Behaviors And Ultimate Strength Of Steel Tubular Joints Located At The Intersection Of The Tower And Cross Arm

At present, in the design of UHV transmission line and Large span transmission line in China the steel tubular tower structures are widely used. The research on the tube-gusset joints are mainly focused on K-joints. There is few scholars home and abroad to reach the joints located at the intersection of the tower and cross arm and there are some irrationalities in the theory existence at present. The joints located at the intersection of the tower and cross arm are the key parts of steel transmission towers. The joints are intersected by various components, which caused very complex stress states, and the stress concentration here is obvious. The behavior and strength of the joint was explored primarily and the following researches are performed:(1)The finite element model of the joint located at the intersection of the tower and cross arm is set up to research the failure modes and failure mechanism. Taking advantage of the finite element results, the stress analysis of the guest plate is performed to get the path of the load and the characteristics of the annular plate and determine the principle of simplification of the joint.(2)The research on the stress of each annular plate in the elastic stage found that the thickness and diameter of tubular and the thickness and height of annular plate are the main factors that influence the stress. Based on the research, the bar-beam model and the formula which can be used to calculate the stress of each annular plate was put forward. The results of the formula turned out to be accurate, compared with the results which calculate by FEM.(3)Taking advantage of the principle of simplification of the joint, the simplified joint model was put forward to research the ultimate strength of gusset-plate. The research shows that the thickness and diameter of tubular, the thickness and height of annular plate and the axial force of the main tube have a significant effect on the ultimate strength of gusset-plate. Based on the sensitivity analysis of geometric parameters, the formula of the ultimate bearing capacity of proposed by using the least square method. Based on FEM, tubular energy theory about the ultimate strength of simplified joints was deducted and a limit analysis model for determining the ultimate loads of tube-gusset plate connections is established using ring-generator separation model. The results of the proposed formulas were compared with those obtained by Japanese standards and the experimentation in other literature. It reveals that the proposed formula has theoretical and practical significance for design.