近断层大跨RC轻柔拱桥纵向阻尼器减震研究

Longitudinal seismic mitigation of near-fault long-span RC soft-lighten arch bridge based on viscous damper

为提升高烈度近断层地区大跨轻柔拱桥的纵向抗震性能,通过非线性时程分析,探讨了某上承式RC拱桥黏滞阻尼器的适用性。对比该新型拱桥与常规RC拱桥结构体系、动力特性的差异,明确了其地震损伤路径,优化了阻尼器布置方案,探究了近远断层地震动下墩柱响应规律及减震效果,考虑了高阶振型的影响,结合易损性说明了减震方案的合理性。结果表明:此类轻柔拱桥在近断层纵竖向设计地震下,中等高度立柱最易损伤,而拱肋保持弹性;在桥台及高柱处布置阻尼器的减震效果最佳;受高阶振型影响,设置阻尼器后的高墩柱墩身剪力及弯矩包络“S”形分布更显著;在近场脉冲及远场长周期地震下的结构响应更大,受位移脉冲的影响阻尼器滞回环会出现突变,但耗能显著、减震效果突出;4类近远场地震动下黏滞阻尼器均可有效降低拱桥墩柱的损伤概率,适用性较优,但需满足大出力、大量程的地震需求。

To improve the longitudinal seismic performance of long-span soft-lighten arch bridges in highintensity near-fault regions, the applicability of viscous dampers was discussed for an upper-deck RC arch bridge through the nonlinear time history analysis. The structural system and dynamic characteristics of the novel arch bridge were compared with those of the conventional RC arch bridge. The seismic damage path was explored and the layout schemes of the viscous damper were optimized. The structural response and the mitigation due to dampers were investigated under the near-field and far-field ground motions. The influence of high-order mode was analyzed. The rationality of the mitigation design was investigated based on fragility analysis. The results show that the medium height column is vulnerable to near-field longitudinal and vertical design earthquake, while the arch rib remains elastic. The overall mitigation effect is the best when the dampers are located on the abutments and high columns. The S-shaped distribution of shear force and bending moment envelope of high column with damper is more obvious than the others due to the influence of high-order mode.The structural responses are larger with significant energy dissipation and efficient mitigation under near-field impulse and far-field long-period earthquakes than the other conditions, and the hysteresis loop of the damper would suddenly change under the influence of displacement pulse. The damage probability of mitigation design with excellent application is effectively decreased under four types of near-field and far-field earthquakes.However, the damper should meet the seismic requirements of large force and stroke.