Comparative Study And Parameter Optimization On Seismic Mitigation System Of Hybrid Cable-stayed-suspension Raid-cum-road Bridges

Cable-stayed suspension cooperative system bridge,as a new structure with great leapfrog potential,will play an important role in bridge construction in the future.However,the theoretical research on this structure is far from enough,especially on the seismic damping system under earthquake.This paper takes the G3 Tongling Highway-Rail Bridge as the research object,and conducts a series of studies on the dynamic characteristics and the damping system of the cable-stayed suspension cooperative system bridge.The main research contents and conclusions are as follows:(1)Based on the Midas Civil modeling software,establish a three-dimensional finite element model of the cable-stayed suspension cooperative system bridge,give a reasonable modeling sequence of the cable-stayed suspension cooperative system,and briefly explain the key points of modeling.Use direct consolidation model,equivalent embedded model,six-spring model and Winkler foundation beam model to simulate the pile-soil effect of cable-stayed suspension cooperative bridges,and study the dynamic characteristics such as natural frequency and mode shape of cable-stayed suspension bridge.The results show that Winkler foundation beam model is most suitable for seismic response analysis of cablestayed suspension bridge.(2)Under the action of a rare earthquake in the lateral +0.5 vertical direction,the lateral seismic response analysis of the cable-stayed suspension cooperative system bridge is carried out.In view of its seismic response characteristics,four types of lateral restraint systems,lateral sliding system,lateral consolidation system,friction pendulum system,and steel damper system were set up for the structure,and their seismic response results were compared and analyzed to explore their seismic damping performance.The results show that the mild steel damper system has more advantages in lateral vibration reduction.The main performance parameter of the C-shaped steel damper in the steel damper system—yield strength is optimized,and the most reasonable parameters are given to provide a reference for the selection of the damper parameters of this project.(3)Under the action of a rare earthquake in the longitudinal +0.5 vertical direction,the longitudinal seismic response analysis of the cable-stayed suspension cooperative system bridge is carried out.Then the semi-floating system,tower beam consolidation system,tower beam elastic restraint system and damping restraint system were set up to analyze the seismic response of the structure,and compared the seismic performance of the four longitudinal restraint systems.The results show that the tower beam damping restraint system has more advantages in the aspect of longitudinal vibration reduction.The speed index and damping coefficient of the liquid viscous damper used in the damping restraint system are optimized,and the most reasonable parameters are selected to provide reference for the project.