Study On Fatigue Performance Of Welded Cantilever Bracket Of LRT

The steel truss bridge usually adopts welded connection,whose stress state is complex.However,it suffers severe fatigue problems due to complex mechanical properties,significant stress concentration and other factors.With the increase of the span of steel bridges and the load of vehicles,the fatigue problem will become more prominent than ever before,which brings a security threat to the operation and maintenance.This paper t.akes Nanjing Dashengguan bridge as engineering background,and study the fatigue problem of the welding part of the main girder and the outer cantilever beam.The stress gradient is large in the joint,where the fatigue failure often appears.In this paper,based on the project of light rail welded cantilever bracket fatigue test,the design and verification of the fatigue test model of welded cantilever bracket have been carried out.The main research work is as follows:1.The background and current situation of the research on fatigue Behavior of Steel Structures fatigue property of steel structures at home and abroad were introduced,the emphasis and method of the research on fatigue property of steel structure were summarized.At the same time,on the basis of existing research results,the author identifies the research ideas.2.The fatigue failure mode and fracture characteristics were elaborated,which providing a reference for the judgment of a failure mode.The calculation method of fatigue loading spectrum and the method of changing actual variable amplitude fatigue loading spectrum to the test and calculation of loading spectrum were introduced.On this foundation,the comparison and analysis of several fatigue cumulative damage theories were carried out,and linear cumulative damage theory is considered be a good choice due to absence of historical data.3.According to the operation of the vehicle,the key position of fatigue failure was determined.This model is a steel truss local scale model,considering the limits of cost and the experimental site and the requirement of forces.In this paper,based on the load and boundary conditions,the stress and displacement of key positions were restricted.By the comparison of the method,the fatigue test model was designed and the related experiment was carried out.4.The variation of strain and stress with the load of cantilever structure under the action of load is analyzed by experiments.