Design Criterion and a Technical Approach for the Controlled Seismic Behavior of Continuous Girder Bridges

Abstract

Seismic design involving “fuse components” between the superstructure and substructure can improve the seismic performance of continuous girder bridges during strong earthquakes by ensuring an elastic working state. The mechanical properties of the “fuse components” directly affect the seismic behavior of continuous girder bridges, and many theoretical and experimental studies of isolation devices to achieve the controlled seismic behavior of continuous girder bridges have been carried out, and some devices are in use in large-scale construction projects. However, there is a lack of evidence from structures that have been subject to earthquakes. Test results show that the shear behavior of isolation bearings is unpredictable and the friction behavior is uncontrollable. Further, limiting devices often suffer from an insufficient deformation capacity and have large space requirements. Therefore, we propose a new type of spherical steel bearing and two kinds of large-stroke steel damping devices with different space requirements. The full-scale test results reveal that the bearing has strong controllability with respect to shearing, stable friction behavior after fracture, and little unpredictability in the friction-based processes. Furthermore, the large-stroke steel damping device shows a full hysteresis curve and excellent energy dissipation characteristics. Finally, using a continuous girder bridge as an example and combined with the results of mechanical tests, the effectiveness of the controlled design criterion was verified using numerical simulations. The calculated results show that, compared with conventional fixed bearings, the shear and bending moments are decreased by 60% and 53%, respectively, and the ratio of both the shear and bending moment response of the pier bottom to its capacity is less than 0.5. However, the ratio of the maximum deformation of the damper to its capacity is only 0.28, and the residual displacement is 0.01 m. Therefore, an alternative scheme is provided for postearthquake maintenance and replacement.