed as a recommendation for its use.
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Index – Face Panels
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Index – Plan Bracing
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Index – Hip Bracing & Cross-Arms
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D & V Face Panels
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X Face Panels
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K Face Panels
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M Face Panels
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W Face Panels
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XMA Face Panel
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XDMA Face Panel
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DM, DM2 Face Panel
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DMH, DMH2 Face Panel
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DLM, DLM2 Face Panel
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KXM, KXM2 Face Panel
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SH3, SH4
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Plan Bracing
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Hip Bracing
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Cross-Arms
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7:User-Defined Panels
General While MStower has an extensive set of standard panels, there will be times when some variant will be required to model a particular panel. MStower allows you to create your own panels – user-defined panels, or UDPs, for just this purpose. Unlike standard panels, which are scaled to the dimensions specified in the tower data file, UDPs once created are of fixed size. Although data for the UDP is contained in a text file which may be edited, the most expeditious way of creating a UDP is to start by building a tower with standard panels that are as close to the final configuration as possible, and then to extract and graphically edit a panel as required. MStower has facilities (see “8:Graphics Input for UDPs” on page 127) that allow UDPs to be created and manipulated using a CADlike interface. For most UDPs you will never need to edit the text file.
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The UDP File Data for user-defined panels must be included in one or more separate UDP files. The file names are specified in the COMPONENT block of the tower data file. The data may represent a full face, a half face, a quarter of a section of the tower, a pair of adjacent faces, or a complete three dimensional section of the tower, depending on which is most convenient for describing the panel. MStower will generate the complete panel. The data for the user-defined panel is: UDP
udp HT ht TW tw BW bw {PLANE | HALF | QUART | ADJA | 3DIM} NODE n x y z .. MEMB m ia ib ic mp mm pina pinb class [subclass] ..
END
where:
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UDP
Keyword.
udp
Name of user-defined panel as used in the COMPONENT block of the tower data file..
HT
Keyword.
ht
Height of panel. This should be the height of the panel between its points of attachment to the panels above and below. It is not necessarily the maximum overall height of the panel.
TW
Keyword.
tw
Top width of the panel; i.e. the width of the panel at the level at which it attaches to the panel above. If not given, the width of the tower at this level will be interpolated.
BW
Keyword.
bw
Base width of the panel; i.e. the width of the panel at the level at which it attaches to the panel below. If not given, the width of the tower at this level will be interpolated.
PLANE
Keyword indicating that the data applies to a plane face that is to be used to generate a full face panel. The panel lies in the YZ plane with all X coordinates zero.
HALF
Keyword indicating that the data applies to half a plane face lying in the YZ plane with all X coordinates zero.
QUART
Keyword indicating that the data applies to two adjacent half panels disposed about the leg in the positive X and negative Y quadrant.
ADJA
Keyword indicating that the data applies to two adjacent faces. This is used for panels where the adjacent faces differ. The positive X and positive Y faces should be defined.
3DIM
Keyword indicating that the data applies to a full threedimensional section of the tower. MSTower V6
NODE
Keyword.
n
Node number.
x
X coordinate of node.
y
Y coordinate of node.
z
Z coordinate of node. The points of attachment to the panel immediately below should have Z coordinates of zero.
MEMB
Keyword.
m
Member number.
ia
Node number of the “A” end of the member.
ib
Node number of the “B” end of the member.
ic
Reference or “C” node. Face members, such as legs and braces, should have a node in the plane of the face as their reference node. This is of particular importance for legs that have staggered face bracing and for face braces such as unequal angles that must have a particular orientation.
mp
Section property number. The section must be defined in the SECTIONS block of the TD file.
mm
Material number, usually 1.
pina
Pin code for “A” end of member, a six character string of 0s and 1s. From the left, 1s represent force releases for Fx, Fy, Fz, Mx, My, and Mz, respectively.
pinb
Pin code for “B” end of member.
class
Member class code: LEG Leg member. BRC Brace member, other than XBR or KBR. XBR X brace, symmetrically braced. KBR K brace, symmetrically braced. HOR Horizontal member. HBR Hip brace. PBR Plan brace. This code applies only to the internal members of plan bracing. Any plan brace member in the face of the tower must be classified as HOR. RED Redundant member. CRM Cross-arm main member TBR Tension only bracing. WND Wind only. See note below.
subclass
Optional numeric code to allow bolt details for UDP member to be specified. It allows members of a particular class to be differentiated if their bolting details differ. For example: ...BRC 1 – uses bolt details for BR1 ...BRC 2 – uses bolt details for BR2
The UDP name must be an alphanumeric label that cannot be interpreted as a number (e.g. 10, E10, and D1 are not allowed as UDP names). The dimensions of the UDP are taken from its coordinates. The height and MSTower V6
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panel widths are used to locate the UDP in the tower and to allow any standard panels that are above or below the UDP to be correctly scaled. Unlike standard panels, user-defined panels cannot be scaled. Wind-only members attract wind load and are included in the analysis but are not regarded as providing any structural restraint to other members. The strength of wind-only members is not checked.
UDPs
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UDPs
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Making A UDP Using Graphics Input The simplest way to make a UDP is to generate a tower using standard panels that are similar to the required panel and then to use graphical input to extract the panel and make any necessary modifications. MStower has commands to convert this to a UDP but the component references must be included in the tower data (TD) file using the editor. See “8:Graphics Input for UDPs” on page 127 for details and an example. The name of the UDP and its type (PLANE, HALF etc.) will be requested. The HT, TW, and BW will be filled in but should be checked, particularly in the case of cross-arms. If the UDP contains leg members, the HT, TW, and BW values will be determined by examining the coordinates of those nodes that are on legs. The Z coordinates of all nodes will be adjusted so that the lowest “leg node” has a Z coordinate of zero. If the UDP does not contain leg members, the HT value will be set to zero and no adjustment will be made to the Z coordinates. Note: Member classes may be specified directly. It is not necessary to input dummy material numbers as required in previous versions.
UDPs for Poles UDP members may be connected to the nodes on the shaft of the pole or to the nodes at the ends of the radial members. Pole leg and radial members must not be included in the UDP. A good starting point for a pole with UDPs is to generate a pole with cross-arms at the required heights and then to graphically edit the UDPs that form the cross-arms.
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Modifying An Existing UDP
UDP TO GRAPHICS COMMAND
Select the UDP File to Graphics command and the dialog box below will be shown. Select the UDP to be edited and proceed as if part way through making a UDP.
SELECTING UDP FOR GRAPHICAL EDITING
Towers With Unequal Length Legs At times, to save earthworks, towers built on sloping sites will have their leg supports at different levels. This can be modelled in MStower by using a UDP for the lowest panel. However, as the algorithm used in the loading module requires the legs to have the same foundation level, the shorter legs of the UDP must be extended with “dummy” leg members to give the same foundation level as the longest leg. Supports will be required at the true foundation level and also at the base of the dummy extensions. These may be specified within the SUPPORTS block as described previously.
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Creating a UDP from a Microstran Job Note: Any Microstran job from which you want to create a UDP must be compatible with the basic assumptions in MStower: the Z axis is vertical and forms the central axis of the tower and there is a face normal to the positive X axis. It is not difficult to adjust a job in Microstran that does not meet these requirements. Step 1 * Have MStower job (TOWR for example) and Microstran job (MICRO for example) in the same data folder. Do not use the same name for both jobs. Step 2 * Open the Microstran job in Microstran. * Export an archive file using the name of the MStower job (TOWR for example). * Close the Microstran job. Step 3 * Edit the archive file in Microstran and change the name of the Microstran library to that of the MStower library, e.g. change “Ukw.lib” to “Uk.lib”. Step 4 * Open the MStower job in MStower. Step 5 * Select the command: Tower > Build Tower > User Defined Panels > Graphical Edit * Select the command: Files > Import > Archive File to import the Towr.arc file. * Delete members not in the UDP. * Define member classes. * Select the command: Tower > Build Tower > User Defined Panels > Graphics to UDP File * Check that UDP file name is Towr.udp. * Input the UDP name and UDP type.
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Step 6 * Edit tower data file, add UDP to COMPONENT block in usual way, and rebuild tower. * Fix any problems that are apparent. * Save. Step 7 * Repeat steps 5 and 6 to extract further UDPs from the Microstran archive. While step 5 could be repeated without step 6, it is usually better to check each UDP by building the tower as in step 6.
UDP File Names It is simplest to have all UDPs for a job in a single file that is named after the job, i.e. Job.udp, where “Job” is the name of the job. The COMPONENT block in the TD file may then have the form: COMPONENT UDP1 UDP2 .. END
Here, the name of the file containing the UDPs is omitted and MStower assumes them to be in a file named Job.udp, where “Job” is the name of the job. When the job is saved the UDP file will be saved automatically with it. Also, if the job is renamed in a Save As operation the UDP file will be renamed. It is not mandatory for the UDP file to be named after the job. For example, if you have a number of towers all with a particular panel that is a UDP you may place the UDP in a file not named after the job and it may then be referenced by any number of jobs. The main advantage of this is that the UDP needs to be created only once. Any changes to the UDP will apply to all jobs that use the panel when those jobs are rebuilt. If the changes are not required for all towers referencing the UDP you must make the changes in a copy of the UDP file and change the references in the COMPONENT block of each tower that is to use the modified UDP. Note: Only UDPs in a file named after the job are automatically saved when the job is saved.
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8:Graphics Input for UDPs
General Graphics Input is the most efficient input method of inputting a userdefined panel. It involves “drawing” a structure on the screen using the mouse or keyboard, and it includes many simple graphical operations, such as copying, moving, rotating, sub-dividing, and erasing. More powerful graphical operations include intersection, extrusion, and transforming coordinates. In effect, MStower’s graphical input capability is an intelligent CAD system customized for the task of entering structure data.
GRAPHICS INPUT
You may find that the few hours required to become proficient at graphical input will be well rewarded by much increased productivity in creating and editing UDPs.
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Note: Many MStower commands involve the use of the context menu. This is a menu, which is specific to the current operation, that appears when you right-click (press the right mouse button). For example, when you are drawing a series of members, after clicking on the Draw Members button (the one with the pencil), you click the location of each node, and to finish the operation, you right-click and select Break Line or End Line on the context menu. Also, after you have selected nodes or members for any operation, you right-click and choose OK or Cancel on the context menu.
Basic Drawing Graphics Input is started by selecting Tower > Build Tower > UserDefined Panels > Graphics Edit. You will also be in Graphics Input mode when you import an existing UDP by selecting Tower > Build Tower > User-Defined Panels > UDP To Graphics. To start drawing a UDP, click on the toolbar button. This is the same as selecting the Structure > Draw Members command from the main menu. Notice the tooltip “Draw Members” that appears when the mouse cursor crosses this button. As you initiate the Draw command several things happen: 1.
The toolbar button displays in the depressed state, indicating that MStower is in DRAW mode.
2.
“DRAW” is displayed in the status bar at the bottom of the MStower window.
3.
The prompt area of the status bar (on the left) displays the instruction “Click on first point or enter coordinates”.
4.
The cursor becomes a cross.
You may now click anywhere in the main window or enter coordinates from the keyboard to locate the “A” node of the first member. Notice that once the first point is specified the prompt changes to “Click on end point or enter coordinates; press SPACE BAR to break line”. Select another point and you will have drawn the first member. This point is the “B” node of the first member and the “A” node of the next member. You may continue selecting points to define new members.
Keyboard Entry of Coordinates There are many situations where the most convenient way to enter a new node is to type the coordinates. As soon as you start to type, a dialog box appears to accept your input.
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DIALOG BOX FOR ENTERING COORDINATES
Coordinate Systems You may input coordinates in rectangular, cylindrical, or spherical coordinate systems, using standard syntax or AutoCAD syntax. The format of the coordinate string is described below for each syntax. STANDARD SYNTAX •
Rectangular coordinates “X Y Z”, where “X”, “Y”, and “Z” are respectively, the X, Y, and Z coordinates of the point.
•
Cylindrical coordinates “C radius theta h”, where “radius”, “theta”, and “h” are respectively, the radius, horizontal angle, and height of the point.
•
Spherical coordinates “S radius theta phi”, where “radius”, “theta”, and “phi” are respectively, the radius, horizontal angle, and vertical angle of the point.
Trailing zero coordinates do not have to be entered. For example, the point (3,0,0) may be entered as “3”. Coordinates must be separated by a space or a comma. Coordinates relative to the last point are preceded by “R” or “r”. No separator is required after the “R” or “r”. AUTOCAD SYNTAX •
Rectangular coordinates “X Y Z”, where “X”, “Y”, and “Z” are respectively, the X, Y, and Z coordinates of the point.
•
Cylindrical coordinates “radius < theta h”, where “radius”, “theta”, and “h” are respectively, the radius, horizontal angle, and height of the point. The last two values must be separated by a space or a comma.
•
Spherical coordinates “radius < theta < phi”, where “radius”, “theta”, and “phi” are respectively, the radius, horizontal angle, and vertical angle of the point.
Coordinates relative to the last point are preceded by “@”. No separator is required after the “@”. Breaking the Line Press the space bar or right-click and choose Break Line on the context menu. Notice that the cursor, the status bar, and the button show that MStower is still in Draw mode. You may now click a new node that is not connected to the last by a member. MSTower V6
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Ending the Line Right-click and choose End Line on the context menu. Notice the cursor change to the standard arrow. This indicates that the command is finished. The status bar and the button also show that MStower is no longer in Draw mode.
The Drawing Snap Mode Key concept.
Initially, the status bar displays NONE for the snap mode. This means that the coordinates of any node defined by clicking the mouse will be indeterminate to some extent, because the degree of accuracy with which you can position the mouse is limited. Practically, therefore, the snap mode NONE is rarely used. The first few nodes are usually specified by grid points or entry of coordinates. Thereafter, the Mid/End snap mode is usually used. Grid Snap Mode (GRID) In Grid mode the status bar displays GRID. Grid spacing is initially 1 unit in each global axis direction but you may change it with the Structure > Drawing Settings > Grid Spacing command. When the grid is displayed the cursor snaps to the nearest grid point. Thus, with the mouse, you can only draw members from one grid point to another. Enter coordinates to specify a point that is not on the grid. Mid/End Snap Mode (MEND) When drawing in this mode the cursor snaps to a nearby member end or mid-point. Most graphical input is done in this snap mode. When starting a new structure you cannot enter Mid/End snap mode because there are no members to snap to. Intersection Snap Mode (INTR) When drawing in this mode the cursor snaps to a nearby intersection of two or more members. A new node is automatically introduced at the intersection point if there is not already a node there. When starting a new structure you cannot enter Intersection snap mode until there are at least two members. Perpendicular Snap Mode (PERP) In this mode the cursor snaps to the point on a target member that makes the new member perpendicular to the target member. When starting a new structure you cannot enter Perpendicular snap mode until there is at least one member. Orthogonal Snap Mode (ORTH) In this mode you can only draw members in a global axis direction. Nearest Snap Mode (NEAR) In this snap mode the cursor snaps to the point on a target member that is nearest to the cursor location.
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Changing the Snap Mode “On the Fly” A very convenient feature is the ability to change the snap mode during a draw operation. For example, you may click the start point of a new member at the end of another while in Mid/End snap mode and then change to Grid snap mode to select the end point. Right-click to display the context menu with its selection of snap modes (see diagram at the beginning of this chapter).
The Drawing Plane The drawing plane is a plane on which nodes are located when you draw in either the Grid or NONE snap modes. For example, when drawing in Grid snap mode with default settings, the drawing plane is X-Y at an offset of zero along the Z axis. This means that all new nodes drawn in Grid or null snap mode have a Z coordinate of zero. Changing the view with any of the Front View, Back View, Right View, Left View, or Top View commands automatically changes the drawing plane so that it is parallel to the view plane. Use the Structure > Drawing Settings > Drawing Plane command to change the drawing plane as required. If you change the view or the drawing plane so that it (the drawing plane) is at right angles to the view plane (the plane of the screen) you may see the warning message shown below and you may not be able to click a new point.
WARNING THAT DRAWING PLANE IS PERPENDICULAR TO SCREEN
Automatic Removal of Duplicate Nodes and Members At various stages during graphical input operations, MStower removes any duplicate nodes or members that are detected. The first node or member to be drawn will remain and any that are superimposed will be removed automatically. This behaviour has two significant consequences:
MSTower V6
•
Overlapping nodes and members in copy operations are ignored.
•
In drawing members, you may draw over an existing member instead of breaking the line.
8:Graphics Input for UDPs • 131
Cursors Key concept.
MStower displays various cursors at different times, depending upon what is happening. These cursors are shown below: Cursor Description Command mode. MStower is waiting for you to select a command from the menu, click a toolbar button, or select a node or member (the cursor changes as soon as you select a node or member). Drawing mode. MStower is waiting for you to click an end of a member. Look at the right of the status line to determine which snap mode is in effect. You may use the Structure > Drawing Settings command or the context menu to change the snap mode without leaving the current drawing command. Member selection mode. MStower is waiting for you to select one or more members by clicking on them or enclosing them in a selection box. If you drag a selection box from left to right, cut members are excluded. Dragging from right to left includes cut members. Node selection mode. MStower is waiting for you to select one or more nodes by clicking on them or enclosing them in a selection box. This cursor appears when you are selecting a zoom window or panning. When zooming, drag from one corner to the diagonally opposite corner of the rectangle you want to zoom to. When panning, click on any part of the structure and drag to the new location for that part.
Generally, when you have finished a command, MStower allows you to repeat the command until you cancel the command by right-clicking. For example, when you select the Structure > Erase Members command, the cursor changes, you then select members you want to erase and confirm the selection by right-clicking and choosing OK on the context menu. The member selection cursor is still displayed, allowing you to choose more members to erase. To terminate the command, right-click, and the standard arrow cursor will reappear. Many commands are interruptible. This permits you to adjust the view during a command. When drawing members in a large model, for example, having clicked the “A” node of a member, you may need to zoom in to another region of the structure before clicking the “B” node.
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Shortcut Keys MStower permits the use of shortcut keys to some commands. Shortcut keys are also known as accelerator keys. Below is a complete list of MStower’s shortcut keys: Shortcut Command Ctrl+C
Copy
Ctrl+X
Cut
Ctrl+V
Paste
Ctrl+Z
Undo
Ctrl+Y
Redo
F5
Redraw
Ctrl+A
Select All
Delete
Erase Members
Home
Zoom Extents/Limits
Å
Viewpoint Left
Æ
Viewpoint Right
Ç
Viewpoint Up
È
Viewpoint Down
Space
Break Line
The effect of pressing a shortcut key depends on the context. For example, pressing Delete usually deletes selected members, but in a dialog box it may delete text.
Selecting Nodes and Members Key concept.
MSTower V6
In MStower, when you choose a command, you usually select the nodes or members that are the object of the command. This may be done in several ways: •
Clicking each node or member in turn. Clicking again on a node or member deselects it.
•
Dragging a selection box that encloses the nodes or members to be selected. “Dragging a selection box” means clicking (with the left mouse button) a point away from the nodes or members to be selected, then dragging the mouse until the selection box encloses the necessary nodes or members, and finally, releasing the left mouse button. Note that when the selection box is dragged from right to left, a “crossing window” appears, which selects not only members enclosed by the box but also members cut by the sides of the box.
8:Graphics Input for UDPs • 133
•
Clicking a selection box. This is similar to dragging a selection box but instead of clicking, dragging, and releasing the mouse button, you click two points to define diagonally opposite corners of the selection box.
•
All members may be selected by Ctrl+A (see “Shortcut Keys“, above).
In all cases, you confirm the selection by right-clicking and choosing OK on the context menu.
Right-Clicking on Nodes and Members Key concept.
MStower fully implements the Windows protocol for right-clicking on objects to obtain a pop-up of related commands. This provides an alternative method of operation: •
Select node(s) or member(s).
•
Right-click to choose required operation on context menu.
Right-clicking on a node will cause this context menu to appear:
NODE CONTEXT MENU
Double-clicking on a node is the same as selecting Properties on this pop-up menu. The following pop-up menu appears when you right-click on a member:
MEMBER CONTEXT MENU
Double-clicking on a member is the same as selecting Properties on this menu.
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The Node Properties Dialog Box The dialog box shown below appears when you double-click a node or select Properties after right-clicking a node.
NODE PROPERTIES DIALOG BOX
The OK button in this dialog box is disabled. You may use the dialog box to check properties but you will not be able to change them.
The Member Properties Dialog Box The dialog box shown below appears when you double-click a member or select Properties after right-clicking a member.
MEMBER PROPERTIES DIALOG BOX
The OK button in this dialog box is disabled. You may use the dialog box to check properties but you will not be able to change them.
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Properties Dialog Boxes with Multiple Selection Key concept.
You may select several nodes or members, then right-click and choose Properties on the context menu. The dialog box will display common properties of the selected group of nodes or members. Blank edit boxes indicate that the corresponding value is not the same for all of the multiple selection.
