High-Load Elastomeric Bridge Bearings

Abstract

The use of elastomeric bearings as high-load bridge bearings for steel and concrete bridges is discussed. The Washington State Department of Transportation's (WSDOT's) experience with high-load multirotational bearings and search for simpler, more durable, and more economical high-load bridge bearings are described. The results of a survey of state departments of transportation indicate that bridge designers have been slow to design elastomeric bearings for the higher stresses permitted by AASHTO Method B. High-load steel-reinforced elastomeric bearings are defined as bearings that are designed for a compressive service stress of 11 MPa (AASHTO Method B maximum) to 15 MPa (German maximum). Design criteria for elastomeric bearings are discussed. A recent WSDOT project is presented. In the case study a four-span continuous curved steel plate bridge is designed for a seismic acceleration coefficient of 0.22 g. At the intermediate piers, high-load steel-reinforced elastomeric bearings are designed for a service load of 339 Mg with a compressive stress of 11 MPa (AASHTO Method B). The seismic forces at the piers are reduced by 50 percent when compared with those with fixed pin or spherical bearings. Constructibility issues, quality control, testing requirements, design loads, and costs are presented. Future research needs are identified. In addition to supporting high loads, elastomeric bearings are durable, simple to install, and maintenance-free and can reduce seismic loads at bridge piers. These bearings are an economical alternative to more expensive disc, pot, and spherical bridge bearings.