摘要
The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.
由于耐久性不足,常规黏滞阻尼器等动力控制装置不适用于双层钢桁梁斜拉桥减隔震设计。本文提出高性能的新型动力控制装置应用于双层钢桁梁斜拉桥抗震设计的研究思路,基于一座抗震设防烈度Ⅸ度区的跨径(90+128)m的双层钢桁梁斜拉桥,建立三维有限元分析模型,进行地震动时程分析,应用两种新型动力控制装置-弹性索组合黏滞阻尼器以及拉索减隔震支座,进行地震作用下的结构受力分析及数值模拟,针对弹性索组合黏滞阻尼器的设计参数-弹性索水平刚度K及阻尼系数C进行优化设计。研究得出以下结论:(1)由弹性索组合黏滞阻尼器和拉索减隔震支座组合而成的动力控制系统既满足正常使用状态下的耐久性要求,又可以有效减少结构在地震作用下的动力响应。(2)纵向地震动作用下,组合动力控制系统对梁端位移减震率达75%,塔底弯矩减震率达60%;横向地震动作用下,组合动力控制系统对边墩底弯矩减震率达45%,同时可控制墩梁相对位移在0.3 m以内。(3)假定阻尼指数α=0.3,参数优化设计表明,针对场地类别Ⅰ0地区,阻尼系数C推荐值为2000 k N·s·m-1,弹性索水平刚度K推荐值为10000 k N/m;针对场地类别Ⅱ地区,C推荐值为4000 k N·s·m-1,K推荐值为50000 k N/m;针对场地类别Ⅳ地区,C推荐值为6000 k N·s·m-1,K推荐值为100000 k N/m。
