铅芯橡胶支座热量累积和性能退化效应及其对隔震桥梁地震反应性态影响

Lead-rubber bearings（LRBs）are seismic isolators of bridges that have been extensively used at present. Cyclic deformation of LRB in earthquake will cause heating accumulation and temperature rise, which will further bring problems such as the mechanical properties degradation and displacement amplification, and threaten the safety of bridges. Based on the energy method, the relationship is established between dimensionless temperature and dimensionless time and space by theoretical derivation, the mechanical equation of LRBs lead core deformation-heating and temperature is obtained, and the relationship between mechanical properties of LRBs and heating accumulation in combination with the material characteristics of lead and rubber is given. Using finite element analysis of solid elements, the heating transfer and temperature distribution laws of LRBs during cyclic deformation process are revealed, and deformation heating mechanism and degradation effect of mechanical properties of LRBs are discussed. A mechanical model of LRBs considering heating accumulation and performance degradation is established by combining the energy method and finite element analysis. Based on the previous work as described above，from the perspective of dissipating seismic energy, the similarity of reduced-size LRBs is developed to solve the problem of limited load capacity in prototype test or the issue of insufficient similarity design basis in shake table test. The mechanical model and similarity of reduced-size LRBs are validated through the prototype test, reduced-size model test and real-time substructure hybrid test of LRBs. Finally, a hysteretic model of LRBs is established in OpenSees, where the degradation due to heating accumulation is taken into account, then threshold values of displacement amplification are obtained by statistics and presented in graphical format using contour lines, and the actual seismic design methods of bridges will be further improved and promoted in this way.

铅芯橡胶支座(LRB)是目前应用广泛的桥梁减隔震装置，地震中LRB往复变形会引发热量累积及温度升高，进而带来力学性能退化和位移反应放大等问题并威胁桥梁地震安全。本课题基于能量法以理论推导方式建立无量纲温度与无量纲时间和空间之间的关系，得到LRB铅芯变形发热量和温度的力学方程，结合铅材料和橡胶材料特性给出其力学性能与热量累积的关系；采用精细化实体有限元分析技术，揭示LRB往复变形过程中热量传递和温度分布规律；上述二者结合建立LRB热量累积和性能退化力学模型。以此为基础从地震能量耗散角度发展LRB缩尺模型相似率关系，以解决原型试验设备加载能力有限或振动台试验LRB相似设计依据不足的问题。通过LRB原型试验、缩尺模型试验和实时子结构混合试验，验证上述成果。最后，基于OpenSees平台开发LRB考虑热量累积的退化滞回模型，以统计获得的位移放大阈值等高线图形式，将研究成果推向实际桥梁减隔震设计。

随着LRB隔震桥梁在高烈度高寒地区的推广，环境温度和铅芯变形发热效应使得支座力学性能发生改变，并进一步影响了LRB隔震桥梁的抗震性能。以《公路桥梁铅芯隔震橡胶支座》(JT/T 822-2011)中的圆形LRB为对象，建立了40个不同周期的单支座隔震结构模型，研究了考虑铅芯发热与否对LRB的位移、温度、特征强度和滞回耗能等因素的影响，还讨论了铅芯温度增量和特征强度降低率与近断层地震动的关系。此外，对比分析了长、短持时地震动对LRB的剪应变、温度、特征强度和滞回耗能等因素的影响，还探讨了不同地震动持时指标与单支座隔震结构地震响应的相关性。为减小地震作用下桥梁支座的最大位移及残余变形，发展了一种具有良好自复位性能和耗能能力的SMA-LRB减隔震支座，对比评估了LRB和SMA-LRB两类隔震连续梁桥的地震损伤概率，验证了SMA-LRB优异的抗震性能。进一步对其进行参数分析，可为SMA-LRB隔震桥梁的设计提供参考依据。基于BP神经网络搭建了环境温度和桥梁地震响应之间的映射关系，并在地震易损性分析中考虑了区域环境温度变化的影响，对比分析了常温和不同区域下案例桥梁构件和系统的损伤概率。综合考虑区域温度分布和地震危险性的不同，提出一种考虑区域温度分布及铅芯发热的LRB隔震结构剪应变评估方法。进一步以基于性能的地震工程评估框架为基础，将区域温度分布概率纳入到地震风险评估方法。在设计理论方面，将环境温度和铅芯变形发热引入到直接基于位移设计方法中，从保证低温下桥墩后于支座屈服的角度，控制了桥墩的地震损伤，引入考虑高温及变形发热下支座剪应变放大系数，对支座进行抗震性能验算，并分析验证了设计方法的可行性。本项目针对中国LRB行业技术标准中的特点，系统、深入地研究了其变形发热和性能退化效应对隔震桥梁地震反应性态的影响。提出了考虑区域温度分布的地震风险评估方法以及考虑环境温度和铅芯变形发热的基于位移设计方法，为解决LRB隔震桥梁在高烈度高寒地区的推广应用提供理论支撑。

内容获取失败，请点击重试