The Earthquake Engineering Online Archive

Further studies on seismic interaction in interconnected electrical substation equipment

Der Kiureghian, Armen; Hong, Kee-Jeung; Sackman, Jerome L.

PEER-2000/01, Pacific Earthquake Engineering Research Center, University of California, Berkeley, 2000, 92 pages (400/P33/2000-01)

In a previous study, the authors investigated the effect of interaction between interconnected electric substation equipment subjected to ground motion. Two kinds of connecting elements were considered. One was a linear spring-dashpot-mass element, representing a rigid bus conductor, and another was an extensible cable, representing a flexible conductor, in which the flexural rigidity and inertia effects were neglected. This study extends the results of the previous investigation in two important directions. First, it extends the investigation of the rigid bus conductor by accounting for the nonlinear behavior of the flexible strap connector (FSC), which is usually installed at one end of the bus conductor to allow for thermal expansion. Second, it extends the investigation of the flexible (cable) conductor by accounting for its flexural rigidity, inertia and damping characteristics. Both problems are highly nonlinear and advanced finite element models are used to perform the analyses. To idealize the FSC, an elastoplastic, large deformation finite element model is used with more than 500 elements. The material properties are determined from the results of monotonic uniaxial tests of the material coupons performed at the University of California at San Diego (UCSD). More accurate characterization of the material properties is possible if cyclic test data of the material coupons are available. The finite element model of the FSC is used to compute force-elongation hysteresis loops under a prescribed cyclic loading. These predictions show reasonable agreement with the experimental results obtained at UCSD. For dynamic analysis of a combined system, a mathematical model of the hysteretic behavior of the FSC is developed. Using this model, time history analysis of a combined system, consisting of two equipment items connected by a rigid bus with an FSC, is carried out for two recorded ground motions. For the flexible (cable) conductor, a finite element model using frame elements and a Lagrangian formulation is used that accounts for large displacements. The results of these analyses are discussed. Conclusions are drawn regarding the development of refined models for the prediction of the response of the FSC and the flexible cable conductors.

Available online: http://peer.berkeley.edu/publications/peer_reports/reports_2000/0001.pdf