Concrete Slabs En
March 13, 2017 | Author: Stavros Pitelis | Category: N/A
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Description
2D Concrete design-EC2
All information in this document is subject to modification without prior notice. No part or this manual may be reproduced, stored in a database or retrieval system or published, in any form or in any way, electronically, mechanically, by print, photo print, microfilm or any other means without prior written permission from the publisher. Scia is not responsible for any direct or indirect damage because of imperfections in the documentation and/or the software. © Copyright 2008 Scia Group nv. All rights reserved.
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Table of contents Abstract ..............................................................................................................................................1 2
Global settings ........................................................................................................................2
2.1 Project data ......................................................................................................................2 2.2 Setup manager.................................................................................................................3 2.3 Manager of National Annexes ........................................................................................4 2.4 Concrete solver setup .....................................................................................................6 2.5 Design Defaults ...............................................................................................................7 2.6 Concrete Setup action button ........................................................................................7 2.7 Tips & tricks .....................................................................................................................8 2.7.1 Filters .........................................................................................................................8 2.7.2 User defined defaults ...............................................................................................11 2.7.3 Save and loading of global settings to different project ...........................................13 2.7.4 Colour orientation ....................................................................................................14 2.7.5 Description pictures in setup dialog .........................................................................14 3 Concrete tree .........................................................................................................................16 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.5.1 3.1.5.2 3.1.5.3 3.1.5.4 3.1.5.5 3.1.5.6 3.1.3 3.1.3.1 3.2 3.2.1 3.2.2 3.2.2.1 3.2.2.2 3.4.3 3.4.3.1 3.4.3.2 3.4.3.3 3.4.4 3.4.4.1 3.4.4.2 3.4.4.3 3.5 3.6 3.6.1 3.6.2 3.6.3 3.6.3.1 3.6.3.2 3.6.3.3 3.6.3.4 3.6.4 3.6.4.1
Member data ..................................................................................................................16 In general .................................................................................................................16 Type .........................................................................................................................18 Different layers per side ...........................................................................................19 Layers in the centre .................................................................................................20 Advanced mode .......................................................................................................20 Basic data ........................................................................................................20 Longitudinal ......................................................................................................24 Concrete minimal cover ...................................................................................28 Creep coefficient ..............................................................................................29 Position of reinforcement direction arrows .......................................................29 Action buttons ..................................................................................................29 Tips & tricks .............................................................................................................30 Member data labels .........................................................................................30 Member Design ..............................................................................................................32 Design properties.....................................................................................................32 Internal Forces ULS .................................................................................................44 In general .........................................................................................................44 Tips & tricks......................................................................................................46 ULS ..........................................................................................................................58 Theoretical background ...................................................................................58 2D Structures detailing .....................................................................................63 Reinforcement design workflow .......................................................................66 ULS+SLS .................................................................................................................73 Theoretical background ...................................................................................73 Limit bar distances ...........................................................................................78 Reinforcement design workflow .......................................................................79 Section on 2D member .................................................................................................83 2D Reinforcement ..........................................................................................................85 Reinforcement from 2D Member Data.....................................................................85 New Reinforcement¨ ................................................................................................85 Tips and tricks ..........................................................................................................88 Substraction from Required reinforcement ......................................................88 Labels ...............................................................................................................90 Editing the reinforcement parameters ..............................................................92 Editing the shape of the reinforcement region .................................................92 Free bars..................................................................................................................92 New Free bars..................................................................................................92 3
3.6.4.2 Explode to free bars .........................................................................................94 3.6.4.3 Free bars user reinforcement...........................................................................95 3.7 Averaging strip ..............................................................................................................97 3.8 Code Dependent Deflections (CDD) ..........................................................................102 3.8.1 Introduction ............................................................................................................102 3.8.2 In general ...............................................................................................................102 3.8.3 Example .................................................................................................................106 3.8.3.1 Stiffness presentation ....................................................................................109 3.8.3.2 Deformations ..................................................................................................110 References .....................................................................................................................................112
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Abstract Scia Engineer software enables the user to design and check 2D member reinforcement. The main possibilities of the design and checks are presented in the table below. Steps of design and checks for 2D members
Concrete tree for 2D members
The aim of this document is to describe each step of the design and check of a 2D member and to describe some of the tips and tricks which might be important and useful in each part.
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Global settings
Global settings represent a set of parameters which are default values for the design of the whole structure in the project. The user can use these default values, change them or simply create his own sets of parameters reflecting his preferences and needs. General settings can be accessed in several ways: o Project data o Manager of National annexes o Setup manager o Concrete solver o Design defaults in Concrete tree o By pressing action button Concrete setup in Concrete tree > Member design
2.1
Project data
The first possibility to change the global settings of the project is through the project dialog. You can switch between national annexes by National annex button. Each annex has some differences from the Standard EN. After clicking the Edit button next to the name of the annex, the Manager of National annexes dialog is displayed, containing all the implemented national annexes. The Project data dialog for Code EN 1992-1-1 and Standard EN annex is displayed below
Default reinforcement and concrete material for EN Code
Starting from Scia Engineer version 2010, the default reinforcement and concrete material is set directly in Project data dialog. After checking the concrete material check box, the possibility to choose the default concrete and reinforcement material is activated.
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For Eurocodes only one default common material is defined for beams, columns, walls or slabs. This is different from other Codes where for each mentioned member type a separate default material must be defined in the global settings. If we want to change any material for some specific member, we need to define its local settings somehow. We can do this by creating Member data or Punching Data on the member.
2.2
Setup manager
Starting with Scia Engineer 2010, a new library called Setup manager is created. It can be accessed from: o Main tree > Libraries > Setup o Menu > Libraries > Setup Tree
Menu
The user can edit the default settings for all materials in the Setup manager dialog. Each country has its predefined set of parameters. The user is able to create his own set of values with default values he requires. He might also change the appearance and the number of items in the settings of each material. It is possible to work with the items as with any items of a library, so the user can edit, copy, save and load to/from file, etc. It is not possible to switch the national annex here; this action can be done only in the Project dialog or in the Manager of national annexes dialog.
After clicking the Concrete edit button in the Setup manager dialog, the Concrete setup dialog appears. This dialog displays all global parameters for the concrete without parameters specified by the national annex.
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2.3
Manager of National Annexes
It is possible to edit national annex parameters only through this dialog in Scia Engineer. The Manager of national annexes dialog can be displayed in three ways: o Main tree > Project > National annex o Menu > Tree > Project > National annex o
By pressing second flag icon representing the country of the annex in the bottom right corner of the screen Tree
Menu
Flag icon (Czech)
The Manger of National annexes dialog is a library. The content of items is the same as the content of items in Setup manager. It is the same library and the only difference is that parameters are filtered according to some filter applied. It is also possible to get more detailed information about implemented Codes and national annexes in the Manager of National annexes. This can be done via button References.
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By pressing the Edit button ( ) for example for editing of national annex parameters in EN 1992-1-1 (General rules and rules for buildings), another dialog appears, where all appropriate implemented parameters are displayed.
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2.4
Concrete solver setup
Code dependent values (except for national annexes parameters) and Code independent values which influence design and check of concrete structures can be edited in the Concrete setup dialog which can be displayed through Menu > Setup.> Concrete solver.
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2.5
Design Defaults
This is the first item in the concrete tree, and it is possible to set here the default values for member design (such as concrete cover, reinforcement diameters, direction angles, etc.), and also parameters for drawing of user reinforcement.
2.6
Concrete Setup action button
Global settings for design of the reinforcement are adjustable through Concrete setup action button too, which is located in Properties window of both concrete tree and service for defining local parameters.
The main advantages of this action button dialog are: o Only parameters for actual design are displayed 7
o Parameters from all dialogs are displayed o NA parameters from Manager of national annexes dialog o Code independent/dependent values from Concrete solver setup dialog o Default parameters from Design default dialog
2.7
Tips & tricks
Here are some tips and tricks, which might some users find useful and which should provide better overview in the global settings.
2.7.1
Filters
There are quite a many global concrete parameters which influence reinforcement design. To simplify the overview of the global settings, the user may use filters which will restrict the number of displayed parameters. Parameters can be sorted according to these filters: Type of members This filter is activated only in the case that both 1D and 2D members are defined in the project. Then the user may choose from 2 possibilities below: o 1D members (only parameters that influence 1D member design are displayed) o 2D members (only parameters that influence 2D member design are displayed) Type of values Displayed filters depend on where the dialog was displayed from. o Design defaults (parameters of default design such as cover, reinforcement diameters, etc.) o Code independent values o Code dependent values (parameters from Code, without national annex parameters) 8
o Drawing settings (parameters for drawing of the reinforcement) o NA building (national annex parameters from Code EN 1992-1-1) o NA fire resistance (national annex parameters from Code EN 1992-1-2) o NA bridges (national annex parameters from Code EN 1992-2) o NA hollow core (national annex parameters from Code EN 1168) Type of functionality Displayed filters depend on the functionality checked in the Project data dialog, folder Functionality. o Prestressing (parameters for pre-stressed members design, functionality Prestressing must be activated) o Fire resistance (parameters for fire resistance design, functionality Fire resistance must be activated) o Hollow core slab (parameters for hollow core slabs design, functionality Hollow core slabs must be activated)
Type of checks Parameters of selected check are displayed. o Member data o Cross-section characteristics o Internal forces o Design o Automatic reinforcement design o ULS response o ULS design o Crack o CDD Check 9
o Detailing o Allowable stress o SaT o Punching check Displayed filters depend on the location where the Concrete setup dialog was displayed from. The dialog can be started from: Setup manager (see 2.2) All filters are displayed and active. Only national annex filters are not visible in Type of values folder. Manager of National annex (see 2.3) o Type of members filters o Type of values filters(only one, non active, national annex filter is displayed, this filter depends on selected Code ) o Type of functionality filters (active only for EN 1992-1-1 Code) NA for EN 1992-1-1
NA for EN 1992-1-2
NA for EN 1992-2
NA for EN 1168
Concrete solver setup (see 2.4) o Type of member filters o Type of values filters(only Code dependent/independent filters are displayed) o Type of functionality filters Design defaults (see 3.1) o Type of members filters o Type of values filters(only Design defaults and Drawing setup filters are displayed) o Type of functionality filters Concrete setup action button This filter depends on the design service that is currently active and may differ from each other. Only one Design filter is displayed in the SLS design, Crack design filter is added in the SLS+ULS design. Setup manager
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Concrete solver setup
Design defaults
Concrete setup action button (SLS)
2.7.2
User defined defaults
The big advantage of new global settings is the possibility to adjust the global settings to the needs of each user. The layout of the Global parameters can be edited in the Concrete setup dialog by right-clicking on the window with the parameters (the window on the right side). After selecting Edit layout properties, the only possibility from the opened menu, the Property layout manager dialog is displayed.
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We have created a new user layout named User1, where we copied all available parameters and switched off some parameters in group Concrete > Design defaults > Concrete cover. The user may adjust the default layout or simply create a new one using the edit buttons in the middle. After the editing is finished, it is necessary to have check box Show current layout selected. Then this layout will be added to the form of folder Concrete setup dialog. The user may also create more layouts and switch among them. He still may use the default layout by checking check box Show native layout.
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2.7.3
Saving and loading of global settings to different projects
As it was mentioned in a chapter above, the global settings for Code EN are since the Scia Engineer 2010 version implemented as a library, which enables the user to transfer global settings of one project to another. Export and import of global settings is possible through the following two icons in Setup manager or in Manger of National annexes dialogs. o Save to file o Read from file The result of export or import will be the same in both dialogs, because the library is still the same and the only difference is the applied filter in each dialog.
Note
Default global setting (SetupManager.db4 file) is placed in Scia/db folder, together with all other db4 files.
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2.7.4
Colours
For better overview and simplified orientation in the global settings, some of the parameters are marked with colour, where: Blue coloured parameters are those which might be changed using local setting through o Member Data o Punching Data o Green coloured parameters are National annex parameters
2.7.5
Description pictures in setup dialog
Pictures in the global settings dialogs are very useful and might be important for more enhanced description of the desired parameter. On the other hand these pictures take some space in the dialog and might not be so important especially for more experienced users. To avoid any disturbance by displaying those pictures it is possible to turn them off. This can be done in Options dialog (Menu > Setup > Options > Environment), by unchecking the indicated check box. Pictures in the Properties will be turned off too.
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Concrete tree 3.1
Member data
3.1.1
In general
By creating the member data, the user will overwrite default global settings with local settings defined for selected members. Simply said, where the user doesn’t want to use the global concrete settings, the user creates local concrete settings by defining member data. We recognize two types of these local settings for 2D concrete members: o Member data o Punching data These member data may be created by selecting these two items in the Concrete tree and choosing the proper 2D member, where this data are to be defined. These newly created settings will be loaded from the default global settings and can be changed to fit the user needs.
After selection of a 2D member or 2D sub region the Concrete 2D data dialog is displayed and local settings may be defined and confirmed.
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When member data are created, a new folder will appear in the member properties and will be shown in Attributes of the member too.
After the definition of Member data a graphical mark (label) is displayed together with the arrows describing reinforcement directions on the member. After clicking on these marks the user can edit the appropriate attributes in the member properties window. Content of the label can also be edited through the Concrete folder in the View parameters setting dialog.
Orthogonal.,2 directions, same layers
User .,3 directions, different layers 17
The local settings were changed since Scia Engineer version 2010 into attributes. This change enables the user to edit these settings directly through the properties of the selected member. It is possible to manipulate with these settings as with all others attributes by functions Copy attributes and Move attributes in: o geometry manipulations toolbar
o member menu after choosing attribute and right clicking
It is possible to edit these parameters in Member data.
3.1.2
Type
This represents the 2D member type. Default value depends on the type defined in the member’s properties.
There are three types supported for this attribute (plate, wall, shell). The change of type of the attribute does not influence the analysis model, but influences only the presentation and definition of the parameters in the member data properties. In the table below Member data properties for each type selected are displayed, without the advance mode being activated. Plate Wall Shell
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From the table above it is obvious that the type: o Plate enables the user to define different parameters for each member surface (upper, lower) by check box Different layers per side, but it is not possible to define only one layer of the reinforcement in the centre by check box Layers in the centre. o Wall does not enable the user to define different parameters for each member surface (upper, lower) by check box Different layers per side, but it is not possible to define only one layer of the reinforcement in the centre by check box Layers in the centre. o Shell enables to define different parameters for each member surface (upper, lower) by check box Different layers per side and it is also possible to define only one layer of the reinforcement in the centre by check box Layers in the centre.
3.1.3
Different layers per side
This attribute enables the user to define different parameters for upper and lower surfaces and its reinforcement layers. By activating this attribute the user will be able to define different reinforcement material, different directions and different diameters for each surface. This attribute is available only when the Type is set to Plate or Shell. Different layers per side off
Different layers per side on
As you can see the original tree item Longitudinal is divided into item Upper and Lower. If an advanced mode will be activated too, then another items Number of reinforcement layers and their directions will be added.
