近场脉冲型地震动下层间隔震的非线性反应与隔震层限位分析

Analysis on Nonlinear Responses of Mid-story Isolated Structures and Limiting Deformation of Isolation Layers under Near-field Pulse-like Ground Motion

层间隔震的隔震层下部结构类似于抗震体系,其在近场脉冲型地震动下易产生弹塑性变形,且隔震层易发生过大变形,导致其上部结构倾覆失稳倒塌.提出以实际的近场非脉冲型地震为底波,叠加等效脉冲来模拟近场脉冲型地震动.研究在近场脉冲型地震动和常规地震动(远场或近场非脉冲地震动)作用下LRB层间隔震结构的动力反应特性与近场地震动特征参数(脉冲类型、脉冲参与系数、脉冲周期)对隔震结构非线性反应与隔震层最大变形的影响.提出在隔震层增设黏滞阻尼器,形成LRB与黏滞阻尼器相结合的层间混合隔震,对隔震层进行限位保护;并对黏滞阻尼器的参数优化规律进行了分析.结果表明:与常规地震动作用下相比,LRB层间隔震结构在近场脉冲型地震动下的非线性反应与隔震层最大变形均显著增加,近场地震的脉冲类型、脉冲参与系数、脉冲周期及PGV/PGA对LRB层间隔震结构的非线性响应有很大的影响,隔震层变形超越隔震支座容许变形;通过设置参数合适的黏滞阻尼器,层间混合隔震能有效降低非线性反应与隔震层变形,避免隔震支座破坏而导致上部结构倾覆失稳倒塌.

The substructure of the mid-story isolated structure was similar to seismic resistant system. It probably generated elastic-plastic deformation under strong near-field pulse-like ground motion. Excessive deformation of the isolation layer may also occur, which will destroy the isolation bearings and result in the overturning collapse of the superstructure. The artificial generated near-field pulse-like ground motion was simulated by combining the real near-field non-pulse ground motion with simple equivalent pulse, and the different dynamic behaviors of the mid-story isolated structure using LRBs (Lead-Rubber Bearings) were studied under near-field pulse-like and common (far-field or non-pulse) ground motion. In addition, the impacts of the characteristic parameters of near-field ground motion, including pulse type, pulse contribution factor and pulse period, on nonlinear responses of the mid-isolated structure and maximum deformation of the isolation layer were discussed. Also, the mid-story hybrid isolation with viscous dampers installed on the isolation story was developed to limit deformation of the isolation layer, and the optimization law of viscous dampers was explored. The results show that the nonlinear responses of the mid-story isolated structure and the maximum deformation of the isolation layer subjected to near-field pulse-like ground motion are much greater than those under common ground motion, and they are affected by some parameters, such as pulse type, pulse contribution factor, pulse period and PGV/PGA. The maximum deformation of the isolation layer significantly exceeds the allowable deformation of Lead-Rubber Bearings, which destroys the Lead-Rubber Bearings and further results in the superstructure's collapse. It is also found that the mid-story hybrid isolation using the optimal viscous dampers can significantly reduce the nonlinear responses, and can reduce the maximum deformation of the isolation layer, avoiding the superstructure's overturning collapse. © 2015, Editorial Board of Journal of Basic Science and Engineering. All right reserved.