Bridges play an important role in transportation network. After an earthquake, bridges must remain functional. To reach this goal, vulnerability study must be conducted. The aim of this study is to develop a vulnerability index method for bridges. The most important parameters influencing the seismic behaviour of bridges are identified, and a seismic vulnerability assessment model is developed using the analytical hierarchy process (AHP) to quantify the contribution of each parameter. Using the developed model, several bridges are treated and the obtained results show a good adequacy with in situ observations.

The traffic flux is a complex phenomenon that occurs in existing bridges, what makes their dynamic behavior difficult to understand and badly defined. Indeed, all laws and models reflect from idealizations and empirical approximations. For this reason, the present work proposes a methodological approach for a macroscopic modeling of the traffic based on the probabilistic aspect of the phenomenon. The whole system is described using a probabilistic model where all the factors influencing the highway traffic and the safety of bridges are considered. The basic traffic data and results get using this approach lead to describe the crucial phenomena caused by traffic flux which serves to identify the vehicles speeds limits, the appropriate density and the minimum distance between two moving objects on bridges roadways.

The purpose of an isolation system is to provide an additional means of energy dissipation, thereby reducing the transmitted acceleration into the superstructure. In order to demonstrate the effectiveness of seismic isolation and understand the behavior of seismically isolated bridges a three-span continuous deck bridge made of reinforced concrete is considered. The bridge is modeled as a discrete model and the relative displacements of the isolation bearing are crucial from the design point of view of isolation system and separation joints at the abutment level. The systems presented here are passive control systems and the results of some important experimental tests are also included. The results show that the base shear in the piers is significantly reduced for the isolated system as compared to the non isolated system in the both directions of the bridge. This indicates that the isolation systems are effective in reducing the earthquake response of the bridge.

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