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3.1.4
Layers in the centre
In the real life project we come across 2D members which have very small thickness, which does not allow for defining reinforcement layers for both surfaces. It is necessary to design only one layer of reinforcement which lies in the centre of gravity of the member. It is possible to design only one layer of reinforcement by activating attribute Layers in the centre. This attribute is available only when Type is set to Wall or Shell and when it is checked, many parameters in the member data are deactivated. It is not possible to change the attribute type of reinforcement geometry attribute. Only orthogonal direction of reinforcement layers is supported. Only two reinforcement layers are allowed. One lies just above the centre of gravity location and the other one lies just bellow it. Layers in the centre with Advanced mode off
Layers in the centre with Advance mode on
3.1.5 Advanced mode This attribute is a filter for displaying the parameters in member data properties. If it is switched off, then only basic parameters from the global settings (Design defaults) are displayed together with reinforcement material parameters which might be edited. Groups Longitudinal and Minimal concrete cover with the very basic parameters are displayed. When it is activated then the user may edit all available parameters. Those parameters are sorted to a few groups:
3.1.5.1
Basic data
In this group basic attributes and parameters for reinforcement design are located. As you can see from the picture the user can edit reinforcement geometry, type of concrete cover and reinforcement materials here. Also Different layers per side, User reinforcement and User input thickness attributes are here.
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Type of reinforcement geometry There are two types of reinforcement geometry in Scia Engineer: o Orthogonal (default) where user can define only one direction angle for first reinforcement layer. The second reinforcement layer direction will always be perpendicular to the first one. The default value for the first direction angle is loaded from the global settings. o User where it is allowed to define two or three direction angles for each reinforcement layer separately. Number of directions may be edited by the same parameter in the Longitudinal folder.
Orthogonal
User 2 directions
User 3 directions
Note Minimal difference between two reinforcement directions defined directly by user, must be 30 degrees. If the difference is smaller, then the reinforcement design will end up with Error 61 (General error in input data).
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Type of cover It is possible to change the way concrete cover is calculated. Two basic types of cover are supported: o Use minimal cover enables Scia Engineer software to evaluate all appropriate parameters and calculates minimal possible cover according to the selected Code. This will be the minimal value possible. o User, where Concrete cover parameters in Longitudinal folder will be activated and user is allowed to use his own values
User reinforcement User reinforcement is defined by new parameter Basic distance in Longitudinal folder, where user defines the axial distance of reinforcement bars. It is possible to define different value for each reinforcement direction. It is possible to set this attribute ON only in the case that there is no user reinforcement defined by 2D region or Free bars on selected 2D member or its sub region.
Note User reinforcement defined by Member data is the same for the whole 2D member surface. If the user wants to change the Basic distance value only on a part of the 2D member, then he needs to create sub region where this parameter may be defined separately. If the user reinforcement is already active on a certain member and the user defines user reinforcement by 2D region or by free bars, then the user reinforcement defined in Member data will be deleted.
User input thickness Scia Engineer software enables to set different thickness for 2D member or its sub region than is defined in the model. The big advantage of this feature is that it is possible to run reinforcement design for different thickness, without the need of deleting calculation results together with internal forces. The importance of this function is directly proportional to the size of the structure, as the calculation of internal forces for large projects may take very long time. What is important is that the
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user must remember the fact that the self weight of the changed member is not adjusted by the changed thickness by this function and remains the same as originally defined. The user defined thickness of a 2D member or its sub region can be edited by new parameter Thickness. This parameter will be displayed after switching on the attribute User input thickness.
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3.1.5.2
Longitudinal
In this group there are parameters for each reinforcement direction such as number of layers in each direction, their angles, bar diameters and eventually the distances between them. Also very important parameter which influences concrete cover for each layer is here. The Longitudinal group, which defines parameters for both surfaces, may be split into Upper and Lower group if the attribute Different layers per side is switched on. The appearance of this folder may differ quite a lot depending on activated attributes and defined parameters Longitudinal 2 directions, 2 layers, user cover
Upper 3 directions, 4 layers, minimal cover
Number of directions By setting attribute Type of geometry to User, a new parameter Number of directions will be displayed in the Longitudinal group. The user is able to choose from two or three directions where reinforcement will be created. Depending on the choice, the user is able to define appropriate number of direction angles
Direction angles As it was mentioned before, these are the values with direction angles. It may be one up to three. The default value for the first direction angle is loaded from the global settings. These direction angles are used only for reinforcement layers angles definition. It does not mean that this is the angle of the first, second or third reinforcement layer. The user selects the direction for each layer afterwards.
Number of reinforcement layers The user is allowed to define more reinforcement layers for each member or sub region surface through member data. The minimal amount of reinforcement layers is set by the number of defined directions (see above). The maximal number of reinforcement layers for one surface is 10. For each reinforcement layer it is necessary to define its bar diameter, direction angle, type of cover, eventually Basic distance parameter. 24
Diameter Reinforcement bar diameter is defined only for every first reinforcement layer in each direction. The default value is loaded again from the global settings. The other layers in same direction has this parameter disabled (not possible to edit).
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Layer angle It is possible to choose from defined direction angles in this combo box. These angles were defined in the root of Longitudinal group, eventually in the root of Upper or Lower groups. Orthogonal geometry
User geometry
2 directions
3 directions
Type of cover Concrete cover, which is the distance from the outer reinforcement surface to the closer surface of the member, is determined by this parameter. This value can be automatically calculated by the software for the first reinforcement layer. This calculation will respect values from group Minimal concrete cover. The user may also define his own value of the concrete cover. For this feature, attribute Type of cover in Basic data group must be switched on. The location of other reinforcement layers depends on the Type of cover for each of them. It is possible to define different Type of cover for each reinforcement layer. The user can choose from these types: o Layer on previous layer: One layer is laid on the other one. o Cover from previous: The user defines the cover from the previous layer. The cover is measured from the surface of one reinforcement bar to the surface of the other bar. o Cover from edge: The user defines the cover from the edge of the slab. o Distance from previous: The user defines the distance from the previous layer. The distance is measured from the centre of one reinforcement bar to the centre of the other bar. o Distance from edge: The user defines the distance from the edge of the slab.
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Here is the description picture for all Types of cover. Turquoise line at the top represents 2D member surface.
Concrete cover (cu) Shows or provides place for input of the cover value.
Basic distance If the attribute User reinforcement from Basic data group is switched on, then the Basic distance parameter is active and the user may define and edit its value. As it was mentioned before, it represents the axial distance between two reinforcement bars and it is defined only for every first reinforcement layer in each direction. For other reinforcement layers in already defined direction the software sets the same value. During the reinforcement design only certain number of reinforcement layers is being input. This certain number equals to the number of defined directions. This means that if more reinforcement layers are defined in one defined direction, then the following is input for the needs of the design: o Average concrete cover calculated from all reinforcement layers in that direction ∑
,
,
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o User reinforcement area calculated from the first reinforcement layer (after assigning reinforcement layer to the direction which has already one layer defined, it is possible to edit only the concrete cover of this new layer) The conclusion from this is that more layer reinforcement models may be substituted with only one layer with the adjusted value of the concrete cover.
Note If the average concrete cover value for the upper or lower surface is equal or even bigger than half of the member thickness, the design will not be possible and it will end up with Error 61 (General error in input data).
3.1.5.3
Concrete minimal cover
In this group there are parameters that influence the value of the minimal cover calculated by the software. It is also possible to define different parameters for the upper and lower surface separately by switching on attribute Input for side. The user can edit Exposure and Abrasion classes, Type of concrete and its surface, control attributes and values for determination of Delta;cdur.
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3.1.5.4
Creep coefficient
Here in this group there are parameters related to creep.
3.1.5.5
Position of reinforcement direction arrows
Only two parameters are in this group. By editing the default values, the user can move the location of the direction arrow marks along the 2D member or its sub region. It is not possible to set coordinates outside of the 2D member or sub region.
3.1.5.6
Action buttons
Just bellow all Member data attributes and parameters, there are two action buttons which the user might sometimes find useful: o Load default values, which will restore the default settings from the global settings for appropriate parameters such as diameter, angle, etc. o Concrete Setup, which will open the dialog with the global settings, while items in this dialog are filtered according to the member type and member check.
Note Parameters in member data, with the grey background, are parameters visible only when Advanced mode is switched on. 29
3.1.3
Tips & tricks
3.1.3.1
Member data labels
If Member data are defined for a certain 2D member or its sub region, then a graphical mark (label) is displayed together with the arrows describing reinforcement directions and layers on the member. Only the name of the attribute is displayed by default (Concrete 2D data), but this description can be edited or modified in the View parameters setting dialog. It might be accessed by: o clicking by right mouse button on the graphical window and choosing item Set view parameters for all
o using icon Fast adjustment of view parameters on whole model, which is above command prompt, and selecting Setup dialog possibility
After that the View parameters setting dialog, affecting whole model, is displayed and the user can find parameters for concrete structure in folder Concrete
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Member data can be switched on or off in two ways: o by checking and unchecking the check box Display label from the dialog above o by selecting Concrete label button in Fast adjustment of view parameters on whole model menu (see picture below)
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3.2
Member Design
3.2.1
Design properties
Design properties layouts for internal forces ULS, Member design ULS and Member design ULS + SLS differ from the chosen design and attributes selected by user. Internal forces ULS
ULS + SLS design
ULS design
See the description and possibilities for each of the attributes below.
3.2.1.1
Name
The user is allowed to name the design. It might be very useful for better specification and orientation, especially in the Document.
3.2.1.2
Selection
This attribute influences the total amount of members that will be taken into the specific 2D member design. There are four possibilities to be chosen from: o All (all active 2D members will be designed) o Current (only the selected 2D members will be designed) o Advanced (the user may alter the previous selection)
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o Named selection (only 2D members from a certain named selection will be designed. new attribute “Named selection” will appear in the properties)
3.2.1.3
Type of loads
By this attribute the user defines the type of the load for the design generation. There are three possibilities to choose from: o Combinations (the user may choose from all combinations) o Load cases (the user may choose from all load cases) o Class (the user may choose from all result classes) Depending on the selected type of the load, a new attribute Combination or Load cases or Class will appear on the right under this attribute. The user may select the desired Combination, Load case or Class from the filtered list here.
Note Only the Class type can be selected for ULS+SLS design.
3.2.1.4
Filter
It is possible to define the filter for adjusting the already selected type of selection. This will affect the number of 2D members taken into the design. The user may select one from six possibilities: o No (no filter will be applied) o Wildcard (the user may define the attributes for selection) o Material (the user may select a specific material) o Layer (the user may select the desired layer) o Thickness (the user may define the desired thickness) Again, after selecting one possibility a new appropriate attribute will be displayed on the right.
3.2.1.5
System
This attribute defines the used coordinate system. It is not possible to adjust this attribute. It is set to Local.
3.2.1.6
Output
This parameter affects the appearance and detail-level of the table with results which may be shown either in the preview or in the Document. There are three predefined layouts which will display different number and types of parameters and results: o Brief
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o Advanced
o Detailed
Note
The output parameter may be defined only for Type values attribute set to Required areas.
3.2.1.7
Show Errors
If this attribute is active, then error marks with appropriate numbers will be displayed in the graphical window after a non successful design. More information about the error may be found in the Calculation info dialog that opens through the Calculation info action button.
3.2.1.8
Show warnings
If this attribute is active, then warning marks with appropriate numbers will be displayed in the graphical window after a non successful design. More information about the warning may be found in the Calculation info dialog that opens through Calculation info action button.
3.2.1.9
Print explanation of errors and warnings
If this attribute is active, then a table with all errors and warnings will be displayed in the preview window. In fact two tables will be displayed. The first one will display the number of error or warning for each reinforcement type. The second one will display the error/warning description. This is the same table as in the Calculation info dialog.
3.2.1.10
Use user scale isolines
This feature enables the user to define his own scale which will affect the view of the graphical results. Simply said, the user may define his own key points on the scale. This might be very helpful for better orientation in the used types and amounts of reinforcement. By switching this attribute on, another attribute User scale isolines will appear on the right and the user may define his scale through the dialog shown below:
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Name
Specifies the name of the user scale.
New level group
In this group the user can input a new level for the isolines palette. The level is defined by the diameter of the reinforcement bar and by the distance between individual bars. The program then calculates the area of reinforcement and mean diameter and distance. One level can contain one to three different diameters, each of them with a separate spacing.
Copy to legend
When a new level is defined, it can be added to the legend using this button. The new level is positioned in the legend according to total reinforcement area of the level.
Clear level
This button clears all the edit boxes in the New level group.
Legend group
This group displays the defined levels sorted according to the total area of reinforcement in the level.
Delete active level
If required, any defined level can be removed from the legend.
Delete all
This button clears the whole legend.
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If this User scale is used, the scale in the top right corner of the graphical window will look like this:
Note
The user scale isolines feature may be used only for parameter Location set to In nodes, avg., and for Type values set to Required areas only. The user may also use the possibility to draw isolines together with labels. Together with export of the slab picture it might be very useful to transfer these pictures to different CAD systems and reinforce the entity using exported picture as reference layer. This might be used also for mesh reinforcement. Also note that the setting in the 2D result display dialog will be overwritten to User scale isolines and the possibility to choose different type of result representation will be disabled. To change this, the user must deactivate the possibility Use user scale isolines.
3.2.1.11
Averaging of peak
See more information about this feature in chapter 3.7 Averaging strip.
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3.2.1.12
Location
This parameter defines the location where the design will be calculated. This is based on FEM results. If the user changes this attribute, then Scia Engineer needs to make internal calculation of design forces. The user may choose from four possibilities: o In centres, (results represented in the centre of gravity of each element, the design value is calculated directly from “no avg.” values by arithmetic average) o In nodes, no avg. (results represented in mesh nodes, for each element separately, these are the main results which are based for all other design location possibilities) o In nodes, avg., (results represented in mesh nodes, but contrary to the “no avg.” values, all values from all adjacent 2D members in each node are recalculated by Scia Engineer before design and only one value for each node will be represented) o In nodes, avg. on macro (the same as “In nodes, avg.” possibility with one important difference. the recalculation is done only on each 2D member separately, this means that one 2D member will not be influenced by another 2D member, also note that there might be more same values) We can show the differences of the designs for example on required reinforcement amount (As1-) calculated on example from chapter ULS and ULS+SLS design. In centres
In nodes, no avg.
In nodes, avg.
In nodes, avg. on macro
37
3.2.1.13
Type values
By this attribute the user may define the type of the value he wants to be calculated and displayed. The user may choose from a drop down menu, but the content of this menu differs for Internal forces ULS, Member design ULS and Member design ULS+SLS. Internal forces ULS
Member design ULS+SLS
Member design ULS
o Basic magnitudes (magnitudes of internal forces from the FEM analysis) o Design magnitudes (magnitudes of forces used for member design) o Required areas (amount of reinforcement) o Reinforcement ratio (this is the rate between the amount of required reinforcement and concrete area) o Maximal diameters (value of maximal reinforcement bar diameter which might be used for member design) o Maximal distances (value of maximal distance between two reinforcement bars) o Shear stresses (design and capacity stresses in concrete) o Weight (weight of the designed reinforcement)
3.2.1.14
Envelope
The user may choose from two options here. He chooses from minimum and maximum envelope for displaying.