Extrusion Key concept.
There is a check box for “Extrude nodes” in each of the Linear Copy, Polar Copy, and Reflect dialog boxes. When you perform a copy operation you may “extrude” each copied node into a series of members – in other words, there will be a string of new members lying on the path traced out by each node involved in the copy operation. The member x axis is aligned with the direction of extrusion.
Interrupting Commands The diagram below shows the View toolbar, normally docked at the top of the MStower window.
VIEW TOOLBAR
Most commands may be interrupted in order to change the view by clicking on one of these buttons. This is helpful in many situations, for example, when drawing a member, and the view required for displaying the “B” node is different from that in which the “A” node is visible. You may interrupt graphical commands to rotate the view, zoom in to a congested area of the model, or pan the view, as required. You may also interrupt commands by clicking buttons on the Display toolbar, shown below.
DRAW TOOLBAR
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The Stretch Command The Structure > Move > Stretch command applies a linear transformation to the coordinates of selected nodes. The prompts in the status bar guide you through the necessary steps in this command: •
Select nodes
•
Select node as fixed point
•
Select node as start point of stretch vector
•
Select node as end point of stretch vector
An example is illustrated below, where the top chord nodes of a truss are “stretched” to introduce a uniform slope from one end to the other.
Firstly, a member is added to represent the stretch vector. All the nodes to be transformed are highlighted. Node 2 is selected as the fixed node.
Nodes 12 and 13 are selected to define the stretch vector. The diagram below shows the truss on completion of the command.
If you inadvertently click on the wrong node when selecting the fixed node or the start of the stretch vector, you can abort the command by selecting the start of the stretch vector as the end point also. The Stretch command could be used to input tower cross-arms as a parallel chord truss, which is later tapered, as in the example above.
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The Limit Command
VIEW > LIMIT > WINDOW
The commands on the View > Limit menu allow you to restrict activity to a selected part of the structure. The rest of the structure may be greyed out or hidden from view. This has the advantage that the view you are working on is uncluttered by irrelevant detail and the rest of the structure is inaccessible while Limit is in effect. The Limit > Window command, , was used to select one segment of the tower in the diagram below. To hide the rest of the structure rightclick and uncheck Show Outside Limits.
LIMIT > WINDOW 138 • 8:Graphics Input for UDPs
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When the Limit command is in effect, clicking this button, , (equivalent to the View > Zoom > Extents/Limits command) will zoom the view so that the full structure and the limited part alternately fill the screen. The Limit > Boundary command, the tower using a selection polygon. Clicking the Full View button, command.
, may be used to select a part of
, reverses the effect of the Limit
Removing an Intermediate Node You may occasionally want to remove an intermediate node in a member. If you had accidentally sub-divided a member (while drawing in Mid/End snap mode, for example), you may want to restore it to a single member. This can easily be done as follows: 1.
Select Mid/End snap mode if this mode is not already selected.
2.
Right-click on the intermediate node to be removed.
3.
Select Move Node on the context menu – the node should now be attached so you can drag it.
4.
Drag the node to one end of the member containing it and click.
This procedure does not give rise to a duplicate node or a zero-length member.
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UDP Graphical Example This example illustrates the graphical creation and modification of a simple UDP.
Step 1 – Create Data File for a Small Tower * Select the command Tower > Build Tower > Make Tower Data File > Tower/Mast Data and complete the dialog boxes to create a square tower with 4 panels, two X panels of height 2m and 2.5m on top of two K panels, each of height 4m.
GEOMETRY PARAMETERS DIALOG BOX
* Check the box to provide a skeleton block for UDPs and remove checks from all other options. The tower width must be defined at bend points only. In this case, input a top width of 2m for the first panel and zero for the remaining panels. MStower interpolates all intermediate widths.
PANEL DATA DIALOG BOX
This is the data file generated:
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TITL1 Example for UDP input TITL2 UNITS 1 $ 1=metric, 4=US COMPONENT $ TODO - udp list goes here END PROFILE FACES 4 WBASE 4.0000 RLBAS 0.0000 $ $ $
TODO: Remove '$' and replace '?' with appropriate section numbers in following PANEL blocks.
PANEL 1 HT 2.000 TW 2.000 FACE X $ LEG ? BR1 ? H1 ? PANEL 2 HT 2.500 FACE X $ LEG ? BR1 ? H1 ? PANEL 3 HT 4.000 FACE K $ LEG ? BR1 ? H1 ? PANEL 4 HT 4.000 FACE K $ LEG ? BR1 ? H1 ? END END
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Step 2 – Build Tower * Select the command Tower > Build Tower > Process Tower Data File to build the tower and check that the basic geometry is correct. Because the sections have not yet been defined there will be an error but the tower should build and display correctly, as shown below.
BUILT TOWER
Note that the Draw and Attributes toolbars on the right of the screen are disabled at this stage.
Step 3 – Isolate UDP Members * Select the command Tower > Build Tower > User Defined Panels > Graphical Edit MStower is now in graphical editing mode and the Draw and Attributes toolbars are enabled. We wish to convert panel 3 into a UDP and we start by selecting a suitable view and deleting members of other panels: * Click the
button to obtain a front view of the tower.
* Click the
button.
* Click and drag to create in turn two selection boxes as shown below. Note that the top box is a “crossing window”, dragged from right to left to select all members either inside or crossed by the box, while the bottom box is dragged from left to right and only selects members wholly within it.
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ERASING MEMBERS OF OTHER PANELS
* Click the right mouse button to confirm the selection. Only the members of panel 3 should now be displayed. Note: If you are unsure about methods of selection and graphical input you should review material at the beginning of this chapter.
Step 4 – Add Members to UDP * Click the
button to obtain a plan view of the panel.
* Add members to the panel so that it looks like a K1 panel. This is done by drawing the members in the top right corner of the view and then copying the new members to the other corners. * Click the and for easy identification. * Click the
buttons to display node and member numbers
button to start drawing members.
* Click on node 105 (at top of the leg). * Click about half way along member 224 (brace). After each click a “rubber band” line joins the cursor to the point clicked on. * Click about half way along member 221 (leg). * Click about half way along member 205 (brace). * Click on node 105. * Right-click and select End Line to terminate the drawing sequence.
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8:Graphics Input for UDPs • 143
The panel should now appear as shown below (for clarity, node and member numbers are not shown). Notice that when the cursor hovers over a node or member a “data tip” will be displayed. On the original members the data tip has an indication of member class (LEG, HOR, etc.) but on the new members this is absent.
REDUNDANT MEMBERS ADDED TO UDP
Step 5 – Define Attributes of New Members In this step we define the section number, reference nodes, member end releases (if any), and member classes of the new members. * Select the command Structure > Attributes > Section Number and click on the new members; right-click to confirm the selection. Now specify the new section number, say 5, in the dialog box that appears. Note: You may double-click on any member to see all its properties. * Select the command Structure > Attributes > Member Class and click on the new members; right-click to confirm the selection. Now choose class Redundant, sub-class R1.
Step 6 – Copy New Members to Other Faces * Select the command Structure > Copy > Polar and click on the new members; right-click to confirm the selection. The node selection cursor, , is now visible and the prompt reads “Click on 144 • 8:Graphics Input for UDPs
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center of rotation or enter coordinates”. There is no node on the vertical axis of the tower, so the center of rotation must be defined by typing coordinates. * Type 0 and press Enter. A dialog box appears when you type the first number and displays the coordinates of the point to be used as the center of rotation. The zero entered is interpreted as (0,0,0) – i.e. trailing zeroes are ignored. * In the Polar Copy dialog box enter Z as the axis of rotation, 90 as the angle increment, and 3 as the number of copies. Press Enter or click OK. Copies of the new members should now be displayed at all corners.
Step 7 – Set Reference Nodes for New Members * Select the command Structure > Attributes > Reference Node The y axis of each new member will lie in the face plane, so a reference node is chosen in the face. * Select the four new members on the +X face, right-click to confirm the selection, and then click on node 203. * Select the four new members on the +Y face, right-click to confirm the selection, and then click on node 223. * Repeat the last operation for the members in the –X and –Y faces using appropriate reference nodes. Note: A reference node must not lie on the longitudinal axis of the member or the extension of the longitudinal axis.
Step 8 – Check UDP The UDP has now been fully defined but before proceeding further it is advisable to make certain checks. For example, to check that all new members have been assigned a class, use the command Show > Member Classes > Unclassified Members This command highlights any unclassified members.
Step 9 – Convert Graphics to UDP File * Select the command Tower > Build Tower > User Defined Panels > Graphics to UDP File * In the displayed dialog box enter P3 for the UDP name. * Select 3-DIM as the UDP type. * To make the UDP known as a component of the tower select the command Tower > Build Tower > Edit Tower Data
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8:Graphics Input for UDPs • 145
* The UDP file is displayed in the text editor, MsEdit, so you can make the necessary changes: COMPONENT P3 END PANEL 3 HT 4.000 $ FACE K $ LEG ? FACE @P3
BR1 ?
H1 ?
R1 ?
Here, the FACE K line has been commented out with the $ character but retained in the file to indicate the panel type used as the basis for the UDP. * Save the edited TD file and close MsEdit. * Rebuild the tower and inspect to ensure that the UDP is as required. * If the UDP must be modified select the command Tower > Build Tower > User Defined Panels > UDP File to Graphics and select the UDP to be modified (P3 in this case). * After making any necessary modification select the command Tower > Build Tower > User Defined Panels > Graphics to UDP File If the UDP file already exists a message box is displayed…
* Press Enter or click OK. * Rebuild the tower.
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9:Tower Loading
General This chapter describes the operation of the MStower loading module in computing loads on the tower and ancillaries in accordance with the requirements of: •
BS 8100 Part 1 2005
•
BS 8100 Part 4 1995
•
BS 8100 Part 4 Amendment 1 2001
•
AS 3995-1994
•
AS 1170.2-2002
•
Malaysian Electricity Supply Regulations 1990
•
EIA/TIA-222-F-1991
•
TIA-222-G-2005
•
Institution of Lighting Engineers Technical Report No. 7 – High Masts for Lighting and CCTV – 2000 Edition
•
IS 875 (Part 3):1987
•
ASCE 7-95
•
BNBC 93 – Bangladesh National Building Code
Loading types include dead load, ice load (with and without wind), node loads, wind loading on the structure, its ancillaries, feeders, and attachments, and temperature loads. Tower loading represented as node loads are computed for wind acting at any angle to the tower, with and without icing of members, as well as gravity loads due to self weight and icing. Additional node forces may be specified for any primary load case. Combination load cases may also be defined. Code partial safety factors may be specified directly or as factors in combination load cases.
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9:Tower Loading • 147
Tower Faces The faces of the tower are numbered 1, 2, 3 (and 4 for rectangular towers) in an anti-clockwise direction with face 1 normal to the positive X axis. The locations of face ancillaries are specified by reference to the face numbers. Towers With Cross-Arms The wind resistance of a tower is generally computed as a function of the solidity of the faces of the tower. Members internal to the body of the tower are ignored in the determination of solidity. Members external to the body of the tower, such as cross-arms may be taken into account by adding face ancillaries to appropriate panels or by specifying an EXTERN factor for wind load cases. The weight of the all members, including cross-arms and any encrusting ice is taken into account in DL and ICE load cases respectively.
The Tower Loading (TWR) File Data describing the tower loading is entered into a free-format text file called Job.twr, where “Job” is the job name. A tower loading file may be generated by selecting Tower > Load Tower > Make Tower Loading File. A series of dialog boxes will be displayed for you to select the loading code and various parameters. The resulting TWR file will require some editing to customize it to the particular tower you are modelling. The data is organized into logical blocks: 1.
PARAMETERS block
2.
TERRAIN block
3.
VELOCITY block (optional)
4.
Named node block (optional)
5.
Guy list block (optional)
6.
External block (optional)
7.
Loads block
8.
Panel block (optional)
9.
Ancillaries block
Each block commences with a keyword identifying the block and terminates with the keyword END. The keyword EOF is used to terminate the file. Each data block is described in this chapter.
Parameters Block PARAMETERS ANGN an [CODE code] 148 • 9:Tower Loading
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[ICE RO ro RW rw] [ALTOP alt] [PSF-V gamma-v] [PSF-M gamma-m] [PSF-M2 gamma-m2] VB vb vtype VICE vi CLASS-G class TOPCAT-G topcat [OVERLAP n] [GRAV grav] [RHO rho] [RPSERV rpserv] [SDAMP sdamp] [ADAMP adamp] [TDAMP tdamp] [FREQ freq] [DMULT dmult] [CDMIN cdmin] END
where: ANGN
Keyword.
an
The angle, in degrees, measured anti-clockwise from the X axis to geographic north.
CODE
Keyword.
code
Character string indicating the code rules to be followed in computing the wind and other loading: BS8100 Use the rules of BS 8100 Part 1 with Amendment 1 – May 2005. BS8100A1 Use the rules of BS 8100 Part 4 with Amendment 1 – April 2003. BS6399 Use the rules of BS 6399. MER Use the rules of the Malaysian Electricity Supply Regulations 1990 – See note below. AS3995 Use the rules of AS 3995. AS1170 Use the rules of AS 1170. EIA222 Use the rules of EIA/TIA-222-F. TIA222G Use the rules of TIA-222-G. ILETR7 Use the rules of the Institution of Lighting Engineers Technical Report No. 7.
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9:Tower Loading • 149
ASCE795 Use the rules of ASCE 7-95. These wind rules are the same as those in Philippines NSCP C101-01. IS875 Use the rules of IS 875 Part 3 1987. BNBC Use the rules of the Bangladesh National Building Code. If omitted, the rules of BS 8100 Part 1 will be used. Unless specified otherwise all code references are to BS 8100. ICE
Keyword.
RO
Keyword.
ro
Radial ice thickness, mm or inches, in the absence of wind (BS 8100 Fig. 3.9).
RW
Keyword.
rw
Radial ice thickness, mm or inches, in presence of wind (BS 8100 Fig. 3.9).
ALTOP
Keyword.
alt
Altitude of tower top, in m or ft. Used to determine basic ice thickness (BS 8100 Cl. 3.5.2).
PSF-V
Keyword.
gamma-v
Partial safety factor on wind speed and ice thickness, BS 8100 only (BS 8100 Fig 2.1).
PSF-M
Keyword.
gamma-m
Partial safety factor on design strength (BS 8100 Fig. 2.1). For BS 8100 and ILE TR7.
PSF-M2
Keyword.
gamma-m2
Partial safety factor for bolt capacity, BS 8100 only (BS 8100-3:1999 Cl. 8.1).
VB
Keyword.
vb
Basic wind velocity in m/sec or miles/hour (BS 8100 Fig. 3.1).
vtype
Character string whose value depends on loading code as shown below: BS 8100, ILETR7 MEAN = Mean hourly wind speed. AS 1170.2 / AS 3995 GUST = Gust wind speed. EIA-222 Blank = Fastest mile wind speed. MER GUST = No additional gust factor applied by program. Refer to individual codes for a full definition of the wind speed to be used.
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VICE
Keyword.
vi
Wind speed to be used with WL + ICE cases for TIA-222-G.
CLASS-G
Keyword.
class
Tower classification, TIA-222-G Table 2-1, I=1, II=2, III=3.
TOPCAT-G
Keyword.
topcat
Topographic category, integer 1-4, as defined in TIA-222-G p. 13.
OVERLAP
Keyword.
n
Overlap flag; 0 if overlap between bracing and leg members is not to be taken into account; 1 otherwise. If overlap is taken into account, the computed wind resistance will be smaller, but computation time will be marginally longer. Overlap will be taken into account if flag is omitted.
GRAV
Keyword.
grav
Gravitational acceleration in Z direction. If omitted, an acceleration of -9.81 m/sec² or –32.2 ft/sec² will be used in computing gravitational loads from masses.
RHO
Keyword.
rho
Density of air at the reference temperature. If omitted, a value of 1.22 kg/m3 or 0.075 lb/ft3 will be used.
RPSERV
Keyword.
rpserv
Return period in years. Used for calculation of tower and ancillary rotations to BS8100. Ignored for other codes.
SDAMP
Keyword.
sdamp
Damping for structure and foundation. This value depends on the type of structure and its connections and the type of foundation. Values are given in various codes.
ADAMP
Keyword.
adamp
Aerodynamic damping.
TDAMP
Keyword.
tdamp
Total damping, the sum of structural and aerodynamic damping.
FREQ
Keyword.
freq
Frequency in Hertz for the first mode of vibration of the tower or pole.
DMULT
Keyword.
dmult
Dynamic multiplier. Used in some cases to account for the dynamic sensitivity of a pole or tower.
CDMIN
Keyword.
cdmin
Minimum drag coefficient to be used in assessing the wind load on a tubular pole. This may be used where fittings and attachments on a pole make the pole aerodynamically rougher than the bare pole. 9:Tower Loading • 151
Note: If code is specified as MER the following default values will be used unless otherwise specified: gamma-v = 1.0 gamma-m = 1.0 rho = 1.2 kg/m3 vb = 26.82 m/s
Damping British codes BS 8100, BS 6399, and ILE TR7 use the logarithmic decrement of damping, δ. Other codes use the ratio of the actual damping to the critical damping, ζ, where δ = 2π ζ / √(1 – ζ2)
Basic Velocity The definition of the basic velocity vb depends on the code being used. AS 1170.2
VR, regional 3 second gust wind speed for required return period, Fig. 3.1 and Table 3.1.
AS 3995
Vu, basic wind speed for ultimate limit state Fig. 2.2. VR and VU are not the same.
BS 8100 Part 1
Hourly mean wind speed, Fig. 3.1.
BS 8100 Part 4
Hourly mean wind speed, Fig. 2.
BS 6399
Hourly mean, BS 6399 Part 2, Fig. 6.
ILETR7
Hourly mean, BS 6399 Part 2, Fig. 6.
ASCE 7-02
3-second gust wind speed, ASCE 7-02, Fig. 6-1. 3-second gust wind speed, NSCP C101-1, Fig. 207-1.
EIA-222-F
Fastest mile wind speed.
TIA-222-G
3-second gust wind speed.
IS 875 Part 3
3-second gust wind speed, Fig. 1.
BNBC
Fastest mile wind speed, Fig. 6.2.1.
It is important that the basic velocity used in the tower data file is consistent with the specified code. The figures and tables referred to above are in the particular code. Meteorological specialists may need to be consulted for sites for sites in other locations. It is also important that the wind speeds conform to the requirements of the code being used. Non-standard descriptions of wind speeds such as “operational”, “survival”, or “extreme” are not used in any code 152 • 9:Tower Loading
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supported by MStower. Where such terms are used in a specification additional information must be sought so that a wind speed conforming to the code requirements may be calculated. Note: The table on p. 225 of TIA-222-G and Fig. A.1 of BS 8100 Part 1 may assist in the conversion of wind speeds.
Terrain Block This block is used to specify the variation of terrain factor with wind direction around the tower. The data required depends on the loading code being used. The TERRAIN block for BS 8100 Part 1 is as follows: TERRAIN ANGLE angle TCAT tcat [Kd kd] [KR kr] [HH hh]... [BETAH betah] [XLEE xlee] END
where:
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ANGLE
Keyword.
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.
KR
Keyword.
kr
Terrain roughness factor. Interpolated from BS 8100 Table 3.1 if not specified.
KD
Keyword.
kd
Wind direction factor. Interpolated from BS 8100 Fig. 3.2 if not specified. If ice is present a maximum value of 0.85 will be used.
HH
Keyword.
hh
Height of hill above general terrain, in m or ft. Assumed to be zero if not specified.
BETAH
Keyword.
betah
Effective slope of hill , in degrees. Assumed to be zero if not specified.
XLEE
Keyword.
xlee
Downwind distance from the crest of the hill to tower site, in m or ft. Assumed to be zero if not specified.
ABT
Keyword.
abt
The altitude of the general terrain in this direction. If defined this value will be used to apply an altitude correction to the
9:Tower Loading • 153
basic wind velocity vb defined in the parameters block.
The TERRAIN block for BS 8100 Part 4 is as follows: TERRAIN ANGLE angle [SD sd] DSEA ds [XO xo HO ho HE he LU lu END
DTWN dt... X x]
where: ANGLE
Keyword.
angle
Wind angle in degrees east of north.
SD
Keyword.
sd
Direction factor (BS 8100 Part 4 Cl. 3.1.5). If not specified a value will be interpolated from Table 1 of BS 8100 Part 4. If ice is present a maximum value of 0.85 will be used.
DSEA
Keyword.
ds
Distance from the sea, in km or miles.
DTWN
Keyword.
dt
Distance to edge of town in windward direction, in km or miles. Zero for country terrain.
XO
Keyword.
xo
Upwind spacing of permanent obstructions from mast, in m or ft.
HO
Keyword.
ho
General level of rooftops, in m or ft.
HE
Keyword.
he
Effective height of topographic feature above general ground level in upwind direction, in m or ft.
