Research On Wind-induced Response Of UHV Transmission Tower Line System Considering SSI Effect

The high-voltage transmission tower is an important lifeline project.It belongs to the towering and gentle structure and is sensitive to wind loads.Wind loads often play a controlling role in the design of transmission towers.In the past,analysis and design were usually dealt with on a fixed basis.However,in most cases,the foundation is not rigid.The calculation based on the basic fixed support may not be consistent with the actual results.In order to consider the influence of the elastic foundation on the windinduced vibration response of the transmission tower,a series of studies have been carried out on the transmission tower line system considering the SSI effect.The main research contents include the following sections:(1)An integrated finite element model of tower-line-foundation-soil is established through ANSYS finite element software,and modal analysis and wind-induced response time-history analysis are performed.The analysis shows that after considering the coupling effect of the tower line and the SSI effect,the frequency of each order of the transmission tower is reduced to varying degrees.After considering the SSI effect,the displacement response maximum value and RMS of the tower line system of the tower top on soft soil foundation both increase by more than 6%,and the acceleration response of the tower top decreases less;the peak value of reaction force on the tower foot decreases;the peak value of the axial force of the main rod at the bottom of the tower increases.When the foundation soil is medium soft soil or hard soil,response changes of the tower top displacement and acceleration is not obvious after considering SSI effect,and the SSI effect can be neglected.After the basic form is changed from an independent foundation to a pile foundation,the displacement response of the tower top increases,the acceleration response decreases,the peak uplift force on the tower foot decreases,and the peak force of the main rod at the bottom of the tower decreases.(2)The integrated finite element model of tower-line-foundation-soil can realistically simulate SSI,but it requires huge computational resources.Two simplified models for the wind-induced response analysis of a transmission tower line system that can consider the SSI effect are established.One is the simplified model 1 based on ANSYS.The foundation soil is equivalent to a series of COMBIN14 spring units and distributed evenly around the foundation.The other is simplified model 2 based on MATLAB.The transmission line is simplified as a draping chain model,the transmission tower is simplified as a lumped mass model,and the foundation is based on the S-R model.Two simplified models were used to analyze wind-induced response and compared with the integrated finite element model.The analysis shows that for the tower line system,the displacement and acceleration response of the tower top of the simplified model 1 all have high precision,the error of the peak uplift force of the tower foot and the peak force of the main rod at the bottom of the tower on the windward side is about 10%,the response value of the leeward surface is more accurate.The error of the tower top displacement response of the simplified model 2 is within 10%,and the acceleration response error is less than 20%.The two simplified models greatly increase the computational efficiency and ensure the calculation accuracy.(3)Based on the simplified model 2 proposed,parametric analysis of the windinduced response of transmission tower line system considering SSI effect is carried out.The relationship between wind-induced response of the transmission tower line system considering SSI effect and the shear wave velocity of the foundation soil,the foundation size,the spacing of the tower foot,the span of the transmission tower,the size of the wind load and the stiffness of the tower body are analyzed.The analysis shows that as the shear wave velocity increases,the displacement response at the tower top gradually decreases and the acceleration response increases.As the stiffness of the tower increases,the displacement response at the top of the tower decreases,but the influence of the SSI effect tends to increase,and the overall trend of acceleration response at the tower top decreases.