Seismic behavior of concentrically braced frames designed using direct displacement-based method

This study is focussed on the evaluation of seismic performance of concentrically steel braced frames (CBFs) designed using direct displacement-based (DDBD) method. Design displacement profile in this method is derived from the inelastic mode shape normalized based on first story displacement. Design base shear of a structure is determined using design displacement spectrum and the equivalent viscous damping. Two low- and medium-rise CBFs, namely, 3-story and 6-story, are designed using DDBD method as well as current practice. These study frames are modelled and analysed in a computer software OpenSEES to compare their seismic performance under a set of selected ground motions. Braces are modelled using force-based fibre-discretized non-linear beam-column elements simulating the effects of inelastic buckling, large strain and low-cycle fatigue. The main parameters investigated are the maximum story displacements, the interstory drifts, the residual drifts and the yield mechanisms. DDBD frames exhibited the improved seismic response as compared to those design as per current practice.