Research On Fatigue Performance Of Integral Joint Typical Welded Details Of Steel-concrete Composite Truss Bridge

The steel-concrete composite truss bridges with integral joints have been widely used in domestic and foreign traffic arteries.The integral joints are multi-members and welded parts,the forces are extremely complicated.Under heavy traffic loads,the fatigue performance of welded details gradually degrades,which will affect the service safety of the steel truss bridge structure.In addition,the combination of concrete bridge deck and steel truss girder has an important impact on the main truss force and the fatigue damage mechanism of the joint.The fatigue performance of the typical welded details of the integral joint and the joint form of the concrete bridge deck and the main truss on the typical welded details of the integral joint are clarified.The influence mechanism of fatigue performance is the basic prerequisite to ensure the safe operation of the steel-concrete composite truss bridge.Based on a typical steelconcrete composite truss bridge,this thesis has carried out a series of researches on the abovementioned problems.The main contents include:(1)Summarizes the fatigue performance evaluation methods of steel bridges at home and abroad,the current research status of integral joint fatigue research and the research status of steel-concrete composite truss bridge,and discusses the key issues that still need to be further studied in the steel-concrete composite truss bridge with integral joints,clarified research objectives,sorted out research ideas and formulated research content.(2)The fatigue assessment method based on the structural stress method is introduced,and the linear cumulative damage theory in the fatigue calculation method and the method of obtaining fatigue load spectrum and fatigue stress spectrum are sorted out.This is to develop the typical welded details of the integrated joints of the steel-concrete composite truss bridge.Fatigue performance research provides corresponding theoretical basis.(3)For a typical steel-concrete composite truss bridge,a full bridge finite element model and a multi-scale finite element model of the steel-concrete composite bridge deck and steel truss girder in the fully combined and semi-combined manner are established.A comparative analysis of the internal force amplitudes of the intersection members was carried out at the joints,and the fatigue performance control joints corresponding to the typical welding details of the integral joints of the steel truss beams in the two types of combinations were identified,and the multi-scale fatigue damage comparison of the easy cracking modes of the typical welded details was carried out.Analyze and clarify the influence mechanism of the different combination of concrete bridge deck and steel truss beam on the fatigue performance of typical welded details of integral joint.(4)Based on the existing traffic statistics data of the steel truss bridge,the growth curve model is used to reasonably predict the traffic flow of the bridge.The Monte-Carlo method is used to establish the typical welded details of the fatigue control joints of the two types of steel truss girder bridges.Fatigue vehicle load spectrum and stress spectrum are obtained,the fatigue life probabilistic evaluation of the typical welding details of the fatigue control integral joints of the two bridges are carried out,and the typical welded details of the integral joints of the steel truss bridge with different concrete bridge deck combinations are quantitatively analyzed.The effect of fatigue performance,the research results can provide a scientific basis for the operation safety of steel truss girder bridges with integral joints and the selection of steel-concrete combination forms.