Effects Of Bolt Slippage On The Wind Induced Vibration Response Of The Transmission Tower Line System

The transmission tower line system plays an important role in our daily life as a carrier of electric energy transmission.Typically,transmission line system with common characteristics such as high-rise tower,span large,flexible is very sensitive to seismic,wind,ice and other environmental loads.The existence of transmission line for transmission tower-line system has impacts on the dynamic behavior of the tower and the wind induced response.So it is necessary to establish the transmission tower-line model and to research the dynamic characteristics,the wind induced response in order to get conclusion that has reference value of theory research and transmission tower line system design.This dissertation takes a ZM-11 cathead transmission tower as study background which is a part of our practice engineering project developed by research group.The study focused on the dynamic behavior and response to wind induced vibration of transmission tower line system.The main contents are as follows.(1)The simulation of wind field.This paper introduces the basic features of fluctuating wind speed including power spectral density(PSD)function,spatial correlativity and simulation method of fluctuating wind speed time history.In this paper,the autoregressive model(AR)of linear filtering method is used to simulate the fluctuating wind speed.Based on this method and Davenport fluctuating wind speed power spectrum,wind speed time history of some spatial correlative points is obtained using MATLAB.Wind speed time history is processed by a FFT transform.Compare the power spectrum after the FFT transform with the target power spectrum to verify the rationality and validity of the simulation method.Convert the wind speed to the wind pressure to obtain the wind load time history.It provides condition to the calculation of wind induced response.(2)The finite element modeling and dynamic behavior analysis of transmission tower line system.Firstly,for the representative bolted joints in the transmission tower including single,double and three bolts,the load-displacement curves were investigated by tests.Then using the finite element software ANSYS to establish the model to simulate the bolt slip process,and compare with the measured results.Using the simulation parameters obtained from the simulation which has tests to simulate the load-displacement curve of bolt joints in tower legs.The slip model is developed by introducing the load-displacement curves using nonlinear spring elements.Simulation results are compared with the two conventional models and measurements of the full scale tower test.It is verified that the slip model is more close to the test results.Based on these three tower finite element model,the tower line systems including one tower coupled two-lines and twin towers coupled three-lines are established.And then,we study the effects of bolt slippage on the dynamic behavior of transmission tower line systems according to the results of modal analysis and comparison of dynamic behavior among these models.(3)The finite element analysis of wind induced response of transmission tower line system.This paper studies the dynamic response of the transmission tower line systems under different wind speeds at 90° wind angle to obtain the tower line system’s coupling effects,wind speed and bolt slippage effects on the RMS of displacements and accelerations of the wind induced response of transmission tower line system.The bolt slippage effects on the internal forces of the dynamic responses of transmission tower line systems are also studied by compared with the quasi static results.