Nima Tavakoli Shirazi - M.Sc. Civil Engineering Student
Gholamreza Azizyan - Assistant Professor, Department of Civil Engineering, Faculty of Engineering University of Sistan & Baluchestan Zahedan, Iran

Lifeline systems consist of Bridges, Roads, Tunnels, Communication networks, Water and Gas Transmissions, Airports,etc, are known as a general parameter for all cities especially Megacities survival. Any trouble in their operation particularly intimes of crisis (earthquake, flood, tempest, war, etc) will increase irreparable losses of life and property. Large lifeline systems suchas bridges are susceptible to earthquake damages, and their performance, integrity and stability according to their specialapplication in current-day transportation, during and after an earthquake have significant implications on public safety. Bridgesare one of the most importance lines to control rescue operations during and after earthquake. So, there is an urgent need torecognition the effective factors on bridge damages in an unforeseen exigency. Hence, their vulnerability significantly should beunder continual surveillance and bridges stability has to be controlled by retrofitting and rehabilitating. In this study the seismicperformance of various types of bridges during the past earthquakes is presented. The objective of this study is to present typicalfailure modes of bridges and providing some clues in order to reduce the seismic vulnerability of such structures. Results of thisstudy demonstrated that there are some typical failure modes in bridges. Hence, by considering some special practicalconsideration the seismic vulnerability of bridges may decrease.

vulnerability, earthquake, structural properties, retrofitting