Seismic Response Analysis Of Transmission Tower-Line System Considering SSI

With the development of national economy, science, technology and environmental protection consciousness, the electric power industry which is the support of human life now makes great changes. High and ultra-high voltage electricity transmission has become the primary mode of power transmission in nowadays. It is believed that the main design load is wind load and the effect of seismic is smaller due to the tall and slender characters of the power transmission tower. But as the increase of height and span of towers, the failures of power transmission system due to earthquake take place ceaselessly. It is shown that the base of towers and the soil of sites were destroyed seriously in many earthquakes. So the study of dynamic analysis method of interaction among tower, base and site soil is very important now.Presently, there is less study on seismic response analysis of tower considering soil-structure dynamic interaction (SSI). Also few scholars establish full FEM models containing underground part when they do this reach. In this paper, full FEM model is established considering soil-structure dynamic interaction at first. Then the simplified aseismic calculation model is derived and checked. At last the influence factors of soil-structure dynamic interaction in pile-soil-transmission tower-line system are studied.The main contents of this article include:Firstly, the seismic response analysis method of transmission tower in consideration of pile-soil-structure dynamic interaction is given. Pile-soil-transmission tower coupled system (Full Model) is set up using visco-elastic artificial boundary as the soil boundary and modified Goodman element as the pile-soil interaction face. Based on a transmission tower, the seismic response of pile-soil-transmission tower system is calculated and compared with the result that does not consider the effect of pile-soil-structure dynamic interaction under four different site conditions. Some significant conclusions are obtained.Secondly, the simplified aseismic calculation model for transmission tower-line system considering pile-soil dynamic interaction is given. Simplified aseismic calculation model (Simplified Model) for pile-soil-transmission tower-line system is set up and compared with the full model using additional mass method and lumped mass model. Based on a transmission tower, the seismic response of the simplified model is calculated and compared with the full model under three different site conditions. It can be concluded that doing aseismic calculation with simplified model instead of full model is feasible.Thirdly, the influence factors of soil-structure dynamic interaction in pile-soil-transmission tower-line system are studied using the simplified model. Based on three transmission towers with different height, the seismic response of the pile-soil-transmission tower-line system is calculated and compared with the transmission tower-line system under three different site conditions. The relationship among the increment of tower response, height, site condition and direction of seismic considering soil-structure dynamic interaction is analyzed qualitatively and quantitatively. Estimate graphs of tower response increment are given. So the influence of the soil-structure dynamic interaction can be quickly estimated.