Accounting for spectral shape in simplified fragility analysis of case-study reinforced concrete frames

This paper deals with the selection of optimal intensity measures (IMs) for displacement-based seismic demand assessment and fragility derivation of case-study mid-rise reinforced concrete (RC) frames. The considered frames represent distinct RC vulnerability classes in the Mediterranean region. Optimal IM selection is performed by means of probabilistic seismic demand models considering multiple IMs and various engineering demand parameters (EDPs). Based on findings from previous and concurrent studies, a small subset of potential IMs is investigated here, including conventional peak IMs and two advanced scalar IMs accounting for spectral shape over a range of periods. Probabilistic seismic demand models are built on data obtained from analysis of the case-study frames subjected to over nine hundred ground motions by employing an innovative capacity spectrum method using inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. This approach has the advantage of simplicity and rapidity over other methods as nonlinear dynamic analysis. This study concludes that advanced IMs, and particularly the ones accounting for period elongation (due to the nonlinear structural behavior) and structure-specific parameters, can effectively satisfy all the selection criteria, including the hazard computability criterion.