Estimate The Fatigue Life Of Welded Hollow Spherical Joints In Grid Structure Based On Fracture Mechanics

Grid structure is made of rod and node. According to the specification of "design code of steel structure" GB50017-2003 , the rod, as the main metal of the non-junction, belongs to the first type of calculation of components and junctions in the fatigue calculate, and has the best fatigue performance. The node of grid structure because of its complexity, has not yet been included in the basic category, but it is certainly known that its fatigue properties is far bellow the fatigue properties of rods. So the fatigue problem of grid structure can be attributed to fatigue problems of the node and its fatigue life also can be attributed to fatigue life of the node.In this paper, the following studies of welded hollow spherical joints have been made.1. Using the crack growth rate formulas of Paris and Forman, the estimation formula of fatigue life have been derived separately.2. Each parameter value of estimation formula of fatigue life has been studied. 3. Adopting the material constants C1, m1 of Q235 and using fatigue life theory of Paris and Forman, the fatigue life of tube-ball connected nodes have been estimated.4. Adopting the material constants C2, m2 of welded heat-affected zone of low carbon steel and using fatigue life theory of Paris and Forman, the fatigue life of tube-ball connected nodes have been estimated.5. Adopting the material constants C1, m1 of Q235 and using fatigue life theory of Paris and Forman, the fatigue life of cross plate-ball connected nodes have been estimated.6. Adopting the material constants C2, m2 of welded heat-affected zone of low carbon steel and using fatigue life theory of Paris and Forman, the fatigue life of cross plate-ball connected nodes have been estimated.7. The differences between the theoretical and experimental results, as well as among the theoretical results have been Contrasted and analysised.8. Qualitative and quantitative description of parameters or factors effects on the fatigue life of welded hollow spherical joints during Estimation of fatigue life.