考虑地震动摇摆分量作用的输电塔线体系响应

Seismic response of transmission tower-line system under coupled horizontal and tilt ground motion

为探究输电塔线体系在地震动水平-摇摆耦合作用下的响应,进行了振动台试验和理论分析。地震动摇摆分量通过小波分析的方法从原始地震记录中取得,此方法以单摆式地震仪在水平和竖向的响应差别为基础,通过摇摆倾斜位移的傅里叶谱和竖向速度相似作验证。采用实际输电塔线体系的简化缩尺模型,进行单塔模型和三塔两线模型在顺线向作用下的振动台试验,考察在地震动水平、摇摆及水平-摇摆耦合作用下的结构响应。推导了地震动水平、摇摆加速度和摇摆位移耦合作用下输电塔线体系的动力方程,在方程的激励项中以等效侧向力的形式考虑摇摆转角位移产生的附加P-Δ效应。研究结果表明:理论分析和试验结果吻合较好,证明了理论分析的正确性;地震动摇摆分量不可忽略,其对输电塔线体系的地震响应影响较大,其中由摇摆转角位移产生的附加P-Δ效应会增大输电塔线体系的动力响应,并造成塔体产生一定程度的非对称位移响应;本次试验中,在多维地震作用下,输电线会减弱输电塔主体结构的水平位移和加速度响应,但相对于水平地震动作用,考虑摇摆分量后,输电线对输电塔主体结构响应的减弱效果将会被削弱。

Experimental and theoretical studies of seismic response of the transmission tower-line system under coupled horizontal and tilt (CHT) ground motion were conducted. Based on the different responses caused by the tilt ground motion between the horizontal and vertical pendulum in the single-pendulum seismograph and the similarity relation between the Fourier spectrum of the tilt component and that of the velocity of vertical component of ground motion,wavelet analysis was adopted to obtain the tilt component from the uncorrected horizontal component of ground motion.Taking a real transmission tower-line system as the prototype,the shaking table tests of the scaled model for transmission single tower and transmission three towers-two lines system under horizontal,tilt and CHT ground motions were carried out. Dynamic equations for transmission tower-line system under coupled horizontal and tilt ground motion were derived,in which the additional P-Δ effect caused by the tilt was considered as an equivalent horizontal lateral force and was added into the equations as the excitation. Test results were compared with the theoretical analysis,and the results show that: 1) the results of shaking table tests are consistent with the theoretical analysis adopting the developed dynamic equations,which proves that the theoretical analysis is correct;2) the tilt component of ground motion has great influence on the seismic response of transmission tower-line system,and the additional P-Δ effect caused by the foundation tilt not only increases the seismic response of transmission tower-line system,but also leads to a remarkable asymmetrical displacement effect,so the tilt component should not be ignored in the practical seismic design;3) for the transmission tower-line system,the horizontal displacement and acceleration responses of transmission towers are weakened by transmission lines under various ground motions,while the weakening effect of transmission lines on the main structure of system is weakened with consideration of tilt component.