Research About Fatigue Property Of Connection Between Truss Joint And Crossbeam In Steel Bridge

Fatigue property of connection between primary truss joint and crossbeam, has important influence on the bridges' safety, and it becomes more and more, as the development of highway and railway bi-purpose bridges. In the connection angle steels and high strength preloaded bolts are usually adopted. The factors are analyzed, which affect the fatigue property of the connection, under the background of Chongqing Chaotianmen Yangtze Bridge, and results of domestic and foreign research is applied. Furthmore, there is no norm of fatigue load of highway and railway bi-purpose bridges, it is studied that establishing fatigue load spectrum of such bridges. A suggestion is made, which makes fatigue load spectrum of highway and railway bi-purpose bridges.At first, theory of fatigue Strength is introduced, including theory of linear cumulative fatigue damage , and fracture mechanics theory of fatigue crack growth in steel bridge. And then, Comparatively analyse the difference for the detail in several norms. Fracture mechanics is applied for potential cracks, and critical length of crack with assumed depth was obtained. Method of prediction of fatigue life with fracture mechanics is discussed. The semi-rigidness is introduced in the fourth chapter, of which connection between crossbeam and vertical beam or primary truss joint. And the M-φcurve modes of semi-rigid connection is comparatively studied. The reason is studied, of which the domestic and foreign fatigue failure cases.The latter part is under the background of Chongqing Chaotianmen Yangtze Bridge. Potential crack is located on the edge of bolt hole (or on the contact surface between angle steel and high strength preloaded bolt) , based on BS5400. Stress range of the detail is determined with the analysis result of FEM. It is judged with fracture mechanics that whether fracture occur in the position of potential crack, if crack with assumed depth is found out. And the fatigue property of the connection is checked based on domestic and foreign norms. A project of the experimentation was obtained, which tests the fatigue property of the connection between primary truss joint and crossbeam.At last, internal forces influence line of the detail is detemined by BS5400 and AASHTO, based on the anslysis result of FEM. And inner force course of the detail is determined under moving load of standard loading of BS5400 and AASHTO. Loading frequency value spectrum is determined by the reservoir method, on the basis of traffic volume.