The Study On The Dynamic Performance Of Three-Tower Suspension Bridge

Intercontinental engineering over sea and river become another hotspot in bridge engineering recently, and the proposal of three-tower suspension was put into practice by two bridges which are both over The Changjian River. The dynamic response of seismic vibrations,wind-induced vibration and vehecal load may be very important in the design of three-tower suspension bridge.Based on energy principles,the thesis firstly formed the inherent vibration formula of three-tower suspension bridge, and four vertical vibrating fundamental frequency and four torsional vibrating fundamental frequency of the bridge were deduced by the Rayleigh-Ritz method. Then the computation formulas were all verified by caculating two case.The thesis also discussed the related influencing factors which will influence the fundamental frequency result calculated by the formula.In the thesis, four different types finite element model of three-tower suspension bridge, of which main span are all 1,080 meters were established. The deflection, acceleration and internal force of stiffening girder, horizontal tension of main cable, tension of sling, longitudinal displacement in the top of tower and bending moment in the bot of tower respectively of the four model were analyzed in case that impact load acting on the different parts of stiffening girder. The time history responses of the structure were discussed when the duration of impact load and damping of computational model changed. It had also done frequency-domain analysis with time domain response results when impact load act on it,and so the relationship between inherent vibration mode and general dynamic response of the structrue had been revealed. At the end of chapter, simple harmonic loading were applied on the structure and its harmonic response was studied.The thesis analyzed the dynamic response of three-tower suspention bridge model when the simple traveling load moves on road, and internal force,deflection response of the structure were also computed and analyzed here,in case that the velocity or magnitude of traveling load was variable. Considering of vehiclular inertial force may also impact the interaction force between vehicle and bridges,the thesis also discussed the difference results of computational model based on moving loads and moving mass. At last,the thesis simulated a situlation that the equidistant indefinite length moving vehicle passed through the deck of three-span continous suspention bridge one after another,and the respond of it was studied.