Reliability-Based Framework for Structural Robustness Evaluation of Bridges

Long-span bridges, which are critical nodes of the nation's infrastructure system, are frequently exposed to extreme hazards, such as flood, scour, hurricane, earthquake, blast, and impact. In spite of their importance, the structural robustness of long-span bridges is not well understood and has not been adequately quantified. Traditional design approaches are unable to provide explicit measures of residual safety of long-span bridges. Current evaluation approaches to ensure safety through redundancy in the event of any localized damage are mainly intended for short- to medium-span bridges. Therefore, a new robustness evaluation approach that is well suited for short-, medium- as well as long-span bridges is proposed. Applicability and versatility of this approach is demonstrated on a three-span I-girder bridge and three long-span cable-supported bridges and the results are compared with those from available approaches. A significant advantage of this approach is its ability to account for and estimate structural robustness corresponding to different user-specified initiating events and different user-specified limit states on a common and unified basis. Thus, unlike existing approaches, our approach can be used as a comprehensive tool to assess the safety of bridges in their intact and damaged conditions to facilitate critical decisions on design and retrofit needs.