Least Cost Design of Curved Cable-Stayed Footbridges with Control Devices

Cable stayed footbridges have appealing aesthetics but they are flexible and slender and these properties result in vibrational prone structures. Its design is governed by dynamic comfort requirements in particular the horizontal and vertical accelerations and the synchronous lateral instability (also known as `lock-in'). This paper concerns the optimum design of curved cable stayed footbridges with control devices using a three dimensional model. The structure is designed to guarantee the standard static (live loads, wind, temperature and self-weight) and dynamic (pedestrian induced vibration) requirements. An optimization algorithm is employed to find the least cost design for varying bridge lengths. The goals include finding the bridge geometry (tower shape, number of cables and their location), cross section sizes, control devices properties and cable prestressing. Different bridge lengths lead to different minimum costs, design variables, stress distribution and dynamic response and these solutions are compared. The influence of the tower shape and control device properties on the optimum design is included.