Crane Girder Design Procedure

Crane Girder Design to BS 5950-1: 2000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 1- Introduction

2- Using CRANEgirder

3- Crane Classes

4- Single or Double Flange Wheels in the End Carriage

5- Impact Factor

6- Crane Girder Section

7- Calculated Weight of the Crane Girder

8- Plastic Modulus of the Section

9- Section Classification of the Compound Girder Section

10- Structural Deployment of Various Section Parts

11- Horizontal Wheel Loads

12- Crabbing Force of Trolley

13- Partial Factors for Loads

14- Load Combinations

15- Vertical Wheel Loads

16- Vertical and Horizontal Deflection

17- Shear Resistance at Supports Fv < Pv 18- Vertical Moment Resistance x-x

19- Horizontal Moment Resistance y-y

20- Web Bearing & Buckling at Support

21- Local Compression under the Wheel

22- UB-Flange to Top Section Weld

23- Reactions on to the Support Structure

24- Cautions & Limitations of Use

25- References 1 2 3

4

5

Crane Girder Design to BS 5950-1: 2000 User Notes An Excel Template for the Design of Crane Girders to BS5950-1:2000 by Dr Shaiq U.R. Khan BEng (Civil), MEng, PhD, PE, CEng, FIStructE

November 2004 Techno Consultants Ltd www.technouk.com

Contents Introduction Using CRANEgirder Crane Classes Single or Double Flange Wheels in the End Carriage Impact Factor Crane Girder Section Calculated Weight of the Crane Girder Plastic Modulus of the Section Section Classification of the Compound Girder Section Structural Deployment of Various Section Parts Horizontal Wheel Loads Crabbing Force of Trolley Partial Factors for Loads Load Combinations Vertical Wheel Loads Vertical and Horizontal Deflection Shear Resistance at Supports Fv < Pv Vertical Moment Resistance x-x Horizontal Moment Resistance y-y Web Bearing & Buckling at Support Local Compression under the Wheel UB-Flange to Top Section Weld Reactions on to the Support Structure Cautions & Limitations of Use References 1- Introduction This Template helps design simply supported crane girders comprising a UB section at its bottom and a PFC, RSC or a Plate section at its top. By omitting the top section, the girder can also be a UB section alone. The compound section of a girder can be Class 1 Plastic, Class 2 Compact or Class 3 Semi-compact sections. Class 4 slender sections as crane girders are outside the scope of this template. BS5950-1: 2000 appear ambiguous for calculating the necessary Zx effective values and it may not be a good idea to use such sections as crane girders. The crane class can be Q1, Q2, Q3 or Q4 as defined in BS 2573-1:1983. The steel grades can be S275, S355 or S460.

The Template allows storing data for up to 100 Crane girders. Any girder data can be recalled, amended and re-stored later to suit design needs. The method of design used is generally based on the Steelwork Design Guide 2. However there is a difference when it comes to deploying section parts for resisting lateral loads. Whereas the Guide ignores the top flange of UB to resist horizontal bending and deflection, this template optionally allows including it in line with a conventional design practice of the past 5. 2- Using CRANEgirder "Home" worksheet allows navigation to all worksheets through its command buttons. To design a Crane Girder, the data input and output is via "Cranegirder" worksheet. Utilising Windows interface, the use of CRANEgirder is self explanatory. All data input is via green colour cells. The user is responsible for values in these cells to make an engineering sense. The result output is via rest of the non-green colour cells At top of the screen, four command buttons allow storing, retrieving and navigating through the stored information. For example using the NEXT and PREVIOUS buttons, data can be viewed in girder sequence numbers. During its use, CRANEgirder keeps an eye on 7 adequacy checks. It reports the outcome at top left corner of the screen in Cell A2. When a girder passes all 7 checks, "All Checks OK" message is displayed. When it is not so, failing check numbers are displayed and the background colour of the cell changes to red. To improve structural usage of the crane girder, eight usage ratios are calculated and a maximum value displayed in upper part of the worksheet. This ratio represents the actual to permitted values on deflection and strength for the chosen girder. 3- Crane Classes The descriptions as per BS2573-1 are: Q1 - Light - hoisting SWL very rarely and, normally light loads Q2 - Moderate - hoisting SWL fairly frequently and, normally moderate loads Q3 - Heavy - hoisting SWL very fairly frequently and, normally heavy loads Q4 - Very heavy - normally hoisting loads close to SWL 4- Single or Double Flange Wheels in the End Carriage Single or double flange wheels can be specified in the end-carriages via a drop down menu. In the case of single flange wheels, the transverse surge is shared by two wheels in one end-carriage of the crane bridge. In the case of double flange wheels (i.e. one flange on each side of the rails), the transverse surge is shared by four wheels in two end-carriages of the crane bridge. Generally, double flanged wheels are assumed in a routine design. 5- Impact Factor For overhead travelling cranes, Cl 2.2.3 of BS 5950-1:2000 states that the impact effects and the vertical and horizontal dynamic loads should be determined in accordance with BS 2573-1.

As stated in Cl 3.1.4 of BS2573-1, the impact factor applies to the motion of the hook load in a vertical direction and covers inertia forces including shock. In order to calculate dynamic wheel loads for Crane girder design, the hook load is multiplied by an impact factor. For example, Table 4 of BS2573-1 gives a value of 1.3 for medium and heavy workshop/warehouse duty cranes. This Template permits using various impact factors. The values that can be selected from a drop down menu are 1.1, 1.25, 1.3, 1.4, 1.5 and 2. The values of 1.1, 1.3, 1.4, 1.5 and 2 are from Table 4 of BS 2573-1. The value of 1.25 is for a traditional design with dynamic effects based on BS 449. 6- Crane Girder Section The Crane girder section can have up to two parts. The bottom section is always a UB. The top section can be a PFC, RSC, Plate or Nil. To select the main UB section, use its drop down menu and click any desired section. To select the top section, again use its drop down menu and scroll down to click any desired PFC, RSC, Plate or a Nil section. The plate section dimensions can be specified by amending h & b dimensions in worksheet PFC. The cells for these dimensions are shown in green colour. To select a Nil section, scroll to very bottom of the drop down list and select Nil. 7- Calculated Weight of the Crane Girder This weight is obtained by multiplying span length and mass/m of the combined section i.e. = L M. It is calculated for information only as the user may need to include the weight of various attachments e.g. crane rails, packing plates, etc. A conversion factor of 1kN = 101.971621297793 kg is used. 8- Plastic Modulus of the Section The plastic modulus Sx is found by considering 5 strips A1 to A5 to represent the combined section. The root radius areas of the sections are ignored for simplicity in calculations. Starting from top, the width of these areas are Dc, (Bb+2Tfc), (Twb+2Tfc), Twb & Bb. The corresponding heights of these strips are Twc, Tfb, (Bc-Twc-Tfb)>=0, (D-Bc-Tfb) & Tfb. The calculation details for Sx are shown in the table. 9- Section Classification of the Compound Girder Section The combined girder section is classified using Cl 3.5.3 and Table (11) of BS5950-1:2000. The dimensions and the limiting width-to-thickness ratios used are shown and described below

Case a - Outstand element of compression flange - rolled section b/T