Influence of Collapse Definition and Near-Field Effects on Collapse Capacity Spectra

In the present article, the impact of both near fault ground motions and a finite ductility threshold on the collapse capacity is studied. Single-degree-of-freedom systems with non-deteriorating bilinear hysteretic behavior, vulnerable to P-delta effects, are considered. Defining collapse as excessive ductility is investigated, and the difference to collapse associated with instability is elaborated. Medians of individual record dependent collapse capacities are presented as function of the initial structural period for characteristic structural and ground motion parameters. Analytical expressions for influence coefficients, which account for a differing ground motion set, and finite ductility thresholds, respectively, are derived via non-linear regression analysis.