【摘要】 进行液化地基–群桩–超高层建筑相互作用体系的振动台试验,再现饱和砂土地基液化诱发的结构体系侧向大变形的震害现象。通过试验,研究相互作用体系下地基液化、体系侧向大变形前后群桩基础的动力响应,对地基超孔隙水压力、群桩体系的基频、阻尼比、桩身应变、桩底接触压力和桩顶位移进行计算和分析。得到的规律主要有:群桩内外超孔隙水压力变化过程存在差异;随着激励峰值的提高,砂土层达到液化条件,群桩体系的频率降低、阻尼比增大;桩基的动力响应与地震波加速度峰值和频谱特性均有关;桩身应变变化量峰值沿桩身向上逐渐增大,桩顶裂缝多;不同地震波激励下,桩顶位移响应规律差异较大;承台两端角桩在地震波激励过程中表现出明显的一拉一压现象,揭示了结构体系大变形的根本原因。提出:提高群桩的抗压拔性能、改善地基的液化条件可提升超高层建筑–群桩体系的抗震能力。研究结果对超高层建筑–群桩体系抗震研究及防灾减灾具有重要意义。更多还原

【Abstract】 Shaking table test on the interaction between the pile group and super highrise building system on liquefiable foundation was conducted to reproduce the liquefaction-induced large deformation of the system in saturated sandy ground. The excess pore water pressure(EPWP) of ground,the natural frequency,the damping ratio,the strain of pile group,the contact pressure at the bottom of pile and the displacement at pile top was calculated and analyzed before and after large deformation. It was shown that the EPWP response in and out of pile group was different. The sand layer liquefied,the natural frequency of pile group decreased and the damping ratio of pile group increased with the raise of peak acceleration. The dynamic response of piles was relevant to both the peak acceleration and the spectral characteristic of earthquake wave. Besides,the peak strain of pile increased upward along pile body so that there were more cracks on the top of pile. The displacement of pile head varied with the seismic behavior. The primary cause of the large deformation of the system was revealed through the phenomenon which two corner piles were pulled up and pressed down alternately under excitation. Consequently,it is effective to improve the anti-seismic capacity of super highrise building-pile group system by strengthening compressive and tensile resistant property of pile and improving the liquefaction conditions of ground.更多还原