Structural evaluation of steel self-centering moment-resisting frames under far-field and near-field earthquakes

The design formulations, structural performance, and energy-based results of steel buildings of self-centering moment-resisting frames (SC-MRFs) with post-tensioned (PT) connections of three different energy dissipation devices including bolted top and seat angles, beam bottom flange friction devices, and bolted web friction devices are investigated under far-field and near-field earthquakes. The results of nonlinear time-history analysis using DRAIN-2DX program show that the simplified analysis used to estimate the inertial forces distributed through collector beams is not sufficiently precise since it leads to the underestimation of design beam axial forces and connection moments in exterior bays. The overestimation of design displacement demands of SC-MRFs with bottom flange friction devices results in bigger sections of beams and columns than are necessary. In addition, this SC-MRF system is not as effective as other two systems to dissipate the input energy. It is recommended to symmetrically use beam flange friction devices to achieve higher level of energy dissipation and lower fabrication costs. On the other hand, SC-MRFs with web friction devices is identified as the most efficient system to minimize the recoverable energy and SC-MRFs with top and seat angles provides medium level of energy dissipation. Different from far-field earthquakes, the input energies of SC-MRF structures under near-field ground motions are distinguishable by hikes of maximum values at the early stages of earthquakes. Furthermore, absolute energy components are substantially higher than relative energy components under near-field earthquakes. These phenomena should be considered in the formulations of energy factor and energy-based design procedures of SC-MRF systems.