Note
This attribute is displayed only when the Type of load attribute is set to Combination or Class.
3.2.1.15
Reinforcement
The user may choose to design different types of required reinforcement area. There are four possibilities: o Required reinforcement (this is the amount of reinforcement needed for successful member design) o User reinforcement (this is the amount of reinforcement defined by the user. either practical reinforcement already defined on 2D member or reinforcement defined by concrete member data when the User reinforcement check box is active) o Additional reinforcement (this is the difference between the amount of required reinforcement and the amount of user reinforcement, i.e. this is the reinforcement needed in addition to user reinforcement to fulfil the required reinforcement) o Total reinforcement (this is the larger value of the required reinforcement and user reinforcement)
38
Note
This Reinforcement attribute is displayed only in Member design ULS or Member design ULS+SLS when the Type value attribute is set to Required areas.
3.2.1.16
Standard
This attribute is used to determine where the design will be shown in the graphical window. If this attribute is checked, then the designed values will be displayed in the centres of gravity of selected 2D members.
3.2.1.17
Section
This attribute is used to determine where the design will be shown in the graphical window. If this attribute is checked, then the designed values will be displayed on predefined sections which are defined on selected 2D members.
3.2.1.18
Edge
This attribute is used to determine where the design will be shown in the graphical window. If this attribute is checked, then designed values will be displayed on the edges of selected 2D members.
3.2.1.19
Draw
This attribute defines the direction the designed values will be displayed. It is possible to select one of the following possibilities: o Upright to element o Element plane o X direction o Y direction o Z direction
Note
This attribute is displayed only when the possibility to draw designed values on Section or Edge is checked. Also note that to make this feature functional, the user has to set attribute Draw for each 2D section to “Draw similar as for setting in section properties”.
3.2.1.20
Course
The user may also define the way of interpretation of the designed values. It is possible to choose from three possibilities. o Precise (the precise interpretation based on the mesh) o Uniform (this will display the average value for whole edge) o Trapezoidal (this will display trapezoidal distribution of the value)
Note
This attribute is displayed only when the possibility to draw the designed values on Section or Edge is checked. 39
3.2.1.21
Values
This attribute defines the final value to be displayed. The content of this drop down menu differs according to selected design and attribute. Internal forces ULS Basic magnitudes
Design magnitudes
, where values o mx, my, mxy, vx, vy, nx, ny, nxy represent internal forces from FEM analysis o n1-, n2-, n1+, n2+, vd, nc+ and nc- represent design forces. For more information about these values see chapter 3.2.2 Internal Forces ULS. Member design ULS Required areas
Reinforcement ratio
Shear stresses
Weight
, where values o As1-, As2-, As1+, As2+ represents the amount of longitudinal reinforcement for upper or lower surface in a certain direction. Asw value represents the amount of shear reinforcement. These amounts are designed for ULS. o As,perc(1/2,+/-) represents the rate between the amount of required longitudinal reinforcement and concrete area. Asw,perc represents the rate between the amount of required shear reinforcement and concrete area. o tauD represents the shear stress in concrete, tauR is the shear capacity of the concrete 2D member with longitudinal reinforcement involved. o Mass (+/-) is the weight of the upper/lower reinforcement. Mass l is the total weight of the reinforcement. o Member design ULS+ SLS Required areas Reinforcement ratio
40
Maximal diameters
Maximal distances
, where values o As1-, As2-, As1+, As2+ represents the amount of longitudinal reinforcement for upper or lower surface in a certain direction. Asw value represents the amount of shear reinforcement. These amounts are designed for SLS. o fr1-, fr2-, fr1+, fr2+ are maximal possible reinforcement bar diameters o sr1-, sr2-, sr1+, sr2+ are maximal possible distances between two reinforcement bars In Member design ULS+SLS it is also possible to design Reinforcement ratio, Shear stresses and Weight values. They are already displayed and described in Member ULS.
Note
Numbers 1 and 2, eventually 3 indicates the direction of the X axis and Y axis of the selected 2D member’s LCS. Marks + and – indicate the positive and negative direction of the Z axis of the selected 2D member’s LCS. Also note that by selecting possibility More comp the user is able to display more values at the same time in the preview window or in the Document.
3.2.1.22
Extreme
Simply said, this attribute defines which results will be shown in the Preview window or in the Document. The user may choose from three possibilities: o No (results for all elements will be displayed on selected 2D members) o Member (only elements with maximum results on each of selected 2D member will be displayed) o Global (only elements with maximum results on selected 2D members will be displayed)
3.2.1.23
Drawing setup
By selecting the edit button for this parameter, a 2D results display dialog will be open. Here the user may specify the representation of the design results on a 2D member. We can split this dialog into four zones.
41
o Display = red (here the user may define the main type of 2D design representation, he may choose one possibility from the list below)
o blue (where the user may adjust the type of the representation selected in the Display zone, the view of this zone may differ for each type) o green (here the user may define whether to show or not the local extremes and their style) o yellow (it is possible to adjust the range of the scale and user defined isolines)
3.2.1.24
Action buttons
In the lower part of the Properties dialog there are a few action buttons. The user may find these buttons very useful.
42
o Refresh (this button is probably the most important from all of them. It will start the process of design itself and it must be pressed to refresh the previous design results and get new results based on the chosen attributes) o Calculation info (this button will open the Calculation info dialog where errors and warnings related to the design are displayed together with their description)
o Concrete setup (see more info in chapter 2.6 Concrete Setup action button) o New reinforcement (see more info in chapter 3.6.2 New reinforcement) o Export reinf. area to CAD program (by pressing this button the user will be asked to save actual finished design to an *.ASF file which might be loaded into anothers CAD program, such as Allplan, for further reinforcement design) o Preview (this button will open the Preview window with tables containing the results of the finished design, it might be also used for refreshing the results)
43
3.2.2
Internal Forces ULS
3.2.2.1
In general
Before starting the design process itself, it might be useful to check internal forces which will enter the design. It is possible to do so in Internal forces ULS service in Concrete > 2D Member > Member design > Internal forces ULS.
In this service there are presented these types of internal forces which might be changed through the attribute Type value:
o Basic magnitudes (internal forces directly from FEM analysis, presented in the local coordinate system of the appropriate 2D member) o Design magnitudes (design forces in reinforcement, calculated for reinforcement directions and design force in concrete compression strut) As mentioned above, design magnitudes are recalculated into reinforcement directions, moreover in these values also torsion moment mxy is taken into account. It is also possible to calculate with the influence of tension force caused by shear stress. This can be set in Concrete setup dialog with attribute Shear effect control 6.2.3(7), under Concrete > ULS > Shear > 2D structures. This attribute can be set in three ways: o No shear effect considered (the tension force from shear stress will not be considered in the design forces calculation) o Shear effect considered in R2 (the tension force from shear stress will be considered in the design forces calculation only on elements where the shear force is not covered by the concrete capacity, i.e. on elements where shear reinforcement is needed) o Shear effect considered unconditionally (the tension force from shear stress will be considered in the design forces calculation on all elements, regardless whether the shear reinforcement is needed or not)
44
The tension force from shear stress is also dependent on the inclination of the shear strut. In Scia Engineer it is possible to set two types of shear strut inclination calculation. This can be done in Concrete setup dialog through attribute Shear strut inclination control 6.2.3 which is placed at the same location in the Concrete setup dialog as Shear effect control 6.2.3(7). o Variable strut inclination method (inclination is calculated automatically and the aim is to find the minimal value of angle which lies in interval min and max, and condition vd ≤ vRd.max is true, This method optimises the variable strut inclination to determine the minimal amount of shear reinforcement) o Fixed strut inclination method (with this method set the user defines the inclination by defining angle . Default value is set to 40 degrees.) The values that will be available in the value list for Type values attribute set to Design magnitudes depend on: o Type of the structure set during definition of the project itself. For 2D members project it is possible to set three options: Plate XY, Wall XY and general XYZ. o Layers in the centre attribute placed in 2D concrete data. If all 2D members in the project have 2D concrete member data defined with attribute Layers in the centre active, then only n1-, n2-, nc- values will be displayed in the list of values in General XYZ project. o Number of reinforcement directions. If all 2D members have only 2 reinforcement direction defined, then values with index 3 will not be displayed in the list of values. Plate XY
Wall XY
General XYZ
Description of the values above: m1-,m2-,m3-,m1+,m2+,m3+
Design bending moment in reinforcement direction 1, 2 and 3 for lower surface (-) or upper surface (+). These values are used for reinforcement design.
n1-,n2-,n3-,n1+,n2+,n3+
Design normal force in reinforcement direction 1, 2 and 3 for lower surface (-) or upper surface (+). These values are used for reinforcement design.
n1,n2,n3
Design normal force in reinforcement direction 1, 2 and 3 placed in the centre of gravity of 2D member. These values are used for reinforcement design.
mc-, mc+
Design bending moment in concrete compression strut for lower
45
surface (-) or upper surface (+) which must be covered by concrete. If the concrete strut is not able to cover this moment, the design will end up with error message. nc-, nc+
Design normal force in concrete compression strut for lower surface (-) or upper surface (+) which must be covered by concrete. If the concrete strut is not able to cover this force, the design will end up with error message.
nc
Design normal force in concrete compression strut placed in the centre of gravity of 2D member which must be covered by concrete. If the concrete strut is not able to cover this force, the design will end up with error message.
vd
Resultant shear force which takes effect perpendicular to 2D member plane.
Note Upper and lower surface of 2D member is determined by the Z axis direction of the local coordinate system (LCS). The upper surface is in the positive direction of the Z axis and on the other hand the Lower surface is in negative direction of Z axis. The upper surface values are marked with + and the lower values are marked with -.
3.2.2.2
Tips & tricks
3.2.2.2.1 Internal forces in Result tree It is possible to check internal forces directly in Results through Member 2D – Internal Forces item. Here, the user can also view the design magnitudes, if attribute Type of the force is set to Elementary design magnitudes.
The Elementary design magnitudes in tree Results are determined differently than in the Concrete tree. The difference is that the Elementary design forces are expressed for the X and Y axis of local coordinate system of the 2D member, not for reinforcement directions as it is done for determination of the design magnitudes in Concrete tree. In the Elementary design forces the torsion moment mxy is also taken into account, however the tension force from shear stress not. These Elementary design forces might be used only for presentation. For design of the amount of reinforcement the Design magnitudes from Concrete tree are used. The values displayed in the value list when attribute Type forces is set to Elementary design magnitudes possibility are only dependent on the type of the structure set during the definition of the project itself. For 2D members project it is possible to set three options, Plate XY, Wall XY and general XYZ.
46
Plate XY
Wall XY
General XYZ
Description of the values above: mxD+, mxD-
Design bending moment in the X axis direction of the local coordinate system (LCS) for lower surface (-) or upper surface (+).
myD+, myD+
Design bending moment in the Y axis direction of the local coordinate system (LCS) for lower surface (-) or upper surface (+).
nxD+, nxD-
Design normal force in the X axis direction of the local coordinate system (LCS) for lower surface (-) or upper surface (+).
nyD+, nyD+
Design normal force in the Y axis direction of the local coordinate system (LCS) for lower surface (-) or upper surface (+).
mcD+, mcD-
Design bending moment in the concrete compression strut for lower surface (-) or upper surface (+) which must be covered by concrete.
ncD-, ncD+
Design normal force in the concrete compression strut for lower surface (-) or upper surface (+) which must be covered by concrete.
Note The upper and lower surface of 2D member is determined by the Z axis direction of the local coordinate system (LCS). The upper surface is in the positive direction of the Z axis and on the other hand the Lower surface is in negative direction of Z axis. The upper surface values are marked with + and the lower surface values are marked with -.
3.2.2.2.2 Comparison of design internal forces in Concrete and Results trees The Design internal forces magnitudes in Concrete tree and Results tree have the same values only when the selected 2D member: o has only two reinforcement directions defined and these are perpendicular to each other o the first reinforcement direction angle is identical with the value of rotation defined in properties of Member 2D – Internal Forces in the Results tree. Member Data in Concrete tree
Member 2D - Internal Forces in Results tree
47
o influence of tension force is not considered for shear reinforcement,. That means that attribute Shear effect control 6.2.3(7) is set to no shear effect is considered possibility in the concrete setup dialog
Comparison of the results in the Results and Concrete trees will be done for the type of the structure set to Plate XY. The structure is a simple 2D concrete member which dimensions are 6 x 8 meters and the thickness is 200 mm. It has defined concrete C25/30 and it is supported on three sides. It is subject to a constant surface load of 10kN/m2. No member data are defined on this 2D member.
3.2.2.2.2.1 Two perpendicular reinforcement directions, identical with X and Y axes of LCS First direction angle in Member data is set to 0 (zero) degrees and Rotation attribute in 2D Members – internal Forces properties in Results tree is 0 (zero) as well. The influence of tension force is not considered for shear reinforcement. That means that attribute Shear effect control 6.2.3(7) is set to no shear effect is considered possibility in the concrete setup dialog.
48
Reinforcement and LCS directions
Member 2D - Internal Forces attributes
Graphical comparison of moment for lower surface for direction 1 (direction of X axis of LCS) Results, moment mxD-
Concrete, moment m1-
Numerical comparison of the moment for both surfaces and directions for elements 1-24 (half of the 2D member) Moments
Results tree
Concrete tree
Case
Elem.
mxD-
myD-
mcD-
mxD+
myD+
mcD+
m1-
m2-
mc-
m1+
m2+
mc+
LC1
1
0
5,37
-15,73
17,04
8,78
-15,46
0
5,37
-15,73
17,04
8,78
-15,46
LC1
2
15,32
19,72
-34,61
19,29
14,89
-34,61
15,32
19,72
-34,61
19,29
14,89
-34,61
LC1
3
20,37
24,31
-37,97
17,6
13,66
-37,97
20,37
24,31
-37,97
17,6
13,66
-37,97
LC1
4
20,38
25,18
-35,29
14,91
10,11
-35,29
20,38
25,18
-35,29
14,91
10,11
-35,29
LC1
5
18,58
25,07
-31,73
13,16
6,67
-31,73
18,58
25,07
-31,73
13,16
6,67
-31,73
LC1
6
16,58
25,62
-30,36
13,78
4,74
-30,36
16,58
25,62
-30,36
13,78
4,74
-30,36
LC1
7
0
-2,47
-27,44
32,06
9,85
-11,99
0
0
0
32,06
9,85
-11,99
LC1
8
7,47
18,18
-27,91
20,45
9,74
-27,91
7,47
18,18
-27,91
20,45
9,74
-27,91
LC1
9
18,85
27,48
-31,53
12,68
4,05
-31,53
18,85
27,48
-31,53
12,68
4,05
-31,53
LC1
10
21,79
32,58
-29,65
5,42
0
-30,14
21,79
32,58
-29,65
5,42
0
-30,14
LC1
11
20,33
35,78
-26,79
1,07
0
-30,4
20,33
35,78
-26,79
1,07
0
-30,4
LC1
12
16,07
38,62
-25,51
2,98
0
-32,16
16,07
38,62
-25,51
2,98
0
-32,16
LC1
13
0
-5,77
-38,35
41,67
9,81
-7,36
0
0
0
41,67
9,81
-7,36
LC1
14
0
11,56
-17,93
19,42
4,57
-17,63
0
11,56
-17,93
19,42
4,57
-17,63
LC1
15
13,87
24,57
-20,49
3,7
0
-21,66
13,87
24,57
-20,49
3,7
0
-21,66
LC1
16
19,31
32,66
-19,57
-5,33
0
-27,06
19,31
32,66
-19,57
0
0
0
LC1
17
18,47
38,52
-17,79
-6,91
0
-32,3
18,47
38,52
-17,79
0
0
0
49
LC1
18
12,78
43,14
-16,85
-2,31
0
-36,76
12,78
LC1
19
0
-7,29
-44,11
45,31
8,56
-2,47
0
LC1
20
0
4,7
-13,69
15,23
0
-6,25
0
LC1
21
7,2
18,76
-7,07
-2,85
0
-16,04
7,2
LC1
22
14,1
28,37
-6,82
-10,23
0
-25,43
14,1
LC1
23
13,95
35,89
-6,22
-10,54
0
-33,08
LC1
24
7,78
41,62
-5,87
-4,62
0
-38,9
43,14
-16,85
0
0
0
0
0
45,31
8,56
-2,47
4,7
-13,69
15,23
0
-6,25
18,76
-7,07
0
0
0
28,37
-6,82
0
0
0
13,95
35,89
-6,22
0
0
0
7,78
41,62
-5,87
0
0
0
It is obvious from the table that design forces are identical in both trees.
