Fragility curves. The key element of risk assessment for built assets

The aim of risk analysis is to evaluate the expected losses, taking into consideration the exposed structure and the related contents and the consequences to involved people. The quantification of the risk is intrinsically probabilistic because hazards are random actions and the performance of structures, as well as losses and consequences to people, are affected by uncertainties. Therefore, the derivation of fragility curves is critical for risk quantification.   Fragility curves for a given damage state provide the probability that such a damage is reached or exceeded as a function of the intensity measure of the studied hazard and/or the engineering demand parameter.

Bridges are usually the most critical and vulnerable structures of road and rail transport systems, especially when considering earthquake hazard. Hence, extensive research efforts have been conducted to derive seismic fragility curves for such structures.  A comprehensive work on the compilation of seismic fragility curves for bridges can be found here