Relationship between the variation of seismic capacity after damaging earthquakes, collapse probability and repair costs: detailed evaluation for a non-ductile building

Decisions on reparability for damaged buildings after an earthquake are often con-troversial, and they should properly take into account the variation of building safety level due to damage and the repair costs. A significant indicator for the appropriate course of action is the so-called Performance Loss (PL), that is a measure of seismic safety decay. PL can be determined as a function of the variation of building seismic capacity from the intact to dam-aged state. This study investigates, by means of a detailed case study, on the expected PL for increasing seismic demand and its relationship with varied building safety level and repair costs. We simulate the response of an existing non-ductile reinforced concrete building using a finite element model that properly accounts for both flexural, shear and axial failure of mem-bers and accounts for joints behavior. Different definitions of building collapse are introduced, and Incremental Dynamic Analyses are performed with a representative set of input ground motions both for the intact and damaged structure. In order to evaluate aftershock fragilities, multiple Mainshock-Aftershock sequences are built through suitable scaling of selected accel-erograms. Fragility curves for the intact building and the aftershock fragility curves are used to evaluate PL and the variation of collapse probability for main-shocks of increasing return period TR. Also, corresponding repair costs are determined. The study shows interesting rela-tions between damage levels and repair costs that may be simulated with detailed analyses and associated PL, representing a first insight in the establishment of relations between PL and repair and/or upgrade decisions.