| The power system is one of the most critical lifeline systems for cities,and the transmission tower-line system is an important part of the power system.However,it is not uncommon for transmission towers to be susceptible to severe damage or even collapse during an earthquake.In this study,a 500 k V ultra-high voltage transmission tower in Northeast China was taken as an example.A three-dimensional model of a single tower and a double tower with three lines was established in the finite element software ABAQUS,and dynamic characteristics were analyzed.The first six modal shapes and natural frequencies of the single tower and double tower with three lines were compared and analyzed.Four different natural earthquake waves were selected,and the seismic response of the tower-line system under the action of these waves was analyzed by using the non-linear dynamic time-history analysis method,including the tower-top acceleration,displacement,and base support reaction.To mitigate the impact of earthquakes on the tower-line system,a tuned mass damper(TMD)made of U-shaped super-elastic shape memory alloy(SMA-UTMD)was proposed based on the self-recovering characteristics,energy dissipation performance,and characteristics of shape memory alloy.Various models of the damper were established,and the influence of geometric parameters on the mechanical properties of SMA-UTMD was analyzed by using the control variable method.The damper with the resonance frequency closest to the natural frequency of the transmission tower was selected for application.The seismic response of the tower-line system with and without SMA-UTMD under four earthquake waves was compared,and the results showed that the peak acceleration and displacement response were greatly reduced after the installation of SMA-UTMD,indicating good seismic isolation effect.Different schemes for the installation position of the damper were designed,and their influence on the seismic time-history response of the tower-line system was analyzed.Finally,the optimal installation position of the damper was determined to be the top part with the maximum displacement.In the study,the dynamic characteristics of the tower-line system and SMA were affected by temperature changes,and the influence of temperature changes on seismic response was specifically considered.The seismic control effect of the transmission tower-line system using SMA-UTMD under different temperature conditions ranging from-40°C to 40°C was evaluated.Relevant seismic performance indicators,including the peak acceleration and displacement of the tower top,were evaluated,and parameter analysis of seismic motion intensity and frequency ratio was carried out.The research results indicate that the use of SMA-UTMD at different temperatures can significantly reduce the peak acceleration and peak displacement of the transmission tower line system,resulting in significant control of its seismic response. |
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