Study Of Vehicle-induced Coupled Vibration For Composite Truss Bridge With Partially Concrete-filled Rectangular Steel Tube Members

The composite truss bridge with partially concrete-filled rectangular steel tube members is a new type of structural bridge,which has high bearing efficiency and bending stiffness,and has been widely used in engineering construction at home and abroad.At present,the research on this new type of structural bridge mainly focuses on the static and fatigue analysis of the whole bridge,local components and nodes,but there are few reports on the vehicle-induced coupling vibration.Aiming at the problem of vehicle-induced coupling vibration of this new structure bridge,the following work is mainly done in this paper :(1)Based on the principle of separation method,combined with the design of vehicle load in China ’s current highway bridge specifications,a vehicle-bridge vertical displacement coupling method for 15-degree-of-freedom 5-axle vehicle load model is proposed,and the corresponding vehicle-bridge coupling vibration analysis program is compiled.The method of this paper is used to calculate the vehicle-bridge coupling vibration of two examples in the literature.The maximum relative error is within 6.94 %,which confirms the applicability of the method and the self-compiled program.(2)Based on the inverse discrete Fourier transform method,the fitting program of bridge deck roughness is compiled by MATLAB software.The influence of bridge deck roughness excitation on vehicle-bridge coupling vibration is considered by the ’ 0 row 0 column ’ index rule of ANSYS table array and its automatic interpolation function.According to the main truss structure and stress characteristics of truss bridge,the concept of concrete filling coefficient is proposed,and the mathematical expression of its definition is given.On this basis,the dynamic response of the key section of the truss bridge under different concrete filling length,different bridge deck roughness,different vehicle speed,different vehicle weight and multi-vehicle conditions is compared and analyzed.The value range of the concrete filling coefficient of the truss bridge is recommended to be 0.2 ～ 0.4.(3)According to the definition of the impact coefficient of the bridge,the deflection impact coefficient and the axial force impact coefficient of the truss bridge are obtained.The variation law of the calculated impact coefficient of the truss bridge under the influence parameters of different concrete filling length,different bridge deck roughness,different vehicle speed and different vehicle weight is compared and analyzed.The results show that the impact coefficient at the middle and side fulcrums of the truss bridge is greater than the impact coefficient at the middle of the side span and the middle span,and the axial force impact coefficient is greater than the deflection impact coefficient.Based on MATLAB software,the goodness of fit test of the calculated impact coefficient of the key section of the truss bridge under various working conditions is carried out,and the statistical parameters of the impact coefficient of the truss bridge are obtained.The design value of the impact coefficient of the truss bridge under the95 % guarantee rate is 0.418.The study on the performance and impact coefficient of composite truss bridge with partially concrete-filled rectangular steel tube members is carried out,which can provide reference for related engineering design.