3.2.2.2.2.2 Two perpendicular reinforcement directions, identical with X and Y axes of LCS, shear effect considered The same settings as in the previous chapter will be used here with one exception. The influence of the tension force is considered for shear reinforcement. That means that attribute Shear effect control 6.2.3(7) is set to shear effect considered unconditionally possibility in the concrete setup dialog. Graphical comparison of moment for lower surface for direction 1 (direction of X axis of LCS) Results, moment mxD-
Concrete, moment m1-
Numerical comparison of moment for both surfaces and directions for elements 1-24 (half of the 2D member) Moments
50
Results tree
Concrete tree
Case
Elem.
mxD-
myD-
mcD-
mxD+
myD+
mcD+
m1-
m2-
mc-
m1+
m2+
mc+
LC1
1
0
5,37
-15,73
17,04
8,78
-15,46
1,14
12,19
-19,1
16,11
10,66
-11,83
LC1
2
15,32
19,72
-34,61
19,29
14,89
-34,61
16,36
19,66
-34,49
20,44
14,96
-34,73
LC1
3
20,37
24,31
-37,97
17,6
13,66
-37,97
20,01
25,22
-36,8
18,42
15,74
-39,14
LC1
4
20,38
25,18
-35,29
14,91
10,11
-35,29
20,09
27,35
-34,63
15,29
12,94
-35,95
LC1
5
18,58
25,07
-31,73
13,16
6,67
-31,73
18,47
27,86
-31,52
13,27
9,68
-31,95
LC1
6
16,58
25,62
-30,36
13,78
4,74
-30,36
16,7
31,28
-30,59
13,66
10,15
-30,12
LC1
7
0
-2,47
-27,44
32,06
9,85
-11,99
0
1,36
-25,5
33,34
8,98
-6,64
LC1
8
7,47
18,18
-27,91
20,45
9,74
-27,91
10,84
18,74
-28,88
22,85
9,33
-26,95
LC1
9
18,85
27,48
-31,53
12,68
4,05
-31,53
19,83
27,09
-30,23
14,96
4,95
-32,82
LC1
10
21,79
32,58
-29,65
5,42
0
-30,14
21,52
32,98
-28,07
8,29
0
-31,29
LC1
11
20,33
35,78
-26,79
1,07
0
-30,4
20,08
37,19
-26,18
2,19
0
-29,74
LC1
12
16,07
38,62
-25,51
2,98
0
-32,16
16,42
42,86
-26,16
3,76
0
-28,99
LC1
13
0
-5,77
-38,35
41,67
9,81
-7,36
0
0
0
45,64
8,54
-3,65
LC1
14
0
11,56
-17,93
19,42
4,57
-17,63
2,78
13,57
-18,56
23,08
4,16
-16,69
LC1
15
13,87
24,57
-20,49
3,7
0
-21,66
16,19
24,35
-20
6,64
0
-22
LC1
16
19,31
32,66
-19,57
-5,33
0
-27,06
19,92
32,35
-18,31
0
0
0
LC1
17
18,47
38,52
-17,79
-6,91
0
-32,3
18,27
38,92
-16,98
0
0
0
LC1
18
12,78
43,14
-16,85
-2,31
0
-36,76
13,31
45,87
-17,74
0
0
0
LC1
19
0
-7,29
-44,11
45,31
8,56
-2,47
0
0
0
51,31
7,98
-1,19
LC1
20
0
4,7
-13,69
15,23
0
-6,25
0
5,24
-9,48
19,71
0
-5,98
LC1
21
7,2
18,76
-7,07
-2,85
0
-16,04
10,16
18,7
-6,95
0,18
0
-16,07
LC1
22
14,1
28,37
-6,82
-10,23
0
-25,43
15,52
28,19
-6,4
0
0
0
LC1
23
13,95
35,89
-6,22
-10,54
0
-33,08
14,18
35,77
-5,73
0
0
0
LC1
24
7,78
41,62
-5,87
-4,62
0
-38,9
8,49
42,69
-6,72
0
0
0
It is obvious from the table that the design forces are different in both trees. It is due to the fact that in Concrete tree the tension force from shear stress is considered. In this case it is necessary to make check of internal forces only in the Concrete tree.
3.2.2.2.2.3 Two perpendicular reinforcement directions, rotated with 45 degrees according to the LCS First direction angle in Member data is set to 45 degrees and Rotation attribute in 2D Members – internal Forces properties in Results tree is 45 degrees as well. The influence of the tension force is not considered for shear reinforcement. That means that attribute Shear effect control 6.2.3(7) is set to no shear effect is considered possibility in the concrete setup dialog. Reinforcement and LCS directions
Member 2D - Internal Forces attributes
51
Graphical comparison of moment for lower surface for direction 1 (direction of X axis of LCS) Results, moment mxD-
Concrete, moment m1-
Numerical comparison of moment for both surfaces and directions for elements 1-24 (half of the 2D member) Moments
Results tree
Concrete tree
Case
Elem.
mxD-
myD-
mcD-
mxD+
myD+
mcD+
m1-
m2-
mc-
m1+
m2+
mc+
LC1
1
0
3,87
-14,23
17,04
1,58
-8,25
0
3,87
-14,23
17,04
1,58
-8,25
LC1
2
0
17,8
-17,37
17,37
0
-17,8
0
17,8
-17,37
17,37
0
-17,8
LC1
3
0
22,59
-15,88
15,8
0
-22,52
0
22,59
-15,88
15,8
0
-22,52
LC1
4
0
23,24
-12,97
12,76
0
-23,03
0
23,24
-12,97
12,76
0
-23,03
LC1
5
0
22,88
-10,97
10,39
0
-22,3
0
22,88
-10,97
10,39
0
-22,3
LC1
6
0
23,31
-11,46
10,23
0
-22,07
0
23,31
-11,46
10,23
0
-22,07
LC1
7
0
-3,08
-26,84
32,06
20,07
-22,21
0
0
0
32,06
20,07
-22,21
LC1
8
0
14,72
-16,99
17,33
0
-15,06
0
14,72
-16,99
17,33
0
-15,06
LC1
9
0
25,39
-10,6
9,17
0
-23,97
0
25,39
-10,6
9,17
0
-23,97
LC1
10
2,92
32,58
-10,79
3,54
0
-28,25
2,92
32,58
-10,79
3,54
0
-28,25
LC1
11
8,99
35,78
-15,45
0,86
0
-30,18
8,99
35,78
-15,45
0,86
0
-30,18
LC1
12
13,11
38,62
-22,55
2,82
0
-31,99
13,11
38,62
-22,55
2,82
0
-31,99
LC1
13
0
-8,52
-35,6
41,67
34,31
-31,86
0
0
0
41,67
34,31
-31,86
LC1
14
0
10,22
-16,59
19,42
1,8
-14,85
0
10,22
-16,59
19,42
1,8
-14,85
LC1
15
4,08
24,57
-10,7
2,76
0
-20,71
4,08
24,57
-10,7
2,76
0
-20,71
LC1
16
13,09
32,66
-13,36
-4,69
0
-27,7
13,09
32,66
-13,36
0
0
0
LC1
17
20,73
38,52
-20,05
-7,18
0
-32,03
20,73
38,52
-20,05
0
0
0
LC1
18
26,29
43,14
-30,36
-2,87
0
-36,2
26,29
43,14
-30,36
0
0
0
LC1
19
0
-11,93
-39,47
45,31
42,84
-36,75
0
0
0
45,31
42,84
-36,75
LC1
20
1,02
7,01
-17,01
15,99
10,01
-17,01
1,02
7,01
-17,01
15,99
10,01
-17,01
LC1
21
11,69
18,76
-11,55
-3,34
0
-15,55
11,69
18,76
-11,55
0
0
0
LC1
22
21,55
28,37
-14,27
-12,02
0
-23,63
21,55
28,37
-14,27
0
0
0
LC1
23
29,67
35,89
-21,95
-13,87
0
-29,75
29,67
35,89
-21,95
0
0
0
LC1
24
35,75
41,62
-33,84
-7,24
0
-36,29
35,75
41,62
-33,84
0
0
0
It is obvious from the table that design forces are identical in both trees. It is due to the fact that only two perpendicular reinforcement directions are defined and the first reinforcement direction angle 52
is identical with the rotation angle defined in 2D Member – Internal Forces attributes, in Results tree. If different reinforcement direction angles were defined in 2D Member data for lower and upper surfaces, then the results in the Results tree would have to be recalculated separately for each surface.
3.2.2.2.2.4
Two non-perpendicular or three reinforcement directions
Three angles of 0, 45 and 90 degrees are defined in Member data. Rotation attribute in 2D Members – Internal Forces, in Results tree, has 0 (zero) value. The influence of the tension force is not considered for shear reinforcement. That means that attribute Shear effect control 6.2.3(7) is set to no shear effect is considered possibility in the concrete setup dialog Reinforcement and LCS directions
Member 2D - Internal Forces attributes
Graphical comparison of moment for lower surface for direction 1 (direction of X axis of LCS) Results, moment mxD-
Concrete, moment m1-
In this case the results will be different in both trees. Results in Result tree can’t be “fixed“ with LCS rotation or by adjusting Rotation attribute. General transformation would have to be used. In this case it is necessary to make the check of internal forces only in Concrete tree.
3.2.2.2.3 Determination of design internal forces in Results and Concrete tree As it was mentioned before, different methods are used for determination of design internal forces in these two trees. For determination of design values in Results tree, the method described in literature [2] is used, while the method described in literature [3] is used for the determination of design values in Concrete tree. Demonstration of this determination will be presented on the same structure as was used in chapter 3.2.2.2.2.1. It will be done for element number 10 where the moment m1(mxD-) has the largest value.
53
3.2.2.2.3.1
Determination of design internal forces in Results tree
Value
Conditions and formulas (1) mx mxy if mx my and mx mxy (2) mx mxy if
(2) my mxy if
mx my
and mx mxy
(1) 2 * mxy if mx my and mx mxy (2) 2 * mxy if
and my mxy
Condition (1) fulfilled, then:
(4) my
mxy 2 if mx my and mx mxy my
mcD- =-29,66 kNm
and mx mxy
(1) my mxy if mx my and my mxy (2) my mxy if
and mx mxy
if mx my and my mxy
(3) 0 (4) my
mx my
2
mxy if mx my and mx mxy mx
(1) 2 * mxy if mx my and my mxy (2) 2 * mxy if
14 832 17 75
mx =6,96 kNm < my = 17,75 kNm mx =6,96 kNm > -|mxy| = -14,83 kNm my =17.75 kNm > -|mxy| = -14,83 kNm
mcD+ = 30,14 kNm
2
17 75
, ,
Condition (3) fulfilled, then:
,
54
mxy 2 if mx my and mx mxy mx
6 96
yy x mm
(4) mx
mxy 2 if mx my and my mxy my
2
Condition (3) fulfilled, then: myD+ =0 kNm
y m
(3) my
and mx mxy
mxD+ = 5,43 kNm mx =6,96 kNm < my = 17,75 kNm mx =6,96 kNm > -|mxy| = -14,83 kNm my =17.75 kNm > -|mxy| = -14,83 kNm
D c m
mcD+
mx my
, ,
mx my
Condition (3) fulfilled, then:
,
if
mx = 6,96 kNm < my = 17,75 kNm mx = 6,96 kNm < |mxy| = 14,83 kNm my = 17.75 kNm > |mxy| = 14,83 kNm
yy x mm
(4) 0
2 1483
x m
mxy 2 if mx my and my mxy my
,
and mx mxy
2
D x m
(3) mx
mx my
y x m
mxy 2 if mx my and mx mxy mx
(2) mx mxy if
myD+
mx =6,96 kNm < my = 17,75 kNm mx =6,96 kNm > -|mxy| = -14,83 kNm my =17.75 kNm > -|mxy| = -14,83 kNm
(3) mx
(1) mx mxy if mx my and my mxy
mxD+
17 75 1483
myD- =32,58 kNm
D c m
mcD-
mx my
,
if
,
(4) 0
Condition (1) fulfilled, then:
y x m
mxy 2 if mx my and mx mxy mx
mx =6,96 kNm < my = 17,75 kNm mx =6,96 kNm > -|mxy| = -14,83 kNm my =17.75 kNm > -|mxy| = -14,83 kNm
y m
(3) my
and my mxy
6 95 1483
mxD- =21,78 kNm
D y m
myD-
mx my
,
(1) my mxy if mx my and mx mxy
,
mxy if mx my and my mxy my
Condition (1) fulfilled, then:
y x m
2
x m
if mx my a mx mxy
(3) 0 (4) mx
and my mxy
D x m
mxD-
mx my
Calculation mx =6,96 kNm < my = 17,75 kNm mx =6,96 kNm > -|mxy| = -14,83 kNm my =17.75 kNm > -|mxy| = -14,83 kNm
14 832 17 75
3.2.2.2.3.2
Determination of design internal forces in Concrete tree
According to this method the basic internal forces and their directions must be determined first. In Scia Engineer these magnitudes are presented in Results in 2D Members – Inner forces item, if the type of the value is set to Basic magnitudes possibility. Value z
Formulas Determination of effective height and lever arm. z = 0,9d
Calculation dlo = dup= 200-45 = 155mm z = 0,9·d = 0,9·155= = 139,5mm nx.up = -49,89kN ny.up = -127,24kN nxy.up = 106,38kN nx.lo = 49,89kN ny.lo = 127,24kN nxy.lo = -106,38kN
Determination of normal forces for lower and upper surface in LCS nx,lo(up) ny,lo(up) nxy,lo(up)
Determination of principal forces for lower surface
n1,lo = 201,7 kN n2,lo = -24,55 kN n1,up = 24,55 kN n2,up = -201,37 kN
Determination of principal forces directions
αlo = -55 deg αup = 35 deg
Determination of compression strut angle in concrete. The angle of compression strut is optimised to allow for the smallest force in compression strut. Determination of angle between the reinforcement direction and the direction of principal forces. α1,lo = αr1,lo - αlo α2,lo = αr2,lo - αlo α3,lo = αrc,lo - αlo
αlc,lo = 45deg αlc,up = 129deg
n1,lo(up) n2,lo(up)
α,lo(up)
αlc,lo(up)
αj,lo(up)
nj,-(+)
Determination of design forces in reinforcement’s direction, i.e. in direction of compression strut. Baumann transformation formula, adjusted for two reinforcement directions, is used. ,
∙ sin sin
∙ sin
, ,
,
,
,
∙ sin
∙ cos ,
∙ cos
,
,
α1,lo = 0 - (-55) = 55deg α2,lo = 90 - (-55) = 145deg α3,lo = 45 - (-55) = 100deg α1,up = 0 - 35 = -35deg α2,up = 90 - 35 = 55deg α3,up = 129 - 35 = 94deg n1- =156,2 kN n2- =233,5 kN nc- =-212,6 kN n1+ =39 kN n2+ =-0,09 kN nc+ =-216,03 kN
,
55
,
∙ sin sin
,
∙ sin sin
∙ sin
, ,
∙ sin
, ,
,
,
,
∙ sin
,
,
,
∙ sin
∙ cos
,
,
∙ cos ,
∙ cos
,
∙ cos
,
, , ,
While type of the structure is set to Plate, design forces will be transformed into moments by formula m =n·z
mj,-(+)
m1- = 21,79 kNm m2- = 32,58 kNm mc- =-29,66 kN m1+ = 5,44 kNm m2+ = -0,014 kNm mc+ =-30,14 kN
Note
Formulas in the tables are usually named for lower surface only, but the same formulas with changed indexes stands good for the upper surface.
