Composite optimal control for the seismic response of a long-span triple-tower suspension bridge

In the design of super-long-span suspension bridges, the floating system is commonly adopted. To preclude the possible excessive Longitudinal Displacement (LD), various methods were proposed in the previous studies. In this paper, the Taizhou Bridge, a triple-tower suspension bridge with the longest main span in the world, is taken as an example to demonstrate the effectiveness of using three different approaches, i.e. installing elastic links between the main girder and the towers, installing viscous dampers and combined installing of elastic links and viscous dampers (a so called composite control method), to mitigate the possible excessive LD. A total of 24 cases with different parameters of the elastic links and viscous dampers are investigated to examine the effectiveness of the three different methods. It is observed that the mitigation effect of the 24 cases varies significantly with different parameters. To obtain the optimal control of the triple-tower suspension bridge, the modified Analytic Hierarchy Process (AHP) method is introduced at the end of the paper and the steps of the method are explained in detail. Optimized results show that the LD of the girder is reduced significantly by 65.3% while the inner force of towers does not increase excessively.