Screening Procedures for the Retrofit of Bridges

Since the October 1989 Loma Prieta Earthquake in Northern California, interest has revived in seismic criteria for both new design and the retrofit of existing highway bridges. This interest is nationwide and the objective of this paper is to present and evaluate several preliminary screening procedures that can be used to prioritize the existing stock of bridges throughout the United States. Such a program is needed to facilitate the implementation of retrofit programs. At least four states are either pursuing or looking at retrofit programs. These include California, Illinois, Washington and New York. National Guidelines for bridge retrofit are required and as a first step in this direction, preliminary screening procedures need to be established. This paper summarizes those procedures that have been proposed to date and discusses the role of importance, worth, seismicity and structural vulnerability in the rating process. Finally a new ranking scheme is proposed which will be seen to be a composite of existing and new ideas.