Response of Self Centering Steel Moment Resisting Frames Against Cyclic Loading

Abstract

A Self Centering Moment Resisting Frame (SCMRF), an alternative to a conventional Moment Resisting frame, is characterized by gap opening and closing at the beam-column interface under earthquake loading. The beams are post tensioned to columns by high strength post tensioning (PT) strands oriented horizontally to provide self-centering forces when gap opening occurs. A Self Centering Moment Resisting Frame for earthquake resistant structures has the attributes of ductility, requires no field welding and returns the structure to its pre earthquake position which prevents permanent deformations when subjected to seismic loading. Energy dissipation is provided by supplemental elements that deform under the gap opening behavior. Unlike special steel moment resisting frame with welded connections a SCMRF can be designed to survive earthquake without much structural damage which provide immediate occupancy performance. Nonlinear static analysis is performed in ANSYS to investigate the effect of posttension load and bracing configuration on seismic performance of frame. The results indicated that an increase in PT force increases the residual drift and maximum load carrying capacity. Bracing in SCMRF is effective in increasing the load bearing capacity and energy dissipation. Bracing shifts the maximum stress position from beam column connection to gusset plate so that it act as sacrificial element which can easily be replaced without damaging the beams or columns.