Sensitivity of special steel moment frames to the influence of column-base hysteretic behavior including gravity framing system

Special Steel Moment Frames (SMFs) are one of the most common lateral-load resisting systems. Hysteretic energy in these systems is dissipated by the development of plastic hinges at the end of the beams. In order to guarantee the desired collapse mechanism, columns, beam-column, and column base connections are sized employing the capacity design-criteria. Recent research on column base plates indicates that these connections pose high deformation capacity and may be used as part of the dissipative energy system. These findings have motivated studies to evaluate a possible strong-column weak-base connection criterion, implying a reduction on the base demands and, consequently, a nonlinear incursion of these connections. The implication is a potential reduction of connection costs at similar building performance. However, these studies have neglected the influence of the gravity system on the seismic performance of the SMFs analyzed. Consequently, a study that includes the profound influence of gravity system while investigates the consequences of seismic demands reduction of base plates has not been conducted. Against this backdrop, this research presents a parametric study conducted on an 8-story SMF, which evaluates the probability of collapse considering three different levels of base connection strength while including the gravity system. Results indicate that gravity systems tend to enforce the building to deform on the first mode of shape even at large floor displacements while base rotations are increased significantly. The design implication is that base-connections should be kept designed to carry the plastic capacity of the column.