Analysis Of Ice-covered Mechanical Behavior Of Weathering Steel Transmission Tower System With Semi-rigid Joints

The traditional transmission tower adopts hot-rolled galvanized Angle steel,which will not only cause a lot of pollution in the process of hot plating,but also complicate the maintenance work in the future.With the enhancement of environmental protection awareness in China and the central government’s task instructions for carbon peak carbon neutralization,it is particularly important to choose a maintenance-free steel to replace the traditional hot-rolled galvanized Angle steel as a new type of transmission tower material.As a new type of green steel,weathering steel will not continue to corrode after the corrosion layer is formed on the steel surface.However,weathering steel and ordinary high-strength bolts tend to produce electrochemical corrosion at the joints,which reduces the stiffness of the joints,so it is necessary to conduct a more detailed study on the joints.Firstly,in this paper,the finite element model of typical K-type semi-rigid joints of ordinary steel is established,and compared with the test data of ordinary steel joints in reference[1],the failure mode of the control joints and the moment-angle curve of the joints are analyzed to confirm the correctness of the established semi-rigid joints model,which can be further studied.Secondly,Considering the factors such as the friction coefficient of weathering steel is greater than that of ordinary steel（0.55>0.15）and the increase of bolt spacing caused by corrosion of weathering steel,the finite element model of typical K-type semi-rigid joints of weathering steel is established.Through comparison,it is found that:The ultimate bearing capacity of the weathering steel joint model is the same as that of the ordinary steel joint model.Due to the high friction of weathering steel,the bearing capacity provided by bolts is increased by 12.56%.Then the weathering steel joint model is analyzed and studied,and the influence of the main steel width b and thickness t₁,the size of the joint platet₂,the spacing s and diameter of the bolts d,the eccentricity between the joint plate and the main steel e,the bolt preload N and other factors on the bearing capacity of the joint is analyzed.The factors that have significant influence on the bearing capacity of joints include main steel thickness t₁,bolt diameter d and bolt spacing s,while main steel limb width b,joint plate thickness t₂,eccentricity e and bolt preload N have no significant influence on the bearing capacity of joints.The bolt preload N has a significant effect on the initial rotational bearing capacity of the joint,while other factors have little effect on the initial rotational bearing capacity.Thirdly,the influence of each parameter on shape n parameter is discussed and the value of shape n parameter under each parameter is determined.and the fitting formula of initial rotational stiffness K_i,ultimate bending momentM_u and relative plastic Angleθ₀ of weathering steel joints is established.The shape n parameters could be directly calculated and the error analysis was carried out.The calculated results were in good agreement with the simulated values,which verified the accuracy of the formula.Finally,the finite element model of guide wire is established,set up considering semi-rigid nodes connection of 220k V and weathering steel transmission tower tower four wire transmission line system of finite element,simulate actual operation perch ice force,considering the uneven ice and ice two categories a total of 18 kinds of working condition of ice.Through calculation and analysis,it is concluded that:（1）Considering the effect of semi-rigid joints,the stress distribution of the tower body changes with the increase of the load on the inclined auxiliary material.Considering that the semi-rigid joints are compared with the traditional rigid model,the overall displacement of the tower increases significantly under the condition of dead weight and ice covering,with an average increase of 15.98%.（2）Under the same working conditions,due to the high friction coefficient and joint corrosion characteristics of weathering steel,the overall displacement of the tower model with weathering steel increases slightly,with an average increase of 8.72%,compared with that of ordinary steel tower.Therefore,in practical engineering application,the influence of the existence of semi-rigid joints on structure stability should be fully considered.