Selection of optimum intensity measure parameters for seismic fragility analysis of typical Roman aqueduct

Improving seismic risk mitigation actions through the vulnerability assessment of existing structures is a key focus in earthquake engineering. Ground motion intensity measures (IMs), which analyze the correlation between seismic hazard analysis and structural seismic response, are essential for creating reliable, analytically-based fragility curves. This article aims to identify the best IMs for use in probabilistic seismic demand models (PSDMs) for masonry Roman aqueducts and to develop fragility curves for these IMs. Initially, a finite element model was created based on data from field records and laboratory tests on structure samples, followed by response spectrum analysis. In the PSDMs developed in this study, maximum inter-story drift ratio and maximum normal strain were used as engineering demand parameters (EDPs), and 37 different IM parameters commonly cited in the literature were chosen to identify suitable IMs. The Cloud analysis method was applied using 478 unscaled real earthquake ground motion records. Numerous regression analyses were conducted to evaluate the candidate optimal IMs, considering metrics such as correlation, efficiency, practicality, proficiency, and sufficiency. Following detailed analysis and evaluation, the spectral acceleration at the fundamental period of the structure was identified as the optimal IM parameter. Subsequently, fragility curves were derived based on the lognormal distribution assumption for other appropriate structure-based and earthquake-based IMs in addition to the optimum IM parameter. The average value of the probability of exceedance of a certain damage state was calculated for the tested IMs. It was concluded that the IM parameter is highly effective in the probability of exceedance value of the damage state. Consequently, using the appropriate IM is critical for accurately assessing the seismic vulnerability and conducting risk analysis of masonry aqueducts.