软土地基上桩-土-高层结构体系动力特性的振动台试验

Shaking Table Tests on Dynamic Characteristics of Pile-Soil-High Rise Structure System on Soft Soil Foundation

摘要:

为了研究软土地基上桩?土相互作用对高层结构动力特性的影响机理，设计了1：6比例的高层结构?桩?土动力相互作用体系，进行了软土地基上框架结构的模型振动台试验。试验采用层状剪切盒模拟土体的边界，锯末和砂土的混合物作为地基土、以12层钢筋混凝土框架结构模拟上部结构，基础采用3×3群桩基础。通过对比考虑土?结构相互作用（SSI）框架模型和刚性地基框架模型的结构动力特性，总结出本试验中SSI效应对高层框架结构的动力特性影响规律：土体对地震动存在显著的过滤作用，放大土体基频附近的振动，且放大幅度随地震动的加强而减小；小震时土体对加速度峰值起放大作用，而在大震时起减小峰值的作用；考虑SSI效应后，结构的频率降低，阻尼比提高，结构的损伤出现得更晚，发展也更慢。在土体频率处，SSI体系的振型受土体影响显著；在远离土体频率处，SSI体系振型与刚性地基一致。

Abstract:

Shaking table tests are designed and performed on high-rise frame structures considering pile-soil dynamic interaction system and a frame structure model on fixed-base condition with the 1：6 scaling factor in this paper to study the influence mechanism of pile-soil interaction on the dynamic characteristics of high-rise structures on soft soil foundation. The layered shear box is used to simulate the boundary of soil. The mixture of sawdust and sand is adopted as the foundation soil， and the superstructure is a 12-story reinforced concrete frame structure. The foundation adopts the 3 × 3 pile group foundation. By comparing the structural dynamic characteristics of the soil structure interaction （SSI） frame model and the fixed-base model， the influence law of the SSI effect on the high-rise frame structure in this test is summarized. The soil has a significant filtering effect on ground motion. It mainly amplifies the vibration near the fundamental frequency of the soil， and the amplification amplitude decreases with the strengthening of ground motion. The soil amplifies the peak acceleration in minor earthquakes and reduces the peak acceleration in major earthquakes. The frequency of the structure in the SSI system decreases and the damping ratio increases. The structural damage in the SSI system appears later and develops more slowly than that of the fixed-base structure. At the frequency of soil， the vibration mode of SSI system is significantly affected by the soil， and its vibration mode amplitude distribution is obviously different from that of the fixed-base structure. The vibration mode of the SSI system far away from the soil frequency is consistent with that of the fixed-base model.