| Steel-concrete composite bridges take advantages of two materials and have a bettter comprehensive effect and are extensively applicated in bridge constructions around the world.In recent years,with the rise of ultra-high performance concrete(UHPC)materials,the number of projects by using steel-UHPC concrete composite bridges have gradually increased.However,at present,there are few researches on the vertical vibration of the dynamic performance of steel-UHPC composite bridges considering vehicles action.This dissertation takes steel-concrete composite bridges as research objects,and mainly focuses on the vertical vibration issues of bridges of this type considering the action of moving vehicles.The main works in this dissertation are listed as follows:(1)Based on the composite beam theory and the principle of the finite element method,and taking account of the slip effect of the composite girder,the element stiffness and mass matrices of two kinds of composite beam models are derived in detail.The proposed beam element model and program are verified with numerical examples.(2)The mass and stiffness matrices for vehicles such as a five-axis articulated truck model,a two-axis vehicle model,and a railway four-axis vehicle model,are derived.Numerical random road irregularity samples are simulated through program.Combining the theory of vehicle-bridge coupling vibration with the composite beam element derived in this paper,a vehicle-bridge dynamic interaction analysis program is developed on MATLAB,which can be used to simulate the vehicle-bridge vibrations of express-way and railway composite structure bridges;some examples in existing literatures are presented to verify the self-compiled program.(3)Firstly,the self-made program is used to compute vehicle-bridge interactions of a steelUHPC light weight composite continuous beam bridge and a composite simple-supported beam bridge.The dynamic responses and impact factors are analysed and the results show that the vehicle types,road level and velocity all make a huge difference to the impact factors of these bridges.(4)Then,the program is used to analyze the natural vibration characteristics of an expressway steel-UHPC composite beam cable-stayed bridge.Compared with Midas/Civil,the results about several vibrational frequency are basically consistent.The dynamic response of the cablestayed bridge under the action of a single vehicle is calculated,it is found that the change of interface shear stiffness has little effect on the dynamic response of the cable-stayed bridge.The dynamic response of the cable-stayed bridge under the action of vehicle queues is calculated,it is found that when the distance and speed of the vehicle queues meet certain conditions,the resonance about the first mode of the cable-stayed bridge may occur.The impact factors of the displacement of the girder and those of the force of the cable are calculated,it is found that the impact factors of the short cable are larger. |
