Structural Redundancy, Robustness, and Disproportionate Collapse Analysis of Highway Bridge Superstructures

Abstract

Performance-based design and system-level assessment methods are becoming the preferred approaches for evaluating the safety of structures. This is particularly important for highway bridges where, because of their exposure to long-term deterioration as well as sudden localized failures, the generally conservative traditional member-oriented approach does not necessarily lead to an accurate evaluation of the actual structural system’s safety levels nor, consequently, to the efficient allocation of the limited resources available for infrastructure management. The objective of this paper is to quantify the effect of damage size and location on bridge elements and how this affects the performance of the entire superstructure system. The paper also presents a simplified equation for estimating the structural robustness of typical highway girder bridge superstructures as a function of the damage type. A numerical example is presented to illustrate alternative approaches for how these concepts could be implemented during the design and safety assessment of highway bridges. In particular, the analysis showed that the occurrence of damage directly under the live load reduced the ultimate capacity of the system in the range of 70%–95%. This reduction was between 40% and 70% when the damage was located away from the loaded zone.