Optimization of Seismic Isolation Bearing Scheme of RC Long-Span Soft Arch Bridge under Near-Field and Far-Field Ground Motions
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摘要:
为探明不同地震动输入对某大跨轻柔拱桥减隔震的影响，通过非线性有限元模型分析近远场地震下桥梁结构的响应规律，得到大桥支座的优化布置方案. 首先，基于模态分析，对比该桥与传统钢筋混凝土（RC）拱桥动力特性差异；其次，选取不同脉冲周期的近场地震动、近场无脉冲及远场长周期地震动记录；最后，研究近远场地震下拱桥的响应行为和损伤演化路径，得到优化桥梁的减隔震支座设计方案. 研究结果表明：近场脉冲及远场长周期地震下的桥梁结构响应大于无脉冲地震响应；纵竖向地震下高墩柱剪力及弯矩包络曲线呈“S”形，墩身中部易形成塑性铰，高阶振型影响显著；桥梁纵桥向先于横向震损，损伤路径依次为矮柱、高墩柱及拱肋实心-空心截面段；摩擦摆支座减震效果最佳但位移较大，高阻尼支座方案在近场中长脉冲周期及远场长周期地震下仍会发生损伤，板式橡胶支座方案因无法保证支座同步滑移而不能形成准隔震体系；“高阻尼 + 摩擦摆”混合方案的支座位移小，拱肋及墩柱均处于弹性，是近断层大跨轻柔RC拱桥的优选减隔震方案.
Abstract:In order to investigate the influence of different ground motion inputs on the seismic isolation of a long-span soft arch bridge, the response law of the bridge structure under near-field and far-field ground motions was analyzed by nonlinear finite element model, and the optimal arrangement scheme of the bridge bearings was obtained. Firstly, based on modal analysis, the difference in dynamic characteristics between the bridge and the traditional reinforced concrete (RC) arch bridge was compared. Secondly, the records of near-field ground motions with different pulse periods, near-field pulseless ground motions, and far-field long-period ground motions were selected. Finally, the response behavior and damage evolution path of the arch bridge under near-field and far-field ground motions were studied, and the design scheme of the bridge’s seismic isolation bearing was optimized. The research results show that the structural responses of the bridge under near-field pulse and far-field long-period ground motions are larger than those under pulseless ground motions. The envelope curves of shear force and bending moment of high pier columns were distributed in an S shape under longitudinal and vertical ground motions. A plastic hinge is prone to form in the middle of the pier body, and the effect of high-order vibration mode is significant. The longitudinal direction of the bridge first encounters seismic damage, followed by the transverse direction, and the damage paths are successively low column, high pier column, and solid-hollow section of arch rib. The friction pendulum bearing embodies the most excellent seismic isolation performance with larger displacement. High damping bearing scheme fails to avoid damage under near-field middle and long pulse period ground motions and far-field long-period ground motions. The laminated-rubber bearing scheme can not form a quasi-seismic isolation system because it cannot guarantee the synchronous sliding of the bearing. The hybrid scheme consisting of high damping bearing and friction pendulum bearing leads to small bearing displacement, with arch rib and pier column in an elastic state, which is the optimal seismic isolation scheme for long-span soft RC arch bridge in the near-fault regions.
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图 3 各类地震动加速度反应谱均值
Figure 3. Average acceleration response spectra of different ground motions
图 4 主拱拱肋的位移及内力响应包络图
Figure 4. Displacement and internal force response envelops of the main arch rib
图 10 不同地震动下拱肋及墩柱截面损伤状态
Figure 10. Damage of arch rib and pier column sections under different ground motions
图 11 各支座的累计耗能曲线及P9支座滞回曲线
Figure 11. Cumulative energy dissipation curves for different bearings and hysteretic curves of P9 bearing
图 12 混合方案及摩擦摆方案的支座位移包络
Figure 12. Bearing displacement envelopes of hybrid scheme and friction pendulum scheme
表 1 近远场地震下拱肋的位移及内力减震效果
Table 1. Seismic isolation effect of displacement and internal force of arch rib under near-field and far-field ground motions
% 地震动 拱顶位移减震率 拱肋过渡截面剪力减震率 拱肋过渡截面弯矩减震率 准隔震方案 高阻尼支座 摩擦摆支座 准隔震方案 高阻尼支座 摩擦摆支座 准隔震方案 高阻尼支座 摩擦摆支座 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 NSP 29.1 28.5 18.9 31.0 32.8 32.2 15.5 15.6 14.4 18.2 25.8 24.2 12.3 11.1 10.2 12.5 15.2 15.2 NMP 42.5 22.1 25.6 26.5 52.2 28.8 21.0 12.2 17.3 20.2 29.2 26.2 26.8 10.5 25.2 11.2 32.2 16.8 NLP 35.2 15.6 21.2 22.3 40.2 25.5 22.3 12.3 16.8 21.0 35.2 22.1 28.2 5.8 26.7 8.8 29.9 10.2 NNP 12.8 −2.1 8.8 5.2 15.2 9.8 13.3 −8.6 11.2 8.6 14.8 15.6 8.7 −10.5 5.3 5.9 10.2 7.4 FFL 33.5 5.6 20.3 16.5 38.3 20.2 24.5 7.6 22.1 15.6 35.3 18.8 32.2 3.2 30.5 7.5 36.5 8.8 
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表 2 近远场地震下立柱P9的减震效果
Table 2. Seismic isolation effect of column P9 under near-field and far-field ground motions
% 地震动 柱顶位移减震率 柱底剪力减震率 柱底弯矩减震率 准隔震方案 高阻尼支座 摩擦摆支座 准隔震方案 高阻尼支座 摩擦摆支座 准隔震方案 高阻尼支座 摩擦摆支座 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 纵向 横向 NSP 20.2 −2.3 27.7 12.8 38.0 18.2 12.9 5.6 56.6 30.2 69.2 32.4 32.1 5.2 54.4 21.0 69.2 28.1 NMP 25.5 22.3 28.5 25.1 42.1 35.5 38.5 28.2 34.2 49.2 54.5 52.8 61.2 25.2 58.2 35.1 62.3 60.1 NLP 48.2 18.9 55.6 24.2 62.3 32.1 35.2 25.1 33.1 45.1 38.3 49.5 28.3 19.8 62.2 32.3 82.1 50.2 NNP 10.8 −10.2 12.1 10.6 21.5 14.7 8.7 2.2 45.6 25.1 56.1 29.8 20.9 −10.9 20.1 15.6 21.2 23.3 FFL 30.5 15.2 38.8 22.3 50.2 25.6 15.2 19.2 42.3 32.4 71.2 35.6 45.5 14.7 69.2 25.2 79.9 30.3
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