Stochastic seismic dynamic response analysis for coupled transmission tower-insulator-line systems considering soil-structure interaction

The conventional seismic analysis and design of transmission tower-insulator-line systems usually ignore the effects of soil-structure interaction (SSI) and the randomness of ground motions, which might lead to an unreasonable estimation of the system's seismic performance. In addressing this issue, this paper proposes two effective simplified models of coupled transmission tower-insulator-line systems considering soil-structure interaction (CTILSs-SSI), for stochastic seismic dynamic response analysis. In these models, the foundation and tower are simulated by single and multiple degree of freedom models, respectively; meanwhile, the insulator is simulated by a single pendulum model, and the effect of SSI is considered using the swing-rocking (S-R) model. Specifically, for the in-plane vibration, the transmission line is simulated by a multiple degree of freedom rigid-bar assemblage with lumped masses; for the out-of-plane vibration, the transmission line is simulated by a multiple pendulum model. On this basis, the equations of motion for CTILSs-SSI under both in-plane and out-of-plane vibrations are derived utilizing the Euler-Lagrange equation. Subsequently, a non-stationary stochastic seismic dynamic response analysis framework for CTILSs-SSI is proposed by incorporating the proposed simplified models with the probability density evolution method (PDEM). An ultra-high voltage (UHV) transmission tower-insulator-line system is taken as an example. The simplified models of this exemplar system are established and validated using ANSYS software. In addition, the deterministic and stochastic seismic dynamic response analyses of this exemplar system are conducted. The analysis results demonstrate that the dynamic response amplitudes of the tower top and the tower's natural periods increase considering the effect of SSI, and the impact of SSI increases as the subsoil softens. Furthermore, the probability density function (PDF) of the tower top displacement of the CTILS-SSI exhibits distinct shapes at various moments. The mean value of the tower top displacement of the CTILS-SSI fluctuates around zero over time, while the standard deviation increases within approximately 0s–10s and then decreases.