Seismic evaluation of bridge network of urban city considering the post-disaster traffic capacity

In an urban city, transportation network system, which is mainly composed of highway bridges and roads, is a crucial linkage for the development of the economy and society. However, it is usually subjected to natural or man-made hazards, of which earthquake is one of the most common. After a destructive earthquake, the components of transportation network systems will be significantly impaired, leading to huge loss to the economy and society. Especially, the failure or damage of highway bridges in the transportation network system would hinder the efforts of relief and cost large amount money for the repair and reconstruction. Therefore, it is important to evaluate the seismic traffic capacity risk of highway bridge networks. This paper presents a methodology for the regional seismic risk assessment of highway bridge networks considering the post-disaster evacuation capacity of transportation system. Firstly, the framework of the proposed method is introduced based on the quantification of importance and vulnerability of individual bridge in the network system. Then, the approach to evaluate the importance of the bridge is established through the topological structure of the network and traffic flow of bridges carried. Afterward, the vulnerability of highway bridge networks is quantified by using the individual bridge fragility based on which the vulnerability of links is measured. Finally, a numerical simulation is conducted to validate the effectiveness of the proposed methodology based on the highway bridge network in San Jose, California, USA. The simulation results indicates that the methodology that integrates the analysis of importance and vulnerability is rational.