Andrew Sarawit Professor Teoman Peköz Sponsored by: Rack Manufacturers Institute American Iron and Steel Institute C ORNELL U NIVERSITY School of Civil and Environmental Engineering Cold-Formed Steel Frame and Beam-Column Design

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

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

Effective Length Approach (K x >1) Concentrically Loaded Compression Members 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

Effective Length Approach (K x >1) Combined Compressive Axial Load and Bending 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

Notional Load Approach (K x =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

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

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

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

Notional Load Approach Approach 2a Approach 2b Approach 2a Approach 2b

Notional Load Approach Approach 2a Approach 2c Approach 2a Approach 2c

972 pallet rack configurations were studied 972 pallet rack configurations were studied 2 load cases were considered 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 Study 2: Cold-Formed Steel Frames Gravity load case Seismic loads case

Approach 1a Approach 1c Approach 1a Approach 1c Gravity Load Case: Effective Length Approach

Approach 2a Approach 2b Approach 2a Approach 2b Gravity Load Case: Notional Load Approach

Approach 2a Approach 2c Approach 2a Approach 2c Gravity Load Case: Notional Load Approach

Approach 1c Seismic Load Case: Effective Length Approach

Approach 2a Approach 2b Approach 2a Approach 2b Seismic Load Case: Notional Load Approach

Approach 2a Approach 2c Approach 2a Approach 2c Seismic Load Case: Notional Load Approach

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