Stylianos Minas

Spectral shape proxies and simplified fragility analysis of mid-rise reinforced concrete buildings

The objective of this study is to identify an optimal intensity measure (IM) for conditioning probabilistic seismic demands of case-study reinforced concrete (RC) frame buildings, representative of mid-rise RC building classes in the Mediterranean region. The prediction is performed via statistical relationship between multiple IMs (particularly advanced scalar parameters accounting for spectral shape over a range of periods) and various displacement-based engineering demand parameters (EDPs). Such statistical relationships are built on data obtained from analysis of the frames subjected to over nine hundred ground motion records by employing an innovative capacity spectrum method, introduced in the paper, which uses inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. The outcomes of the present work are in a good agreement with previous investigations conducted by other researchers on selecting optimal IMs for predicting structural response by using full nonlinear dynamic analyses for different structural typologies.

Sensitivity Analysis of Different Capacity Spectrum Approaches to Assumptions in the Modeling, Capacity and Demand Representations

Several capacity spectrum assessment methods exist for determination of structural performance of building models subjected to earthquake loading. The repetition of such analysis for earthquakes of increasing intensity will result in the derivation of analytical fragility functions. A comparison of three capacity spectrum assessment approaches (N2, SPO2IDA and FRACAS) has been carried out, highlighting the advantages and limitations of the approaches. Two experimental case studies have been chosen to evaluate the IM-EDP (Sa-Sd, ISDmax%) estimates obtained from the three different capacity spectrum procedures, as well as from non-linear time-history analyses (NLTHA). It is found that all three approaches perform well in estimating the response of a simple steel frame, but that FRACAS provides the best estimate of the response of an irregular reinforced concrete frame. It is concluded that further comparisons of the capacity spectrum approaches with large-scale experiments on structures are required to draw more general conclusions.