LU
Keyword.
lu
Length of upwind slope in wind direction, in m or ft.
X
Keyword.
x
Horizontal distance of site from top of crest, in m or ft.
The TERRAIN block for BS 8100 Part 4 Amendment 1 – 2003, Institution of Lighting Engineers Technical Report No. 7, and BS 6399 is as follows: TERRAIN ANGLE angle [SD sd] DSEA ds [XO xo HO ho HE he LU lu END
DTWN dt... X x] [ABT abt]
where: ANGLE
154 • 9:Tower Loading
Keyword.
MSTower V6
angle
Wind angle in degrees east of north.
SD
Keyword.
sd
Direction factor (BS 8100 Part 4 Cl. 3.1.5). If not specified a value will be interpolated from Table 1 of BS 8100 Part 4. If ice is present a maximum value of 0.85 will be used. A value of 1.0 should be used for ILE TR7
DSEA
Keyword.
ds
Distance from the sea, in km or miles.
DTWN
Keyword.
dt
Distance to edge of town in windward direction, in km or miles. Zero for country terrain.
XO
Keyword.
xo
Upwind spacing of permanent obstructions from mast, in m or ft.
HO
Keyword.
ho
General level of rooftops, in m or ft.
HE
Keyword.
he
Effective height of topographic feature above general ground level in upwind direction, in m or ft.
LU
Keyword.
lu
Length of upwind slope in wind direction, in m or ft.
X
Keyword.
x
Horizontal distance of site from top of crest, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.
ABT
Keyword.
abt
Altitude base for terrain in this direction.
The TERRAIN block for AS 1170.2-2002 is as follows: TERRAIN ANGLE angle TCAT tcat reg [MD md]... [H h LU lu X x] [MSH msh] [MLEE mlee] END
where:
MSTower V6
ANGLE
Keyword.
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.
reg
Regional code – A1,..A9, W, B, C, or D, as defined in Fig. 3.1 of AS 1170.2. 9:Tower Loading • 155
MD
Keyword.
md
Wind direction multiplier. If not specified, a value will be interpolated from Table 3.2 of AS 1170.2.
H
Keyword.
h
Height of feature, in m or ft.
LU
Keyword.
lu
Horizontal distance upwind from the crest of the feature to a level half the height below the crest, in m or ft.
X
Keyword.
x
Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.
MSH
Keyword.
msh
Shielding multiplier, 4.3 of AS1170.2. If not defined, 1.0 will be used.
MLEE
Keyword.
mlee
Lee multiplier, 4.4.3 of AS1170.2. If not defined, 1.0 will be used.
The topographic multiplier, Mt (AS 3995 Cl. 2.2.4), is computed in each direction from the values of h, lu, and x entered in the TERRAIN block. The TERRAIN block for ASCE 7-95 is as follows: TERRAIN ANGLE angle END
TCAT tcat
[MD md]
[H h
LH lh
X x]
where:
156 • 9:Tower Loading
ANGLE
Keyword.
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.
MD
Keyword.
md
Optional wind velocity multiplier (see below).
H
Keyword.
h
Height of feature, in m or ft.
LH
Keyword.
lh
Horizontal distance upwind from the crest of the feature to a level half the height below the crest, in m or ft. See Fig 6.2 in ASCE 7-95.
X
Keyword.
MSTower V6
x
Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.
The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular direction will be determined as the product (md × vb). If not defined in the terrain block md will be taken as 1.0. The wind specification in the Philippines code NSCP C101-01 is the same as that in ASCE 7-95. The TERRAIN block for TIA-222-G is as follows: TERRAIN ANGLE angle END
TCAT tcat
[MD md]
[H h]
where: ANGLE
Keyword.
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Exposure category, 2=B, 3=C, 4=D (TIA-222-G p. 12).
MD
Keyword.
md
Optional wind velocity multiplier (see below). It should not be confused with the wind direction probability factor, Kd, in TIA-222-G Table 2-2, which is taken into account automatically in MStower.
H
Keyword.
h
Hill height (TIA-222-G 2.6.6.1 p. 13).
The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular direction will be determined as the product (md × vb). If not defined in the terrain block md will be taken as 1.0. Note that the importance factor, Table 2-3 p. 39, is computed automatically by MStower. The TERRAIN block for IS 875 (Part 3):1987 is as follows: TERRAIN ANGLE angle END
TCAT tcat
[MD md]
[Z z
LU lu
X x]
where: ANGLE
MSTower V6
Keyword.
9:Tower Loading • 157
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Terrain category in Arabic numerals. Intermediate terrain categories may be given as a decimal, e.g. 2.5.
MD
Keyword.
md
Optional wind velocity multiplier (see below).
H
Keyword.
h
Height of feature, in m or ft.
LU
Keyword.
lu
Horizontal distance upwind from the crest of the feature to a level the full height of the feature below the crest, in m or ft. See Fig. 13 in IS 875.
X
Keyword.
x
Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.
The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular direction will be determined as the product (md × vb). If not defined in the terrain block md will be taken as 1.0. The TERRAIN block for BNBC is as follows: TERRAIN ANGLE angle END
TCAT tcat
[MD md]
[H h
LU lu
X x]
where:
158 • 9:Tower Loading
ANGLE
Keyword.
angle
Wind angle in degrees east of north.
TCAT
Keyword.
tcat
Exposure condition in Arabic numerals. Intermediate terrain conditions may be given as a decimal, e.g. 2.5. Note that while the code defines exposure conditions alphabetically, they must be entered into the terrain block numerically, with A=1, B=2, etc.
MD
Keyword.
md
Optional wind velocity multiplier (see below).
H
Keyword.
h
Height of feature, in m or ft.
LU
Keyword.
lu
Horizontal distance upwind from the crest of the feature to a MSTower V6
level half the height below the crest, in m or ft. See Fig 6.2.9 in BNBC. X
Keyword.
x
Horizontal distance upwind or downwind from the structure to the crest of the feature, in m or ft. Use positive values to indicate that the site is downwind of the crest and negative values to indicate that the site is upwind.
The wind velocity multiplier may be used to modify the specified basic wind velocity if the site conditions are such that the basic wind velocity is judged to vary with direction. The basic wind velocity for a particular direction will be determined as the product (md × vb). If not defined in the terrain block md will be taken as 1.0. No TERRAIN block is required for the Malaysian Electricity Supply Regulations. Terrain factors for up to eight directions may be entered. If necessary, intermediate values will be obtained by interpolation. If there is no variation in terrain with angle, enter a single set of values for angle zero. The TERRAIN block may be omitted, in which case a terrain category of 1 will be assumed (tcat = 1). The TERRAIN block will be ignored if a user-defined velocity profile is specified.
Velocity Profile Block This optional block may be used to specify a velocity profile that takes precedence over any profile that may be computed from the code terrain rules. VELOCITY ZF z VF vfact .. END
where: ZF
Keyword.
z
Height above ground level at which velocity factor is specified, in m or ft.
VF
Keyword.
vfact
Velocity factor at height z. The actual velocity is: Vz = Vb × gamma-v × vfact
The velocity profile should be entered in increasing order of height. Additional wind profiles may be defined for determining patch loads on masts: PVEL_MAST ZF z VF vfact MSTower V6
9:Tower Loading • 159
.. END PVEL_GUY ZF z VF vfact .. END
If PVEL_MAST and PVEL_GUY blocks are defined a number of “patch” load cases will be generated as described in this chapter. A user defined velocity profile may be used where the terrain is more complex than can be modelled adequately by the topographic models in the code. Only a single user defined profile is allowed and will be used for all wind directions. Where the tower is mounted on top of a building, its elevation in the wind stream may be modelled by setting the value of RLBAS in the tower data file the distance of the tower base above ground level, as in the following diagram. This does not take account of any change in the velocity profile caused by the presence of the building.
VELOCITY PROFILE
Named Node Block Up to 40 nodes may be “named” by being assigned an alphanumeric tag: NODENAME [ZREF zref] name X x Y y Z z .. END
where: 160 • 9:Tower Loading
MSTower V6
ZREF
Keyword.
zref
Location of the origin from which the Z coordinates of the named nodes are measured. Valid values are: zr Z coordinate in m or ft. TOP Keyword indicating that the Z coordinates of the nodes are measured from the topmost node of the tower. Nodes will have negative Z coordinates. BTM Keyword indicating that the Z coordinates of the nodes are measured from the lowest node in the tower.
name
An alphanumeric string of characters. It is limited to 8 characters and must not be recognizable as a number.
X
Keyword.
x
X coordinate of the node, in m or ft.
Y
Keyword.
y
Y coordinate of the node, in m or ft.
Z
Keyword.
z
Z coordinate of the node, relative to the origin defined by ZREF, in m or ft. If ZREF has not been defined the Z coordinate will be relative to the global origin.
The node list establishes node number aliases that may replace a node number anywhere in the TWR file. The aliases may be useful where modifications to the geometry results in node numbers changing, for example, when the tower is being studied for strengthening or a number of different bracing patterns are being considered. If a family of transmission towers is being designed the node list could define the loading points with only the ZREF parameter being changed as extensions are added.
Guy List Block This optional block allows you to group a number of guys together and to refer to them by name when considering asymmetrical ice loading in ice and wind load cases. Up to 8 lists of guys may be input: GUYLIST name g1..gn .. END
where:
MSTower V6
name
An alphanumeric string of characters. It is limited to 8 characters and must not be recognizable as a number.
g1..gn
List of member numbers for the guys in this list. 9:Tower Loading • 161
A particular guy may belong to more than one list. Note: You may obtain the member number for a guy from the data tip that appears when the cursor is placed on it, with the Query > Member Data command, or by double-clicking on it.
External Factor Block This optional block allows greater control over the factor applied to external members when computing wind loads. EXTERNAL name ZB zb .. END
ZT zt
EXTFACT f1..fn
where: name
An alphanumeric string of characters. It is limited to 8 characters and must not be recognizable as a number.
ZB
Keyword.
zb
Height from.
ZT
Keyword.
zt
Height to.
EXTFACT
Keyword.
f1..fn
External factors applied to external members whose mid-points occur between the heights zb and zt. There are 8 factors for square towers, applying to wind at 0º, 45º, 90º, 135º, 180º, 225º, 270º, and 315º to the X axis and 6 factors for triangular towers, applying to wind at 0º, 60º, 120º, 180º, 240º, and 300º to the X axis.
Any EXTERN factor defined with wind load data will take precedence over factors defined in an EXTERNAL block.
Loads Block This block describes the load cases that are to be computed. Each primary load case consists of a CASE description, a specification for a wind, dead, or ice load, and optionally, additional node loads that are to form part of that load case. Combination load cases consist of a CASE description and a number of load case references and factors. All loads on the tower should be described in the LOADS block. LOADS CASE.. 162 • 9:Tower Loading
MSTower V6
Wind, dead, ice, earthquake, or miscellaneous load Additional node loads Additional member temperatures CASE.. Wind, dead, ice, earthquake, or miscellaneous load Additional node loads Additional member temperatures .. CASE.. Combination load case .. END
Each load case must start with the line: CASE
lcase
title
where: lcase
1-5 digit load case reference number.
title
Load case title – up to 50 characters.
Wind Load Cases WL
{ANGLX wangx | ANGLE wangn} [{ICE|NOICE}]... [BARE] [CROSS] [{PATCH|NOPATCH}]... [UNICE list] [EXTERN extern]... [ZGUST z1] [ZGUST2 z2] [GFACT gf]
where:
MSTower V6
ANGLX
Keyword.
wangx
Angle in degrees (anti-clockwise) from the global X axis. It is recommended that wind direction be specified with respect to the tower X axis rather than as a bearing (clockwise from north). The latter is included for compatibility with prior versions of MStower.
ANGLE
Keyword.
wangn
Angle in degrees (clockwise) from geographic north.
ICE
Keyword indicating that ice is to be considered for this case.
NOICE
Keyword indicating that ice is not to be considered for this case.
BARE
Keyword indicating that wind load is to be computed for the bare tower, i.e., the tower without any ancillaries.
CROSS
Keyword indicating that MStower is to generate sub-load cases 9:Tower Loading • 163
in the cross-wind direction. PATCH
Keyword indicating that patch load cases will be generated for guyed masts.
NOPATCH
Keyword indicating that patch load cases will not be generated for guyed masts.
UNICE
Keyword.
list
Name of a guy list defined in the GUYLIST block. The guys nominated in this list will have wind loads applied to the bare guy, not to the iced diameter of the guy.
EXTERN
Keyword.
extern
Factor applied to all external members. External factors varying with height may be applied in an EXTERNAL block.
ZGUST
Keyword.
z1
Height above ground level.
ZGUST2
Keyword.
z2
Height above ground level.
GFACT
Keyword.
gf
Factor by which wind forces between z1 and z2 will be multiplied.
If the MEAN wind speed is being used the basic wind load case lcase contains the loads due to the mean hourly wind applied to the equivalent bare tower. This is followed by sequentially numbered sub-cases, the first containing the fluctuating component of the wind load on the large ancillaries, and the second the sum of the mean hourly loads on the tower and ancillaries. The CROSS wind load cases are required additional sub-cases containing the loads due to cross-wind on the equivalent bare tower and the fluctuating component of the cross-wind on the ancillaries are generated. If the GUST wind speed is being used, the along-wind loads on the large ancillaries are accumulated into the basic wind load case and no additional sub-loads are formed. You must leave gaps in the numbering of wind load cases to accommodate the sub-cases; a difference of 10 between successive cases is sufficient and convenient. The SMEAR keyword used in previous versions to compute the uniform load on guys for BS 8100 Part 4 patch load cases is no longer required. The optional data item ZGUST z1 .. GFACT gf may be used to:
164 • 9:Tower Loading
•
Modify the wind loads over a section of the tower when dealing with a tower that is Eiffelized.
•
Model the variation of the gust response factor with height for dynamically sensitive towers when computing wind loads to AS 3995 or AS 1170.
•
Model patch load cases for masts when using TIA-222-G. MSTower V6
Cross-arms and Similar Members External to the Main Tower Body Wind loads are computed on all members external to the body of the tower as: 0.5 × ρ × Cd × L × B × V2 × sin2 (psi) × extern where: ρ
= density of air
Cd
= drag coefficient
L
= member length
B
= width
V
= velocity at midpoint of member
psi
= angle of incidence of wind on member
extern= user input factor New data added to WL line: WL ANGLE ang .. EXTERN extern extern – factor to account for solidity and shielding of members
external to the tower body. Taken as 1.0 if not input. If EXTERN is used load is computed on all external members. MStower is not able to ignore members in faces of cross-arms parallel to the wind. Members above the body of the tower or mast are treated as external members. Flat and circular external members are differentiated using a Cd of 2.0 and 1.2, respectively. The factor will be applied to all external members. Guys are not treated as external members. External factors varying with height may be applied in an EXTERNAL block.
Guyed Mast Patch Loadings For a guyed mast, the program can generate a set of patch load sub-cases as defined in BS 8100 Part 4 Cl. 5.3.2.2. These are:
MSTower V6
1.
On each span of the mast column between adjacent guy levels (and on the span between the mast base and the first guy level).
2.
Over the cantilever, if relevant.
3.
From midpoint to midpoint of adjacent spans.
4.
From the base of the mid-height of the first guy level.
5.
From the mid-height of the span between the penultimate and top guy to the top guy if no cantilever is present, but including the cantilever, if relevant. 9:Tower Loading • 165
For BS 8100, the patch loads are derived from equivalent velocity profiles derived from the equations in Cl. 5.3.2.2 and Cl. 5.3.2.3 for the mast and guy, respectively. If specified, the various wind profiles needed to form patch load cases will be obtained as follows: VELOCITY
Mean wind profile.
PVEL_MAST
Patch wind profile on mast.
PVEL_GUY
Patch wind profile on guys.
Formation of patch sub-cases may be prevented by using the keyword. NOPATCH when specifying the wind load. If patch loading is specified, you must leave a sufficient gap in the numbering of successive wind load and combination load cases to accommodate the sub-cases that will be generated. The total structural response for the mean wind and patch cases is computed in accordance with BS 8100 Part 4 Cl. 5.3.2.4. Patch loading for other codes may be input using the optional WL parameters ZGUST z1 .. GFACT gf to specify sections of the mast over which the wind load is to be modified.
Dead Loads DL
[BARE]
[GUYS]
where: DL
Keyword signifying a dead load case. The weight of all ancillaries will be included in the load case.
BARE
Keyword. If present, the dead load is computed for the tower structure only, without ancillaries.
GUYS
Keyword. If present, the dead load of the guys only will be computed. For use with TIA-222-G, where different load factors are applied to the guys and shaft of the mast.
Ice Loads ICE
DENS dens
{WIND|NOWIND}
[BARE]
[UNICE list]
where:
166 • 9:Tower Loading
ICE
Keyword signifying a gravity load due to icing of the tower. The weight of ice coating structural members and ancillaries will be taken into account.
DENS
Keyword.
dens
Specific weight of ice, in kN/m3 or lb/ft3.
WIND
Keyword indicating presence of wind.
MSTower V6
NOWIND
Keyword indicating absence of wind.
BARE
Keyword indicating that ice load is computed for the tower structure only without ancillaries.
UNICE
Keyword.
list
Name of a guy list defined in the GUYLIST block. The guys nominated in this list will not have ice applied.
Miscellaneous Loads Load cases not falling into one of the above categories may be included as miscellaneous loads. These could include construction, maintenance, or similar loads. MI NDLD ..
list
FX fx
FY fy
FZ fz
where: MI
Keyword.
NDLD
See “Additional Node Loads”, below.
Additional Node Loads Additional node loads may specified for any wind load, dead load, or ice load case. NDLD
list
FX fx
FY fy
FZ fz
where: NDLD
Keyword.
list
The nodes to which the forces are to be applied, in one of the following forms: n1 n2 .. nn A list of node numbers. n1 TO n2 INC n3 Includes n1 to n2 in steps of n3. ALL All nodes.
FX FY FZ
Keywords indicating direction of force.
fx fy fz
Forces in the global X, Y, Z directions, respectively, in kN or kips.
Additional Member Temperatures Additional member temperatures may be specified for any wind load, dead load, or ice load case. MSTower V6
9:Tower Loading • 167
MTMP
list
TEMP
t
where: MTMP
Keyword.
list
The members to which the temperatures are to be applied, in one of the following forms: m1 m2 .. mn A list of node numbers. m1 TO m2 INC m3 Includes m1 to m2 in steps of m3. ALL All members.
TEMP
Keyword.
t
Centroidal temperature. Transverse temperature gradients will be set to zero.
In addition to being used to model the effects of temperature change, MTMP loads may be used to simulate a broken guy, by specifying a temperature increase sufficient to make the guy slack.
Eathquake Load Cases Earthquake loading may be modelled using •
uniform acceleration,
•
equivalent lateral force, or
•
equivalent modal analysis.
The necessary data for each of these methods is given below. Uniform Acceleration EQ
{ACCEL|GACCEL}
X x
Y y
Z z
where:
168 • 9:Tower Loading
EQ
Keyword.
ACCEL
Keyword indicating that acceleration values are in absolute units of either m/sec2 or ft/sec2.
GACCEL
Keyword indicating that acceleration values are to be multiplied by “g”, the acceleration due to gravity.
X
Keyword.
x
Acceleration in the global X direction.
Y
Keyword.
y
Acceleration in the global Y direction.
Z
Keyword.
z
Acceleration in the global Z direction. MSTower V6
A uniform inertial forces will be applied to the structure in the direction specified by the acceleration components, x, y, and z. A set of node forces will be generated in the directions of the global axes. Equivalent Lateral Force EQ
ELF1
X x
Y y
VSM vsm
[KE ke]
[FT ft]
where: EQ
Keyword.
ELF1
Keyword indicating that the equivalent lateral force method is to be used.
X Y
Keywords.
x y
Components of the vector defining the direction of the eathquake.
VSM
Keyword.
vsm
Seismic shear multiplier.
KE
Keyword.
ke
Seismic force distribution component. Default values are 1.0 for structures having a fundamental frequency of 2 Hz and higher, 2.0 for structures with a fundamental frequency of 0.4 Hz or less, and by linear interpolation for frequencies between 0.4 and 2.0 Hz.
FT
Keyword.
ft
Seismic force factor at top of structure.
The total seismic shear, Vs, is obtained as the product of vsm and the weight of the structure. The seismic force at the top of the structure is (ft × Vs) with the remainder of the seismic force being distributed over the height of the structure according to the formula: Fsz = wz hz ke / Sum (wi hi ke ) × Vs (1 – ft) Equivalent Modal Analysis EQ
EMA2 X x SDS sds
Y y F1 f1... SD1 sd1 [I i]
[R r]
where:
MSTower V6
EQ
Keyword.
EMA2
Keyword indicating that the equivalent modal analysis method is to be used.