3.2.2.2.4 Determination of design internal forces for General XYZ structure Normal forces in reinforcement and compression strut directions for both surfaces are presented when structure type is set to General XYZ possibility. Sometimes, for further checks, it is necessary to replace these normal forces with the effect of moment and normal force which are located in the centre of gravity of the member. If reinforcement directions for both surfaces are identical, then it is possible to determine these effect using the formulas bellow. mj =(dj- – 0,5h)·nj- + (0,5h - dj+)·nj+ nj =nj- + nj+ Where
j stands for reinforcement direction dj-(+) stands for effective height in j reinforcement direction for lower (-) and upper (+) surface nj-(+) stands for the values of normal forces in reinforcement direction for lower (-) and upper (+) surface presented in numerical values
If reinforcement directions for both surfaces are not identical, then the determination is more difficult, because it is necessary to calculate normal forces for upper surface (nvj+) and lower surface (nvj-) separately. Then the calculation uses the formulas bellow. mj- =(dj- – 0,5h)·nj- + (0,5h - dj+)·nvj+
(moment in lower reinforcement direction)
mj+ =(0,5h - dj+)·nj+ + (dj- – 0,5h)·nvj-
(moment in upper reinforcement direction)
nj- =nj- + nvj+
(force in lower reinforcement direction)
nj+ =nj+ + nvj-
(force in upper reinforcement direction)
Recalculation will be done for identical reinforcement directions for both upper and lower surface and structure from chapter 3.2.2.2.2.1. Only Structure type of this project will be changed from Plate XY to General XYZ. After the change, these design magnitudes will be displayed in Concrete tree.
56
Recalculation of normal forces for both surfaces to forces which take place in the centre of the gravity will be done for mesh element number 10. Value dj
m1 n1
m2 n2
Formulas Determination of effective height. dj = h- cj – 0,5dsj Determination of normal forces in reinforcement direction 1 (0 degree). m1 =(d1 – 0,5h)·n1- +(0,5h- d1)·n1+ n1 =n1+ + n1-
Calculation d1= d1- = d1+= 200-35-0,510 = 160mm d2= d2- = d2+= 200-45-0,510 = 150mm n1+= 146,5kN/m n1-= 53,1kN/m m1 = 5,6kNm/m n1 = 199,6kN/m
Determination of normal forces in reinforcement direction 2 (90 degree). m2 =(d2 – 0,5h)·n2- +(0,5h- d2)·n2+ n2 =n2+ + n2-
n2-= 219,8kN/m n2+= -19,73kN/m m2 = 11,97kNm/m n2 = 200,1kN/m
3.2.2.2.5 Determination of inner forces with influence of shear force As it was mentioned in previous chapters, values of design magnitudes in Concrete tree depend on whether the influence of tension force from shear is taken into consideration. This influence may be changed in Concrete setup dialog under Concrete > ULS > Shear > 2D Structures. If this influence is taken into consideration, then resultant of tension force from shear (value Ftdj) is incremented to the resultant of principal forces. More on this issue can be found in chapter 3.2.2.1. Again, calculation will be done for structure from chapter 3.2.2.2.2.1 for mesh element number 10, where the design moment m1- (mDx-) reaches its maximum. Value
Formulas Determination of resultant shear force.
Calculation vd = 10,79 kN
Determination of resultant shear force direction.
β = 56,53 deg
vd
57
vdj,lo(up)
Ftdj,lo(up)
n1,lo(up) n2,lo(up)
Recalculation of resultant shear force to the principal forces directions, where 50% will be added to upper and 50% to lower surface. 0.5 ∙ ∙ cos , 0,5 ∙ ∙ sin , Determination of tension force increment from shear. ∆ , , ∙ cot ∆ , , ∙ cot Principal inner forces with shear increment ∆ , , , ∆ , , , For recalculation of principal force is compression strut angle determined and design values calculated.
vd1,lo = -1.98kN vd2,lo = -5kN vd1,up = 5kN vd2,up = -1,98kN Ftd1,lo= -4,95 kN Ftd2,lo= 12,55 kN Ftd1,up= 12,55 kN Ftd2,up= -4,95 kN n1,lo = 199,7 kN n2,lo = -12 kN n1,up = 37,1 kN n2,up = -206,32 kN
Note During the calculation of tension force from shear according to the EN 1992-1-1, chapter 6.2.3 (7) condition MEd/z + Ftd ≤ MEd,max/z is being checked. Resultant shear force is presented directly in Design magnitudes in Concrete tree as vd and also in Results tree in 2D Members – Internal forces, for attribute type forces set to Principal magnitudes possibility. It is named as qmax-b. Resultant shear force angle is presented in Results tree under 2D Members – Internal forces, for attribute type forces set to Principal magnitudes possibility. It is named as beta. In Concrete tree it can be found under Member design ULS, for attribute output set to Advanced or Detailed, for Asw value. Shear strut inclination (angle ) is displayed in Concrete tree and it can be found under Member design ULS, for attribute output set to Advanced or Detailed, for Asw value.
3.4.3
ULS
3.4.3.1
Theoretical background
Reinforced concrete 2D structures handled by Scia Engineer (Walls, Plates and Shells) are usually reinforced by two systems of steel reinforcement nets consisting of 2 or 3 reinforcement courses situated more or less close to both surfaces of the 2D member. Scia Engineer puts no principal restrictions upon the absolute position of reinforcement courses within the cross-section, its axial concrete cover describes the position of each reinforcement course. However, there are relative restrictions: all concrete covers must fulfil some rules to prevent ambiguousness of the geometric definition of the design task. These rules are described in the part of the Scia Engineer manual. Yet it must not be forgotten that there might be other, more complex situations in the cross-section than symbolised by the figure 1: o The crossing reinforcement bars of individual layers do not need to touch each other; they might be placed at larger distances from each other within the cross sections. o The surfaces of bars are usually corrugated so that there is, as a rule, a greater distance between two crossing bars than expressed by their characteristic bar diameters. o Last but not least, in very thick plates, e.g. foundation slabs, two layers or bars bundles in one layer are used, so that the representative axial distance (of the point of gravity) and the representative bar diameter itself are two independent quantities and qualities, which must be defined independently on input in order to carry out reliable analysis.
58
In Walls, being (theoretically) subjected to forces acting in their planes, the (by definition symmetric) positions of reinforcement nets are of no static interest; however, the cross-section geometry (concrete covers and bar diameters) is of interest for the Crack Proof algorithm (if implemented). Thus, the Wall design branch comprises the same cross-section input dialog as the Plate and Shell models. In Plates and Shells, on the contrary, the reinforcement covers influence the effective static height of the reinforcement courses in the cross-section subjected (also) to bending, thus having fundamental meaning for the design process. The covers are related to the faces. Thus, it is necessary to distinguish them clearly from each other. Because Plates are (still) the structural type most frequently used in the practice, Scia Engineer use originally common terms distinguishing the two faces: upper and lower face. These concepts have to be given mathematically exact meaning, which makes them acceptable for Shells, too: the lower face is the structural plane edge in direction of the positive planar axis Zp; the upper face is opposite to it. Finally, the symbol -Zp appears generally in the output protocol instead of the term upper face; the symbol +Zp symbolises lower face. In Walls, there is no need of distinguishing both structural edges; nevertheless, out of formal reasons (simplification), if the concept of upper face appears in connection with Walls it means both faces. The reinforcement courses are, correspondingly to their relative position in the cross-section, called the outer(most), middle (if any) and inner(most) ones. This verbal distinguishing is in the mathematical formulation replaced by assigning them the ordinal numbers 1, 2 and 3 (if three reinforcement courses are specified). The same double identification may be given to other associated terms like reinforcement angles, design forces, effective static heights, internal forces levers, etc. So we can say, e.g., about reinforcement angle α, β, γ meaning the same, when alternately indicating α1, α2, α3. There is no indication that this ambiguity of terms should cause confusion; as a fact, there is no ambiguousness for the correspondence of both systems of denotation is clearly defined. Note that each reinforcement course can hold up to 10 reinforcement layers. The terms of the reinforcement concrete theory are used in accordance with the general structural use or they strictly follow the rules postulated by the standards implemented in Scia Engineer. However, for Scia Engineer deals with several national codes, it is probable that this or that term or formulation would appear somewhat unfamiliar to some readers focused on the use of one code branch only. It is hardly possible to create a manual text on such special topic for international use being in all respects verbally fully conform to every country’s verbal usage. In doubts, the terminology of Eurocode will be given preference. The design task and the output of results are performed in basic and derived units of the SI system.
3.4.3.1.1 Wall Design Once a positive design force is assigned to its associated reinforcement course, the corresponding statically required reinforcement amount ai is calculated from the elementary relation: ai = ni /σsd (i = 1,2 (,3)) [m²/m]
(6)
(6) has symbolic meaning only, as we do not want to write down at this stage all the exact calculation rules for codes implemented in NEDIM (the original development name of the 2D design module system, used internally by SCIA developers, testers and supporters for quick communication).
59
The symbol σsd stands for the effective design steel strength. Both ni and σsd may be, according to the actual code, charged with security coefficients. We are not going to discuss the problem of 1D reinforcement design; the NEDIM algorithm strictly follows special rules stipulated by national codes and associated Standards, as far as they are applicable to the 2D design. The virtual stiffening strut of the heterogeneous concrete-steel continuum represents quite a substantial issue of the design process. While it is possible (unless the upper reinforcement percentage limit has been exceeded) to improve the bearing capacity of the cross-section on the side of the reinforcement by augmenting its amount, the bearing limit of the concrete strut is given by the height of the cross-section and the quality of concrete only; thus its limits are predestined by the input data. The concrete strut bearing capacity condition is described by the following relation: –n3 General > Calculation > 2D structures.
Req,shear reinforcement > c–s height >= 20cm A 2D member is provided with shear reinforcement only if the thickness of the member is higher than 200mm. If it is less, then the shear reinforcement will not be designed and calculation finishes with error message. (EN 1992-1-1:2004, §9.3.2(1)) Structural reinforcement of deep beams If the check is active, then construction reinforcement for deep beams will be taken into account. (EN 1992-1-1:2004, §9.7.1)
65
3.4.3.3
Reinforcement design workflow
We can demonstrate the basic possible workflow for reinforcement design on example similar to the previously used for demonstrating internal forces. It is a concrete plate defined in XY project, supported according to the picture. It is made from concrete C25/30 and is 200 mm thick. It is loaded with self weigh in LC 1 and with constant surface load of 10KN/m2 in LC2. Results will be described on combinations which contain both previous load cases.
The reinforcement design will be shown only for lower reinforcement in the direction of the y axis of the member LCS, where we expect more amount of reinforcement. We need also redefine design defaults settings, where the reinforcement 1 direction is identical with the X axis of the member LCS. This will be done by defining member data and setting Layer angle parameter for first direction to 90 degrees. This layer will be now closer to the surface and will decrease the amount of designed reinforcement little bit. We could change the reinforcement direction also by adjusting the first direction angle and rotating the whole reinforcement system.
On the picture below there is magnitude of m1-, which will be determining for the reinforcement design. We will use location In nodes, avg. on macro and isobands will be used for presentation.
66
Now we are ready to run ULS reinforcement design by adjusting ULS service properties and pressing Refresh action button. After this dialog with a progress bar will appear and then final message with conclusion of the design will be displayed. After confirmation of this dialog, the results will be displayed.
For better orientation in the design process, all types of reinforcement will be shown in the table below.
67
Required reinforcement
User reinforcement
Additional reinforcement
Total reinforcement
As we can see, no user reinforcement is defined yet. Therefore amounts of required, additional and total reinforcement are equal. We can also check the design values in preview window. The user may switch to brief, detailed or advanced mode, as we did in this example. We can see that maximal amount of reinforcement for lower surface and direction 1 is designed to 1295mm2/m.
Now the user has to decide how he wants to reinforce the designed member. Whether he wants to define each reinforcement layer manually or if he wants to use automatic definition of reinforcement from concrete member data. The second possibility is much common and more useful, so we will show this one. The user has to activate User reinforcement check box in the concrete data first. This will enable him to define Basic distance of bars.
