On the traffic action in cable-stayed bridges. Application to the optimal fati-gue design of stays

Abstract

Over the years, cable-stayed bridges had became more and more popular in mediumand long-span bridge design. Their progress has been paralel to the technological achivements in the design of stays and anchorage devices. At present, the uncertainty in the fatigue resistance of these elements when different stress ranges are applied and the lack of knowledge on the real solicitations of traffic during the service-life are still important. Hence, the fatigue design criteria normally used in stays and anchorages seem to be highly overconservative, leading to unnecessary budget expenses. A computer pro-gram for the simulation of traffic flow over bridges is used in the present work to show a methodology of analysis to derive the most efficient cross-section area of backstays. Based on that. design criteria are summarized to be in the safe side, but still be optimal from the point of view of fatigue action in highway cable-stayed bridges. The results presented are still preliminar due to the simplifications assumed because of the existing lack of data on S-N curves of cables and anchorages. Therefore. in the future up-dating and enhancement of the results will be possible as more experimental data will be available.