X Y
Keywords.
x y
Components of the vector defining the direction of the 9:Tower Loading • 169
eathquake. F1
Keyword.
f1
Fundamental frequency of the tower in the direction of the earthquake.
SDS
Keyword.
sds
Design spectral response acceleration at short periods.
SD1
Keyword.
sd1
Design spectral response acceleration at a period of 1.0 sec.
I
Keyword.
i
Importance factor, 1.5 if not specified.
R
Keyword.
r
Response modification coefficient – 3.0 for self-supporting latticed towers, 2.5 for latticed guyed masts, 1.5 for tubular pole structures.
The equivalent modal analysis procedure uses the equations of Cl. 2.7.8 of EIA-222-G.5. Each earthquake load case will normally be used in at least two combination load cases with positive and negative factors.
Combination Load Cases COMBIN ..
lcase
factor
where: COMBIN
Keyword.
lcase
Load case reference number. This must be a load case reference numbers specified in a CASE record – do not refer to sub-cases generated for groups of large ancillaries or cross-winds or patch load cases.
factor
Factor by which the loads in lcase are to be multiplied.
Panel Block The panels into which the tower is divided are defined by listing nodes at the panel boundaries in order from the top of the tower. The Z coordinates of these nodes will be used when determining the panel to which projected areas of member and ancillaries are allocated. The list of nodes may extend over one or more lines. If the PANEL block is not specified panel heights will be obtained from the Job.TWM file, generated by the tower builder. The PANEL block is not usually required.
170 • 9:Tower Loading
MSTower V6
Ancillary Block This block is used to describe the ancillaries attached to the tower. Data for each ancillary is given on a separate line as a series of keywords and numeric items. Ancillary libraries, containing the dimensions and other properties of ancillaries, are used to reduce the amount of data required. Ancillaries are sub-divided into the following types: •
Linear ancillaries.
•
Face ancillaries.
•
Large ancillaries.
•
Insulators.
ANCILLARIES
MSTower V6
9:Tower Loading • 171
ANCILLARY AXES
Linear Ancillaries Linear ancillaries are items such as wave-guides, feeders and the like. Usually they are either attached to the face of the tower or contained within the body of the tower. The following data is required: LINEAR LIB libr name XB xb YB yb ZB zb [XT xt] [YT yt] ZT zt... [SELF] LIB lname [FACT fact] [SHADE shade]... [SHADY shady] ANG anga ..
where:
172 • 9:Tower Loading
LINEAR
Keyword.
LIB
Keyword.
MSTower V6
MSTower V6
libr
Name of library containing linear ancillaries. It is assumed that the library is located in the data folder unless the name is prefixed with “P:” or “L:”. “P:” indicates that the library is in the program folder and “L:” indicates that it is in the library folder.
name
Identifier for the ancillary, 1-16 characters, not recognizable as a number.
XB
Keyword.
xb
X coordinate of the base of the ancillary, in m or ft.
YB
Keyword.
yb
Y coordinate of the base of the ancillary, in m or ft.
ZB
Keyword.
zb
Z coordinate of the base of the ancillary relative to the base of the tower, in m or ft.
XT
Keyword.
xt
X coordinate of the top of the ancillary, in m or ft. If not entered, the X coordinate of the base of the ancillary is used.
YT
Keyword.
yt
Y coordinate of the top of the ancillary, in m or ft. If not entered, the Y coordinate of the base of the ancillary is used.
ZT
Keyword.
zt
Z coordinate of the top of the ancillary relative to the base of the tower, in m or ft. This value must be entered.
SELF
Keyword indicating that the linear ancillary is self-supporting. The mass of the ancillary will be allocated to panels when computing the equivalent static factor but its self weight will not be added to the tower when computing DL cases. If omitted, the weight of the ancillary will be added to that of the tower.
LIB
Keyword.
lname
Name of ancillary in library – 1-16 characters.
FACT
Keyword.
fact
Number of ancillaries of this type at this location.
SHADE
Keyword.
shade
Coefficient used to factor exposed area of a linear ancillary.
SHADY
Keyword.
shady
Coefficient used to factor exposed area of linear ancillaries for wind in the “y” direction.
SHEFF
Keyword.
sheff
List of multipliers used to factor the calculated or input shielding or interference factors to account for the shielding effects between ancillaries.
ANG
Keyword. 9:Tower Loading • 173
ang
Angle between the “x” axis of the ancillary and the X axis of the tower measured clockwise from the X axis.
Face Ancillaries These are ancillaries mounted on the faces of the tower and consisting of small items whose wind resistances will be added to that of the panel of the face to which they are attached. FACE name FACE flist ZA za MASS mass AREA area AICE aice {FLAT|CYL} ..
CN cn...
where:
174 • 9:Tower Loading
FACE
Keyword.
name
Identifier for the ancillary – 1-16 characters, not recognizable as a number.
FACE
Keyword.
flist
List of faces to which ancillaries of this type are attached, as a concatenated string of the digits 1, 2, 3, and 4, with no embedded spaces, e.g. 13 means the ancillaries are on faces 1 and 3.
ZA
Keyword.
za
Z coordinate of the mounted level of the ancillary, in m or ft.
MASS
Keyword.
mass
Mass of the ancillary, in kg or lb.
CN
Keyword.
cn
Drag coefficient for wind normal to the face to which the ancillary is attached.
AREA
Keyword.
area
Projected area of the ancillary on the face of the tower, in m2 or ft2.
AICE
Keyword.
aice
Surface area that can be coated with ice, in m2 or ft2. The volume of ice is obtained by multiplying this area by the thickness of ice.
FLAT
Keyword indicating that the ancillary is to be considered as sharp edged.
CYL
Keyword indicating that the ancillary is to be considered as cylindrical.
MSTower V6
Large Ancillaries These are discrete ancillaries too large to be considered as “facemounted” ancillaries, usually positioned on the face of the tower or external to the tower. LARGE LIB libr name XA xa YA ya ZA za LIB lname... [FACT fact] [SHADE shade] ANG ang... [{AMASS|TMASS}] [ATTACH nlist] ..
where:
MSTower V6
LARGE
Keyword.
LIB
Keyword.
libr
Name of library containing large ancillaries. It is assumed that the library is located in the data folder unless the name is prefixed with “P:” or “L:”. “P:” indicates that the library is in the program folder and “L:” indicates that it is in the library folder.
name
Identifier for the ancillary – 1-16 characters, not recognizable as a number.
XA
Keyword.
xa
X coordinate of the ancillary, in m or ft.
YA
Keyword.
ya
Y coordinate of the ancillary, in m or ft.
ZA
Keyword.
za
Z coordinate of reference level of the ancillary relative to the base of the tower, in m or ft. If an antenna, the reference level is usually the center of radiation.
LIB
Keyword.
lname
Name of ancillary in library – 1-16 characters.
FACT
Keyword.
fact
Factor by which the library dimensions and areas of the ancillary are multiplied. If not given, a value of 1.0 is used.
SHADE
Keyword.
shade
Coefficient used to factor exposed area of a large or linear ancillary.
SHEFF
Keyword.
sheff
List of multipliers used to factor the calculated or input shielding or interference factors to account for the shielding effects between ancillaries.
ANG
Keyword.
ang
Bearing of the ancillary, the clockwise angle between north and the negative “x” axis of the ancillary.
AMASS
Keyword. 9:Tower Loading • 175
TMASS
Keyword.
mass
Mass, in kg or lb, with the following meanings depending on which keyword it follows: AMASS Additional mass, to be added to the library mass. TMASS Total mass, to be used instead of the mass in the library.
ATTACH
Keyword.
nlist
List of nodes to which the ancillary is attached. If attachment data is omitted, the program will allocate the forces from the ancillary to leg nodes closest to the level of the ancillary. The forces of the ancillary will be transferred into the tower by a statically equivalent set of forces on the listed nodes.
New optional keyword for shielding efficiency factors: SHEFF sheff1 sheff2
.. sheff8 (for square towers)
SHEFF sheff1 sheff2
.. sheff6 (for triangular towers)
Shielding efficiency factors may be specified for large ancillaries to wholly or partly exclude the particular ancillary from solidity and shielding calculations. The factors are in the range 0 to 1.0 and each pair of factors specifies the proportion of the projected area and resistance of the large ancillary that will be included for that wind direction. For square towers the order of the factors is for wind directions 0º, 45º, 90º, 135º.. from the positive X axis. For triangular towers the order of the factors is for wind directions 0º, 60º, 120º, 180º.. from the positive X axis. If the SHEFF keyword is omitted all factors are taken as 1.0. An ampersand, “&”, may be used at the end of a line to indicate that the data for an ancillary extends to the next line. If the mean wind speed is being used, the gust factor for each large ancillary will be computed and the product of the gust factor and the mean hourly loads will be accumulated to form a single sub-load case for each wind load case.
Resistances Resistance, either additive or total, may be used to model the loading on sections of the tower. For example if a section of a tower is completely clad in panels, it may be more accurate to use an overall resistance for this section that to use a sum of the loads on individual panels and section of the tower. The data required is: RESISTANCE name ZB zb ZT zt [ARES|TRES|BRES] res ..
where:
176 • 9:Tower Loading
MSTower V6
RESISTANCE
Keyword.
name
Identifier for the ancillary, 1-16 characters, not recognizable as a number.
ZB
Keyword.
zb
Z coordinate of the lowest extent of the resistance relative to the base of the tower, in m or ft.
ZT
Keyword.
zt
Z coordinate of the topmost extent of the ancillary relative to the base of the tower, in m or ft.
ARES
Keyword indicating that the wind load from the resistance is to be added to that computed from other ancillaries or section of the tower that occur in the range zb to zt.
TRES
Keyword indicating that the wind load from the resistance is to be total wind load occurring on the section of the tower in the range zb to zt.
BRES
Keyword indicating that resistance is due to tower body including linear ancillaries. Thus, total resistance is the BRES resistance plus that of large ancillaries.
res
List of resistances/m for the set of directions around the tower. Resistance must be entered in directions anticlockwise from the X axis as follows: Square towers and monopoles 0, 45, 90, 135, 180, 225, 270, 315 degrees. Triangular towers 0, 60, 120, 180, 240, 300 degrees.
Insulators These may be used to separate sections of a multi-segment guy. They are described as: INSULATORS name NODE node AREA area MASS mass CN cn ..
AICE aice...
where:
MSTower V6
INSULATORS
Keyword.
name
Identifier for the insulator – 1-16 characters, not recognizable as a number.
NODE
Keyword.
node
Node number at which the insulator is located.
AREA
Keyword.
area
Projected area of the insulator, in m2 or ft2. It is assumed that the projected area is the same for all angles of wind incidence. 9:Tower Loading • 177
AICE
Keyword.
aice
Surface area that can be coated with ice, in m2 or ft2. The volume of ice is obtained by multiplying this area by the thickness of ice.
MASS
Keyword.
mass
Mass of the insulator, in kg or lb.
CN
Keyword.
cn
Drag coefficient, assumed to be the same for all angles of wind incidence.
Note: You may obtain the node number for an insulator from the data tip that appears when the cursor is placed on it, with the Query > Node Data command, or by double-clicking on it.
Output The following tables of intermediate results computed by the loading module are written to a loading log file and may be viewed by selecting the File > List/Edit > Loading Log command or printed by selecting the File > Print > Loading Log command. Velocity Table The input and computed parameters used in computing the velocity profile and the variation of velocity with height above the base of the tower are reported. Member/Face Table Each member is allocated to a tower face and its projected length in the face is reported. Leg members will belong to two faces while internal members, such as hip and plan bracing, will not belong to any face. The length of bracing members that intersect leg members is adjusted for the overlap between the IP and the edge of the leg member if the overlap flag in the PARAMETERS block is set to 1. Face Results The area of each panel, its solidity ratio, and drag coefficient, the resistance of ancillaries, shielding factor, Sf, and the normal resistance of the face as a single frame are reported for each face. Resistance Table The effective resistance, Re1 and Re2, and the total wind resistance, Rwt, for the specified wind angle are reported, along with the total mass (structural and ancillary) of each panel. The factor determining whether the equivalent static method is valid is also reported.
178 • 9:Tower Loading
MSTower V6
Computation of Wind Resistance The program uses the procedures set out in Section 4.4 of BS 8100 for the computation of resistances. If the mean-hourly wind speed is being used and if large ancillaries are specified in a wind load case, the wind loads on the equivalent shielded tower will be computed and additional sub-load cases will be generated for each wind direction for the large ancillaries. This case will contain the sum of the gust-factored wind loads on the large ancillaries. If the gust wind speed is being used, the loads on the equivalent shielded tower and large ancillaries are computed separately and added together to form a single load case before being output. Patch loadings for codes other than BS 8100 may be computed using the optional ZGUST z1 .. GFACT gf parameters applied to the wind load specification.
BS 8100 The velocity, VB, should be specified as MEAN. MStower uses the general method of BS 8100 for computing the wind resistance of towers. This method allows for towers with faces that are asymmetrical, either structurally or due to their complement of ancillaries. It also allows the resistance to be computed for any wind incidence angle. When using the general method, the resistance of the single frame comprised in each face is computed, along with shielding factors and Kth. The resistance of the complete tower is built up from these values. Methods of computing drag coefficients of panels made of flat and circular sections (both sub-critical and super-critical) are also given. BS 8100 also uses a simpler method for symmetrical towers, whereby the resistance for the complete tower can be determined from drag factors for the overall tower. If a panel contains ancillaries, the projected area of the ancillary is used when computing panel solidity ratios and single panel drag coefficients. The wind forces on the ancillary are then computed using the drag coefficients from the ancillary library and a statically equivalent set of node loads is applied to the nodes to which the ancillary is attached. Gust Factor Correction If BS 8100 Part 1 is specified with a mean hourly wind speed, each wind load case will consist of:
MSTower V6
1.
A load case containing forces on the equivalent bare tower due to the mean wind.
2.
A sub-load case containing forces on the large ancillaries due to the mean wind multiplied by the gust factor appropriate to each ancillary’s size and height above ground level.
3.
A sub-load case containing the sum of the mean wind loads on the tower and ancillaries. 9:Tower Loading • 179
MStower computes and applies gust factors to member forces for the cases of wind on the bare equivalent tower, adds in the member forces due to gust wind on the ancillaries, and then recomputes the combination cases. Note: The above applies only where mean wind speeds are used. If gust wind speeds are used the loads on large ancillaries will be computed separately and added to the loads on the equivalent bare tower before output. No additional sub-cases will be produced.
AS 3995 When AS 3995 is specified MStower uses the general method as described above but with single frame drag coefficients that give overall drag coefficients equal to those in Table 2.2.8.2 of AS 3995. This allows the program to maintain the ability to deal with towers that are asymmetrical or composed of mixed section shapes. It also allows wind forces to be computed for angles of incidence other than face and corner. For a tower carrying large dishes, the critical wind may occur at some other angle, which may vary from member to member.
AS 1170 When AS 1170 is specified wind forces are computed as the sum of the wind load on the tower structure and that on the linear and large ancillaries. The area of face ancillaries is added to that of panels in computing solidity ratios. The drag force on ancillaries is multiplied by an interference factor, KIN, whose magnitude depends on the solidity of the tower and location and type of ancillary.
Malaysian Electricity Supply Regulations 1990 If the code in the PARAMETERS block is specified as MER (Malaysian Electricity Supply Regulations), the program uses the formulae and methods of BS 8100, but with the following differences: •
Wind velocity is constant over the full height of the tower. A velocity equal to the product of the basic wind velocity and the partial safety factor on wind speed is used.
•
A solidity ratio of 0.1 is used to determine the single frame drag coefficient (BS 8100 Fig. 4.5). When used with the wind velocity specified in the regulations this gives a wind pressure of 810 N/m2 on the projected area of a face made up of flat sided members.
The effective shielding factor in C1.4.4.1 of BS 8100 is taken as 0.5, giving an additional 405 N/m2 on the leeward face.
180 • 9:Tower Loading
MSTower V6
EIA/TIA-222-F The wind velocity, VB, should be the fastest mile wind speed. No modifying keyword (MEAN or GUST) is required. Unless a user-defined profile is used, the velocity profile will be computed in accordance with Cl. 2.3.3. A TERRAIN block is not required. When EIA-222 is specified, MStower uses the general method as described above but with modifications to coefficients that give overall drag coefficients equal to those derived from Section 2.3 of EIA/TIA222-F for the wind directions specified in Table 2. This allows the program to maintain the ability to deal with towers that are asymmetrical or composed of mixed section shapes. It also allows wind forces to be computed for any incidence angle instead of just face and corner wind. For a tower carrying large dishes, the critical wind may occur at some other angle, which may vary from member to member. All wind loads, including any NDLD forces specified in a WL case, are multiplied by a gust response factor determined in accordance with Cl. 2.3.4.
TIA-222-G The wind velocity, VB, should be the 3-second gust wind speed. No modifying keyword (MEAN or GUST) is required. MStower computes the solidity of each face from the projected area of members and those linear ancillaries that are within the face zone. The solidity of the most windward faces is then used in computing the EPA (equivalent projected area or resistance) of each panel of the tower. All wind loads, including any NDLD forces specified in a WL case, are multiplied by a gust response factor determined in accordance with Cl. 2.6.7.
MSTower V6
9:Tower Loading • 181
Computation of Deflections BS 8100 Cl. 5.2.5 of BS 8100 Part 1 gives two serviceability criteria that may be used. The gust-factoring process in MStower V6 modifies the deflections for wind load cases and sub-load cases to provide deflections that may be used in clauses (a) and (b) of Cl. 5.2.5. After gust-factoring the deflections for towers are: Base WL case (see 1 above): [ (1 + GB) DTE + (1 + GA) DAW ] (SP / γV )2 Mean wind load case (see 3 above): DMW (SP / γV)2 where: GB
Gust factor for leg loading at the base of the tower.
DTE
Deflection for hourly mean wind on the equivalent bare tower.
GA
Gust factor for ancillaries.
DAW
Deflection for hourly mean wind on large ancillaries.
SP
Probability factor computed from BS 6399 Part 2 Annex D for serviceability return period. See RPSERV in Parameter block.
γV
Partial safety factor on wind speed.
DMW
Deflection for hourly mean wind on tower and ancillaries.
The gust-factored deflections from the base wind load case will be used to update any combination load case that references a wind load case. The gust-factored deflections are in a form that may be more readily used in Cl. 3.3.2 of the code. For masts, the gust-factored deflections are the deflections from the analysis multiplied by the factor (SP / γV)2.
Other Codes If the wind speed for serviceability differs from that used in member checking, additional serviceability combinations will be required. In these load cases the load factor applied to the wind load component must be multiplied by the square of the ratio of the service wind speed to the basic wind speed.
182 • 9:Tower Loading
MSTower V6
Dynamic Amplification of Wind Loads The displacements and member forces in the structure will be increased if the natural frequency of the structure is close to the frequency of the wind gusts. The dynamic effects are small and are usually neglected if the natural frequency is above 1.0 Hz. In assessing the natural frequency of a latticed tower some care may be required to avoid modes that represent the local vibration of small areas and to ensure that an overall vibration mode is obtained.
BS 8100 There is no codified method of taking dynamic effects into account. The code recommends a spectral analysis if the equivalent static factor is above 1.0. This type of analysis requires specialist knowledge and experience. It is not available in Mstower. If necessary, such effects may be accounted for by applying increased factors to wind loads in combination load cases.
AS 3995 For towers, dynamic effects are taken into account by applying gust response factors, GS, specified in Cl. 2.3.8 of the code, to the wind forces obtained by applying the design mean wind speed. The gust response factor varies over the height of the tower. A number of load cases may be required for each wind direction to model the variation in gust response factor. The codified method is not applicable to guyed masts. The following data is required in the PARAMETERS block: FREQ freq TDAMP tdamp
The program computes the value of the gust response factor at the height of each panel top and for each WL case outputs a table of these factors in the loading log and also in the file Job.gfa, where “Job” is the job name. To use them you will need to create sufficient WL cases for each wind direction to model the variation of the gust response factor with height: CASE WL CASE WL CASE WL ..
n WL direction1 ANGLX ang1 .. ZGUST zgust1 n+1 WL direction1 ANGLX ang1 .. ZGUST zgust2 n+2 WL direction1 ANGLX ang1 .. ZGUST zgust3
GFACT gfact1 GFACT gfact2 GFACT gfact3
The program will multiply all wind forces above level zgust by gfact. Each combination load case that references a wind load will have to be expanded in a similar fashion.
