Seismic evaluation of cable-stayed bridges considering bearing uplift

Abstract

Past earthquakes revealed that bearing uplift has possibly occurred at several cable-stayed bridges and is regarded as a critical cause for significant structural damage. To investigate the influence of bearing uplift, a sophisticated bridge model is constructed on an existing cable-stayed bridge and the seismic response of the bridge is evaluated. Nonlinear time-history analysis results show that bearing uplift of the bridge could occur several times under a design earthquake, resulting in an extensive pounding force at bearings and a large uplift displacement at deck end. The pounding force of bearing uplift would damage the bearings, cause shear cracks and even failure of the pier crossbeams. Viscous fluid dampers (VFDs), often used for controlling deck horizontal displacement, are investigated on its potentiality to restrict bearing uplift. It is revealed VFDs are able to slightly reduce the pounding force and effectively control the uplift displacement of deck end, but cannot avoid bearing uplift. To prevent seismic damage from bearing uplift, tension bearings is recommended for the bridge. The effect of VFDs to control the bearing vertical response is utilized in designing the tension force of the bearings. After implementing VFDs, the design tension force of the bearings is reduced by 25% comparing to that of the bridge without VFDs.