68
After this, the amount of user reinforcement is determined directly from concrete member data and the user may simply adjust it by changing appropriate parameters (diameter, basic distance). Default values are loaded from Concrete setup dialog, which might be changed in Design defaults. Let’s see the differences in designed amounts of reinforcement just after activating the user reinforcement check box. Required reinforcement
User reinforcement
69
Additional reinforcement
Total reinforcement
Now the user reinforcement has non-zero values and accordingly to this change, amount of designed additional reinforcement has been changed too. However the reinforcement amount defined is not sufficient enough, so we have to adjust the concrete data to fulfil the requirements. Before this we can check the preview window for more information. It is clear from here, that additional amount of 902mm2/m has to be added to fulfil the required amount. Let’s redefine the reinforcement diameter to 12mm and basic distance to 100mm. Now we get these results. Required reinforcement
70
User reinforcement
Additional reinforcement
Total reinforcement
From this results we can see that the defined reinforcement is sufficient on mostly whole 2D member area. However there is requirement for additional 174 mm2/m of reinforcement on the right side of the designed member. We don’t want to define more reinforcement for whole member area and we will handle this requirement afterwards, by creating a separate reinforcement polygon. We can now proceed to creating practical reinforcement from user reinforcement. We have the User reinforcement check box active, so we can simply double click the Reinforcement 2D item in the concrete tree. The dialog below will be displayed and a new practical reinforcement will be created from the user reinforcement previously defined by concrete 2D data.
After confirmation of this dialog, practical reinforcement is created and input into 2D member. Now we will also define additional reinforcement to cover the requirement on the right side of the member. Let’s double click the 2D Reinforcement again and define it.
71
The designed 2D member has now two reinforcement polygons defined for lower surface and direction 1. One is on the whole 2D member and the second one is only on the mentioned right side. See picture below.
72
Required reinforcement
User reinforcement
Additional reinforcement
Total reinforcement
At this time we have fulfilled the requirements for direction 1 at the lower surface. No additional reinforcement is needed. The upper surface and other directions might be handled in a similar way we have shown here.
3.4.4
ULS+SLS
3.4.4.1
Theoretical background
The most important serviceability proof is the Crack Proof. As first implementation in NEDIM the crack proof was introduced in 1997.
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The contemporary theories of crack development in a concrete-steel compound medium have become very complex. Practical engineers, confronted with a plenitude of contradictory ideas and formulae, may feel doubts on the reliability of such calculations. However, it should be understand that all crack theories have probabilistic a nature. They try more or less successfully to give analytical explanation to empirical data of the crack behaviour of real structures. In 2D structures even the fundamental question, in what direction the main (first) cracks arise, has not been decided uniquely: o perpendicular to the direction of 1st principal forces nI or mI (Fig. 13a,b) o perpendicular to the reinforcement courses (Fig. 13c) o parallel to the virtual stiffening concrete strut o erratic (combined) crack patterns etc. This assumption comes, no doubt, most closely to the reality; on the other hand, it is obviously least productive in stimulating efficient, simply crack control methods. The NEDIM crack proof algorithm follows formally the assumption of Fig. 13c. However, it appears contradictory to the Baumann transformation theory, which prefers the assumption of crack parallel to the virtual stiffening concrete strut. Nevertheless, the NEDIM approach to the crack proof may be defended by following considerations: o The design forces ndim, assigned to the reinforcement courses, attain, as a rule, values comparable with the governing principal forces nI,II (mI,II), since the strut force n3d is negative (n3d denotes, strictly speaking, the strut force in 2-course nets; as a fact, in 3-course reinforcement nets the strut force need not to be assigned the subscript ‘3’). Only in three-course nets the relation max |nd| < nI,II may become true under elliptic states of stress. However, such states of stress are the less critical for the cross-section resistance, and the cracks may the more tend to erratic patterns distributed over all three courses. o The NEDIM crack proof algorithm is able, as will be demonstrated below, to distinguish qualitatively between different states of stress of the structure. Thus the formal “linearization” of the crack proof process does not ignore the 2D character of the reinforcement concrete medium. o All codes stipulate crack control formulae primarily for a 1D state of stress. The NEDIM calculation assumption of cracks developing perpendicular to reinforcement courses enables to organise the crack proof in quasi 1D steps running over individual reinforcement courses, in the same manner like with the ULS design.
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Figure 13 Assumptions about crack propagation in 2D continuum : (a) Cracks perpendicular to the direction of principal tension (trajectory reinforcement); (b) Cracks perpendicular to the direction of principal tension, yet non-perpendicular to reinforcement courses; (c) Cracks perpendicular to reinforcement courses The basic Problem of the 2D crack proof is obvious from the only formula dedicated by the Norms of the Eurocode family, here exemplary EN 1992-1-1:2004, formula (7.15)), to 2D structures: sr,max = 1 / {cos φ/ sr,max,1 + sin φ/ sr,max,2} [mm]
(271)
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In (271) the symbols sr,max denote the maximum allowable or calculated, respectively, crack distances, which play a distinguished role in most code proof theories (besides the crack width wmax). The indices 1, 2 in (271) refer to 1st and 2nd reinforcement course, here assuming orthogonality. Formula (271) and the following discussion refers to Fig. 13a,b. It relates the crack distances sr,max,1 und sr,max,2 to the direction of principal tension. The relation is, however, contradictory, what is obvious from Fig. 13b : the principal direction divides symmetrically the right angle between the reinforcement directions 1 and 2, i.e. φ = 45°. From (271) follows thus sr,max = sr,1 / √2 ≈ 0,707 sr,1 (where sr,1 ≡ sr,max,1 = sr,max,2). The announced contradiction consists in the fact that this most ineffective reinforcement geometry, which causes about 200% of required as in ULS compared with the corresponding trajectory reinforcement is assigned a significantly lower design crack distance sr,max (about 71%). This conclusion is unacceptable, obviously defective. Thus, the NEDIM approach, as symbolized by Fig. 13c, proves, also from this point of view, to be the most realistic in a 2D reinforced concrete continuum. The proof methods are based on similar assumptions of crack propagation mechanism: o High tension stress in a reinforcement bar causes high steel strain. The adhesion between concrete and the reinforcement bar is disturbed, and cracks arise in the concrete continuum. The higher is the ratio of steel stress and the adhesion resistance, the wider become the cracks along the reinforcement bar. Thus, the higher the representative reinforcement diameter ϕ, the higher the ratio of the steel stress and the adhesion resistance, since the cross-section area of a bar grows with the square of ϕ whereas the surface of (unit length) of bar depends linearly on ϕ. o Cracks arise not only close to the reinforcement bars yet merely between them. Thus, the transversal distance s of reinforcement bars may also become a crucial factor of the cracks width development. However, some codes, like ÖNORM B 4700, do not introduce the distance s as independent factor of the crack proof at all. To limit or reduce, respectively, crack widths (as a fact, not the number of cracks but the representative crack width is of interest for the crack proof) the following measures have to be taken: o Specification of as small reinforcement diameters ϕ as possible. o Reduction of the representative (transversal) reinforcement bar distance s. However, there is a dependence between ϕ and s : with given ϕ and provided as, s is determined by s = 0.25 × π × ϕ ² / as [mm]
(272)
o Augmenting the statically required reinforcement amount. Due to this provision the steel stress in the serviceability state is lowered, thus the crack widths are reduced as direct consequence. This steel amount control (augmenting of reinforcement amount from the ULS design) is the basic concern of the NEDIM crack proof algorithm. Practically, NEDIM follows a two-step thread : (a) ULS design, yielding statically required reinforcement amount; (b) SLS design, referring to the characteristic bar diameter ϕk and/or a characteristic bar distance sk as specified by the user on input. NEDIM carries out the crack proof according to the code proof approach and increases the statically required reinforcement amount where it is needed to meet completely the crack proof requirements. NEDIM, however, allows for merging of load cases for the ultimate and serviceability states within a calculation process in order to enable the crack proof procedure outlined above. In the following paragraphs it is shown that different attributes may be assigned to the load cases, in accordance with the individual stipulations of the codes. In Chapter Program Theory and Algorithm in literature [1] the notion of the virtual cross-section design force nvirt was introduced. The effect of this algorithmic enhancement is, along with that discussed with the shear proof and the minimum compression reinforcement, a consistent description of the state of stress in the cross-section, especially in case of non-congruent reinforcement at both faces. Since most codes consider the stress distribution pattern (bending ↔ centric tension) as 76
important a factor of the crack development, the knowledge of nvirt is indispensable to reliable crack proof design. Upon the analysis types dealt with by NEDIM it has the following impact: o Walls : the general inner forces vector (3) degenerates to { nx, ny, nxy }
(281)
There is no use of nvirt, since nvirt ≡nd in this model. All design forces are membrane forces with zero eccentricity, causing either tension or pressure in the cross-section. o Plates : the general inner forces vector (3) degenerates to { mx, my, mxy, vx, vy }
(282)
Thus, instead of the design forces nd, design moments md and shear force vd are active in Plate design. There is effectively no (virtual) normal force nvirt in pure flexural members, even if hyperbolic cases suggest that such an interpretation of the rather complicated type of stress state may be discussible: both reinforcement courses at upper/lower face appear to be under tension, thus the conclusion seems to be justified that there is a normal force action upon the cross-section. However, in such hyperbolic cases, the prevailing stress is shear, not tension, and that also the reinforcement is, effectively, subject to shear rather than to tension; the representative stress pattern in the design section is thus the shear stress triangle. As a fact, it was made an attempt in NEDIM to deal with such states of stress as with “prevailing tension”. This had, however, serious consequences to the crack and shear proof results unacceptable crack reinforcement increments to statically required reinforcement were casually obtained. o Shells : the general inner forces vector (3) applies to Shell design, rewritten here : { mx, my, mxy, vx, vy, nx, ny, nxy }
(283)
Although the two-step reinforcement design (running separately for both faces) assigns a half cross-section to each reinforcement course, the crack proof must take into consideration the total cross-section, even if there is no congruent reinforcement at opposite (actually inactive) face. The information needed is delivered by the virtual normal force nvirt and the complementary virtual bending moment mvirt. All possible states of stress have to be correctly interpreted and managed by the NEDIM crack proof algorithm. As symbolized by Fig. 14, for the crack proof procedure it is not enough to determine tensile stresses at the actual face, yet also the stress pattern over the cross-section is of eminent importance; especially, the s. c. “disconnection cracks” are of interest.
Figure 14 Typical stress patterns considered by NEDIM’s crack proof procedure : (a) bending crack – neutral axis within cross-section; (b) disconnection crack due to tension force with low eccentricity; (c) over-pressed cross-section – no crack proof According to the basic notion of EC 2 [9], §4.4.2 two possible crack proof strategies are at choice : 77
o §4.4.2.3 : crack limiting without direct calculation. This method is almost identical to the elementary crack limiting method stipulated by DIN 1045 [5]. By meeting the requirements of §4.4.2.3 the mean crack width will be limited to the value wk = 0.30 [mm]. o §4.4.2.4 : method of calculating mean crack width wk by formula (4.80) : wk = β srm εsm
(30)
with wk – calculation value of the crack width; β – security factor distinguishing force induced cracks (β = 1.7) and cracks induced by imposed deformations (β = 1.3); srm – mean crack distance in case of fully developed crack pattern; εsm – mean steel strain, considering tension stiffening between the cracks. Formula (30) represents a sophisticated procedure taking several factors into account. The procedure by Heft 400 [23] as enhancement of the DIN 1045 [5] crack proof is almost identical to that described by formula (30) of EC 2. The enhanced procedure acc. to formula (30) enables to control the mean crack width wk in the structure by varying bar diameter ϕ or bar distance s. However, the NEDIM procedure, with given input values of ϕinp or sinp, is aimed at controlling the statically required reinforcement as,ULS : if required by crack proof, as,ULS is augmented in order to lower the steel stress σs, which is the crucial factor affecting the value of mean strain εsm in (30). This procedure is called crack reduction, since generally cracks wk < 0.30 [mm] are aspired to. NEDIM controls the crack proof procedure of the EC 2 branch by distinguishing four different load case attributes acc. to the same principles as described in the paragraph on the DIN 1045 7/88 branch.
Note For more information about this chapter see literature [3], where more detailed description may be found.
3.4.4.2
Limit bar distances
ULS+SLS design is also affected by the reinforcement amount checks mentioned in chapter 3.4.3.2. But here, another two checks are to be introduced. They are located under Limit bar distances chapter.
Limit bar distance on face Zp+ Maximal allowable distance between reinforcement bars at the surface with positive Z coordinate (in the local co-ordinate system of the 2D member). Default value = 200mm. 78
Limit bar distance on face ZpMaximal allowable distance between reinforcement bars at the surface with negative Z coordinate (in the local co-ordinate system of the 2D member). Default value = 200mm.
3.4.4.3
Reinforcement design workflow
To describe the basic workflow, we can use the structure already used in ULS design 3.4.3.3 chapter and continue with it. We will also focus only on the lower surface and direction 1. At the end of ULS design, two reinforcement regions are defined on the 2D member. See the picture below for recapitulation.
Now we will run the ULS+SLS reinforcement design for lower surface and direction 1 with the settings below. Location will be set to In nodes, avg. on macro possibility again. Previously created reinforcement for ULS design will take effect here as well.
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Required reinforcement
User reinforcement
Additional reinforcement
Total reinforcement
As we can see in the pictures above, the required reinforcement is a little bit larger than reinforcement provided for ULS design. It is clear that additional 165mm2/m has to be defined and reinforcement polygon has to be enhanced, in order to ensure that cracks at the lower surface in direction 1 will not be larger than 0.2mm (for the XC3 exposure class). We can delete the reinforcement and create a new one which will be sufficient for both ULS and ULS+SLS design, but we will adjust already defined practical reinforcement to fulfil the ULS+SLS design requirements. The changes may be checked at the
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Then if we run the reinforcement amount design of the 2D member, we will get these results. Required reinforcement
User reinforcement
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Additional reinforcement
Total reinforcement
Now we have successfully fulfilled the requirements for both ULS and ULS+SLS design and no further steps are needed at the moment.
Note For reinforcement design of structures without any additional layer of hydroizolation, the user would like to calculate reinforcement amount with crack width converging to 0mm (zero). It is not possible in Scia Engineer to use direct zero value and user has to input minimal value of 0.01mm in the Concrete setup dialog, to successfully finish the ULS+SLS design.
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3.5
Section on 2D member
Sometimes the user might find useful or necessary to display his results in specified position on the 2D member. Then he is allowed to define his own section across the 2D member where the designed result values may be displayed separately or in addition to other drawing styles. Definition of 2D member section can be done through Section on 2D member service.
In this Section on 2D member dialog user defines name of the section, vector of direction of the section and the way, results will be graphically represented. User may choose from few possibilities to draw results: o Upright to element – values will be drawn upright to the element o Element plane – values will be drawn in the element plane o X Direction – values will be drawn in X direction o X Direction – values will be drawn in Y direction o X Direction – values will be drawn in Z direction o Draw similar as for setting in section properties – when this possibility is chosen, then the values will be drawn the way it is already defined in appropriate service by Draw parameter. After definition of the section parameters, the user confirms the dialog and manually defines the position itself. When this is done, also coordinates of the definition points will be displayed in previous dialog and user may also edit them either there or in section properties. Section geometry may be also again adjusted in graphical window and all geometry functions may be used together with it. To display results on already defined 2D member section, it is necessary that user checks the marked check box Section in properties of appropriate service. Then after the refresh, results will be displayed on defined section as well (or only).
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Note Also note that by activating Section check box, Drawing setup 1D option appears in the service properties. Here user may adjust the view of the values representation. This will be the same for Edge representation too.