MSTower V6
9:Tower Loading • 183
AS 1170 For towers, dynamic effects are taken into account by applying dynamic response factors, CDYN, specified in Section 6 of the code to the wind forces from applying the design wind speed. The dynamic response factor varies over the height of the tower. A number of load cases may be required for each wind direction to model the variation in the dynamic factor. The codified method is not applicable to guyed masts. The following data is required in the PARAMETERS block: FREQ freq TDAMP tdamp
The program computes the value of the dynamic response factor at the height of each panel top and for each WL case outputs a table of these factors in the loading log and also in the file job.GFA. To use them you will need to create sufficient WL cases for each wind direction to model the variation of the gust response factor with height: CASE WL CASE WL CASE WL ..
n WL direction1 ANGLX ang1 .. ZGUST zgust1 n+1 WL direction1 ANGLX ang1 .. ZGUST zgust2 n+2 WL direction1 ANGLX ang1 .. ZGUST zgust3
GFACT gfact1 GFACT gfact2 GFACT gfact3
The program will multiply all wind forces above level zgust by gfact. Each combination load case that references a wind load will have to be expanded in a similar fashion.
EIA-222-F There is no codified method of taking account of the dynamic amplification of wind loads. If necessary, such effects may be accounted for by applying increased factors to wind loads in combination load cases.
TIA-222-G There is no codified method to take account of the dynamic amplification of wind loads. If necessary, such effects may be accounted for by applying increased factors to wind loads in combination load cases. If the fundamental frequency and total damping are defined in the PARAMETERS block, the gust effect factor will be computed in accordance with 6.7.8 of SEI/ASCE 7-02.
ASCE 7 For towers, dynamic effects may be taken into account by applying a gust effect factor, G, that allows for a resonant effect in the response as
184 • 9:Tower Loading
MSTower V6
set out in the Commentary of the code. The codified method is not applicable to guyed masts. The following data is required in the PARAMETERS block: FREQ freq TDAMP tdamp
The program will compute and use a gust effect factor that takes account of the dynamic effects.
IS 875 For towers, dynamic effects may be taken into account by applying a gust factor, G, specified in Section 8, to the mean load. The codified method is not applicable to guyed masts. The following data is required in the PARAMETERS block: FREQ freq TDAMP tdamp
The program will compute and use a gust effect factor that takes account of the dynamic effects.
BNBC For towers, dynamic effects may be taken into account by applying a gust factor, Gbar, specified in Section 8, to the load computed from the fastest mile wind speed. The codified method is not applicable to guyed masts. The following data is required in the PARAMETERS block: FREQ freq TDAMP tdamp
The program will compute and use a gust effect factor that takes account of the dynamic effects.
ILE TR7 The loads from the design wind are multiplied by a factor that is a function of the pole natural frequency, height, and damping ratios. The following data is required in the PARAMETERS block: [FREQ freq] SDAMP sdamp [ADAMP adamp] [TDAMP tdamp]
The program will compute and use a gust effect factor that takes account of the dynamic effects. The parameters enclosed in square brackets are optional; if not input they will be computed by the program.
MSTower V6
9:Tower Loading • 185
Ancillary Libraries Ancillary libraries are text files containing blocks of data giving the dimensions and drag characteristics of ancillary items. Separate libraries are used for large ancillaries and linear ancillaries. The libraries remain text files and unlike the section library, do not require further processing before use. The libraries supplied with MStower are called Ms_lin.lib and Ms_anc.lib. Because of the wide variety of ancillaries, there is no doubt that you will have to add information to the libraries. It is recommended that the distribution libraries are not modified. Instead, for each project, you may copy the distribution versions to libraries with names of your choice. All changes should then be made to the project libraries. Note: Ancillary libraries use metric units. The structure of an ancillary library file is: ANCILLARY
.. END COEFFICIENTS
.. END
Large Ancillary Library The ANCILLARY block in the large ancillary library contains the following data for each ancillary type: name coeff dim mass af asf aice zref xcg xicg... fcx fcy fzm ishape sx sy sz
where:
186 • 9:Tower Loading
name
Name by which the antenna is referenced in the TWR file.
coeff
Name of set of coefficients to be used in calculating the projected area and wind resistance of the antenna.
dim
Reference dimension, in m, the dish diameter or height, used in computing forces and moments about the antenna axes and the BS 8100 gust factor for the antenna.
mass
Mass of the ancillary, in kg.
af
Frontal area of the antenna, in m2.
asf
Side area of antenna, in m2. This will be used to compute the projected area of the antenna at different angles if the projected area coefficients are zero. In this case, the projected area will be computed as: af × cos² (angle) + asf × sin² (angle) MSTower V6
aice
Surface area of a the antenna that may be coated with ice, in m2. Used in computing the weight of ice on an iced antenna.
zref
Z dimension from the antenna origin for wind loads and the level of the antenna in the TWR file, in m. Usually, either the centerline of radiation or the mounting level of the antenna.
xcg
Horizontal offset from the antenna origin to the center of gravity of the un-iced antenna, in m.
xicg
Horizontal offset from the antenna origin to the center of gravity of a uniform ice coating on the antenna, in m.
fcx
Correction factor to be applied to drag coefficient for drag force along the axis of the antenna.
fcy
Correction factor to be applied to drag coefficient for horizontal drag force normal to the axis of the antenna.
fzm
Correction factor to be applied to drag coefficient for yawing moment (twisting about the vertical axis of the antenna).
ishape
Shape code for the antenna, used to select a symbol for plotting.
sx,sy,sz
Scale factors for icon graphics.
A list of icon numbers is given in the text file Mstower.icn in the MStower program folder. The drag coefficients are contained in the ancillary library in a separate COEFFICIENTS block, which may contain any number of sets of coefficients: COEFFICIENTS coeff FACT fact... ang afact Cfx Cfy .. END
Cfz
Cmx
Cmy
Cmz
where:
MSTower V6
coeff
Name of set of drag and projected area coefficients.
FACT
Keyword.
fact
Factor by which the coefficients in the table must be multiplied so that when used with kg and meter units, the resulting forces and moments will be in N and N.m.
ang
Angle of wind incidence for which drag coefficients apply.
afact
Area angle factor. The projected area on a plane normal to the angle of wind incidence is obtained as: af × afact
Cfx
Coefficient for drag along the “x” axis of the antenna.
Cfy
Coefficient for side force along the “y” axis of the antenna.
Cfz
Coefficient for lift force along the “z” axis of the antenna.
Cmx
Coefficient for moment about the antenna “x” axis, i.e. the rolling moment. 9:Tower Loading • 187
Cmy
Coefficient for moment about the antenna “y” axis, i.e. the pitching moment.
Cmz
Coefficient for moment about the antenna “z” axis, i.e. the yawing moment.
The forces and moments at the origin of the antenna are given by: Fx
= 0.5 ρ × Cfx × Af × V2
Fy
= 0.5 ρ × Cfy × Af × V2
Fz
= 0.5 ρ × Cfz × Af × V2
Mx
= 0.5 ρ × Cmx × a × Af × V2
My
= 0.5 ρ × Cmy × a × Af × V2
Mz
= 0.5 ρ × Cmz × a × Af × V2
where “a” is a lever-arm. If necessary, the coefficients for the angle of wind incidence are interpolated from the coefficients table. All dimensions and forces for an antenna are measured in the ancillary axes, a set of right-handed orthogonal axes (see diagram in “Ancillary Block” on page 171).
Linear Ancillary Library The ANCILLARY block in the linear ancillary library contains the following data for each ancillary: name
coeff
mass
af
asf
aice
shape
where:
188 • 9:Tower Loading
name
Name by which the antenna is referenced in the TD file.
coeff
Name of set of drag curves to be used for the antenna. Use NONE if the standard drag coefficients given in BS 8100 are to be used.
mass
Mass of the ancillary per unit length, in kg/m.
af
Frontal are of the antenna, in m²/m.
asf
Side area of antenna. This will be used to compute the projected area of the antenna at different angles if the projected area coefficients are zero. In this case, the projected area will be computed as: af × cos²(angle) + asf × sin²(angle)
aice
Surface are of the antenna that may be coated with ice, in m²/m. Used in computing the weight of ice on an iced antenna.
shape
An integer code indicating the ancillary shape. Used for the selection of standard drag coefficients and in computing the thickness of ice coating: 0 = Cylindrical. 1 = Sharp-edged flat section.
MSTower V6
Drag Coefficients The drag coefficients are contained in the ancillary library in a separate COEFFICIENTS block, which may contain any number of sets of coefficients: COEFFICIENTS coeff FACT fact... ang afact Cfx Cfy .. END
where: coeff
Name of set of drag and projected area coefficients.
FACT
Keyword.
fact
Factor by which the coefficients in the table must be multiplied so that when used with kg and meter units, the resulting forces and moments are in N and N.m.
ang
Angle of wind incidence to which drag coefficients apply.
afact
Area angle factor. The projected area on a plane normal to the angle of wind incidence is obtained as: af × afact
Cfx
Coefficient for drag along the “x” axis of the ancillary.
Cfy
Coefficient for side force along the “y” axis of the ancillary.
The forces and moments at the origin of the ancillary are given by: FX
= 0.5 ρ × Cfx × Af × V²
FY
= 0.5 ρ × Cfy × Af × V²
If necessary, the coefficients for the angle of wind incidence are interpolated from the coefficients table. All dimensions and forces for an antenna are measured in the ancillary axes, a set of right-handed orthogonal axes (see diagram in “Ancillary Block” on page 171).
MSTower V6
9:Tower Loading • 189
190 • 9:Tower Loading
MSTower V6
10:CAD Interface
General The CAD interface is an integral part of MStower that offers the capability of exporting 3-D data to a CAD system, forming the basis for a CAD drawing. This function is selected with the File > Export > CAD DXF command. Structure information is exchanged by means of an AutoCAD DXF. Note: You can use the Windows Paste command to transfer any part of an MStower image into CAD.
Exporting a CAD DXF Each member center-line is represented by a single LINE entity in the DXF. The section shape may also be represented by a number of planes. The section shapes may be curtailed at member ends to avoid overplotting at the intersections. On selecting the File > Export > CAD DXF command the dialog box below is displayed.
CAD DXF EXPORT PARAMETERS
MSTower V6
10:CAD Interface • 191
The DXF contains only an Entities section without a drawing header. In AutoCAD, you may import the file with the “DXFIN” command and then use the “ZOOM E” command to fill the screen with the drawing. The limits may then be adjusted as required. You may suppress hidden lines and render the drawing in AutoCAD.
Exporting a Steel Detailing Neutral File Select File > Export > SDNF to create a file that can be imported into a steel detailing program that recognizes the SDNF format (e.g. Xsteel). The file will be created in the data folder with the name Job.sdn, where “Job” is the MStower job name. At present, this command will transfer only the structural geometry and section sizes to the SDN file.
192 • 10:CAD Interface
MSTower V6
Section Alias File Section names in CAD systems often vary from the standard names used in MStower. In order to export SDN files with the correct names for the target CAD system, an “alias file” is used. The file is a look-up table relating MStower section names to the equivalent CAD system section name. For example, the first part of the file Xsteel.ali is shown below. When an appropriate alias file is present in the library folder MStower uses it to replace its section nomenclature with that of the target CAD system. $ $ Microstran - Xsteel grades and sections alias file. $ GRADES 250L0 300 350 C250 C350 C450 C450L0 43 50 END
250 300 350 C250 C350 C450 C450L0 43A 50B
SECTIONS
$ AS sections
$ MStower 690UB140 690UB125 610UB125 610UB113 610UB101 530UB92.4 530UB82.0 460UB82.1 460UB74.6 460UB67.1 410UB59.7 410UB53.7
Xsteel UB690*140 UB690*125 UB610*125 UB610*113 UB610*101 UB530*92 UB530*82 UB460*82 UB460*74 UB460*67 UB410*60 UB410*54
Windows Clipboard Operations MStower facilitates use of the Windows clipboard for transfer of images to CAD programs by using the Enhanced Metafile Format (EMF) for the Windows clipboard when you select the View > Copy command. In programs such as AutoCAD, you can then use the Paste command to directly insert an image of the main MStower view. Pressing the Print Screen key on the keyboard writes a Windows bitmap to the clipboard. Both of these formats may be pasted into Microsoft Word documents. MSTower V6
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11:Analysis
General MStower offers a number of static and dynamic analysis options, each of which employs exhaustive consistency checking and highly efficient equation solution procedures. The analysis engines used in MStower are derived from those used in Microstran, a widely-used and extremely versatile program for analysing and designing structural frameworks in steel and reinforced concrete. Linear Elastic Analysis is a first-order elastic static analysis in which non-linear effects are ignored and the stiffness equations are solved for only the primary load cases. Solutions for combination load cases are obtained by superposition of the solutions for the primary load cases. Non-Linear Analysis is a second-order elastic analysis, which enables you to take into account the non-linear actions arising from the displacement of loads (the P-∆ effect), the change in flexural stiffness of members subjected to axial forces (the P-δ effect), and the shortening of members subjected to bending (the flexural shortening effect). Nonlinear analysis is an iterative procedure in which the behaviour at each step is controlled by a number of parameters. Each selected case, whether a primary or combination load case, must be solved separately, as superposition of results cannot be used. Members defined as tensiononly will be checked at each iteration and included or excluded accordingly. Elastic Critical Load Analysis calculates the frame buckling load factor, λc, for selected load cases and computes the corresponding member effective lengths for each load case. Dynamic Analysis computes the natural vibration frequencies of the structure and the associated mode shapes. The dynamic loads on the structure due to earthquake or other support acceleration may then be assessed using the response spectrum method. The Profile Optimizer is used in all analyses to minimize analysis time and storage requirements. Nodes and members can therefore be numbered for maximum convenience in data generation and interpretation of results.
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Method MStower uses the well-documented direct stiffness method of analysis in which the global stiffness matrix, [K], is assembled from the stiffness contributions of individual members. For large structures, [K] can be quite large and is stored on disk in blocks sized to maximize the use of available memory and to minimize solution time. Load vectors, P, are formed from the applied loads and node displacements, u, are determined by solving the equation: P = [K] u The forces in each member are then determined by multiplying the member stiffness matrix by the appropriate terms of the displacement vector, resolved into member axes.
Consistency Check MStower performs an automatic check of all input data prior to analysis. The consistency check will detect a range of modelling problems related to geometry and loading. Data errors and warnings are shown in the Output window and are also written to the error report, which can be listed and printed using options on the File menu.
Accuracy All analyses use double-precision arithmetic to minimize the loss of precision inherent in the many arithmetic operations required for solving large, complex structural models. After the decomposition of the [K] matrix MStower reports the maximum condition number, a measure of the loss of precision that has occurred during the solution. For “wellconditioned” structural models (those in which little numerical precision is lost) the condition number will be less than 104. If the condition number exceeds this value you should treat the results with caution and look for evidence of “ill-conditioning”. For example, the large displacement of a node or group of nodes may indicate that the structure is acting, to some extent, as a mechanism, and the results could be meaningless. An important independent check on the accuracy of the solution is provided by the node equilibrium check. At unrestrained nodes the sum of all the member end actions is compared to the sum of external forces acting on the node. Any difference is a force residual, the out-of-balance force. The maximum residual is reported to the screen after the analysis. The maximum residual should be considered in conjunction with the magnitudes of the applied loads in assessing the adequacy of the solution. Note: A satisfactory equilibrium check, by itself, is not sufficient to ensure an accurate solution – the condition number must also be satisfactory.
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MStower will choose the appropriate method of analysis when Tower > Analyse is selected. Linear analysis will be used unless the tower contains tension-only members or guys (cables).
Linear Elastic Analysis Linear elastic analysis cannot be performed if there are any tension-only or cable members in the model. An error message will be displayed if you attempt linear analysis of a model containing these member types. All load cases are analysed when you choose linear analysis. Results for combination load cases are determined by superposition of the results of the component primary load cases. Note: If you perform a non-linear analysis and then a linear analysis, the settings in the Select Analysis Type dialog box will be lost (see “Selecting Load Cases for Non-Linear Analysis” on page 200). Performing a linear analysis sets the analysis type flag to L (linear).
Non-Linear Analysis Non-Linear analysis (also called second-order analysis) performs an elastic analysis in which second-order effects may be considered. The different second-order effects are described below. Non-linear analysis uses a multi-step procedure that commences with a linear elastic analysis. The load residuals, computed for the structure in its displaced position and with the stiffness of members modified, are applied as a new load vector to compute corrections to the initial solution. Further corrections are computed until convergence occurs. There is no single method of iterative non-linear analysis for which convergence is guaranteed. It may therefore be necessary to adjust the analysis control parameters in order to obtain a satisfactory solution. The solution may not converge if the structure is subject to gross deformation or if it is highly non-linear. This may be the case as the elastic critical load is approached. Note: You should not attempt to use non-linear analysis to determine elastic critical loads. Results of non-linear analysis should be treated with caution whenever the loading is close to the elastic critical load.
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Second-Order Effects The most important second-order effects taken into account in non-linear analysis are the P-Delta effect (P-∆) and the P-delta effect (P-δ). These are discussed in detail below.
P-∆ AND P-δ EFFECTS
You may independently include or exclude these two major effects. Different combinations of the P-∆ and P-δ settings affect the operation of non-linear analysis as set out in the table below.
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Node Coordinate Update
Axial Force Effects
NO
NO
Linear elastic analysis with tension-only or compression-only members taken into account. This can be achieved for any load case by selecting linear analysis
YES
NO
Analysis includes the effects of displacement due to sidesway but not changes in member flexural stiffness due to axial force. These settings will usually yield satisfactory results for pin-jointed structures.
NO
YES
Full account is taken of the effects of axial force on member flexural stiffness while the effects of node displacement are approximated by a sidesway correction in the stability function formulation. These settings normally give minimum solution time with second-order effects taken into account.
YES
YES
This is the default analysis type, which provides the most rigorous solution for all structure types.
Analysis Type
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Node Coordinate Update – P-Delta Effect The P-Delta effect (P-∆) occurs when deflections result in displacement
of loads, causing additional bending moments that are not computed in linear analysis. P-∆ is taken into account either by adding displacement components to node coordinates during analysis or by adding sidesway terms to the stability functions used to modify the flexural terms in the member stiffness matrices. Either small displacement theory or finite displacement theory may be used with node coordinate update. As shown in the diagram below, finite displacement theory takes into account the rotation of the chord of the displaced member in computing the end rotations and the extension of the member. Only where large displacements occur would the use of finite displacement theory produce results different from those obtained with small displacement theory.
SMALL AND FINITE DISPLACEMENT THEORIES
Axial Force Effects – P-delta Effect The bending stiffness of a member is reduced by axial compression and increased by axial tension. This is called the P-delta effect (P-δ) and is taken into account by adding beam-column stability functions to the flexural terms of the member stiffness matrices. Member stiffness matrices therefore vary with the axial load and are recomputed at every analysis iteration. The stability functions are derived from the “exact” solution of the differential equation describing the behaviour of a beamcolumn. The additional moments caused by P-δ are approximated in some design codes by the use of moment magnification factors applied to the results of a linear elastic analysis.
Flexural Shortening Flexural shortening, also called bowing, is the reduction in chord length caused by bending. If the ends of the member are completely restrained against axial movement very high tensions may develop with transverse MSTower V6
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loading. In practice, however, it is difficult to obtain such restraint. In most structures the effect is small but can give rise to considerable difficulty in obtaining convergence of the analysis. Inclusion of the flexural shortening effect is rarely required for a tower or mast.
Changes in Fixed-End Actions Member fixed-end actions may change between successive analysis iterations owing to displacement of the member and variations in its flexural stiffness caused by axial force. MStower automatically recalculates the fixed-end actions at each analysis iteration and updates the load vector accordingly.
Non-Linear Members Analysis of structures containing tension-only, or cable members requires non-linear analysis. At the conclusion of each analysis step, all members nominated as tension-only or compression-only are checked and either removed from or restored to the model for the next analysis step, according to their deformation. If the removal of non-linear members causes the structure to become unstable, no solution is possible.
Running a Non-Linear Analysis Selecting Load Cases for Non-Linear Analysis Non-linear analysis lets you specify the load cases to be analysed and the analysis type (linear or non-linear) to be used for each. For non-linear analysis a load vector is formed for each load case to be solved, whether a primary load case or a combination load case. There is no need to analyse any load cases for which results are not required. On selecting the Analyse > Non-Linear command, the following dialog box is displayed so you may specify the load cases to be analysed and the analysis type. In the Type column, load cases are identified as Primary or Combination. The second character is a code that specifies whether the load case is to be processed with Linear analysis or Nonlinear analysis, or is to be ignored (Skipped).
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The ability to use different analysis types is used for obtaining results for both linear and non-linear analysis in a single pass. This may be necessary where the model includes members to be designed to different codes with different analysis requirements. In general, only “realistic” load cases should be selected for non-linear analysis – there is no point in analysing a wind load case because this load will never exist in isolation. This is particularly important for structures containing cable elements where realistic loads including self weight are required to determine the equilibrium position of each cable, and a solution may not be possible for load cases containing only some load components. Note: The settings in this dialog box will be lost if you subsequently perform a linear analysis. In this case, the analysis type flag (S/L/N) will be unconditionally set to Linear. You must reinstate the analysis type flag if you revert to non-linear analysis.
