New Developments in CALTRANS Seismic Analysis and Design Procedures for Bridges


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Title: New Developments in CALTRANS Seismic Analysis and Design Procedures for Bridges

Author(s): M. Yashinsky

Publication: Special Publication

Volume: 187


Appears on pages(s): 89-130

Keywords: nalysis; bridges (structures); ductility; earthquakes; seismic loading; shear strength

Date: 6/1/1999

This paper describes current practices and proposed changes for the seismic analysis and design of bridges at Caltrans. It includes an explanation of the new performance criteria for ordinary and important bridges. It provides a description of Caltrans' new site-specific ground input motions which are based on magnitude, acceleration, and the shear wave velocity of the surrounding soil. A variety of new bridge analysis tools and new bridge models, many of which seek to describe the nonlinear behavior of bridges and bridge elements, are described in the paper. Finally, current and proposed seismic design procedures for columns, joints, and superstructures are briefly illustrated. Caltran's seismic bridge procedures reflect the geological, industrial, and economic conditions of California. California's high seismicity requires analysis and design methods that are state-of-the-art. Often, new procedures are implemented only days after the research is completed. Since most bridges in California are made of cast-in-place reinforced concrete, there are few breaks in the structure for the placement of isolators or dampers. Dissipation of energy must occur in ductile columns rather than in special devices. Because, California's economy is dependent on its highway system, methods of protecting vital transportation arteries during and after disasters are being studied.