Seismic performance of transportation structures

Revolutionary changes which have taken place in the USA over the past 50 years in earthquake engineering as applied to transportation structures (highway bridges, and transit and high-speed rail aerial structures) are reviewed, giving emphasis to seismic design criteria, characterization of seismic ground motions, dual strategy of seismic design, modelling and dynamic analysis, assessment of seismic performance, design detailing, and retrofitting of existing structures. To reduce the large uncertainties which still remain, it is pointed out that research is needed for improving the predictions of future ground-motion characteristics, developing better seismic design criteria in support of the dual strategy of design, establishing more realistic analytical models of components and systems based on laboratory and field-test results, advancing nonlinear dynamic analysis procedures and associated computer programs, developing more effective measures of active and passive control, and implementing concepts of performance-base design. quirements for buildings developed prior to 1961 by the Structural Engineers Association of California (SEAOC). 1.3 Standard specifications, 1975-1992 As a result of the 1971 San Fernando, California earthquake during which many highway bridges were severely damaged, some of which even collapsed, the California Department of Transportation (Caltrans) issued new seismic design criteria for bridges in 1973, which formed the basis of the 1975 AASHTO Interim Specifications for Highway Bridges. The equivalent static lateral force loading specified in this document for bridges having supporting members of approximately equal stiffness was of the form