Non-Linear Analysis Parameters The next dialog box determines the type of non-linear analysis that will be performed for load cases selected for non-linear analysis.
. NON-LINEAR ANALYSIS PARAMETERS
The dialog box contains the following items:
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Node coordinate update (P-∆) This flag is set if node coordinates are to be updated at each analysis step. It is automatically set for structures containing cable elements. The default setting is on.
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Small/finite displacement theory If the node coordinate update flag has been set, either small or finite displacement theory must be selected. Small displacement theory is the default setting.
•
Axial force effects (P-δ) If this flag is set member stiffnesses are modified at each analysis step. The default setting is on.
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Residual / displacement Specifies the criterion to be used for convergence of the solution. 11:Analysis • 201
Residual uses a function of the maximum out-of-balance force after analysis. When Displacement is selected, convergence is checked by comparing the convergence tolerance against a generalized measure of the change in displacement between successive iterations. For a satisfactory solution there must be acceptably small changes in the displacement and the residual must be of a low value. The default setting is Residual.
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•
Displacement control Increasing the setting of this control will assist convergence in situations where displacements appear to diverge with successive analysis iterations, or for structures that are initially unstable but become stable as they displace under load. You normally leave this control at minimum and only increase the setting if difficulties are encountered in solution.
•
Convergence tolerance This value determines when the analysis has converged, determined by checking the change in the convergence criterion between successive analysis cycles. Too small a value will prolong the solution time and may even inhibit convergence. The default value is 0.0005. Do not attempt to achieve “convergence” by increasing the tolerance.
•
No. load steps You may apply loads in a stepwise fashion which may assist in obtaining a solution for flexible structures by keeping displacements small at each load increment. This parameter is usually left at its default value of 1.
•
Iterations per load step The maximum number of analysis iterations for each load step. This parameter is used to stop the analysis if convergence is taking an excessive time. The default value is 50, but larger values are often applicable for very flexible structures or models containing large numbers of cable elements.
•
Relaxation factor The relaxation factor is applied to incremental displacement corrections during analysis. The optimum value for the relaxation factor depends on the type of the structure. As a general rule, structures which “soften” under load (i.e., displacements increase disproportionately with load) have an optimum relaxation factor between 1.0 and 1.2 while structures which “harden” under load have an optimum relaxation factor as low as 0.85. Caution is recommended in changing the relaxation factor from the default value of 1.0; if the relaxation factor is too far from optimum the analysis may require an excessive number of iterations for convergence or it may not converge at all.
•
Oscillation control This control facilitates convergence when the solution oscillates
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owing to the removal and restoration of tension-only or compression-only members. The default setting is off. As the analysis proceeds, the analysis window displays key information for each selected load case. At each analysis iteration the maximum values of residual and displacement are displayed in correct user units. Note that at this stage the values shown are from the most critical degree of freedom, i.e., residuals may be either forces or moments, and displacements may be either translations or rotations.
Troubleshooting Non-Linear Analysis It is possible to perform a successful linear analysis for structures that are incapable of resisting the imposed loads. Non-linear analysis is a more complete simulation of the behaviour of a structure under load and the procedure may fail to provide a solution where a linear analysis succeeds. This may occur, for example, if some compression members are slender and buckle. Where non-linear analysis fails to converge, the following tips may be helpful: •
Make sure that a linear analysis can be performed. If not, troubleshoot the linear analysis before continuing with the nonlinear analysis.
•
Is a full non-linear analysis necessary? If the only significant nonlinear effect is the presence of tension-only or compression-only members, set the analysis type to L for these load cases. In other cases, a successful analysis may result if either node coordinate update or axial force effects are excluded.
•
Examine the analysis log file. It contains information about members that have become ineffective because of slenderness or member type.
•
Perform an elastic critical load analysis to check the frame buckling load. If it is greater than the imposed load non-linear analysis is not possible.
•
Is the structure too flexible? Remove excessive member end releases (pins). Sometimes, in diagnosing convergence problems, it is helpful to remove ALL releases and reinstate them in stages.
•
Adjust non-linear analysis parameters.
Instability Instability detected during linear analysis is usually due to modelling problems and some of the common causes of these are discussed elsewhere. Because a non-linear analysis considers the effects of axial force on member stiffness it is able to detect a range of instability that linear analysis cannot. For example, non-linear analysis may detect buckling of individual members or of the whole frame. The manner in which a structure is modelled and the analysis parameters used can have some MSTower V6
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bearing on the stage of the analysis when instability of individual members is detected and the way in which it is subsequently treated. If an unstable member is detected during the update process at the end of each iteration, it will be deleted from the following iteration in much the same way that a tension-only member would be. The presence of unstable members is reported in the Analysis window and details are written to the static log file. However, if the instability is not in a single member but localized in a small group of members it may not be detected until the completion of the analysis. In this case, the presence of the instability will be reported in the Analysis window and some diagnostic information will be written to the static log file to assist you in correcting the problem. Even though the analysis has failed, results are available and may be used to determine corrective measures, e.g. increase some member sizes or, perhaps, change to tension-only members. The results of an analysis in which instability has been reported are useful for diagnosis but should not be used for other purposes. An elastic critical load analysis will often assist in locating the cause of local instabilities.
Elastic Critical Load Analysis Elastic critical load (ECL) analysis (also referred to as stability, or buckling analysis) performs a rational buckling analysis of the model to compute the elastic critical load factors (λc) and the associated buckling modes. Member effective lengths can also be determined from the elastic critical load. The buckling behaviour depends on the distribution of loading on the frame and buckling parameters are computed separately for each load case to be considered. The buckling load factor for any load case is the factor by which the axial forces in all the members must be multiplied to cause the structure to become unstable (lateral torsional buckling of individual members is not taken into account). The elastic critical load of the structure is a function of the elastic properties of the structure and the pattern of loading. The effective length of a member is defined as the length of an ideal pinended strut whose Euler load is the axial load in the member when the structure is at its critical load. The effective length may be expressed as a factor multiplying the actual member length (k). The effective length factor is calculated separately for each of the member principal axes for each load case. A load factor of less than 1.0 for any load case indicates that the structure is unstable under the applied loading. A linear elastic analysis is often used for the initial analysis, but nonlinear analysis must be used when the structure contains non-linear members. For most structures the load factor will not be influenced
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greatly by the type of initial analysis and a linear analysis is recommended in order to reduce the overall solution time. Restraints affecting the flexural buckling behaviour of the structure must be included in the structural model. For example, if out-of-plane buckling behaviour is to be considered for a plane frame, the frame would have to be modelled as a space frame with nodes located at the positions of lateral restraints (restraint can be introduced only at nodes). Elastic critical load analysis is not recommended for structures containing cable elements because of the highly non-linear nature of structures of this type.
Selecting Load Cases for ECL Analysis Select Analyse > Elastic Critical Load from the main menu. The dialog box below is displayed for you to select the required load cases. Usually, only combination load cases required for design are selected.
SELECTING LOAD CASES FOR ECL ANALYSIS
Analysis Control Parameters After selecting load cases, the dialog box shown below appears. The settings in this dialog box determine the type of elastic critical load analysis that will be performed.
ECL ANALYSIS PARAMETERS
The dialog box contains the following items: •
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Initial analysis The initial analysis determines the distribution of axial forces to be used for the elastic critical load analysis. It is normally Linear but
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should be Non-linear if the structure contains tension-only, compression-only, or cable members. •
Tolerance The tolerance is the relative accuracy to which the load factor is required. Too small a value will prolong the solution time. The default value is 0.01.
•
Max. load factor The search for the elastic critical load will terminate if the load factor exceeds this limiting value. The default value is 1000.
•
No. modes The number of buckling modes to be computed for each selected load case. Normally, only the first mode is required, though higher modes may be of interest if lower modes are inhibited or represent localized buckling behaviour.
When the analysis is finished a summary of results appears in the analysis window. The summary shows for each selected load case the critical load factor and the most critical member with associated k values.
Why ECL Analysis May Give High k Factors The effective length of a given member in a frame is the length of an equivalent pin-ended member whose Euler load equals the buckling load of the frame member. The effective length factors, kx and ky, are factors by which we multiply the actual length of the member in order to obtain the effective lengths for buckling about the section XX and YY axes, respectively. When designing the frame member by traditional methods, we take account of the stiffness of connected members to obtain the effective length and then we consider it as if it were an isolated member of an appropriate length. We could then determine the axial load required to cause column buckling in this equivalent member. ECL analysis allows us to determine the frame buckling load factor for a given load case. Frame buckling occurs when the axial forces for the given load case are factored to the point where the frame collapses. Display the buckling mode shape of the frame and you can see how the frame buckles. Frame buckling for a given load case is usually a complex interaction of several members – there is not necessarily any one member that “causes” the buckling of the frame. In this situation, if we apply our definition of effective length, we find that the effective length of a given member for a given load case is the length of an equivalent pin-ended member whose Euler load equals the load in that member when frame buckling occurs. Thus, any member carrying a small axial load at frame buckling will have a large effective length. Also, the effective length of a member will vary from one load case to another. It is only where a member could be said to be critical (i.e. participating to a very large degree in the buckling mode), that the effective length factor could be compared with the value used in traditional methods. 206 • 11:Analysis
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In general, traditional effective length factors relate to the buckling load of the member being considered whereas the effective length factor computed by ECL analysis relates to frame buckling.
Dynamic Analysis Dynamic analysis computes the frequencies and mode shapes of the natural vibration modes of the structural model. Only the mass and stiffness of the model are considered in computing natural frequencies and mode shapes. Static load cases are ignored. The frame mass is computed automatically and modelled as node masses. Member masses are computed automatically as the product of the cross-sectional area and the mass density. The masses of ancillary equipment are taken into account by masses lumped at attachment nodes. Select the Analyse > Dynamic command to start dynamic analysis.
Analysis Control Parameters After selecting load cases, the dialog box shown below appears. The settings in this dialog box determine the type of dynamic analysis that will be performed.
DYNAMIC ANALYSIS PARAMETERS
The dialog box contains the following items:
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No. modes The number of natural frequencies and mode shapes that can be computed is limited by the number of dynamic degrees of freedom, and, for large structures, by the amount of available memory. Solving for a large number of modes is usually not warranted.
•
Tolerance This is the tolerance to be used in determining the convergence of eigenvalues. If the value is too small, convergence may not be possible or an excessive number of iterations may be required. If the value is too large, the eigenvalues found may not be the lowest. The default value is 0.00001.
•
Verify eigenvalues Check this box if you wish to verify that no eigenvalues have been skipped in the computation (see above).
•
Lumped mass / Consistent mass The mass matrix may be computed using either a consistent mass or 11:Analysis • 207
lumped mass formulation. The consistent mass matrix has a firmer theoretical basis but gives rise to a global mass matrix that is similar in shape and size to the global stiffness matrix, requiring greater storage and computational effort than the lumped mass matrix, which leads to a diagonal global mass matrix •
Initial state load case Non-linear behaviour is not taken into account in dynamic analysis but it is possible to specify a load case that defines the initial state. For example, a leeward cable in a guyed mast subjected to wind load may be slack. If the corresponding load case is specified as the initial state load case, the slack cable will be eliminated from the analysis. The default value is zero.
•
Response spectrum analysis You must check this box if you wish to proceed to a response spectrum analysis after the dynamic analysis.
Dynamic Modes After completing a dynamic analysis it is important to check the mode shapes to ensure that you have the required dynamic modes. MStower computes all dynamic modes, including torsional modes. The easiest way to examine the results is to display an animated view of the computed mode shapes. The diagram below shows the mode shape computed for the first mode in dynamic analysis of the TWEX5 example.
NATURAL MODE SHAPE
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Response Spectrum Analysis Response spectrum analysis (RSA) is used to determine peak displacements and member forces due to support accelerations. Spreadsheets AS1170_4.XLS and NZS1170_5.XLS, which are available on request, set out detailed procedures for performing response spectrum analysis complying with the design codes AS 1170.4 and NZS 1170.5, respectively.
Defining Load Cases Load cases to receive RSA results are defined as miscellaneous cases in the tower load file (.TWR), for example: CASE 105 Earthquake X direction MI CASE 106 Earthquake Y direction MI
Note that no node loads (NDLD lines) are defined for these cases. Messages displayed during processing that these cases contain no loads may be ignored. The primary cases that are to contain the RSA results may be referenced in combination cases in the usual way.
Running a Response Spectrum Analysis The procedure for performing a response spectrum analysis is:
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1.
Set up load cases and perform the static (linear) analysis. The earthquake load cases are empty – results from the response spectrum analysis will be added automatically.
2.
Select dynamic analysis, set the number of modes, and check Verify eigenvalues and Response spectrum analysis.
3.
Select the first RSA primary case (105 in the above example).
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4.
For each earthquake load case you must enter parameters to determine the response spectrum direction and the number of modes to be considered. The direction factors determine the direction of the support acceleration in terms of components in the global axis directions. These components will be reduced to a unit vector before being used. The number of modes must be sufficient to satisfy the earthquake code requirement that 90% (typically) of the seismic mass is accounted for. It must not be greater than the number of modes computed during dynamic analysis (Step 2, above).
5.
For each earthquake load case damping ratios are specified. The “Complete Quadratic Combination” method (CQC) for combining modal responses is used to determine the peak response. This is equivalent to the “Square Root of the Sum of Squares” (SRSS) method if all modal damping ratios are zero.
6.
For each earthquake load case a response spectrum curve and scaling factor must be specified. The response spectrum curve is chosen from a list of names of digitized response spectrum curves contained in file Response.txt (described below). You may edit the response spectrum curves or add new ones using the Configure > Edit Response Spectra command. Response spectrum curves are MSTower V6
usually normalized in terms of g, the gravitational acceleration. The scaling factor will be the product of g and any other code-defined factors that take account of the structure type and foundation.
7.
After Steps 3-6 have been completed for each earthquake case, the dynamic analysis proceeds. On completion, select the Analyse > Response Spectrum command to scale the computed actions and combine them with the static analysis results (note that this item is greyed out on the menu until all the necessary preconditions for response spectrum analysis have been completed). The total reactions (base shears) are displayed for each earthquake case and you now enter scale factors for each case. The spreadsheets referred to above will assist you in computing scale factors to comply with code requirements.
MStower now adds the results from the response spectrum analysis to the static analysis results. Earthquake load cases may now be treated as any other load case for the display and reporting of results and for design. If loads are computed to BS 8100, select Tower > Gust Factor to apply gust factors to wind loads. The complete procedure must be repeated if either the static or dynamic analysis is re-run. Note: The displaced shape represents the peak values of the displacement during the earthquake event. There are no negative values. Interpretation of the results should take this into account. Response Spectrum Scale Factor The scale factor used in Step 6, above is used to multiply the spectral acceleration values to give the actual support acceleration to be used in the analysis. Many codes give spectral accelerations in a normalized MSTower V6
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form that have to be multiplied by site acceleration factors. For convenience, file Response.txt uses normalized spectral values. The results of the static analysis are updated with the results of the response spectrum analysis. As this process takes place, the sum of the reactions for each dynamic load case will be displayed and you may enter factors that will be used to scale the results to ensure compliance with codes that require minimum base shears (Step 7, above). The factor should be based on the base shear in the direction of the support acceleration. Note that the values given for the reactions are the sum of absolute values, as the methods used to combine individual modal responses result in loss of sign. The results for each dynamic load case are inserted in the results files for the previously defined empty load cases. Any combination case that refers to the dynamic case is updated by adding the specified dynamic case, factored as specified. By updating combination cases instead of computing them completely from the results of primary cases, any nonlinearity in the previously computed results is preserved. However, the static analysis must be repeated if the dynamic analysis is to be amended. Note: After running response spectrum analysis you should look at the dynamic analysis log file, which contains important data including mass participation factors.
Response Spectrum Curves The digitized data for the response spectrum curves must be entered into the Response.txt file, which resides in the library folder. This is a text file that may be edited by the user to add additional response spectrum data. The format of each set of data in the file is as follows: Name T(1) T(2) T(3) ..... T(n) END
Sa(1) Sa(2) Sa(3) Sa(n)
where:
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Name
String of alphanumeric characters used to identify each curve.
T(n)
Period in seconds for the nth point on the curve.
Sa(n)
Spectral acceleration for the nth point on the curve. The spectral accelerations may be in normalized form or as absolute accelerations with a scale factor, described previously, being used to effect any required conversion.
END
Keyword indicating the end of data for this curve.
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Errors There are some types of error that only become evident during analysis and it is not possible for the consistency check to warn of this type of error before the analysis commences. For example, if a structure is unstable because some part of it actually forms a mechanism, analysis will be terminated and an error message will be displayed on the screen. The error message is of the form: STRUCTURE UNSTABLE AT NODE nnnnn DOF f
where: nnnnn
=
The node number at which instability was detected.
f
=
The DOF number, as shown in the table below, in which there was found to be no resistance to displacement.
Sometimes in linear elastic analysis a modelling problem may manifest itself as gross linear or angular displacement. This kind of problem may not be obvious in the member force plots but may be evident in the plot of displaced shape. Modelling problems of this type can usually be fixed by the addition of one or more node restraints to inhibit the gross displacement. In non-linear analysis very large displacements can occur in the analysis of structures containing very flexible tension members. If displacements are sufficiently large the analysis will be terminated with a message of the form: EXCESSIVE DISPLACEMENTS
A solution can sometimes be obtained in cases like this by adjusting the analysis parameters but it is preferable to model very flexible tension members as cables. The above error message may also be obtained where the automatic deletion of tension-only bracing members during non-linear analysis renders a structure unstable.
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12:Member Checking
General This chapter describes the MStower modules for checking the strength of members in latticed towers and masts in accordance with the rules set out in the following codes. Towers and Masts • BS 8100 Part 3 • BS 449 • ASCE 10-90 • ASCE 10-97 • EIA-222-F • TIA-222-G • AS 3995 • IS 802 Monopoles • Institution of Lighting Engineers Technical Report 7 (ILETR7) • ASCE Manual 72 • BS5950 Part 1 • AS 4100 • EIA-222-F • TIA-222-G The member checking modules use data generated by the tower builder, loading modules, and the results of the static analysis. Important Note: Good engineering practice requires fully triangulated bracing in tower structures. Non-triangulated bracing relies on the flexural stiffness of the brace in one tower face to provide restraint to the brace in an adjacent face. In some cases this may be satisfactory but in general it will not provide the same degree of restraint offered by a fully triangulated system; in particular, under corner winds the braces in adjacent faces can have approximately equal compression forces and they will provide little or no mutual restraint.
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Important Note (cont.): If non-triangulated redundants are detected they will be ignored in assessing the capacity of restrained members. MStower may not find all instances of non-triangulated bracing. It is the responsibility of the tower designer to ensure that the tower is fully triangulated, or if not, that additional checks are carried out to ensure the adequacy of the restraint system.
Operation Start the code checking module by selecting the appropriate code from the Member Check > Towers/Masts or Member Check > Poles menus. The report may be limited by selecting classes of members to be checked and setting the report limit on the ratio of design load/capacity. Two forms of report are produced, a summary report and a detailed report. They may be viewed or printed by selecting File > List/Edit and File > Print, respectively. The utilization ratios may be displayed graphically by selecting Results > Design Ratios.
Loading Parameters It is of the greatest importance to use loading parameters that are consistent with the code being used for checking the capacity of members. Loading parameters required for each design code are listed below. These lists are not exhaustive and should not be used as a replacement for the relevant code.
BS 8100 Part 3 CODE VB PSF-V PSF-M
BS8100 or BS8100P4 or BS8100A1 Mean hourly (MEAN) From Part 1 or Part 4 of BS 8100 From Part 1 or Part 4 of BS 8100 or as amended in Part 3
Combination for compression: γDL × DL + WL
BS 449 CODE VB PSF-V PSF-M
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BS8100 3 sec. gust (GUST) 1.0 1.0
MSTower V6
Velocity profile block: Use velocity factors from CP3 Chapter 4 to describe the velocity profile. Combination for compression: DL + WL
ASCE 10-90, ASCE 10-97, ASCE Manual 72 CODE VB
ASCE795 3 sec. gust (GUST)
Combination for compression: 1.2×DL + 1.6×WL
EIA-222-F CODE VB
EIA222 Fastest mile
Combination for compression: DL + WL
TIA-222-G CODE VB
TIA222G 3 sec. gust (GUST)
Combination for compression: 1.2×DL + 1.6×WL
AS 3995 CODE VB
AS1170 3 sec. gust (GUST)
Combination for compression: DL + WL
IS 802 CODE VB
IS875 3 sec. gust (GUST)
Combination for compression: DL + 1.5×WL
ILE TR7 CODE VB PSF-M SDAMP
ILETR7 Mean hourly from BS 6399 Part 2 1.15 Logarithmic decrement of damping for structure
Combination for compression: DL + 1.25×WL
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ILETR7 is for cantilevered (unguyed) poles only. The wind loads will incorporate the response factor and size factor from Figures 1 and 2 in ILETR7. Guyed poles should be checked using BS 5950, see below.
