Seismic response of steel frames considering the hysteretic behaviour of the semi-rigid supports

The influence of the steel column base plate semi-rigid behaviour on the seismic behaviour of steel frames was examined. In order to evaluate this influence, three typical frames with different types of semi-rigid column base connections were modeled. The investigation of the seismic behaviour of these frames was performed with the implementation of nonlinear dynamic analyses using a recorded ground motion of the fault normal component of the 1995 Aigion earthquake in Greece. The analyses were performed using a sequence of hysteretic curves corresponding to the axial load levels during the process evaluation, including the base plate flexibility related phenomena of joint materials' yielding (base plate, anchor bolts and concrete). The direct comparison of the response analyses results, in terms of variation of the fundamental periods, the peak displacements, the column base bending moments and shear forces and the plastic hinges sequence, indicated that the column base flexibility strongly affects the seismic response of the frames and therefore should be always considered.