Force Transfer Characteristics Of Complex Bridge Structures Based On Stress Wave Theory

The dynamic response of bridge structure under the impact load of automobile is a concern problem in the engineering field.The dynamic response of the structure can be roughly divided into two kinds of problems : stress wave problem and global response problem.The global response ignores the perturbation transfer process in the structure.However,for long span complex bridge structure,the transfer process of disturbance can not be ignored.In this paper,the characteristics of stress wave in complex bridge structures are studied,and the main research work is as follows:(1)A bending wave equation considering the effects of bonding prestress and internal damping is derived by force analysis of Euler beam micro-segments.Fourier change was used to solve the equation,and the form of complete solution was obtained.The formulas for calculating the phase velocity and group velocity of the flexural wave in the prestressed beam considering the effect of internal damping are derived.The effects of bonding prestress and internal damping on phase velocity and group velocity of flexural wave are discussed in the engineering background of a real bridge structure.Suggestions are put forward to reduce the delay effect between transfer paths.(2)The propagation path of stress wave in bridge structure is introduced from the perspective of wave front.Taking a simply supported beam as an example,the influence of the time difference between different transfer paths on the total effect of reflection,transmission and stacking of stress waves is analyzed.Finally,the path of stress wave in cable-stayed bridge,suspension bridge and arch bridge is introduced.(3)Based on the finite difference method,the difference schemes of constant cross-section beam and continuous variable cross-section beam considering the effect of internal damping are constructed.The stability conditions of the difference scheme are discussed by Fourier method,and a complete numerical algorithm is formed together with boundary conditions and initial conditions.The cable-stayed structure should also consider the displacement coordination and internal force continuity at the girder-cable connection.MATLAB software is used to prepare the corresponding calculation program,and the results are compared with the finite element software ABAQUS /Explicit and Midas FEA time history analysis module.The algorithm is proved to be accurate and efficient.(4)According to the algorithm proposed in(3),the dynamic response characteristics of simply supported girder Bridges,continuous variable cross-section girder Bridges and cable-stayed structures under the impact load of vehicles are studied with the background of actual engineering.The displacement field and force transfer process of the structure are obtained.The difference between the time required for the stress wave to reach the foundation along the characteristic scale of the structure and the duration of impact load is analyzed.The wave response and the overall response of the structure under different speed and load position are compared.The delay effect of stress wave transmission on the dynamic response is discussed.Finally,the effects of internal damping and piecewise impact load on the transmission of stress waves in the structure are analyzed.(5)The jumping experiment of a simple supported beam bridge is carried out.On the Honghe Bridge in Zhuhai,a traffic obstacle test was carried out.The correctness of the theory is verified by collecting and analyzing the vibration signal of the beam.