Cold-Formed Steel Frame and Beam-Column Design

1. CORNELL UNIVERSITY School of Civil and Environmental Engineering Cold-Formed Steel Frame and Beam-Column Design Andrew Sarawit Professor Teoman Peköz Sponsored by: Rack Manufacturers Institute American Iron and Steel Institute

2. Objective Project Outline To verify or modify the RMI and the AISI provisions for frame design Column Bases Beam to Column Connections Members Cold-Formed Steel Frames FREE Computer Programs

3. Cold-Formed Steel Frames Two approaches are begin considered 1. Effective length approach (Kx > 1) - Concentrically Loaded Compression Members - Combined Compressive Axial Load and Bending 2. Notional load approach (Kx = 1)

4. Effective Length Approach (Kx>1) Concentrically Loaded Compression Members Approach 1a elastic critical buckling load is determined by using the AISI torsional-flexural buckling provisions Approach 1b elastic critical buckling load is determined by performing an elastic buckling analysis

5. Effective Length Approach (Kx>1) Combined Compressive Axial Load and Bending Approach 1c elastic critical buckling load is determined by using the AISI torsional-flexural buckling provisions Approach 1d elastic critical buckling load is determined by performing an elastic buckling analysis

6. Notional Load Approach (Kx=1) Approach 2a  Approach 2b Approach 2c and a 10% reduced flexural stiffness analysis model is used This can done by using a reduced flexural stiffness for all members and connections in the analysis model

7. C4 C5 C6 C1 C2 C3 P P C7 C8 C9 Isolated Rotationally Restrained Sway Column Study 1: The finite element method was used as the basis for evaluating the accuracy of the design approaches 540 models were studied - 3 material yield stresses (33, 55, 70 ksi) - 20 different rotational end-restraints GA ranging from 0 to 60 GB ranging from 0 to  - 9 column sections

8. Effective Length Approach Buckling load from AISI TFB Eq. Buckling load from FEM Approach 1aApproach 1b

9. Effective Length Approach Buckling load from AISI TFB Eq. Buckling load from FEM Approach 1cApproach 1d

10. Notional Load Approach Approach 2aApproach 2b

11. Notional Load Approach Approach 2aApproach 2c

12. Study 2: Cold-Formed Steel Frames 972 pallet rack configurations were studied 2 load cases were considered - 3 frame dimensions (bays x stories: 2x3, 6x3, 6x6) - 2 upright frame configurations - 9 column sections - 3 Material yield stresses (33, 55, 70 ksi) - 6 beam to column connection stiffnesses Gravity load case Seismic loads case

13. Gravity Load Case: Effective Length Approach Approach 1aApproach 1c

14. Gravity Load Case: Notional Load Approach Approach 2aApproach 2b

15. Gravity Load Case: Notional Load Approach Approach 2aApproach 2c

16. Seismic Load Case: Effective Length Approach Approach 1c

17. Seismic Load Case: Notional Load Approach Approach 2aApproach 2b

18. Seismic Load Case: Notional Load Approach Approach 2aApproach 2c

19. Conclusion • Notional load approach agrees better with the finite element results than the effective length approach does • Notional Load Approach 2c is recommended • Use the effective length factors Kx = 1, Ky = 1, and Kt = 0.8 • Use the notional load parameter  = 1/240 • A 10% reduced flexural stiffness analysis model is used - This can done by using a reduced flexural stiffness for all members and connections in the analysis model