BS 5950 CODE VB PSF-M SDAMP
BS6399 Mean hourly from BS 6399 Part 2 1.0 Logarithmic decrement of damping for structure
Combination for compression: 1.2×DL + 1.4×WL Wind loading will be computed using ILETR7 / BS 6399 methods. If the pole is cantilevered, the wind loads will incorporate the response factor and size factor from Figures 1 and 2 in ILETR7. If the pole is guyed, these factors are not appropriate and any dynamic increase in loads must be allowed for by increasing the factor applied to WL in the loading combinations.
AS 4100 CODE VB SDAMP
AS1170 3 sec. gust (GUST) Damping ratio for structure
Combination for compression: 1.2×DL + WL
Design Loads Axial loads are taken from the results of the analysis (and any subsequent gust-factoring) for legs, braces, and horizontals. Secondary or redundant members are used to stabilize primary load carrying members. Codes specify hypothetical forces that the redundant system should be able to resist, usually as a percentage of the load carried by the member being stabilized. The percentage may be fixed, or it may be dependent on the slenderness of the stabilized member. Previous versions of MStower checked all redundant members for the full stabilizing force. For face members MStower V6 applies the stabilizing force transversely to the member and distributes it through the redundant systems using a truss analysis. No distribution is done for redundants, such as hip and plan bracing that are not part of the tower faces. Stabilizing forces are determined as follows: BS 8100 Part 3 Two cases are considered, as described in Section 5.4 (a) and (b) of Part 3.
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ASCE 10-90, ASCE 10-97, AS 3995, IS 802 A stabilizing force of 2.5% is used. EIA-222-F A stabilizing force of 1.5% is used. TIA-222-G The stabilizing force is dependent on the slenderness of the member being restrained. The factors used to determine the stabilizing forces for face redundants are printed in the detailed design report.
Member Checks to BS 8100 Part 3 Code Type BS 8100 is a limit states code. The capacity of members at the strength limit state is checked. MStower V6 follows the rules of BS 8100 Part 3 instead of DD 133, as required by Amendment 1 to Parts 1 and 4. Note that Cl. 6.1 (a) and (b) of Part 3 use different values for γm, the partial safety factor on strength, than those given in Parts 1 and 4. Structural Configuration and Buckling Lengths MStower uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the rules set out in Section 5 of BS 8100 Part 3 to determine buckling lengths. If the face has cross-bracing that is not braced against out-of-plane buckling, the forces in both diagonals are determined so that the critical L/r ratios and design capacities may be assessed in accordance with Cl. 5.3.3 of BS 8100 Part 3. Selection of Buckling Curves Effective slenderness factors are selected in accordance with BS 8100 Part 3 Section 5.5, using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces, and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. Calculation of Ultimate Member Stresses The ultimate stress of the member is calculated from the rules in of BS 8100 Part 3 Section 6. If the section is not one tabulated in BS 8100 Part 3 the reference stress is determined by application of the rules for hot-rolled angles to any elements of the section that have an unsupported free edge.
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Bolts Bolts are checked for shear on the bolt and bearing on the member using the rules in accordance with Section 8. If any of the dimensions x, y, and z are not specified or set to zero, the checking module assumes that these are equal to or greater than the minimums specified in the code to allow an ultimate bearing strength of 2.0 × (D.T.fy) to be attained. Report For each panel in the tower, the report lists the member number, the classification (leg, brace, etc.), the section size and yield strength, the most critical load case, the K value, the slenderness ratio, and whether it is about the x-x, y-y, v-v axes, the axial design force, the capacity and the ratio of design load to capacity. An expanded version of the report, more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of MStower has the following restrictions: •
Members are checked for axial force only.
•
No check is made on “man-load” on horizontal or nearly horizontal members.
Member Checks to BS 449 Code Type BS 449 is a permissible stress design code. The stresses in members at service conditions are checked. BS 449 is a superseded code that should generally not be used in design. Structural Configuration and Buckling Lengths MStower uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the end bolting arrangement to determine effective length factors. Calculation of Permissible Member Stresses The permissible stress in the member is calculated from the formulae in Appendix B of BS 449, with a user-supplied wind overstress factor applied if the member forces due to wind loads increase the member forces due to other causes. Bolts Bolted joint checks are not implemented for this code. Report For each panel in the tower, the report lists the member number and classification (leg, brace, etc.), the section size and yield strength, the 220 • 12:Member Checking
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most critical load case, the effective length factor, the slenderness ratio and whether it is about the x-x, y-y, v-v axes, the axial design force, the actual and permissible stresses (and whether a wind overstress factor is included), and the ratio of the actual to permissible stresses. An expanded version of the report more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of MStower has the following restrictions: •
Members are checked for axial force only.
•
No check is made on “man-load” on horizontal or near-horizontal members.
•
Joint capacities are not checked.
Member Checks to AS 3995 Code Type AS 3995 is a limit states code. The capacity of members at the strength limit state is checked. Structural Configuration and Buckling Lengths MStower uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the rules set out in Appendix H of AS 3995 to determine buckling lengths. If the face has cross-bracing that is not braced against out-of-plane buckling at the intersection point, the forces in both diagonals are determined so that the critical L/r ratios and design capacities may be assessed in accordance with Figure H2 of AS 3995. Effective Slenderness Ratio Effective slenderness ratios are determined in accordance with Section 3.3.4 of AS 3995, using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces, and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. Calculation of Ultimate Member Strength The capacity of a member is calculated from the rules of Section 3.3 for angles in compression and with AS 4100 for other sections in compression and all sections in tension. Bolts Bolted are checked for shear and bearing using the rules of AS 3995 Cl. 3.5.4. No checks are made on the detailed requirements of Cl. 3.5.4.6. MSTower V6
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Report For each panel in the tower, the report lists the member number, the classification (leg, brace, etc.), the section size and yield strength, the most critical load case, the sub-clause of Section 3.3.4 of AS 3995 used in determining the effective slenderness ratio, the effective slenderness ratio and whether it is about the x-x, y-y or v-v axes, the axial design force, the capacity, and the ratio of design load to capacity. NOTE: In conformity with common international practice, the rectangular axes for ALL sections are nominated as x-x and y-y. For symmetrical sections these axes are also the principal axes. For angles the minor principal axis is nominated as v-v. An expanded version of the report more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of MStower has the following restrictions: •
Members are checked for axial force only.
•
No check is made on “man-load” on horizontal or nearly horizontal members.
Member Checks to ASCE 10-90 1991 & ASCE 10-97 1991 Code Type ASCE 10-90 and 10-97 are limit states codes. The stresses in members at the strength limit state are checked. References to ASCE 10-97 are shown below in brackets. Structural Configuration and Buckling Lengths The checking module uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the recommendations set out in the Commentary to the ASCE “Guide for Design of Steel Transmission Towers” – Second Edition (1988), to determine buckling lengths. If the face has cross-bracing that is not braced against out-of-plane buckling at the intersection point, the forces in both diagonals are determined so that the critical L/r ratios and allowable stresses may be assessed in accordance with Example 7 of the design guide or Example 7 of ASCE 10-97.
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Effective Slenderness Ratio Effective slenderness ratios KL/r are determined in accordance with Section 5.7.4 (3.7.4), using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces, and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. Calculation of Allowable Stresses The allowable stresses are calculated from the rules of Section 5.6 (3.6) for compression members and Section 5.10 (3.10) for tension members. Flexural stresses are not checked. Bolts Bolts are checked for shear and bearing using the rules of Cl. 6.3.2 (4.3.2) and Cl. 6.4 (4.4). No checks are made on edge distance or spacing requirements. Report For each panel in the tower, the report lists the member number, the classification (leg, brace, etc.), the section size and yield strength, the most critical load case, the sub-clause of Section 5.7.4 (3.7.4) used in determining the effective slenderness ratio, the effective slenderness ratio, and whether it is about the x-x, y-y or v-v axes, the axial design force, the capacity and the ratio of design load to capacity. An expanded version of the report more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of member checking to ASCE 10 has the following restrictions: •
Members are checked for axial force only.
•
No check on “man-load” on horizontal or nearly horizontal members is made.
Member Checks to EIA-222-F 1998 Code Type EIA-222-F is an allowable stress code. The stresses in members under service loads are checked. Structural Configuration and Buckling Lengths The checking module uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the recommendations set out in the Commentary to the ASCE Manuals and MSTower V6
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Reports on Engineering Practice No. 52 – “Guide for Design of Steel Transmission Towers” – Second Edition (1988), to determine buckling lengths. If the face has cross-bracing that is not braced against out-of plane buckling at the intersection point, the forces in both diagonals are determined so that the critical L/r ratios and allowable stresses may be assessed in accordance with Example 7 of the design guide. Effective Slenderness Ratio Effective slenderness ratios KL/r are determined in accordance with the rules of ASCE Manual 52 using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces, and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. Calculation of Allowable Stresses The allowable stresses, including any appropriate wind overstress factors, are calculated from the rules of Section 3. Flexural stresses are not checked. Bolts Bolts are checked for shear and bearing using the rules in Chapter J of the AISC “Specification for Structural Steel in Buildings – 1989”. No checks are made on edge distance or spacing requirements. Report For each panel in the tower, the report lists the member number, the classification (leg, brace, etc.), the section size and yield strength, the most critical load case, the sub-clause of Manual 52 used in determining the effective slenderness ratio, the effective slenderness ratio and whether it is about the x-x, y-y or v-v axes, the axial design force, the capacity, and the ratio of design load to capacity. An expanded version of the report more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of member checking to EIA-222-F has the following restrictions:
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•
Members are checked for axial force only.
•
No check is made on “man-load” on horizontal or nearly horizontal member.
MSTower V6
Member Checks to TIA-222-G 2005 Code Type TIA-222-G is a limit states code. The stresses in members at the strength limit state are checked. References to TIA-222-G are shown below in brackets. Structural Configuration and Buckling Lengths The checking module uses output from the tower builder (in which the tower data is assembled from a list of panel types and dimensions) to determine the nature of a member and its configuration related to the recommendations set out in the code when determining buckling lengths. If the face has cross-bracing that is not braced against out-of-plane buckling at the intersection point, the forces in both diagonals are determined so that the critical L/r ratios and design strengths may be determined. Effective Slenderness Ratio Effective slenderness ratios KL/r are determined in accordance with Tables 4-3 and 4-4, using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces, and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. Calculation of Design Strengths The design strengths are calculated from the rules of Section 4.5 for compression members and Section 4.6 for tension members. Flexural stresses are not checked for towers and masts. Bolts Bolts are checked for shear and bearing using the rules of Section 4.9. No checks are made on edge distance or spacing requirements. Report For each panel in the tower, the report lists the member number, the classification (leg, brace, etc.), the section size and yield strength, the most critical load case, the equation used in determining the effective slenderness ratio, the effective slenderness ratio, and whether it is about the x-x, y-y or v-v axes, the axial design force, the capacity and the ratio of design load to capacity. An expanded version of the report more suitable for detailed checking of the results for particular members is available. This report may be quite large. Restrictions This version of member checking to TIA-222-G has the following restrictions: • MSTower V6
Members are checked for axial force only in structures other than poles. 12:Member Checking • 225
•
No check on “man-load” on horizontal or nearly horizontal members is made.
Member Checks to IS 802 Code Type IS 802 is a limit states code. The capacity of members at the strength limit state is checked. Structural Configuration and Buckling Lengths MStower uses output from the tower builder to determine the nature of a member and its configuration related to the rules set out in Annex B to determine buckling lengths. Slenderness Ratios Slenderness ratios are determined in accordance with Section 6 using member classification and continuity information generated during tower building. Unless otherwise specified in the tower data file, the checking module assumes that legs, braces and horizontals are connected with two or more bolts and that redundants and plan and hip bracing are connected with single bolts. If the face has cross-bracing that is not braced against out-of-plane buckling at the intersection point, the forces in both diagonals are determined so that the critical L/r ratios and design capacities may be assessed in accordance with Annex B. Calculation of Ultimate Member Strength The capacity of a member is calculated from the rules of Section 5. Note: Although this section is headed “Permissible Stresses”, the maximum compressive and tensile stress in a member is the yield stress. Bolts Bolts are checked for shear and bearing using the rules of Section 5.4.
Member Checking to ILE Technical Report 7 ILETR7 is a limit states code for cantilevered steel poles. MStower determines the capacity of the pole using the rules of Section 2.4 where the section is circular or has 16 or more sides. For other polygonal sections the rules of BS 5649 Part 7 1985 are used. MStower checks the strength capacity of the pole without openings or other penetrations. Openings in steel tubes can dramatically reduce their capacity.
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Member Checking to BS 5950 BS 5950 is a limit states code. It may be used to check both cantilevered and guyed steel poles. MStower classifies the section using the plate slenderness limits of Table 11 or 12 for webs. For Class 3 semi-compact sections, the effective plastic modulus is computed in accordance with Section 3.5.6. For slender Class 4 slender sections, effective section properties are computed in accordance with Section 3.6. Member capacities under combined actions are checking using the simplified equations of Section 4.8.3. MStower checks the strength capacity of the pole without openings or other penetrations. Openings in steel tubes can dramatically reduce their capacity.
Member Checking to AS 4100 AS 4100 is a limit states code. It may be used to check both cantilevered and guyed steel poles. MStower classifies the section using the plate slenderness limits of Table 5.2 or 6.2.4. The effective section modulus is computed in accordance with Section 5.2. The effective area is computed in accordance with Clause 6.2. For slender polygonal sections, the effective properties are computed by omitting from each flat the width in excess of yield slenderness limit of the plate. Capacities under combined actions are checking using the equations of Section 8.3.4 and 8.4.5. MStower checks the strength capacity of the pole without openings or other penetrations. Openings in steel tubes can dramatically reduce their capacity.
Member Checking to ASCE Manual 72 ASCE Manual 72 is a limit states code for cantilevered and guyed steel poles. MStower uses the rules from the manual to compute the capacity of circular sections, and polygonal sections with 8, 12 or 16 sides. MStower checks the strength capacity of the pole without openings or other penetrations. Openings in steel tubes can dramatically reduce their capacity.
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Obtaining Design Results After checking members the results may be displayed or reported in a number of ways: •
Use the Results > Design Ratios command to display design results with members color-coded to show the percentage of member capacity actually utilized in the critical load case. With this display, all members that have failed a design check are shown in a shade of red.
•
Use the Query > Design Member command to show a summary of design results in the Output window for any selected member.
•
The design reports may be previewed with the File > Print Preview command and may be printed with the File > Print File command. Note that there are extensive facilities for formatting the design report using the File > Page Setup command.
The report files are automatically deleted when the job is closed. The member check reports are created in the data folder and are named: Job.rpt – summary report Job.rp2 – detailed report, where “Job” is the job name. You may save a steel design report file by dragging it to another folder using Windows Explorer. See “14:Reports” on page 239.
Steel Detailing Information may be exported in SDNF format for transfer to third-party steel detailing programs (e.g. Xsteel). Refer to “Exporting a Steel Detailing Neutral File” on page 192.
Editing Ancillary & Guy Libraries The File > Configure > Edit Ancillary/Guy Library command allows you to change ancillary and guy libraries. There are template records in each library file to help you add new data correctly. On selecting the above command, a dialog box is displayed for you to choose one of the library source files. These are displayed with a prefix, “Prog:”, “Data:”, or “Libr:”, indicating the folder in which it is located. The MsEdit program then starts for you to edit the selected file. The data required in each of these library types is set out in “Guy Library” on page 61 and “Ancillary Libraries” on page 186. The File > Configure > Library Viewer command is convenient for viewing, but not changing, the contents of ancillary and guy library files. 228 • 12:Member Checking
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13:Editing the Section Library
General MStower refers to one or more steel section libraries for information required for analysis and checking of members. Section library files may be in the program folder, the data folder, or in an optional designated library folder (see “Folders” on page 10). The library name is prefixed in TD files with P:, D:, and L:, respectively, for these folders. The File > Configure > General > Library File Folder command allows you to select the library folder. You may edit any steel section library using the File > Configure > Section Library Manager command or the File > Configure > Edit Section Library command. New section libraries may also be created. The File > Configure > Library Viewer command is convenient for viewing library contents files, in addition to ancillary and guy library files.
Section Library MStower’s library files must have no more than 8 characters in their file name and have the file name extension “lib” (e.g. As.lib, Uk.lib). They cannot be listed, printed, or edited. For each library file there is a corresponding source file, an ordinary text file having a file name extension “asc”. Library source files may be manipulated by the Section Library Manager or a text editor. Section Name Each section has a unique section name with up to 15 characters. Blanks are not permitted. The section name must have one contiguous alphabetic group between 1 and 4 characters long. This is the section mnemonic. Section Mnemonic The section mnemonic is used in MStower for specifying sections to be chosen automatically in design. It is embedded in the section name and, apart from “X”, is the only part of the name that may be alphabetic. An “X” character contiguous with the section mnemonic is part of the MSTower V6
13:Editing the Section Library • 229
section mnemonic. Apart from the section mnemonic, “X” characters with numeric characters before and after may be included in the section name. Examples of valid section names are, “200UB25.4”, “88.9X2.6CHS”, “CTT380X100”, “100XX”, “XX100”, and “W14x311”. Invalid names include “200UB25.4H1” (two separate alphabetic groups), “CTT380X100X” (trailing X), “X200UB25.4” (leading X), and “XXBOX100” (mnemonic exceeds 4 characters). When adding new sections to a library you may choose any suitable section mnemonic. A single character “E”, however, cannot be used as a section mnemonic because the section name would then be confused as a number in exponential format. Design Type For design purposes each section is classified according to its design type. The design type number is shown in the library source file under the heading DT. The design type is used to interpret the section properties and it determines the applicable design code rules. The table below lists valid design types, together with some of the common section mnemonic codes for these types. DT
Mnemonic Section Type
1
TFB
Taper flange beam
2
UB, WB
Universal beam or welded beam
3
UC, WC
Universal column or welded column
4
RHS
Rectangular hollow section
5
SHS
Square hollow section
6
CHS
Circular hollow section
7
PFC
Parallel flange channel
8
BT, CT
Tee section
9
EA, L
Equal angle
10
UA, L
Unequal angle
11
DAL
Double angles, long legs together
12
DAS
Double angles, short legs together
16
STA
Starred angles
22
QAN
Quad angles
13
UBP
Universal bearing pile
17
TFC
Taper flange channel
18
ROD
Round
19
BAR, FLAT
Rectangular bar
20
CTT
Double channels, toes together
21
CBB
Double channels, back-to-back
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24
CA
(DuraGal) cold-formed angle
25
POLY
(DuraGal) cold-formed channel
26
POLY
Regular polygon with 6 sides
27
POLY
Regular polygon with 8 sides
28
POLY
Regular polygon with 10 sides
29
POLY
Regular polygon with 12 sides
30
-
31
POLY
Regular polygon with 16 sides
32
POLY
Regular polygon with 20 sides
37
ASX
60º (Schifflerized) angle
38
VU
60º channel
Section with analysis properties only
Steel Grades MStower does not use steel grades. The library contains two yield stress values for each section – if the second is not used it is input as zero. Residual Stress Code Some design codes (e.g. AS 4100) require information about the level of residual stresses in a section. This is provided by the parameter designated “f”. It is also used to distinguish between cold-form and hotrolled sections with the same design type (e.g. Schifflerized angles). f
Section Type
1
Stress relieved
2
Hot-rolled
3
Cold-formed
4
Lightly welded
5
Heavily welded
60º (Schifflerized) Angles MStower section libraries may contain both cold-formed and hot-rolled Schifflerized angles but member checking may not be available for these sections in all design codes. Section Library Manager allows you to change any equal angle to a Schifflerized angle. You may right-click on any of these sections in the destination library and choose the Schifflerize command on the pop-up menu. 60º Channels The VU section is a cold-formed channel whose flanges are bent through 60º, rather than 90º. This section may appear in MStower section libraries but member checking may not be available for these sections in all design codes.
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60º SECTIONS
Compound Sections Compound sections made up of angles or channels are available as shown in the diagram below. Section Library Manager allows you to change an angle or channel to a compound section. You may right-click on any of these sections in the destination library and choose the required compound section type in the pop-up menu.
COMPOUND SECTIONS
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Section Library Manager Library source files may be manipulated with the section library manager. As MStower may refer to libraries in three locations, the first step is to choose the folder containing the destination library.
CHOOSING FOLDER FOR DESTINATION LIBRARY
Then you enter the name of a new library in this folder or choose the name of an existing library. Valid library source files have no more than 8 characters in the file name (excluding the .asc file name extension).
ENTERING NAME OF DESTINATION LIBRARY
You may edit any library source file supplied but it is preferable to copy it to a new library and edit that – otherwise, you will lose your changes when you next update library files.
