Generalità

One of the hot topics in earthquake engineering is the assessment of the existing structures with regard to seimic actions. In Italy (but not limited to), the majority of the existing structures is designed without a proper "anti-seismic" philosopy. Focusing on bridge structures, it is clear that they assume a much higher importance level since in most cases they play a key role in transportation webs. Therefore, their performance must be guaranteed also in the aftermath of major earthquakes.
For public authorities, it is fundamental to have clear information about the consistency level of bridges portfolios, to plan inspection, mantainence and mitigation actions. However, due to the high number of involved bridges, this process may be particularly onerous. Therefore, more simplified methods are needed, with respect to common analyses that involve a single bridge. Therefore, the main goal of such regional scale analyses is to construct priority lists. These allow to plan immediate inerventions for some bridge, and proceed to more refied analyses for the remaining ones.

Regional-scale seismic vulnerability

Typically, regional-scale seismic vulnerability analyses are based on check-lists that can be used for visual inspections. Hence, numerical indices are calculated that are related to the actual damage reported for the bridge, its vulnerability (related to a reference seismic action) and it's loss of functionality (That allows to quantify indirect losses).
However, such analyses are affected by a level of subjectivity. In fact, the above-mentioned indices are based on parameters whose numerical value is assigned by the engineer performing the inspection. Moreover, each parameter is assigned with a weight coefficient which is selected by the author of the used procedure.

Objective of this work

The objective of this work is to provide a mechanically-based method, thus objective, to perform vulnerability analyses of RC bridges. The proposed method is particularly simple and it is based on a low level of knowledge of the structure. This reflects in a low cost of the inspection. The method is based on mechanical models appropriate for the modern seismic engineering.