Study On Wind Resistance Evaluation Of Transmission Tower And Line System In Coastal Strong Typhoon Area

The existing scale of China’s transmission lines is huge,and entering the"14th Five-Year Plan",China’s economic development will continue to maintain steady and rapid growth,the scale of transmission lines will continue to grow.Transmission tower line system as an important part of the transmission line,mainly by the transmission tower and its foundation,guide ground,insulators,line gold and other components,is a complex tower-line coupling system.Transmission tower is the main load-bearing structure in the tower-line system,with high structure,flexibility,self-importance and other characteristics,more sensitive to the excitation of wind loads.The southeastern coastal region is a more developed socio-economic area in China,with a very high demand for electricity,but it is also an area where natural disasters such as typhoons are frequent.Past disasters have shown that typhoons and strong typhoons are one of the major causes of power transmission tower collapses and accidents.Therefore,it is important to strengthen the assessment of the wind resistance of transmission towers in the southeast coastal area to ensure that the transmission line tower system operates safely under typhoon loads.The new single-circuit linear catenary tower ZMG32-28.5 and the tower system in which it is located are taken as the object of study for the 3572 line in Dongtou,Wenzhou.Firstly,the dynamic characteristics of tower N32 ZMG32 were tested in the field,and the vibration pattern and dynamic characteristics parameters of the transmission tower were obtained using the random subspace method;on this basis,the finite element model of the test tower and its tower line system was established using ANSYS software,and the theoretical analysis of the vibration force characteristics of the single tower and the tower line system was carried out,which was compared with the test results and further revised the finite element In order to further grasp the dynamic characteristics of the cathead tower,a finite element model with multiple sets of equal and unequal tower legs was established to study the effect of tower leg changes on the dynamic characteristics of the cathead tower;combined with the characteristics of the dynamic characteristics of the series of cathead towers,the first-order self-oscillation period approximation formulae for the typical cathead tower type in the cross-line and down-line directions were fitted.Secondly,the static load analysis of the ZMG32-28.5 tower is carried out under0°,45°,60°and 90°wind angle conditions with the design wind speed of the line（v10=35m/s）;the typhoon wind spectrum is used to simulate the pulsating wind speed time course with typhoon characteristics through the harmonic superposition method;the pulsating wind loads are applied to the corresponding positions of the single tower and the tower line system respectively,and the 0°,45°,60°and 90°The wind vibration response under different wind angles such as 0°,45°,60°and 90°is analysed;the effect of guide wire,earth wire and wind speed on the wind vibration response of the tower under 90°wind angle is investigated;on this basis,the deterministic wind resistance of the cathead tower is assessed using the assessment parameters such as transmission tower top offset ratio and main material pole compression and yield ratio.Finally,in order to further consider the uncertainties of the transmission tower structural parameters and pulsating wind loads,80 sets of random samples of the tower line system were generated using the Latin hypercube sampling method,and 80sets of pulsating wind time courses were simulated and generated using the harmonic superposition method.The wind vibration response of the 80 sets of tower line systems was analysed by combining the random samples with the wind loads in one-to-one correspondence.A statistical regression analysis was carried out to obtain the mean and mean squared deviation of the wind load effect function and the wind vibration response of the transmission tower considering the tower-line coupling effect;in addition,Pushover analysis was carried out using the generated 80 sets of random samples of transmission towers to determine the limit state limits and the mean and mean squared deviation of the displacement of the transmission tower structure.Based on the results of the above two analyses,the wind vulnerability of transmission towers considering the tower-line coupling effect was investigated and wind load vulnerability curves were obtained for minor damage,moderate damage and collapse damage under 0°down-line and 90°cross-line wind direction angle conditions.The study shows that the ZMG32-28.5 tower has better wind resistance performance:the wind direction of the horizontal line is 8.2%more likely to damage than the wind direction of the down line,and the probability of collapse damage in the horizontal line direction is 13.24%when subjected to 50-year wind speed(v₁₀=35.77m/s)in the recurrence period;when subjected to 100-year wind speed(v₁₀=41m/s)in the recurrence period,the probability of collapse damage is 38.7%.