APPLICATION OF THE NEW LRFD GUIDELINES FOR THE SEISMIC DESIGN OF HIGHWAY BRIDGES

In July 1996 the National Highway Institute presented Course No. 13063, titled Design of Highway Bridges. This course provided step-by-step guidelines for the seismic design and analysis of bridges using the American Association of State Highway and Transportation Officials (AASHTO), Division IA design specifications. In conjunction with the course, seven seismic design examples of common bridges were published. Recently, new Recommended LRFD Guidelines for the Seismic Design of Highway Bridges have been developed based on National Cooperative Highway Research Program (NCHRP) Project 12-49, FY '98. Since the new Guide Specifications differ significantly from the AASHTO, Division IA Specifications, an example illustrating use of the new Guide Specifications will help bridge engineers learn the new guidelines more quickly. This paper utilizes Design Example #1 from the set of design examples previously published and applies the new seismic guidelines to the example. It provides a discussion on the designers' perspective on using the new Load and Resistance Factor Design (LRFD) Guide Specifications by comparing a structure designed with both specifications. Since the design examples have been widely distributed and used by many practicing bridge engineers, this comparison may help designers to understand the application of the new methods along with any resulting differences from the previous method, Division IA-Seismic Design, for the example selected.