Construction of Seismic Retrofit Strategies of the US 40/I-64 Double Deck Bridge Complex

摘要

The 1989 Loma Prieta Earthquake collapsed part of the Interstate 880 Freeway (Cypress Street Viaduct) taking the largest human toll exacted on a highway system. As a result, the Federal Highway Administration began a program requiring immediate evaluation of all double deck highway bridges in the United States. This paper presents the evaluation of one such structure in St. Louis, Missouri highlighting seismic retrofitting techniques designed to improve the performance of concrete elements and overall bridge performance in an urban setting. The Daniel Boone Expressway in downtown St. Louis, Missouri, is one such multi-level bridge providing a major east-west transportation link for Interstate 64 in this Midwestern city. Built in the mid 1960s, the bridge complex is about 1.5 miles in length comprised of equal part side by side elevated structure and over-under elevated structure. The mainline bridge is typically concrete slab on steel I-girder with reinforced concrete substructure units. The substructure units vary from single column bents to multi-frame column bents. The elevated ramps leading to or from the bridge complex vary from concrete slab on steel I-girder to continuous voided slab or box-girder spans. Given the variety of structural elements, this project, now in its tenth year, has provided a wealth of experience in seismic retrofit for the Central United States.