REFINED ANALYTICAL COLLAPSE CAPACITY SPECTRA

Recently, two of the authors have introduced the collapse capacity spectrum methodology, which allows the assessment of the collapse capacity of highly inelastic P-delta sensitive regular frame structures without performing non-linear time-history analyses. The main ingredient of this method is the collapse capacity spectrum, which represents the seismic collapse capacity of an inelastic non-deteriorating single-degree-of-freedom system vulnerable to the P-delta effect as a function of its initial period, negative post-yield stiffness ratio, viscous damping coefficient, and the shape of the hysteretic loop. In the present study, multiple linear regression analyses are applied to provide enhanced analytical expressions of these spectra. The record-to-record uncertainty of the collapse capacity is captured through median, 16th and 84th percentile spectra. For several test systems analytical collapse fragility functions based on these spectra are set in contrast with the corresponding sorted individual collapse capacities. These examples prove the superiority of the proposed analytical expressions compared to its original formulation.