| Steel truss bridges are widely used in railway bridges because of their convenient assembly,low steel consumption,strong span and bearing capacity,good permeability and durability.The gusset plate is an important connecting component of the steel truss bridge.Due to the initial defects caused by welding and construction technology,it is easy to cause fatigue problems under the action of fatigue load.The fatigue damage of the gusset plate has become the fatigue damage of the steel truss bridge.One of the main reasons.Therefore,studying the fatigue failure mechanism of steel truss gusset plates and evaluating the fatigue crack growth life of joint details have certain practical significance for the normal operation of steel bridges in the future and the prevention of fatigue accidents of steel bridges.This paper takes a three-span continuous steel truss arch bridge as the research engineering background,uses ABAQUS software to establish a local model of the research node,simulates the crack propagation of the integral gusset plate with cracks under train load,and calculates the crack propagation life The evaluation was carried out,and the main research contents are as follows:(1)The basic theory involved in fatigue analysis is introduced in detail,stress spectrum counting method and fatigue analysis theory based on linear elastic fracture mechanics are described,and three fatigue crack growth models and fatigue crack life evaluation methods are summarized mainly;(2)Based on Midas/Civil finite element analysis software,the full bridge finite element space model of the steel truss arch bridge in the above engineering background was established,and the force of the full bridge members under the action of dead load and fatigue check train load was analyzed.Comprehensive analysis determined the most unfavorable joints of continuous steel truss arch bridges;(3)Calculate the axial force history curve of each connecting member of the research node according to the influence line of the member axial force in the finite element result combined with the wheelbase and axle load of the standard fatigue car.Calculate the equivalent stress amplitude at the boundary of the local model of the gusset plate by the rain flow counting method and the equivalent stress criterion;(4)Based on the secondary development function of ABAQUS,the crack propagation program is written by Python software to realize the automatic expansion function of the cracked structure.The accuracy of the program is carried out through two numerical examples of the central horizontal cracked plate and the unilateral slanted cracked plate.Checking.The program was used to simulate the propagation path of the gusset plate under multi-axial load.According to the calculation results,the crack propagation life was evaluated based on the Paris crack propagation model.The effects of different structural parameters and fracture mechanics parameters on the stress intensity factor and growth life of fatigue cracks are studied. |
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