Steel Columns under Multi-Axis Seismic Loading: Experimental Findings and Design Recommendations

This paper summarizes the findings of two test programs that investigated the hysteretic behavior of wide-flange columns in steel moment-resisting frames. Both deep and shallow steel columns were examined. The members were subjected to unidirectional and bidirectional lateral loading histories coupled with constant and varying axial load demands. The experimental findings highlight the dependence of the steel column response on the member end boundary conditions, the biaxial bending, the loading history, as well as the test-scaling. Steel columns subjected to high axial load demands do not behave as force-controlled elements as suggested by current nonlinear modeling recommendations in North America. Accordingly, an updated axial force limit is proposed in this case. Moreover, in light of the test findings, seismic design recommendations are proposed to limit column damage during strong earthquake shaking.