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Inelastic Response of the Cypress Viaduct to the Loma Prieta Earthquake.


pdf icon Inelastic Response of the Cypress Viaduct to the Loma Prieta Earthquake. (892 K)
Kunnath, S. K.; Gross, J. L.

Engineering Structures, Vol. 17, No. 7, 485-493, 1995.

Keywords:

bridges (structures); damage evaluation; dynamic response; highways; elevated highway structures; failure analysis; modeling; reinforced concretes; seismic analysis

Abstract:

The inelastic damage evaluation of a typical double-deck bent of the Cypress Viaduct which collapsed during the 1989 Loma Prieta earthquake is presented. A model of the bent consisting of spread plasticity-based beam-column elements to represent the piers and deck, and shear panel elements to represent the pedestal region was developed. To accurately determine beam and column moment-curvature relationships, separate computer analyses using an element fibre model were conducted. In addition, a smeared-crack approach finite element analysis was employed to determine the lateral load-deformation relationship of the pedestal regions. The model of the Cypress Viaduct was subjected to the Oakland Outer Harbor Wharf ground acceleration record in the plane of the bent. The analytical model was calibrated using static lateral load tests, ambient and forced vibration tests, and observed performance. The results of time-history analyses, which include a prediction of member damage, indicate that collapse was initiated by a shear failure of the pedestal regions.