Effect of Seismic-Induced Bearing Uplift of a Cable-Stayed Bridge

In the past, seismic-induced bearing uplift of cable-stayed bridges was seldom recognized or valued, and a conventional sliding bearing, which cannot resist uplift forces, was often used for cable-stayed bridges. In this study, identification of the bearing uplift of cable-stayed bridges was performed, and the bearing uplift effect was estimated according to a nonlinear response-history analysis of a cable-stayed bridge model subjected to longitudinal earthquake excitation. The findings revealed that deck end developed large vertical displacement during bearing uplift, and intense bearing compression force was generated through pounding of the deck against the bearings after bearing uplift. Because of bearing uplift, bearings and piers might suffer severe damage from a large bearing compression force, but the maximum response of the deck and the tower was slightly affected. In addition, bearing uplift is quite sensitive to ground motion characteristics. Particularly, bearing uplift is more prone to develop under soft soil conditions than stiff soil conditions because the predominant periods of the former are closer to the periods of significant structural modes. To avoid damage from a bearing uplift effect, uplift-restraint bearings, which introduce uplift-restraint mechanisms to sliding bearings, are recommended as substitutes for conventional sliding bearings.