An advanced intensity measure for residual drift assessment of steel BRB frames

To assess the safety of structures after the occurrence of an earthquake or decide about demolition or repair of structures, maximum residual interstory drift ratio (MRD) is one of the most important engineering demand parameters. For evaluating the probability of exceedance of MRD in structure from a specified limit, nonlinear dynamic analyses are performed by employing an intensity measure (IM). IMs link the structural seismic response analyses with the seismic hazard analysis. Employing an optimal IM in seismic evaluation of structures makes the results more realistic and reliable. The power of an IM to predict the seismic response of structures with low dispersion is called efficiency. Moreover, the ability of an IM for rendering the seismic response of structures independent from the other features of the ground motion is named sufficiency. In this study, the efficiency and sufficiency of some traditional and advanced IMs (including scalar and vector ones) for predicting MRD capacity of steel buckling restrained braced frames are evaluated. It is shown that all of the IMs considered do not have sufficiency with regard to scale factor ( SF ). Then, ( Sa ( T 1 ), SaRatio Op‒D ) as an optimal vector IM (optimized by multi-objective particle swarm optimization algorithm) having improved sufficiency with regard to SF is proposed.