地震动特性对隔震结构弹塑性位移反应谱的影响研究

根据特定震源机制、震级、断层距和场地条件选取69条地震动记录并进行分组,利用Nspectra软件计算隔震结构的弹塑性位移反应谱,分析断层距、场地条件、震级、阻尼比对弹塑性位移谱的影响,探讨隔震层的力学参数对地震能量耗散的影响。研究结果表明:相较于远场,处于近场的隔震结构最为不利,隔震层位移谱值受场地条件、地震加速度和速度大小影响较大;随着断层距的增大,位移谱值衰减较快,且在软土场地中隔震层的位移谱值衰减幅度大于硬土场地;地震震级大小对位移谱形状的影响不明显,但能够使隔震层的位移谱值产生整体缩放效应;阻尼比在小于0.4的范围内,隔震层在不同地震动特性作用下位移谱值差别较大,但在大于0.4以后,位移谱值及谱形基本趋于一致;屈服力较小(恢复力/重力小于等于1)的隔震层随自振周期增大其耗能性能更加突出。

Influence of Ground Motion Characteristics on the InelasticDisplacement Spectra of Isolated Structures

Based on the specific focal mechanism, magnitude, fault distance, and site condition, 69 ground motion records are selected and grouped. Nspectra software is used to calculate the inelastic displacement response spectrum of a single isolated structure under ground motion. The influence of fault distance, field condition, magnitude, and damping ratio on the inelastic displacement spectrum is analyzed, and the influence of the mechanical parameters of seismic isolation layer on the seismic energy dissipation is discussed. The results indicate that compared with the far field, the base-isolated structure in the near field is more unfavorable. Moreover, the seismic isolation layer displacement spectrum is greatly influenced by field conditions, earthquake acceleration, and speed. With the increase of the fault distance, the attenuation of displacement spectrum values increases, and the displacement spectrum of the base isolated layer in the field of soft soil is more than that of hard soil. The influence of earthquake magnitude on the spectrum shape is not obvious; however, it can cause a scaling effected on the displacement spectrum of the base isolated layer. When the damping ratio is less than 0.4, the value of displacement spectrum of the seismic isolation layer differs largely with different ground motion characteristics; when the damping ratio is greater than 0.4, the value of displacement spectrum basically become the same. The energy dissipation of the seismic isolation layer with a small yielding force (restoring force/gravity less than or equal to 1) increases with the increase of natural period.