Lateral Isolation System of a Long-Span Cable-Stayed Bridge with Heavyweight Concrete Girder in a High Seismic Region

This paper primarily introduces a new lateral isolation system proposed for the seismic control of a long-span cable-stayed bridge, namely, the Yongning Yellow River Bridge, with high seismic activity and a heavyweight concrete girder. Elastic cables (used in pairs to provide a uniaxial tension/compression constraint) in association with a fluid viscous damper (FVD) for supplemental energy dissipation were employed to form a new lateral isolation system at the girder–tower connections. The cable pairs provided the essential lateral stiffness in service conditions, the desired flexibility and sufficient deformation capacity for seismic isolation, and the ability to recenter the girder following an earthquake. At the pier locations, buckling restrained braces (BRBs) were used for lateral isolation of the piers. A three-dimensional nonlinear finite-element model was developed, and three lateral earthquake-resisting systems (i.e., the traditional fixed system, an isolation system using steel dampers, and the presented system) were analyzed through nonlinear time-history analysis. Sensitivity analyses were conducted to determine the design parameters of the new system, and the serviceability limit states were also checked. A further comparison of the seismic behaviors and cost-effectiveness between a typical isolation system with steel dampers and the proposed system was undertaken. Results show that the new lateral isolation system can provide a capable, cost-effective, durable, and resilient solution for lateral seismic control in long-span bridges in critical seismic conditions.