| In the seismic design calculation of the transmission tower-line system,which is an important power facility,only the horizontal component of ground motion is considered,but the influence of the tilt component of ground motion is ignored.However,a large number of seismic damage shows that the tilt component of ground motion has a significant influence on the seismic response of such high-rise flexible structures as transmission tower-line system.In fact,because of the lack of actual measured records of the tilt component,the research on the seismic response of transmission tower-line system under multi-component ground motion which is coupled horizontal and tilt components is restricted,and the influence of the tilt component has not been paid much attention.Therefore,this paper makes a further comprehensive exploration on the method of obtaining the tilt component and the related issues of seismic response of transmission tower-line system under coupled horizontal and tilt ground motion(CHT).The main research contents and conclusions are as follows:(1)Elastic wave theory method and frequency-rate method which are two commonly used methods to obtain the tilt component are further discussed.Wavelet transform and wavelet threshold denoising are used to improve the frequency-rate method,and the accuracy of the frequency-rate method is improved.Then based on the improved frequency-rate method and the elastic wave theory method,a new method is established to obtain the tilt component,and this method is named the comprehensive method.In the comprehensive method,the low-frequency parts of the tilt component are obtained by using the improved frequency-rate method,and then the highfrequency parts of the tilt component are obtained by using the elastic wave theory method and the low-frequency parts,and finally the frequency component of the obtained tilt component is complete.Therefore,the comprehensive method effectively combines the two methods mentioned above,and realizes advantageous complementarities.(2)Shaking table tests of the simplified scale models of the actual transmission single tower and transmission towers-line system under horizontal and CHT ground motion are carried out.At the same time,theoretical analysis is carried out to derive the dynamic equation of the transmission tower-line system under multi-component ground motion which is coupled horizontal and tilt components,in which the influence of the seismic excitation term equivalent to the additional P-(35)effect caused by tilt motion is mainly discussed.Test results were compared with the theoretical analysis and indicated some useful conclusions.First,the shaking table test results are consistent with the theoretical analysis from improved dynamic equations and proved its correctness.Second,the tilt component has great influence on the seismic response of the transmission tower-line system,and the additional P-(35)effect caused by the foundation tilt,not only increases the seismic response of the transmission tower-line system,but also leads to a remarkable asymmetric displacement effect.Third,for the tower-line system,the weakening effect of transmission line on seismic response of tower will be decreased with consideration of tilt component.Therefore,in the seismic design,the tilt component should be taken seriously.(3)According to the actual engineering situation,the finite element analysis model of transmission tower-line system considering the SSI effect is established.Under different site soil conditions.Then the dynamic characteristics of the structure and seismic response of the structure under horizontal and CHT ground motion are analyzed and compared to explore the influence of the SSI effect.The results show that the SSI effect can reduce the natural frequency of the transmission tower-line system,and increase the seismic response of the structure.Moreover,the SSI effect can also significantly increase the enhancement effect of the tilt component on the seismic response of the transmission tower line system under CHT ground motion.At the same time,these effects of the SSI effect are more obvious as the site soil becomes weaker.Therefore,when the site soil is not hard,the influence of SSI effect on the seismic response of transmission tower-line system under multi-component ground motion should be taken seriously. |
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