ABSTRACT
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.
