Development of Fragility Curves for Single-Column RC Italian Bridges Using Nonlinear Static Analysis

The main objective of this study is to assess the accuracy and suitability of Nonlinear Static Procedures (NSPs) in the development of analytical damage fragility curves for seismic risk assessment of large portfolios of Reinforced Concrete (RC) bridges. Seven NSP approaches, from widely used single-mode conventional pushover-based approaches to the more rigorous multi-mode conventional or adaptive pushover-based procedures are implemented. By systematically comparing fragility curve estimations in terms of shape and accuracy in predicting mean annual rates of exceeding predefined damage limit states, results indicate that when bridges can be classified as higher mode sensitive, multi-mode-based approaches offer a powerful alternative to rigorous time history analysis. In particular, Generalized Pushover Analysis and Adaptive Capacity Spectrum methods offer a better performance with respect to other multi-mode alternatives. For first mode dominated bridges, with a classical first mode shape, the performance of all methods is similar. Single-mode based procedures present an acceptable alternative only in such particular cases, for which the N2 method represents a viable approach when compared to other single-mode or multi-mode procedures.