RELATIONSHIP BETWEEN THE VARIATION OF SEISMIC CAPACITY AFTER DAMAGING EARTHQUAKES, COLLAPSE PROBABILITY AND REPAIR COSTS: DETAILED EVALUATION FOR A NON-DUCTILE BUILDING

Abstract eng:
Decisions on reparability for damaged buildings after an earthquake are often controversial, 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 damaged 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 members 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 accelerograms. 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 relations 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.

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