Abstract
This paper focuses on the seismic isolation design of near-fault bridges under the seismic excitations of near-fault ground motions in high-intensity earthquake zones and proposes a combined control system using lead rubber bearings (LRBs) and cable displacement restrainers (CDRs) along with ductility seismic resistance for the reinforced concrete piers. As part of the performance-based seismic design framework, this study provides the quantitative design criteria for multilevel performance-based objectives of a combined control system under conditions of frequent earthquake (E1), design earthquake (medium earthquake), and rare earthquake (E2). Moreover, in this study, a preliminary performance-based seismic isolation design for a near-fault actual highway bridge in high-intensity earthquake zones (basic peak of ground acceleration 0.4 g) was developed. Using nonlinear time-history analysis of the actual bridge under near-fault ground motions, the feasibility of a performance-based design method was validated. Furthermore, to ensure the predicted performance of the isolated bridges during a strong earthquake, a relatively quantitative design in structural details derived from the stirrup ratio of piers, expansion joints gap, supported length of capping beams, and limited vertical displacement response was obtained.
Highlights
Since the 1970s, seismic isolation technology has been applied to bridge engineering, and it has been used increasingly in bridge design and strengthening in meizoseismal areas
Some highway bridges in high-intensity earthquake zones with a peak of ground acceleration (PGA) of >0.4 g and near active fault sites were constructed in Yunnan, Tibet, Gansu, and other western provinces of China
Based on the displacement-based seismic design method of medium-span seismic isolation bridge developed by Shi et al [16], seismic isolation was performed for every continuous unit under medium earthquakes. en, to adjust the multilevel performance of the overall structure, the time-history analysis was conducted
Summary
Since the 1970s, seismic isolation technology has been applied to bridge engineering, and it has been used increasingly in bridge design and strengthening in meizoseismal areas. Bolu Viaduct, Iceland jorsa River Bridge, and Oseyrar Bridge, all of which have withstood the test of near-fault ground motions during real earthquakes [4,5,6,7] Those bridges had suffered some damage, they showed that seismic isolation still has some positive effects under the near-fault ground motions with velocity pulse effects. Studies related to seismic disasters indicate that near-fault ground motions will cause large displacements of bridges at the earlier stage and that the energy-dissipating function of the seismic isolation elements is not completely developed and they will be damaged early during the earthquake. According to multilevel performance objectives, performance-based seismic isolation design of near-fault highway bridges in high-intensity earthquake zones was achieved
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