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3.6
2D Reinforcement
Generally there are two ways, how to define practical reinforcement for 2D concrete members in Scia Engineer. The first and very often used way is to use previously defined 2D Concrete data. The second way is to define each reinforcement area manually and separately from each other.
3.6.1
Reinforcement from 2D Member Data
This is very useful feature which will create reinforcement layers according to the settings which are already defined in 2D Member data on 2D member. To use this feature it is necessary to have attribute User reinforcement checked. If so, then it is possible to input and edit Basic distance attribute for each reinforcement layer.
Now if settings in Member data attributes fit the user’s needs, user may double-click the 2D Reinforcement service. After that a decision dialog will appear and user may choose to use this feature, or not. If Yes possibility is chosen, then all reinforcement layers are automatically defined. If No possibility is chosen, then nothing is created and the ordinary Reinforcement 2D dialog for manual definition of reinforcement is displayed.
3.6.2
New Reinforcement¨
Sometimes the user may find manual definition of the Reinforcement more useful. To do so, the user may simply use the item Reinforcement 2D in concrete tree or click action button New
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reinforcement. This will display the Reinforcement 2D dialog where the user may define reinforcement parameters. Only one layer may be defined at a time.
Attributes in Reinforcement 2D or Reinforcement 2D mesh dialog are similar to 2D Member data properties. Name
Specifies the name of the reinforced region.
2D member
Shows the name of the member, where the reinforcement is placed.
Type o Bars
User defines numbers, diameters, etc. of bars in individual layers.
o Mesh User selects a pre-defined reinforcement mesh (usually made by a stainless steel mesh manufacturer) from a library of reinforcement meshes. After selection of this possibility the user may define his own reinforcement mesh or choose already predefined one from library.
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Material
Defines the material for the reinforcement.
Surface
Specifies the surface: lower, upper.
Number of directions
The reinforcement can be defined in one or two perpendicular directions.
Direction closest to surface
Defines in which direction the layer of the reinforcement is closer to the surface.
Angle of the first direction
Specifies possible inclination of the first direction.
Diameter
Defines the diameter of the reinforcement bars.
Concrete cover Defines the thickness of the cover. Bar distance
Defines the distance of individual bars.
Offset
The zero offset means that the first bar is put directly along the edge of the reinforced region (usually a slab of sub region). Nonzero offset means that there is a gap between the first bar and the edge of the reinforced region.
Reinforcement area Total weight
This is informative attribute. It shows the total reinforcement area per one-metre-section of the slab. This is informative attribute. It shows the total weight of the reinforcement in the reinforced region. This item has no meaning in the input dialogue. It gives the correct value only when the existing reinforcement region is edited.
Mesh
Selects the required mesh from the library of reinforcement meshes.
The reinforcement is always defined for a particular region. The reinforcement is distributed uniformly over this region. It is not possible to input separate bars of reinforcement. The shape of the reinforced region is defined by means of the following parameters.
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o Geometry defined by Point - reinforcement region is defined by its centre, width, length and possible inclination. o Line - reinforcement region is defined by its centre line and width. o Polygon - reinforcement region is defined by the polygon outlining the region.
3.6.3
Tips and tricks
3.6.3.1
Subtraction from Required reinforcement
Normally, as shown in chapters above, for example, when Additional reinforcement is needed, it is calculated as simple difference between required and user defined reinforcement. Similarly the other reinforcement types calculate with it. The user may come across two possible situations when this is declined: o If there is already defined practical reinforcement (the one, which physically exist in the model), which has different material, than the material defined in Member data. If this happens, then user will be warned by the error message below and this user reinforcement is not recognized.
o Second situation may happen when the user has also practical reinforcement defined on the member and has activated the possibility “Check of concrete cover for subtracting 2D user reinforcement from required reinforcement”. This can be done under Concrete > General > Calculation > 2D user reinforcement. When this check box is activated, new input parameter appears just below and the user may define required value. All reinforcement layers within this range will be ignored by the design. The error dialog is also displayed and design will end up in same results as in the first case.
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Let’s demonstrate this on an example from chapter ULS design when only main reinforcement on the whole slab was defined. There is diameter of 12mm used and the distance between the bars is set to 100mm. We can change the material of this reinforcement polygon for example to B500A contrary to B400A, which is defined in member data for first option. Activating the mentioned check box, together with setting the value to 0.1 and changing concrete cover of the reinforcement to for example 60mm. Then we will get these results:
Required reinforcement
User reinforcement
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Additional reinforcement
3.6.3.2
Total reinforcement
Labels
The user may control the display style of the reinforcement through a set of view parameters, which can be found in View parameters setting dialog. These parameters are located under Concrete folder > Reinforcement regions 2D.
Display
This parameter must be ON if the reinforcement is to be displayed.
Display style
This will define the way reinforcement will be displayed. There are four different types of display. o Simple – only the main symbol of the reinforcement directions will be displayed.
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o Distribution - the main symbol of the reinforcement directions will be displayed together with the indication of the distance between individual bars.
o Distribution full - The "real" distribution of the reinforcement is displayed. That will be displayed in the central plane.
o Real positions - All the option mentioned above draw the reinforcement schematically into the middle plane of the reinforced slab. Option Real positions displays the reinforcement in its real (actual) position.
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Upper layer
Switches ON/OFF the layer of the reinforcement at the upper surface.
Lower layer
Switches ON/OFF the layer of the reinforcement at the lower surface.
Display label
This parameter must be ON if the reinforcement labels are to be displayed.
Name Shows the name of the bars. Diameter+distance Shows the diameter and distance of the reinforcement bars.
3.6.3.3
Editing the reinforcement parameters
If the user wants to change some existing reinforcement parameters he might simply edit and modify parameters in the reinforcement attributes. 1. Select the reinforcement that needs editing. 2. The properties of the selected reinforcement are shown in the Property Window. 3. Modify the required parameters. 4. Clear the selection.
3.6.3.4
Editing the shape of the reinforcement region
If the reinforced region was input as a polygon, you can later modify its shape by following procedure below: 1. Select the reinforcement the region of which is to be modified. 2. The properties of the selected reinforcement are shown in the Property Window. 3. Click action button Edit geometry. 4. You can use the right-mouse button to invoke the pop-up menu and insert or delete vertices. 5. Or you can drag-and-drop the vertices by mouse. 6. To finish the editing, invoke the pop-up menu and select End polygon edit. If the reinforced region was input as a point or line object, you can simply modify its shape by adjusting appropriate parameters in the properties.
Note Any function for geometric manipulations can be used to modify the reinforced area. That means that functions like Move, Copy, Stretch, Rotate, etc. can be used.
3.6.4
Free bars
3.6.4.1
New Free bars
The normal way in Scia Engineer is to define the reinforcement in 2D members through 2D member data or by placing some kind of polygon directly using 2D reinforcement service. On the other hand, it may be sometimes more convenient to input separate bars. This feature is also necessary when the reinforcement is imported from a third party program (e.g. Allplan). The principle is that the user defines the shape of the reinforcement bars and then selects the members into which these bars are included. Free bars are considered in all calculations (design and 92
checks). On the other hand, free bars are not included in the bill of material and scheme of reinforcement.
Name
Specifies the name of the reinforced region.
Layer
Defines the layer into which the entity is located.
Position number
Informative parameter, which defines the position number of the bar.
Diameter
Specifies the diameter of the bar.
Mandrel
Specifies the mandrel.
Material
Specifies the material of the bar.
Long/Stirrup
Determines if the bar is a longitudinal bar or a stirrup.
Detailing
If ON, the bar is ignored in design and checks. It is just a structural bar.
Number
It is possible to input a set of bars at a time. This parameter specifies the total number of the bars in one set.
Dir X
This parameter defines the distance between individual bars in the set in X direction.
Dir Y Dir Z
This parameter defines the distance between individual bars in the set in Y direction. This parameter defines the distance between individual bars in the set in Z direction.
Horizontal
Defines the horizontal position of the description (label) of the reinforcement bar.
Vertical
Defines the vertical position of the description (label) of the reinforcement bar.
Location
Defines if anchorage length is to be defined with the bar or not. It is possible to define these five locations:
o None
No anchorages will be defined.
o Begin Anchorage will be possible to be defined at the beginning of the free bar. 93
o End
Anchorage will be possible to be defined at the end of the free bar.
o Both Anchorage will be possible to be defined both at the beginning and at the end of the free bar. o Both separated Anchorage will be possible to be defined both at the beginning and at the end of the free bar independently. Add/subtract
Specifies whether the specified anchorage length is to be added to the input bar or whether the effective length of the bar is obtained from the defined bar by subtracting the specified anchorage length.
Length
Specifies the anchorage length.
Curve type
Defines the type of the curve in bents of the reinforcement.
Curve parameter
Defines the parameter of the selected curve.
Once a free bar is input, it represents a standalone entity that has no relation to any of the defined beams, columns, plates, etc. in the model. It is necessary to allocate the bar to required members. The allocation can be done through the corresponding action buttons. o Manual allocation The user manually selects the members where the reinforcement free bar is allocated. To do so, select the required free bar and click action button [Select allocation]. Then follow with the selection of appropriate members. o Automatic allocation The program automatically selects the members where the reinforcement free bar is allocated. To allocate bars automatically, click action button [Allocate automatically]. The program does the allocation on its own.
3.6.4.1.1 Editing the reinforcement parameters If user want to change some existing free bar parameters he might simply edit and modify parameters in the reinforcement attributes. 1. Select the required free bar. 2. Its properties are displayed in the Property window. 3. Make necessary changes. 4. Clear the selection.
3.6.4.1.2 Editing the free bar geometry Sometimes the user also needs to adjust or redefine the free bar geometry. This can be done by following few steps below. 1. Select the required free bar. 2. Its properties are displayed in the Property window. A few action buttons are displayed in the Property window as well. 3. Click button [Table edit geometry] to get a table with bar coordinates. You may modify the shape in this table. 4. Alternatively, you may click button [Edit free bar geometry] to be able to edit graphically the shape of the bar. When this option is activated, the vertices of the selected free bar are highlighted and can be moved, etc. 5. Clear the selection when everything is done.
3.6.4.2
Explode to free bars
Any standard reinforcement can be exploded into free bars. Once this is done, the reinforcement bars lose all their original properties and become free bars. This operation is irreversible. To go through the procedure follow the steps bellow: 1. Open service Concrete. 2. Start function New free bars > Explode to free bar. 3. Select the required reinforcement. End the selection with ESC 4. You are asked if the reinforcement elements are to be deleted or not. 94
5. Select YES if you want to have just the free bars (the original reinforcement is transformed into free bars.) 6. Select NO f you want to keep the original reinforcement and have its copy converted into the free bars.
3.6.4.3
Free bars user reinforcement
Free bar is a different entity than reinforcement polygon and the displayed user reinforcement consisting of free bars may, and usually does, look differently. We can show the difference on a simple slab, already used in previous chapters. We will display one-directional user reinforcement for lower surface of the slab. Reinforcement is defined in the global x-axis direction. In the first picture, there is a standard reinforcement polygon defined with bars (diameter 10mm) and 500mm spacing. In the second picture, there are free bars created from the reinforcement polygon that is in the first picture. Reinforcement amounts are the same on both slabs. We are displaying the user reinforcement defined on the slabs. Reinforcement polygon
Free bars reinforcement
As it is clear from the pictures, displayed amounts of reinforcement are NOT equal, although amounts of reinforcement defined on those two slabs are identical. This is due to the inner algorithm of free bar recalculation. This algorithm may be described in a few steps: o software checks the free bar diameter and calculates the free reinforcement bar area. In our case it is π (10/2)2 = 78,5mm2. o then a “virtual reinforcement polygon” is internally created on 300mm long section of the slab (virtual reinforcement polygon area equals 300*free bar length) o the intensity of this “virtual reinforcement polygon” is calculated from the arithmetic product of the free reinforcement bar area and hardcoded value of (1/0,3). In our case it is 78.5 * 1/0,3 = 262 mm2
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o the last step is to assign the appropriate intensity of reinforcement into each mesh element which lies (even a part of it) under our internal virtual reinforcement polygon. The value will be proportional to this area under the virtual reinforcement polygon. As we have set 2D mesh element size to 200mm, there are a few “situations” on our slab” Let’s delete a few free bars to analyze different possible free bar layouts. The virtual reinforcement area is represented by red area and free bars are highlighted by purple line: o
the edge – mesh element size is 200mm, virtual reinforcement area width above the element is 300/2 = 150mm. User reinforcement amount in adjacent mesh element is 262 * 150/200 = 196mm2
o
free bar on mesh line – similar to the previous case. mesh element size is 200mm, virtual reinforcement area width above the elements is 300/2 = 150mm. User reinforcement amount in both adjacent mesh elements is 262 * 150/200 = 196mm2
o
free bar in the middle of mesh element –. mesh element size is 200mm, virtual reinforcement area width above the middle element is 200mm and virtual reinforcement area width above the adjacent elements is (300-200)/2 = 50mm. User reinforcement amount in the middle mesh element is 262 * 200/200 = 262mm2 User reinforcement amount in both adjacent mesh elements is 262 * 50/200 = 65mm2.
Now it should be clear how the algorithm works and two possible solutions for improving the displaying results can be introduced. o minimising free bar distances will cause that virtual reinforcement polygons will overlay the ones laying next to it and will provide more continuous results o as the user may not want to change the distance between reinforcement bars, increasing the 2D mesh element size will result in more continuous results as well. In the picture below, there is the same slab with the 2D mesh element size set to 400mm. These results are much more consistent then the results at the beginning.
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3.7
Averaging strip
This functionality provides automatic averaging of peak results around defined points or along defined line strips on slabs. The users can define several styles how to calculate the averaged values. The averaging can be applied to internal forces on slabs and to required reinforcement areas used in the design of reinforcement in concrete slabs. The averaging algorithm uses only the FE nodes that are located inside the averaging strip. This may cause certain inaccuracies especially in the combination with larger finite elements. Therefore, it is recommended to redefine mesh or define internal edges along the averaging strips. This ensures that finite element nodes are generated along the edge of the averaging strip, which may significantly improve the accuracy. The averaging algorithm can be applied to internal forces in slabs and required reinforcement areas in slabs. Each of the averaging is performed separately. It means that averaging internal forces are calculated from non-averaged internal forces and averaged required reinforcement areas are calculated from non-averaged required reinforcement areas. Thus it is NOT true that the averaged required reinforcement areas are calculated from averaged internal forces. The averaging strips are defined as what is termed additional data. This fact together with some other characteristics of the averaging strips leads to the following rules concerning the manipulation with the already defined strips: o No geometrical manipulation is supported (i.e. the averaging strip cannot be copied, moved, etc.) The only exception is the direct editing of the coordinated of the definition points in the Property Window. o The averaging strip can be normally deleted. o The removal or editing of the defined averaging strip DOES NOT influences the results. o If the slab that contains the averaging strip is moved, copied, etc. the averaging strip "goes with" its master slab. o The averaging strips react to the activity of the slabs. It means that only averaging strips that are defined on active slabs are visible. o Check of data verifies the position of the strips and all invalid strips (e.g. located out of the master slab) are deleted. To create a new averaging strip the user may simply double click item Averaging strip in concrete tree. The dialog shown below appears. The user may define in it a few parameters which will determine the averaging strip location and its parameters. After confirmation the user defines averaging strip location in the graphical window.
