【作者】 洪浩；

【导师】 郑史雄；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2013， 硕士

【摘要】 为了使桥塔能够在强震下基本保持弹性,悬索桥通常采用全漂浮和半漂浮的隔震体系来减小地震反应。这两种体系将会导致相当大的梁端位移,梁端的过大位移可能会导致主梁与引桥的碰撞、落梁等事故,给大桥的整个安全性造成威胁。地震动空间变异性(场地效应、行波效应、相干效应)对于桥梁地震响应的影响是当今研究的一个热点。桩土相互作用在抗震计算中不可忽略,半无限空间地震动人工边界在桩土相互作用上的研究还比较少。为了研究以下几点：粘弹性人工边界法在桩土相互作用上的实现,桩土相互作用对大桥自振特性和地震响应的影响；大桥主梁与引桥梁间碰撞和行波效应对桥梁地震响应的影响；最优非线性阻尼器的选择,及其对大桥地震响应的影响。采用大型通用有限元软件Midas Civil建立有限元模型,土体采用实体单元模拟,地震动从实体单元边界节点输入。阻尼器、碰撞单元均采用软件自带的内力模型,对其进行参数敏感性分析。采用大质量法考虑行波效应,分析不同视波速下行波效应对大桥地震响应的影响。对于大跨度悬索桥,用于分析的结构响应主要包括：梁端位移、塔底剪力、塔底弯矩、阻尼力、碰撞力等。研究分析结果显示：(1)大跨度悬索桥主要以长周期振动为主,采用固结模型进行抗震设计偏于安全,采用粘弹性人工边界法时则相反,m法是一个比较好的选择。(2)考虑引桥梁与主梁间的碰撞后,主梁与引桥梁间的相对位移、引桥墩内力明显减小。碰撞刚度和恢复系数对于碰撞响应有很大的影响,合理的恢复系数应通过实验确定,碰撞初始间隙是一个不确定的影响因素。(3)桥址的地质情况良好,对大桥进行行波效应分析后发现可不用考虑行波效应对其影响。(4)粘滞性阻尼器的减震效果主要体现在对梁端位移的控制和主塔内力的减小。最优阻尼器参数C=2000kN(sec/m)ξ,阻尼指数ξ=0.2-0.4,单个阻尼器的额定阻尼力可取为2250kN。更多还原

【Abstract】 The seismic isolation system as all floating or half floating system is usually taken by the suspension bridge to keep the tower in elastic state. These two systems will bring out large displacement in earthquake, the large displacement at the end of main beam will cause the collision between main beam and the approach bridge, the safety performance of whole bridge will be in danger. The seismic response of the bridge influenced by the spatial variation of ground motions is studied by many scholars. The spatial variation of seismic ground motions is produced primarily by the three factors:geometric incoherency effect, wave-passage effect and local site effect. The pile-soil interaction cannot be ignored in the seismic computation and the application of viscoelastic artificial boundary is little researched.In order to study the following points:how to realize the viscoelastic artificial boundary when considering the pile-soil interaction; the influence on seismic response of the pile-soil interaction, wave-passage effect and collision between the main beam and the approach bridge; optimal selection of nonlinear damper.The finite element model was established by the software Midas Civil, the soil was simulated by the solid element and the ground motion was input on the boundary nodes. Damper and the collision units were simulated by the software’s model. The large mass method was used to consider the wave passage effect and the seismic response under different apparent wave velocity was studied. For the long-span suspension bridge, structural response used to be analyzed includes the displacement at the end of main beam, shear force and bending moment at the bottom of tower, damping force and collision force.The results showed that:The main natural period of vibration was very long and influenced by the pile-soil interaction. It was safer but less economic when using the seismic response of fixed model to design. When using the viscoelastic artificial boundary model, it was more economic but safe. M method was a good way to consider the pile-soil interaction.When considering the collision between the main beam and the approach bridge, the displacement between the main beam and approach bridge was decreasing and same for the internal force of pier of approach bridge. Collision stiffness and recovery coefficient had big influence on the collision reaction; the reasonable recovery coefficient should be confirmed by the test. The width of initial gap was an uncertain factor.The geological condition was good and the wave-passage effect could need not to be considered.The seismic reduction effect was good for the suspension bridge with viscous dampers, and the reduction effect was mainly reflected on the displacement at the end of main beam and the internal force of main tower. The optimal damper parameters were C=2000kN(sec/m)ζ, ζ=0.2～0.4, rated damping force of one single damper could be2250kN.更多还原