Optimum seismic design of curved cable-stayed bridges

One of the current advances in cable-stayed bridges design is the ability to create curved geometries to fulfill architectural requirements or site constraints. There are currently 68 curved cable-stayed bridges under opera-tion, 56 of which have been completed in the current millennium. Most of them are footbridges, but the number of road and railway applications is increasing. However, there is not much information concerning the design of these structures. This paper concerns a 350 m long curved cable-stayed road bridge with a special emphasis on the seismic optimum design. The tower-deck connection is a key aspect for the seismic response. The longitudinal movement between tower and deck is released, the transverse and vertical support stiffness and damping are considered as design variables. For this structural-control optimization, linear viscous dampers are sought. The spatial variability of the seismic ground motion and construction erection stages for curved CSB are considered. An entropy-based algorithm is used to find the optimum solutions for two designs, S1 where the seismic loading is scaled to 30% and S2 with full seismic intensity. The results show that optimum design S2 costs 21.5% more than S1 optimum and 43% more than a similar straight bridge.