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Name
Specifies the name of the strip.
Type
Specifies the averaging strip input type o Strip
The averaging strip is defined by a line with a specified width.
o Point The averaging strip is defined by a point, width, length, and angle (that specifies the direction of the strip). Width
Defines the width of the averaging strip.
Length
Active only if Type = Point. Defines the length of the averaging strip
Angle
Active only if Type = Point. Defines the direction of the averaging strip.
Direction
Specifies the direction in which the averaging is to be calculated
o Longitudinal The averaging is done along the defined strip. We can imagine that the strip represents a 1D member and we want the program to smooth the distribution of the result along that 1D member. o Perpendicular The averaging is performed in the direction that is perpendicular to the length of the strip. This option is for special purposes only. o Both The averaging is made in both directions. Again, this option is for special purposes only, e.g. heads of columns. o None No averaging is made. This option may be useful if one (or several) defined averaging strip(s) should be temporarily ignored while other strips are still required to be used. We can demonstrate the functionality on a simple example. Let’s create a 4x4 meters concrete slab with thickness of 200mm, made of concrete C20/25. It will be supported according to the picture and subject to self weight. The mesh size is set to 1 meter. Two meter wide averaging strip was input in the Y direction with the averaging direction set to 'Perpendicular'.
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Non-averaged result of moment my with location parameter set to In nodes, no avg.
Results of moment my averaged with averaging strip, with location parameter set to In nodes, no avg.
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Manual verification Create sections perpendicular to the inputted averaging direction. In this example, the averaging was set to 'perpendicular' => create sections in longitudinal direction. o 2D section A is input just outside the strip from (0;3,001) to (4;3,001) o 2D section B is input just inside the strip from (0;2,999) to (4;2,999) o 2D section C is input in the middle of the slab from (0; 2) to (4;2) Non averaged result of moment my on 2D sections with location parameter set to In nodes, no avg. Parameter course is set to Precise possibility.
Non averaged result of moment my on 2D sections with location parameter set to In nodes, no avg. Parameter course changed to Uniform possibility.
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The conclusion is that in 2D section A the moment my has value -1,38 KNm, in 2D section B 4,45 KNm and in 2D section C -7 KNm. Numerical results of moment my averaged with averaging strip, with location parameter set to In nodes, no avg.
Conclusion Now if we compare this averaged numerical results in mesh nodes and the non averaged results on 2D sections, we come to the conclusion that the values are equal.
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Note Basic size of the averaging strip should be, in general, sum of the width of the support and thickness of the slab doubled. Nevertheless, the final size of the averaging strip should be always checked by an experienced engineer. If the averaging strip is not in the coordinate system of the macro, then the transformation of internal forces to the averaging strip LCS is done before the averaging itself. After that, a backward transformation of the averaged internal forces back to the macro coordinates is performed. A special view parameter can be found in the View parameters setting dialogue, under folder Structure/Averaging strips. Tick option Display to see the averaging strips (default) or clear the option to hide them.
3.8
Code Dependent Deflections (CDD)
3.8.1
Introduction
The names PNL calculation (or analysis) (physically non-linear calculation) and PGNL calculation (or analysis) (physically and geometrically non-linear calculation) are taken from previous versions of the software. These terms are very similar and may be a bit misleading. Therefore, it is useful to start with a few words about the features and principles of the two types of analysis. First of all, it may be reasonable to establish more explanatory names. What was known as a PNL calculation should be called calculation of deflections according to a standard. Starting from version 2008.1 the term PNL was replaced by more suitable Code Dependent Deflections (CDD) What was known as a PGNL calculation should be called physically (and geometrically) nonlinear calculation. This fact in turn may lead to shortening of the name of the second calculation type to "physically non-linear calculation" which may be abbreviated PNL. Now you can see one of the reasons why a more reasonable naming should be introduced. The second reason is that the old PNL calculation (CDD from 2008.1 on) is not a real physically non-linear calculation in terms of finite element method (contrary to PGNL that is a real nonlinear calculation). It is a two-step solution following exactly the regulations given in technical standards for design and checking of concrete structures. Both analyses are aimed primarily at concrete structures. The "calculation of deflections according to a standard" has been designed exclusively for concrete beams and plates, as it is based on the wording of technical standards for design and checking of concrete structures. The "physically (and geometrically) non-linear calculation" is a general procedure tailored for the analysis of concrete frames (as it takes into account the provided reinforcement), but it is not limited to such structures.
3.8.2
In general
This calculation of deflections depends (is based) on standards. Therefore, it represents a standard-related calculation that is performed in two steps. First, a normal linear calculation is carried out and the computed internal forces are used to input the reinforcement (the provided reinforcement) or at least to determine the required reinforcement areas. The procedure continues with the calculation of cracks and their effect on the stiffness of individual elements. This weakening is then input into the solver. Finally, the calculation (linear one) is run once more with this reduced stiffness’s taken into account. Which is exactly what the technical standards require. The short-term deflection is calculated. This deflection is multiplied by the creep coefficient and the long-term deflection is obtained. It is known that the elastic deflection multiplied by the creep coefficient equals to the deflection due to creep. Then, we add the long-term deflection to the shortterm deflection and get the total deflection that can be assessed in accordance with the standards. This calculation of the effects of creep is simplified and can be used for a limited set of situations. In fact, in case of reinforced concrete it covers most possible situations, as the history of assembly does not have to be followed. In other words, if the history of assembly steps does not have to be followed, this procedure can be applied. The solution consists of a simplified method of calculation. An equivalent flexural stiffness is used to take into account the effects of cracking, material nonlinearity and creep. Creep is taken into the analysis using the effective modulus of elasticity for concrete according expression 7.20 of EN 1992-2-2
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The deformation for other codes than NEN 6720 is calculated by reducing the stiffness’s using the following so-called Stiffness/Moment diagram:
Where:
Mr is the cracking moment Mu is the ultimate moment
The physical non-linear deformations are calculated based on the concept of “quasi”-nonlinearity. This means that linear calculations are used to model non-linear behaviour of the construction. Four steps are used to perform the calculation. o Using the short-term stress and strain diagram for concrete, the deformations for ‘creep’load is determined. The ‘creep’-load is commonly the quasi-permanent load (1.0 × DEAD LOAD + FACTOR × LIFE LOAD). The factor is in most cases around 30%. o Using the long-term stress and strain diagram for concrete the deformations for ‘creep’load is determined. o Subtracting the short-term deformation from the long-term deformation the ‘creep’deformation is obtained. Adding the creep-deformation to the linear deformation caused by the representative load (1.0 × DEAD LOAD + 1.0 × LIFE LOAD), the total quasi-non-linear deformation is obtained. To calculate the immediate deformation, the deformation of the permanent load is calculated using the short-term stress and strain diagram. Additionally by subtracting the immediate deformation from the total deformation, the program determines the additional deformation. The calculated deformations in Scia Engineer are: o
o Elastic deformation: Using the short-term stress and strain diagram and representative load combinations. (1.0 × DEAD LOAD + 1.0 × LIFE LOAD) o Creep deformation: Using the long- and short-term stress and strain diagrams and momentaneous load combinations. (1.0 × DEAD LOAD + X × LIFE LOAD) o Total deformation: Elastic deformation + Creep deformation. o Immediate deformation: Using the short-term stress and strain diagram and permanent combination.(1.0 × DEAD LOAD) o Additional deformation: Elastic deformation + Creep deformation – Immediate deformation.
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The short- and long-term stiffnesses are calculated using a so-called creep factor. This creepfactor is dependent on the relative humidity, outline of the cross-section, reinforcement percentage, concrete class, etc. is used to divide the short-term stiffness and obtain the long-term stiffness. There are two check boxes for determining key concrete combinations, for determining the creep factor, in the dialog below.
Use to determine Code Dependent Deflections (CDD) caused by creep option is ON, combination will be used for calculation with creep.
If
this
Use to determine permanent Code Dependent Deflections (CDD) If this option is ON, selected combination will be used for calculation of permanent deformation. Only one permanent combination may be defined. The following steps must be performed before running the CDD calculation: o
Special load concrete combinations must be created. These combinations must contain static loads only.
o
Practical reinforcement should be defined and this reinforcement should fulfil the ultimate state designs
o
If no practical reinforcement is input, then at least some required reinforcement must be calculated
o
If no required reinforcement is designed, calculation is determined without changes of stiffness
As it is clear from what is mentioned above, calculation can be performed using both theoretical and practical reinforcement Use of practical reinforcement, .e.g. the reinforcement which is really assumed in the concrete member is a more realistic assumption to perform the analysis. However, the program doesn’t warn the user in the case he doesn’t use the practical reinforcement. In the general setup of concrete, part general calculation, the user can set the default assumption for the reinforcement steel in the CDD calculation
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As,designed The total area of reinforcement is used for the calculation on condition that the design function has been already run and that the program has already calculated the required area of reinforcement. Otherwise, zero value is used (even if the user has manually inserted some reinforcement bars). The total area of reinforcement is the sum of the user-defined reinforcement (through basic reinforcement, through reinforcement zones/regions or through free bars) and calculated additional required reinforcement. The additional required reinforcement may be zero, if the user has already inputted enough user-defined reinforcement. IMPORTANT: Keep in mind that the function calculating the required areas of reinforcement MUST HAVE BEEN run before. Otherwise, the user-defined reinforcement is ignored and ZERO value is used. As, user The user-defined reinforcement is used for the calculation. The term userdefined reinforcement covers the basic reinforcement specified in member data, reinforcement bars inputted through reinforcement templates in reinforcement zones (1D members) or regions (2D members), and free bars of reinforcement. In order: [ As, user ]; [ As,designed] If there is any user-defined reinforcement, it is used, otherwise, the total reinforcement is used (which in fact means the calculated required area of reinforcement). Remember, that for the second option, the design function must have been already run. In order: [ As,designed]; [ As, user] If the design of reinforcement has been already performed and the required area of reinforcement has been already calculated, it is used. Otherwise, the user-defined reinforcement is used. The reduced stiffness for Walls is not calculated when the CDD – deformations calculation is performed. Deformations of beams, plates and shells are calculated by integrating the non-linear curvatures over the length of beam or slab. However, if some element has the value of Md larger than Mu, than the stiffness according to Mu is taken. Since the finite element method can give large internal
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forces due to singularities, etc. the calculation is allowed to continue without an error message, but supplies messages after the calculation has finished. The program always converges to a solution. The program does not warn the user when the loading is bigger than the capacity of the cross section. It is assumed that the user did in a first step a proper design of the reinforcement in the concrete members.
Note The user can define the creep coefficient, or let the program determine the creep coefficient using the EC appendix B1. Please find the setting in the concrete setup at the SLS settings An error message concerning about not sufficient mesh may appear during the CDD calculation. If so, mesh should be improved and then linear and CDD calculations should be started again. In the solver setup, the user can change the amount of reinforcement for the CDD. This option is intended to correct the theoretical reinforcement by this coefficient. Default value is 1. Let’s remark that the program doesn’t display a warning when you use this option when practical reinforcement has been defined in the member.
3.8.3
Example
To demonstrate this functionality we can continue with the example used in previous chapters of ULS and ULS+SLS designs. As a first step we need to create concrete combinations necessary for calculation of code dependent deflections. We will set Load case 1, where only self weight is defined, for determining permanent code dependent deflections and Load case 2, where all load are defined, for determining the code dependent deflection caused by creep. We will also define reinforcement for second direction and also for upper surface. User reinforcement for both surfaces and both directions will satisfy the ULS design only. For information about the input reinforcement see table below:
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User reinforcement As1-
User reinforcement As2-
User reinforcement As1+
User reinforcement As2+
After the reinforcement design of the user reinforcement for ULS state, it is time to define the reinforcement determining the Code dependent deflections. It can be done in Setup dialog in Menu > Setup > Concrete solver. Picture of this dialog is shown in the previous chapter. We will set this parameter to User reinforcement possibility. Then we must run the design once again to regain the amounts of reinforcement. Now if we start the FE analysis dialog, possibility Concrete – Code Dependent Deflections (CDD) is activated and may be chosen. After selection of this option we can proceed to calculation itself by pressing Ok button.
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After confirmation of the FE analysis dialog a warning error may appear. This will warn the user about non-consistent location parameter of 2D design.
If the user accepts the dialog above, the calculation itself is started and process of determining the deflections should be finished with informational End of analysis dialog. Here maximal values of translation and rotation is displayed.
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Now if we go back to the concrete service, two new items Stiffness presentation and Deformations, may be found here. They are both under Member check item. See picture below.
3.8.3.1
Stiffness presentation
In this service the user may choose to display two types of results. Location is set permanently to “In centres” possibility. The parameter type of values may be set to: o Required area As1-
longitudinal reinforcement for lower surface and direction 1
As2-
longitudinal reinforcement for lower surface and direction 2
As1+
longitudinal reinforcement for upper surface and direction 1
As2+
longitudinal reinforcement for upper surface and direction 2
As1
overall longitudinal reinforcement for both surfaces and direction 1
As2
overall longitudinal reinforcement for both surfaces and direction 2
o Stiffness EI1,s
bending stiffness from short term load in direction 1
EA1,s
normal stiffness from short term load in direction 1
EI2,s
bending stiffness from short term load in direction 2
EA2,s
normal stiffness from short term load in direction 2
EI1,l
bending stiffness from long term load in direction 1
EA1,l
normal stiffness from long t term load in direction 1
EI2,l
bending stiffness from long term load in direction 2
EA2,l
normal stiffness from long term load in direction 2
There may be also displayed values for required areas and stiffness for the third direction, but it must be defined in advance. Here is an example of the bending stiffness from short-term load in direction 1.
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3.8.3.2
Deformations
In this service, the user may display the code dependent deflection calculated from the settings already defined in whole process. The user may choose to set parameter Deformation to three possible options: o linear
will display linear deformation
o nonlinear
will display nonlinear deformations
o nonlinear with creep
will display nonlinear deformations including creep
Parameter type of values may be set to another three options: o Uz
deformation in Z-axis direction
o Fix rotation around X-axis direction o Fiy rotation around X-axis direction In the table below, we can compare the deformation in the Z-axis direction with different Deformation parameter. Linear
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Nonlinear
Nonlinear with creep
As it is clear from the table, the largest values of Code Dependent Deflections are for Nonlinear with creep deformations.
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References [1]
EN 1992-1-1: 2004 Eurocode 2 : design of concrete structures – Part 1: General rules and rules for building
[2]
ENV 1992-1-1: 1991 Eurocode 2 : design of concrete structures – Part 1: General rules and rules for building
[3]
Hobst, Ed.: ESA-PRIMA WIN & SCIA.ESA PT REINFORCED CONCRETEDESIGN OF 2D STRUCTURES, Theoretical background
[4]
Internal Scia Engineer manuals
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