Redundancy and Robustness in the Design and Evaluation of Bridges: European and North American Perspectives

Abstract

In this paper, current and proposed methodologies for assessing the robustness and redundancy of bridge structures are discussed and an overview of the latest advances in research is presented along with proposals for implementation in bridge design and evaluation codes. In particular, European and North American standard codes and guidelines, including the Eurocode, AASHTO, and the Canadian Standards Association (CSA), as well as some national European codes and related guidelines, are compared. Research projects, including those of the European Cooperation of Science and Technology (COST) and the U.S. National Cooperative Highway Research Program (NCHRP), represent key links between research activities and the need for implementing concepts of structural redundancy and robustness into the codes. The activities undertaken by COST and NCHRP constitute attempts to synthetize, simplify, and implement theoretical concepts that have been discussed over many years. This review shows that the U.S. approach concentrates on developing tools and criteria for the numerical evaluation of the capability of a bridge structure to continue to carry load after the failure of a member, whereas the European approach, still in a more theoretical phase, lacks specific guidelines for bridges and uses available building recommendations. This paper also presents a critical assessment of the state of the art and argues that criteria implementable in future generations of bridge codes should be based on quantifiable measures of risk, which is a subject still in its very early stages of development.