The Fatigue Research Of Joint To The Railway Steel Bridge

China’s steel truss bridge in recent years toward the span of more and more large transverse width is wider and wider, more diverse structure direction. The combined railway traffic in recent years has increased year by year, axle load increase, which improves speed and other factors the higher and higher demands on the steel truss bridge. Along with welding techniques become more sophisticated, the overall node using gradually become the choice of these large-scale steel bridge design. For large-span steel truss bridge, the node fatigue failure is the main failure mode of dense node at the weld, weld various types, vehicle moving loads repeated, this complex welded structures fatigue issues deserve attention. The research work is based on Nanchang through steel truss bridge engineering background, using the method of combining theory and experiment, focusing on the bridge Beams and main truss bottom chord nodes the fatigue performance of the connection.This paper first describes the basic knowledge about fatigue crack initiation and propagation, S-N curve, fatigue damage accumulation theory important basic theory of fatigue strength, and analyzed several effects important factor in fatigue strength.Secondly, the analysis describes the key issues related to the fatigue properties of the node connection structure, factors such as the characteristics of the welded steel structure and impact of node connections fatigue strength.Then, Nanchang through steel truss bridge as the background, with specific design, the establishment of full-bridge finite element analysis model. Based on the design documentation, select the fatigue loading car, according to the results of the analysis, find the risk of fatigue node.Rational design of the test model, based on the structure and stress state of the node,set the node finite element analysis model, based on similarity theory and finite element analysis to develop a pilot program. Test load force is obtained by theoretical calculations.Finally,Start the Nanchang through steel truss bridge across the crossbar main truss bottom chord connection node1:4scale nodes fatigue test.Nanchang train schedule estimate the design life, this life based on the test results verify the fatigue strength of the structure and specifications meet the design requirements.