Long-term extreme response analysis of a long-span pontoon bridge

For the assessment of extreme load effects needed in design of marine structures, a full long-term analysis is recognized as the most accurate approach. However, due to the very large number of structural response analyses traditionally needed for this approach, the computational effort is usually considered to increase above acceptable levels for complex structures such as floating bridges. In this paper, a framework for full long-term extreme response analysis is demonstrated for a long-span pontoon bridge subjected to wave loads. This framework utilizes some recently developed approaches which are based on the inverse first- and second-order reliability methods (IFORM and ISORM). Using the IFORM and ISORM approaches, characteristic values of the long-term extreme response are calculated in an efficient manner. By comparing with results obtained by full numerical integration, the accuracy of the methods is investigated. Particularly the ISORM method is seen to provide high accuracy. The full long-term analysis is also compared with the environmental contour method.