In this monograph, we study the definition of possible damage in bridges by using simplified structural models. The state-of-the-art of the seismic vulnerability of bridges is first discussed and the theoretical background of the methods to evaluate their vulnerability is commented. The existing methodologies to evaluate the vulnerability of bridges are then described in detail; The methods are classified as: (1) methods based on the vulnerability index; (2) methods based on structural analyses; (3) methods based on expert opinion and statistical evaluations; and (4) methods based on statistical evaluations of the observed damages. A simplified methodology to estimate the seismic vulnerability of reinforced concrete bridges with simple pier bent and elastic girders is then proposed. The methodology is applied to an existing bridge, built 30 years ago. The elastic and the non-linear procedures of evaluation are first discussed. The non-linear procedure includes an analytical methodology to estimate the local damage in the piers, using a continuous damage model, and the global damage of the bridge. Thereinafter, a numerical process allows considering artificial seismic actions compatible with the velocity spectrum of deterministic records. Finally, an application of the proposed analytical procedure to estimate the seismic vulnerability of the real bridge is given. The obtained damage results show that the studied bridge would suffer only a minor damage when a seismic action similar to that of the expected seismic scenario is considered. The proposed methodology is compared with previous experimental results and with analytical results obtained by using commercial codes. It is shown that the proposed simplified methodology is less computational time consuming and that it provides reliable values of the maximum damage suffered by the bridge piers.