The Analysis Of Semi-Rigid Joint And Single Angle Stablity Bearing Capacity Of Transmission Tower

As an important part of power lines, transmission tower is prone to be damaged under ultimate loads. And the overall instability caused by bucking angle components is the most common failure mode of transmission tower. The tower joints have obvious feature of semi rigidity, but the constraint conditions of single angles are treated as rigid connection or articulated connection in current calculation, which is inconsistent with real constraint. So the current calculation methods may cause material waste or likelihood of danger. Therefore, the study of single angle stability considering the semi rigidity of angle joints contributes to the improvement of calculation accuracy of tower ultimate bearing capacity, which is also significant to ensure the safety operation of electrical facility. The semi rigidity of transmission tower angle joints and stability bearing capacity of single angle are studied in this paper, and the main research content is as follows:1 Numerical simulation method of single angle stabilityBased on the platform of ANSYS, by building the refined finite element models of typical steel tower joints, the moment-rotation curve of angle joint is established after the analysis of its semi rigidity. And the calculation method of single angle stability bearing capacity considering initial imperfection and residual stress is presented by spring elements, which is used to simulate the semi-rigid end constraints, and its accuracy is verified by relevant test data. Then, the bearing capacity of single angle under different constraint conditions such as rigid connection, semi-rigid connection and articulated connection is calculated, and the results show that it is necessary to consider the influence of joint stiffness in single angle bearing capacity analysis.2 Parametric analysis of transmission tower joints’ semi rigidityIn total 135 refined finite element models of single angle joints are built based on selective parameters, such as the section size of secondary and main angle, the diameter, distance and number of bolt, the thickness of node plate and the steel strength of angle, and then the influences of these parameters on semi rigidity of joints are analyzed. According to the results of numerical simulation, the calculation formulas for initial rotation stiffness, ultimate bending moment and shape factor of joints are obtained with least square method, and the practical calculating method of establishing moment-rotation curve of angle joint is proposed based on Kishi-Chen power model.3 Calculation method of single angle bearing capacity considering joint stiffnessThe calculation methods of single angle stability bearing capacity in current codes are summarized. With uniform design method, 12 typical angle-joint models are built, and the bearing capacity of the secondary angles under different constraint conditions is calculated. On this basis, the calculation formulas for equivalent slenderness ratio of single angle with rotation constraint at double ends, one end and none are obtained. Thus, the method for calculating stability bearing capacity of single angle is proposed. The accuracy of this method is proved by experimental results, and the method is compared with current codes.