The research on progressive collapse of structures generally focuses on gravity and blast loadings and the design objective is to increase the redundancy and robustness of structures to prevent progressive collapse. Studies of bridges damaged by earthquake in past major earthquakes have shown that better methodology for earthquake resistant design of new bridges can be developed. Moreover, effective retrofit and strengthening strategies can be devised to enhance the performance and safety of existing deficient bridges if progression of damage from initial failure to ultimate collapse, and its impact on the failure mechanisms of structures, is better understood. This paper presents the modelling and analysis of progressive collapse behaviour of bridges during earthquakes using the Applied Element Method that can take into account separation of structural components resulting from fracture failure and contact or impact forces of falling debris. The results show significant influence of the progressive collapse phenomena on the performance of bridges during major earthquakes. These also demonstrate the need to consider progressive collapse mechanisms in seismic design performance assessment and evaluation of bridges that would lead not only to a safer and more reliable earthquake resistant design for new structures but also more effective retrofit and strengthening strategies for older structures.

Hartanto Wibowo, S.M.CSCE; Silvena S. Reshotkina; and David T. Lau, F.CSCE: Modeling Progressive Collapse of RC Bridges during Earthquakes, CSCE Annual General Conference 2009: On the Leading Edge, May 2009.