MSTower V6
After you have selected the destination library, either an existing library source file or a new one, the dialog box below is displayed. A tree view of the destination library, empty if new, is shown on the right while all available library source files are shown on the left. Each library may be expanded to show the sections contained.
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SECTION LIBRARY MANAGER
You may select any library or section on the left and click the arrow button to send it to the destination library on the right. Double-clicking a section on the right will display a dialog box in which you may alter any value. When the section library manager combines sections from existing libraries units are automatically converted to those of the destination library. Example In the following example an angle section from the UK library is added to a pole library.
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1.
Start the section library manager and select the existing pole library as the destination file.
2.
Select the source library, Uk.asc, and expand to display section names. Select the desired angle section, say EA100x100x8.
3.
Click on the green arrow button to add the angle section to the pole library.
4.
Click OK to save and compile the library file.
MSTower V6
Section Properties Dialog Box The properties of any section in the destination library may be displayed by right-clicking the section and choosing Section Properties on the popup menu. Double-clicking the section will also display the section properties dialog box. The dialog box shows all the values stored in the library for the section. Any values that are not disabled in the dialog box may be changed. Click the button at the top and then click on any item for help. Clicking the Compute button computes all derived values from the current dimensions. The Restore button sets all edit boxes back to their original values.
SECTION PROPERTIES DIALOG BOX FOR EQUAL ANGLE
Section property dialog boxes for some sections have an Ax, Ay button, which computes shear areas. For an I section Ax is computed as the nett web area and Ay is computed as 5/6 of the flange area. For SHS, RHS, and box sections, Ax is the nett “web” area where the web is considered to include both sides. Similarly, Ay is the nett area of the top and bottom “flanges” – this does not include overhang in the case of the box section. Note: Shear areas are usually set to zero, causing MStower to ignore shear distortion.
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Compiling a Library When you click the Save button you can initiate the compilation of the library source file into an MStower library. Click Yes in the dialog box below to do this.
COMPILING THE LIBRARY
The library compiler reads and interprets the library source file and writes an MStower library file. The value of any section property value input as zero is computed automatically provided sufficient dimensions for the calculation have been input.
Editing a Library with a Text Editor MsEdit has powerful “column editing” facilities like those in Microsoft Word. Press the Alt key and you can make a rectangular selection that includes one or more columns.
The File > Configure > Edit Section Library command may be used instead of the Section Library Manager to edit section library source files directly. This command allows you to add section properties to library files or to generate new library files using a text editor, MsEdit.
On selecting the above command, a dialog box is displayed for you to choose one of the library source files. These are displayed with a prefix, “Prog:”, “Data:”, or “Libr:”, indicating the folder in which each is located. The MsEdit text editor then starts for you to edit the selected file. When you close MsEdit a message box asks if you want to make the library file. Answer Yes for MStower to create the new library file. There are template records in the library source file specifying the format for each design type. The value of any section property input as zero is computed automatically provided sufficient dimensions for the calculation have been input. In these calculations, fillets and chamfers are neglected. For compound sections, dimensions are for a single component. Note: You should be careful when directly editing a library source file not to introduce errors. It is safer to use Section Library Manager.
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Library Viewer The File > Configure > Library Viewer command allows you to see several library files simultaneously. This is helpful when editing TD files, allowing you to refer to section, ancillary, and guy libraries in several locations. The Library Viewer window displays the names all text files in the Program, Data, and Library folders. To open any of the listed files in a new MsEdit window, double-click on its name.
LIBRARY VIEWER
The image below shows an MStower window overlaid with an MsEdit window from the Tower > Build Tower > Edit Tower Data File command, the Library Viewer window, and MsEdit windows for a section library and guy library in the Program folder. The Library Viewer window and MsEdit windows will be hidden by clicking the MStower window. Any of these windows may then be brought to the front of the display by typing Ctrl+Tab. The Library Viewer may be closed or minimized at any time to save screen space.
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DISPLAYING LIBRARIES WHILE EDITING TD FILE
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14:Reports
Report Types MStower can create report files at several stages during the building, loading, analysis, and checking of a tower. Commands for printing or displaying reports show the dialog box below, in which there is a button for each available report. If the button is disabled it means that the report file does not yet exist. Each report is discussed in this chapter. Input files, such as the TD and TWR files may also be displayed or printed from this dialog box.
SELECTING A FILE FOR DISPLAY OR PRINTING
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Display and Printing of Files The commands used for display and printing of files are: File > List/Edit File This command is used for displaying or editing a file in MStower’s text editor, Msedit. It is possible to print files with this command but it is usually better to use the File > Print File command. File > Print File This command allows you to print files as neatly formatted reports. The formatting is controlled by the Page Setup command, which allows you to set page orientation, margins, text size etc. File > Print Preview This command allows you to check a report and its formatting before printing it.
Input/Analysis Report The Input/Analysis report is obtained at any stage by selecting the Reports > Input/Analysis command. The dialog below then allows you to select the items you require in the report.
SELECTING REPORT OPTIONS
The Input/Analysis report is not available if you attempt to include reactions after gust factoring. To obtain the reactions after gust factoring you must use the Member Check > Reactions command.
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Error Report The Error report file, containing a list of geometry errors, is created automatically when errors are detected prior to analysis. The Analysis > Check Input command will also create this report file when errors are detected. Error Report File Microstran consistency check Job: "XM3H" checked on 31-OCT-05 12:48:44 -----------------------------------------Error: member 1 property 111 undefined Error: member 2 property 111 undefined Error: member 3 property 111 undefined Error: member 4 property 111 undefined Error: member 25 property 8 undefined Error: member 26 property 8 undefined Error: member 41 property 111 undefined Error: member 42 property 111 undefined Error: member 43 property 111 undefined Error: member 44 property 111 undefined Shortest member: 25, length: 1.2673 Longest member: 126, length: 3.5830 24 error(s), 0 warning(s) ----- end of report -----
Static Log The static log is a file created during linear or non-linear analysis that lists several analysis parameters, including the condition number, a measure of the numerical quality of the analysis.
Dynamic Log The dynamic log is a file created during dynamic analysis that lists several analysis parameters, including the natural vibration mode frequencies.
Design Summary The design summary report file contains a summary of the results of any member checking operation including those performed by the Member Check > Reactions and Member Check > Ancillary Rotations commands. It reports the critical load case and condition for the various member classes in each panel. It also contains a table of quantities and may note any geometric or other problems encountered during the checking process. Where possible, symbols similar to those in the particular code of practice to which the check is done are used in the report.
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Detailed Design Report The detailed design report is automatically produced by the member checking modules. It reports the information for all load cases and for every member in the tower. It may be used to check the calculations for any member but is generally too voluminous to print.
Reaction Report The reaction report file is created by the Member Check > Reactions command and appended to the Design Summary report. It contains the reactions at the tower supports in the global axes and also transformed into the direction of the individual leg axes.
Rotation Report The rotation report file is created by the Member Check > Ancillary Rotations command and appended to the Design Summary report. It is in two sections: •
A rotation envelope giving maximum rotations about the global axes for the selected load cases. These rotations are computed by considering the displacement of a plane through the leg nodes at the top of each panel.
•
The rotation of each large ancillary for each selected load case. The rotations are computed by considering the displacement of a plane through the first three attachment nodes and are given in the axes of the ancillary.
The tabulated rotations are those due to deflection of the tower. They do not account for any deflection in the ancillary mounting items.
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15:Examples
General Use the following procedure to run an MStower job: 1.
Start MStower (see “Starting MStower” on page 11).
2.
Select the File > Open command and in the dialog box browse to the Examples folder (see “Folders” on page 10). Choose one of the example jobs, say TWEX1, and then click the Open button. The tower should now be displayed – if not, select the Tower > Build Tower > Process Tower Data File command
3.
Select the Tower > Build/Load/Analyse command.
4.
Close the analysis window when it displays “Linear analysis completed”.
5.
If checking to BS 8100 select the Tower > Gust Factor command.
6.
Select the appropriate design code on the Member Check menu. If checking to BS 8100, select only the first load case of each set of combinations as the results of the gust factoring and square root of the sum of the squares is written to this case.
7.
Select the Results > Design Ratios command and the structure will be displayed with overstressed members colored red.
8.
To display the results of the member checking select the File > List/Edit command and then click either the Summary or Detailed button. The selected report file will now be displayed in the MsEdit text editor. You may use the File > Print Preview command to see each page of the report, exactly how it will appear when printed.
To run a mast job, proceed as set out above but when the Analysis Load Cases dialog box appears select Case 100 and all combination load cases. When the Non Linear Analysis Parameters dialog box is displayed click OK to accept the default values. The non linear analysis required for masts takes longer than linear analysis. To run an existing MStower Version 4 job select the File > New command, confirm the job file folder, enter the job name and then proceed from Step 3, above.
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When MStower is installed a number of job files are located in the Examples folder (see “Folders” on page 10). These jobs, which have simplified data and loading files, are described below. Plots are shown on the previous page. Analysis of masts requires the catenary cable option and non-linear analysis. Example Towers TWEX1 – A plain tower to illustrate member checking to BS 8100. TWEX2 – A communications tower composed of standard panels with a number of linear, large, and face ancillaries. TWEX4 – A power line tower using UDPs with asymmetrical crossarms. TWEX7 – A 152 m guyed mast to illustrate member checking to BS 8100 Part 3.
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EXAMPLE TOWERS
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TWEX1 This example is a plain tower for checking to BS 8100.
TWEX1
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TD File – TWEX1 TITL1 TWEX1 TITL2 UNITS 1 $ Metric units ---------------------------PROFILE FACES 4 WBASE 2.000 RLBAS 0.0000 $ Section 1 -----------------------------------------PANEL 1 HT 1.000 TW 1.500 FACE DR LEG 1 BR1 5 H1 4 BOLT BR 1 M16-8 H 1 M16-8 PANEL 2 HT 1.000 FACE DL0 LEG 1 BR1 5 PANEL 3 HT FACE DR PLAN PL1A BOLT LEG
1.000 LEG 1 BR1 6 H1 6 PB1 0 PB2 4 PB3 0 4 M16-8 BR 1 M16-8 H 1 M16-8 PB 1 M16-8
$ Section 2 -----------------------------------------PANEL 4 HT 1.000 FACE DL LEG 2 BR1 6 H1 8 BOLT LEG 0 PANEL 5 HT 1.000 FACE DR LEG 2 BR1 6 H1 8 PLAN PL1A PB1 0 PB2 4 PB3 0 PANEL 6 HT 1.000 FACE DL LEG 2 BR1 6 H1 0 PANEL 7 HT 1.000 FACE DR LEG 2 BR1 6 H1 0 PANEL 8 HT 1.000 FACE DL LEG 3 BR1 7 H1 0 BOLT LEG 4 M16-8 $ Section 3 -----------------------------------------PANEL 9 HT 1.500 FACE K LEG 3 BR1 5 H1 8 BOLT LEG 0 PANEL 10 HT 1.500 FACE K LEG 3 BR1 5 H1 8 PLAN PL1A PB1 0 PB2 4 PB3 0 PANEL 11 HT 2.000 FACE K LEG 3 BR1 7 H1 8 BOLT LEG 4 M20-82
$ Bolts in double shear
END SECTIONS LIBR P:UK IFACT .001
$ Use UK if library is in the data area $ IFACT Load Tower > Process Ancillary DB File command. This command will not be available unless a tower geometry has been built and the CSV file exists in the data folder. The prototype TWR file, Ctistd.twr must be present in the data folder and the geometry of the structure must have been created. A tower loading file is output. When CTIDATA is run a number of dialog boxes are presented for you to choose codes and enter parameters that will be substituted into a copy of the prototype TWR file. A set of wind angle and load combinations is entered for generation of a new LOADS block. All wind load directions are referred to the tower X axis, simplifying the generation of face and corner winds. Any or all face or corner wind directions may be chosen. In addition, for triangular towers, winds parallel to faces may also be chosen. Any large ancillary data in the prototype file is replaced with data derived from the CSV file. If the tower loading file exists before CTIDATA is run, only the large ancillary data will be replaced. The PARAMETERS and LOADS blocks will be unchanged and previously existing ancillary loads will be commented out and remain in the file for possible future reference. Arrangements may be made to customize this program to user requirements.
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Index
A ACCEL keyword 168 Accelerator keys 133 Additional member temperatures 167 Additional node loads 167 AICE keyword 174, 178 ALTOP keyword 150 AMASS keyword 175 Analyse menu 26 Analysis Buckling 204 Dynamic 207 Elastic critical load 204 Linear 197 Non-linear 197 Response spectrum 209 Second-order 197 ANCILLARY block 171, 186, 188 Ancillary libraries 186 Ancillary rotations 242 ANGLE keyword 153, 154, 155, 156, 157, 158, 163 ANGLX keyword 163 ANGN keyword 149 Archive file 41 AREA keyword 174, 177 ARES keyword 177 ATTACH keyword 176 Attributes toolbar 34 AutoCAD 192 Axes 40
B BARE keyword 167 Basic velocity 152 BH keyword 56 Blocks ANCILLARY 171 BOLTDATA 58 MStower V6
COMPONENT 45 EXTERNAL 162 GUYLIST 161 GUYS 54 LOADS 162 MATERIAL 58 NODENAME 160 PANEL 170 PARAMETERS 148 PROFILE 46 PVEL_GUY 160 PVEL_MAST 160 SECTIONS 55 SUPPORTS 53 TERRAIN 153 Title 45 VELOCITY 159 BOLT keyword 47 BOLTDATA block 58 Boundary 139 Break line 129 BRES keyword 177 Buckling 204
C Cable 200 CAD DXF 191 CN keyword 178 CODE keyword 149 COEFFICIENTS block 187, 189 Colors 14 COMBIN keyword 170 Combination load cases 170 Compiling a library 236 COMPONENT block 45 Condition number 241 Configuration 14 CONNECT keyword 56 Connections 60 Context menu 12, 128, 134 COORD keyword 53 Coordinate systems 40, 129 Coordinates 128 CROSS keyword 51, 163 Cross-arms 77, 115 Crossing window 133 Ctrl+A 133, 134 Ctrl+C 133 Ctrl+V 133 Ctrl+X 133 Ctrl+Y 133 Ctrl+Z 133 Cursor 132 Customize 37 Index • 255
Cylindrical coordinates 129
D D & V face panels 78 Damping 152 Data tip 21 Dead loads 166 Deflections 182 Delete 133 DENS keyword 58, 166 Design summary 241 Design type 230 Detailed design report 242 Detailing 192, 228 Display toolbar 33 DLM face panels 102 DLM2 face panels 102 DM face panel 100 DM2 face panel 100 DMH face panels 101 DMH2 face panels 101 Double-click 13, 134 Draw toolbar 34 Drawing 128 Drawing plane 131 Duplicate members 131 Duplicate nodes 131 Dynamic amplification 183 Dynamic analysis 207 Dynamic log 241
E E keyword 58 Earthquake loading 168 ECL 204 Editing a section library 236 Effective length 204 Elastic critical load analysis 204 ELF1 keyword 169 EMA2 keyword 169 E-mail 19 EMF 193 End line 130 EQ keyword 168, 169 Error report 241 Errors 41 Example 65, 66, 67, 68, 70, 140 Examples 11 Explorer 13 Export Archive file 41 DXF 191 SDNF 192 256 • Index
EXTERN keyword 164 EXTERNAL block 162 EXTFACT keyword 162 Extra Buttons toolbar 36
F F5 133 Face ancillaries 171, 174 FACE keyword 48, 174 Face panels 72 Face Panels D & V 78 DLM 102 DLM2 102 DM 100 DM2 100 DMH 101 DMH2 101 K 84 KXM 103 KXM2 103 M 94 W 96 X 79 XDM 99 XDMA 99 XM 98 XMA 98 Face results 178 FACES keyword 46 FACT keyword 173, 175 File menu 22 File type 13 Fixed-end actions 199, 200 Folders 10 Frame buckling 203 FREQ keyword 151
G GFACT keyword 164 Graphics input 122, 127, 140 GRAV keyword 151 Gust factor correction 179 Guy library 61 Guyed mast patch loadings 165 GUYLIST block 161 GUYS block 54 GUYS keyword 61
H Hardware lock 9 MStower V6
Help About dialog box 19 Help menu 31 Help toolbar 33 Hip bracing 77, 112 HIP keyword 50 Home 133 Hot-links 19
I ICE keyword 150, 163, 166 Ice loads 166 Icon 187 Import Archive file 124 DXF 192 UDP 128 Input load case 21 Input/Analysis report 240 Instability 203 Installation 9 Insulators 171, 177 INSULATORS keyword 177 Interruptible commands 132
J Job size 14 Joints 60
K K face panels 84 KXM face panel 103 KXM2 face panel 103
L Lambda 204 Large ancillaries 171, 175 LARGE keyword 175 Launch 13 LIB keyword 54, 172, 175 LIBR keyword 55 Library Ancillary 186 Section 229 Library Viewer 237 Limit 138 Linear analysis 197 Linear ancillaries 171, 172 LINEAR keyword 172 Loads
MStower V6
Additional member temperatures 167 Additional node 167 Dead 166 Guyed mast patch 165 Ice 166 Miscellaneous 167 Wind 163 LOADS block 162 Local axes 40, 57
M M face panels 94 Main toolbar 31 Main window 21 MASS keyword 174, 178 MATERIAL block 58 MCAP keyword 49 MEMB keyword 119 Member axes 40 Member checking 41 Member Checking menu 25 Member orientation 51 Member properties 135 Member/face table 178 Members Non-Linear 200 Menu bar 21 Menus 21 MI keyword 167 Miscellaneous loads 167 Modifying a UDP 123 Monopole 104 MsEdit 236 MTMP keyword 168 Multiple selection 136
N NDLD keyword 167 NODE keyword 119, 177 Node properties 135 NODENAME block 160 NOICE keyword 163 Non-linear analysis 197 NOPATCH keyword 164 NOWIND keyword 167
O OK/Cancel toolbar 35 Orientation 57 Output 178 Index • 257
Output window 21, 37
P Page Setup 16 PANEL block 170 PANEL keyword 47 PARAMETERS block 148 PATCH keyword 164 P-delta effect 198, 199 P-Delta effect 198, 199 Plan bracing 70, 76, 105 PLAN keyword 50 Pole SH3 104 SH4 104 Pop-up menu 12, 134 Printing in MStower 15 PROFILE block 46 Prompt 21 PVEL_GUY block 160 PVEL_MAST block 160
Q Query menu 29
R Reaction report 242 Rectangular coordinates 129 Reference axis 40 Reference node 40, 51, 57 Relative coordinates 129 Report Design summary 241 Detailed design 242 Dynamic log 241 Error 241 Reaction 242 Rotation 242 Static log 241 Report files 228 Reports 239 Reports menu 27 Residual stress code 231 RESISTANCE keyword 177 Resistance table 178 Resistances 176 Response spectrum analysis 209 Results menu 27 Results toolbar 35 Right-click 128, 134 Rotation report 242 258 • Index
Rotations Ancillary 242
S Schifflerized angles 231 SDAMP keyword 151 SDNF 192 Second-order analysis 197 Section alias file 193 Section axis 57 Section library 18, 229 Section Library Manager 233 Section mnemonic 229 Section name 229 Section properties 235 Sections 41 SECTIONS block 55 Select members 133 Select nodes 133 Selection box 133 SELF keyword 173 Serial number 19 SH3 pole 104 SH4 pole 104 SHADE keyword 173, 175 SHEFF keyword 173, 175 Shortcut 13 Shortcut keys 133 Show menu 28 SMEAR keyword 164 Snap mode 21, 130 Grid 130 Intersection 130 Mid/End 130 Nearest 130 Orthogonal 130 Perpendicular 130 Space 133 Spherical coordinates 129 Static log 241 Status bar 21 Steel detailing 192, 228 Steel grade 231 Steel poles 62 Stretch 137 Structure menu 25 Subset 138 Support 19 SUPPORTS block 53
T TD file 39, 43, 44, 65, 66, 67, 68, 70 Technical support 19 MStower V6
TEMP keyword 168 Tension-only 200 TERRAIN block 153 Text editor 39 Text file 39, 229 Title block 45 TMASS keyword 176 Toolbars 21, 36 Reset 36 Tower menu 24 TRES keyword 177 Troubleshooting 203 TWR file 39
Y Yield stress 231
Z ZF keyword 159 ZGUST keyword 164, 179 ZGUST2 keyword 164 ZREF keyword 161
U UDP example 140 UDP file 39 UDP file names 125 UDP from Microstran 124 UDP keyword 118 Unequal leg length 123 UNICE keyword 164, 167 Units 40
V VB keyword 150 VELOCITY block 159 Velocity table 178 View menu 23 View toolbar 32
W W face panels 96 Web update 20 WIND keyword 166 Wind load cases 163 Wind resistance 179 Window 138 Window menu 30
X X face panels 79 XDM face panel 99 XDMA face panel 99 XM face panel 98 XMA face panel 98 Xsteel 192, 228
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Index • 259
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