Research On Refinement And Reinforcement Optimization Analysis Method Of Steel Truss Bridge Joints

Steel truss bridge is widely used in engineering because of its advantages of light weight,good ability of span,easy repair and good integrity.The joints of steel truss bridges are of complex stress and weak structure,which are the key local structures of steel truss bridge.However,there are some problems in the design and analysis of joints,such as inaccurate calculation method and incomplete optimization.Therefore,in order to give full play to the function of joints,it is important to analyze their mechanical performance and optimize the design of detailed structures.Taking the engineering examples of steel truss bridge as the research background,this paper studies the mechanical performance analysis and joint structure optimization of integral joints and steel pipe joints.(1)The stress analysis of high-strength bolt connection is carried out.The finite element model of high-strength bolt connection specimen is established to simulate the mechanical performance of the specimen under uniaxial tension,and the accuracy of the finite element model is verified by comparing with the load-displacement curve and deformation under the test.Then the effects of steel grade,friction coefficient,pretension and bolt loss on the shear capacity of specimens of pressure bearing high-strength bolts and friction high-strength bolts connecting are discussed.(2)The finite element analysis model of steel truss bridge is established,and Comparing the finite-element calculated stress and deformation with the measured results,the difference between the calculated value and the measured value is within 25%,and the results are in good agreement.A multi-scale finite element model considering bolts connection is established for the integral joint(E8)of the lower chord at the main pier.On the basis of considering the overall structure,the stress of the joint is finely simulated,and the calculation accuracy and cost of the joint and the overall structure are balanced.By comparing the multi-scale model with the full bridge frame model and the test results of the real bridge,the accuracy of the multi-scale model is verified from three aspects:displacement,stress and interface connection.(3)The parameters of the integral joint structure are analyzed and optimized.First,based on the multi-scale finite element model of the joint,the effects of five parameters on the stress of the gusset plate are analyzed: the thickness of the middle diaphragm(N1),the thickness of the diaphragm(N2)at the edge of the support,the thickness of the gusset plate,the thickness of the stiffener and the height of the stiffener: increasing the thickness of the N1 diaphragm can effectively improve the stress concentration at the connection with the beam;Moderately increasing the thickness of N2 diaphragm has a certain effect on reducing the stress concentration in the web at the support;The peak stress of the joint decreases approximately linearly with the thickness of the gusset plate;Increasing the height of the stiffener has better effect on reducing the maximum stress of the joint than increasing the thickness of the stiffener.Then through the GABP neural network model to optimize the joint structure parameters,it is obtained that under the same steel consumption,the maximum stress of the joint decreases by 10.1 MPa,and the error of the predicted value of the model is 5.1%.Therefore,the neural network model has a good effect on the optimization of joints.(4)The reinforcement analysis of Rainbow Bridge is carried out,and the "global-local" analysis method is proposed to analyze the mechanical performance of the strengthened web member joints.Based on this method,the structure of the joints after the addition of web members is optimized,and three optimization schemes of direct connection,external joint plate and local pouring concrete are proposed for comparison.The results show that pouring concrete in the joint range of web members with new members can effectively improve the mechanical performance of the joint.The reinforcement analysis of concrete filled steel tube truss bridge is carried out,and the joint structure after adding web members is optimized by using the " global-local " analysis method,that is,three optimization schemes of direct connection,external joint plate and local pouring concrete are proposed.The results show that pouring concrete in the joint range of web member joints with new members can effectively improve the mechanical performance of joints.