Optimum design of a cable-stayed steel footbridge with three dimensional modelling and control devices

摘要

Cable-stayed footbridges exhibit significant flexibility and lightweight leading to vibration prone structures. Safety and comfort of the pedestrians crossing the bridge are guaranteed by limiting both the horizontal and vertical dynamic response of the bridge. In particular, the control of the synchronous lateral excitation (also known as 'lock-in') is a governing criterion in the design of long span footbridges. One of the most common ways to mitigate the dynamic response is to install control devices. In the traditional approach both the structure and control devices are designed separately. This paper concerns the integrated optimum design of a cable stayed steel footbridge and its control devices (here viscous dampers) by using three dimensional analysis. The optimization algorithm finds the minimum cost solution which simultaneously satisfies all the static and dynamic design criteria. Both ultimate and service limit states are considered, such as stresses throughout the structure, buckling of the structure and the members, displacements, accelerations and the dynamic stability of the structure when subject to synchronous lateral excitation. The analysis model includes both cable and geometric nonlinearities.