Seismic response analysis method for composite bushing considering coupling effects

Composite bushing is composed of the outer sleeve and metal conductor, which has a high seismic vulnerability. A simplified theoretical model is established by the free-body strategy based on equilibrium equations, and its effectiveness is verified by a shaking table test and finite element analysis of full-scale ultra-high voltage (UHV) electrical equipment. The interaction mechanism between the outer sleeve and conductor is revealed, seismic design parameters of relative displacement reduction are analyzed and the design methods are given. The results show that frequency drift occurs in the process of high amplitude excitation due to the nonlinear mechanical properties of the composite bushing. The acceleration power spectrum of high modes is several times greater than that of the fundamental mode, as the peak ground acceleration (PGA) reaches 0.5g. The regularity of relative displacement along the height direction between the outer sleeve and conductor shows an asymmetrical distribution on both sides of the midpoint of the conductor, and the maximum value occurs between the gravity center and bottom flange. For engineering design of relative displacement reduction, section characteristic of metal conductors is the crucial factor, and subfactors are flexural stiffness of the conductor base and outer sleeve, respectively. The seismic response of composite bushing can be obtained by the simplified theoretical model considering coupling effects, and great concern should arise in the influence of high modes.