强震近断层区地震动特性及其对基础隔震结构破坏影响机理研究

In China, there are many seismic belts and earthquake faults, many important cities are located near or even crossed by large active fault. It is not very clear that what kind of impact, which result from the characteristics of velocity pulse of near-fault ground motion, is going to act on the base isolated structures of these cities if strong earthquake occurs in these cities or nearby. It should be further researched that how to consider the negative influence of velocity pulse on seismic response of base isolated structure. Based on the actual ground motions with velocity pulse and artificial earthquake wave without velocity pulse whose acceleration response spectrum are consistent, the validity of typical isolation scheme of base isolated structures are studied quantitatively under the actual ground motions with velocity pulse. And the damage natures and mechanisms of the base isolated structures under the ground motions with velocity pulse are revealed. In term of the negative influence of velocity pulse on seismic response of base isolated structure in near-fault area, the optimal settings (that is, appropriate height-width ratio and isolation bearing parameters) of base isolation structure are discussed, from the perspective of the advantage frequency band of base isolated structure and the energy concentrating frequency band of ground motion with velocity pulse should be avoided. This study can provide scientific reference and technology support for building base isolated structures in near-fault areas.

我国境内的地震带及地震断层众多，而且许多重要的城市均有大型活动断层穿越或位于附近。若在这些城市及其附近发生强烈地震，近断层地震动的速度脉冲特性将会对基础隔震结构造成什么样的影响还不是十分清楚，在强震近断层地区进行基础隔震结构设计时应如何考虑速度脉冲对其地震反应的不利影响也有待进一步研究。本申请基于加速度反应谱一致的具有和不含速度脉冲的实际强震动记录和人工地震动时程，定量地分析强震近断层速度脉冲地震动作用下基础隔震结构现有典型隔震方案的有效性，揭示近断层地震动的速度脉冲作用下基础隔震结构的破坏特性及其形成机理；针对近断层地震动速度脉冲的长周期特性对基础隔震结构地震反应的影响，从基础隔震结构的优势频段应避开速度脉冲地震动能量集中频段的角度，提出强震近断层地区基础隔震结构的优化设置即适宜的高宽比及隔震支座参数等建议，以为基础隔震结构在强震近断层区的建设提供理论和技术支撑。

为了研究强震近断层区地震动特性及其对基础隔震结构地震反应的影响，广泛收集了多条典型的近断层地震动，根据速度脉冲形成机制的不同，选取了6条具有不同特征参数的含有向前方向性效应、滑冲效应速度脉冲的典型近断层地震动。完善了一种以绝对加速度反应谱和峰值加速度、峰值速度、峰值位移多参数为控制目标的人工地震动时程合成的方法。以选取的6条速度脉冲地震动的弹性反应谱为目标，分别合成了6条无速度脉冲特性的人工地震动时程。采用MIDAS-GEN软件，建立了不同高宽比的4个传统抗震结构和4个基础隔震结构模型，输入选取的6条含有速度脉冲特性的近断层地震动，开展了结构地震反应计算，探讨了速度脉冲对传统抗震结构和基础隔震结构地震反应影响。结果表明：速度脉冲及脉冲强度对基础隔震结构的减震能力有显著的影响；对于高宽比H/B为1、2、3的结构，基础隔震装置具有较好的隔震效果，且高宽比越小其减震效果越好；当结构高宽比H/B=4时，基础隔震的效果较差，甚至会因结构较低层或隔震支座的位移过大而导致结构破坏。以6条近断层速度脉冲地震动和具有相同反应谱而不具有速度脉冲的人工地震动作为输入，在具有一致加速度反应谱的前提下，定量的分析了近断层地震动的速度脉冲特性对具有不同高宽比结构位移反应的影响。结果表明：地震动的速度脉冲导致非隔震结构、基础隔震结构的层间位移角响应增大；速度脉冲对基础隔震支座位移的影响随着高宽比的增大而逐渐减小；在加速度反应谱一致的情况下，速度脉冲导致隔震支座位移平均增大34%。