Seismic Fragility and Damage–Hazard Compatibility Curves of Historical Masonry Arch Bridges Under Near- and Far-Fault Ground Motions

This study presents a performance-based seismic assessment of the historical multi-span Çobandede masonry arch bridge using an experimentally calibrated 3D finite-element model. The bridge is analyzed within a cloud analysis framework using 557 unscaled ground-motion records, classified into far-field, near-fault without forward directivity, and near-fault with forward-directivity effects. Four global engineering demand parameters (EDPs) are considered. Regression analyses were performed to develop probabilistic seismic demand models relating the four EDPs to thirty-five candidate intensity measures (IMs). The models were assessed using correlation, efficiency, practicality, proficiency, sufficiency, and hazard-computability metrics. Considering all metrics and the three ground-motion subsets together, peak ground acceleration is identified as the optimal earthquake-based IM and elastic spectral acceleration at the fundamental period, as the optimal structure-based IM. Furthermore, fragility curves were developed for these optimal IMs using all four EDPs for each subset. The fragility functions were then integrated with site-specific seismic hazard to derive damage — hazard compatibility curves in terms of a physical damage ratio. Finally, at a given hazard level, these curves were used to quantify the influence of each subset, the selected optimal IM, and EDP on the expected damage ratio, supporting hazard-compatible, risk-informed evaluation and preservation of historical multi-span masonry arch bridges.