Analysis Of The Dynamic Response Of Reinforced Concrete Pole And Wire System Of Distribution Lines Under Seismic Excitation

The distribution lines are an important part of the power system,and their operation state has a significant impact on the safety and reliability of the entire power system.As a pole structure exposed to the outdoors,reinforced concrete pole and wire system of distribution lines is very sensitive to natural disasters such as wind loads and seismic loads.In previous seismic disasters,the tilting of towers,partial damage to components,or overall damage from collapse often occurred,which seriously threatened the operation safety of my country’s power grid and caused economic losses.At present,there is no mention of seismic design of distribution lines below 110kV in relevant China’s codes,and scholars at home and abroad have relatively little research on the seismic resistance of distribution lines.Therefore,it is of great significance for seismic design to analyze the stress of reinforced concrete pole and wire system of distribution lines under seismic excitation and understand its bearing capacity.Taking the structure of reinforced concrete pole and wire system of 10kV distribution line in central China as engineering background,the finite element model of reinforced concrete pole and the three-pole and two-wire system was established by using ANSYS finite element software,and the dynamic response of the structure under seismic excitation was analyzed.The main research contents and conclusions of this paper were as follows:(1)The influence of conductor span on reinforced concrete pole and wire system under seismic excitation was analyzed.The results showed that the conductor reduced the natural frequency of the pole and wire system,and the influence of the conductor on the dynamic response of the pole in the reinforced concrete pole and wire system was different with the change of the conductor span;In practical engineering,the stress amplification effect of pole caused by conductor vibration should be considered when the ratio of conductor span to pole height was between 5～6.7.It was suggested that the dynamic amplification factor should not be less than 1.17 in seismic design.(2)The influence of concrete strength class on reinforced concrete pole and wire system under seismic excitation was analyzed.The results showed that increasing the concrete strength class could reduce the displacement of the top of the pole in the pole and wire system,but amplified the stress response.It was suggested that the concrete pole with a strength class of C50 should be preferred in the actual project for the seismic design with stress as the control standard.(3)The influence of concrete pole height on reinforced concrete pole and wire system under seismic excitation was analyzed.The results showed that the dynamic response of a 15m high pole was larger than that of a 12m high pole,for the pole and wire system with the same conductor span.The maximum displacement amplification factor at the top of the pole was 2.32 and the maximum stress amplification factor at the connection between the pole and the ground was 1.39.A large number of cracks were generated on the tensile side of the 15m high pole body in the area two meters above the ground,and the pole tends to be cracked and damaged when the conductor span of the pole and wire system is 80m and 100m respectively.(4)The influence of three-dimensional seismic excitation on reinforced concrete pole and wire system under seismic excitation was analyzed.The results showed that the reinforced concrete pole and the pole and wire system with a pole height of 15m are damaged,and the dynamic response of the structure under three-dimensional seismic excitation was greater than that under unidirectional seismic excitation.Therefore,it was suggested that the influence of three-dimensional seismic excitation on the structure should be considered in the seismic design of pole and wire system,and the envelope design of the structure should be carried out.