IMPROVED FRAGILITY FUNCTIONS FOR RC BRIDGE POPULATIONS

Abstract eng:
When carrying out loss assessment of a road network within a certain region, the characterization of the vulnerability of the existing population of bridges is one of the most relevant aspects. To such extent, in the last decades, the engineering community has recognised fragility curves as one of the fundamental and most effective tools in seismic risk assessment, correlating the probability of exceeding of specific limit states, which can instead be correlated with damage and loss, for different levels of intensity measures (IMs). The available literature mainly provides such curves as function of peak ground acceleration (PGA) or spectral acceleration (Sa), often preferred for the availability of national hazard information in terms of such parameters. However, when dealing with a bridge population of reinforced concrete bridges, Fajfar Index, peak ground velocity and root mean square velocity have been recently identified as the most promising intensity measures, in terms of efficiency, proficiency and sufficiency, notwithstanding the acceptable performance of PGA and Sa. As such, this paper intends to further extend the analysis of RC populations of bridges by providing a statistically sound comparison of analytical fragility curves based on traditional and innovative intensity measures of an extensive bridge population. Nonlinear static analyses of 3D RC bridge models are carried out. The bridge population is randomly generated using Latin Hypercube sampling in order to include geometrical variability, in addition to aleatory and epistemic uncertainties. For what concerns the seismic ground motion, a proper selection of records was performed, according to a recent selection and scaling procedure (Conditional Spectrum Method).

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