Safety Margins of Suspension Bridges Under Seismic Conditions

The American Association of State Highway Transportation Officials (AASHTO) 1983 code, “Seismic Design of Highway Bridges,” does not cover explicitly suspension bridges. Nevertheless, if AASHTO earthquake excitation is applied to some existing suspension bridges, even those of strategical importance, for example, the Golden Gate bridge, the structural safety of these bridges cannot be proven. The need for new standards is also widely recognized in Japan. Analyses that have appeared in the literature are reviewed. A criterion to select the design earthquake is proposed and its relevance on the previous safety analyses is shown.