强震区近断层桥梁桩基础时程响应振动台试验

为进一步探明强震区近断层桥梁桩基动力时程响应规律,采用1g振动台模型试验,开展相同强度不同类型地震波作用下,近断层桥梁桩基加速度动力时程响应、桩顶相对位移动力时程响应、桩身弯矩动力时程响应及桩基损伤分析。结果表明：近断层桥梁桩基础的动力响应特征比无断层桩基更为明显,相比于非断层场地桥梁桩基础,近断层桥梁桩基加速度峰值、桩顶相对位移及桩身弯矩均较大。受发震断层及断层破碎带散体材料特性等因素的影响,改变了桩周土体半无限体性质,近断层桩基础桩顶加速度峰值出现时刻较为滞后,桩底加速度时程响应曲线规律与输入地震动更为接近,而桩顶加速度时程曲线振幅远大于桩底,且峰值出现时刻明显滞后于桩底和输入地震波；近断层桩基础桩顶加速度及相对位移时程响应在10s左右振幅较大,位移响应在30s作用开始衰减,此时段内桩基础动力响应特征最为明显；近断层桩基础桩身弯矩最大值均未超过其抗弯极限承载能力,且有20.36%~28.41%的抗弯承载能力富余；近断层桩基础基频没有发生变化,表明满足抗震设防烈度Ⅷ度的要求。综上所述,近断层桥梁桩基础抗震设计时,应考虑地震波频谱特性的差异对结构产生的影响,重点关注动力时程响应变化规律,根据多种类型地震波对近断层桥梁桩基础进行抗震分析与验算。

Shaking table test of time-history response of bridge pile foundation near fault in strong earthquake area

In order to further explore the dynamic time-history response law of near-fault bridge pile foundation in strong earthquake area, 1g shaking table model test was used to carry out the action of different types of seismic waves of the same intensity. Near-fault bridge pile acceleration dynamic time-history response, pile top relative displacement dynamic time-history response, pile bending moment dynamic time-history response and pile foundation damage analysis. The results show that the dynamic response characteristic of near-fault bridge pile foundation is more obvious than that of non-fault pile foundation. Compared with non-fault bridge pile foundation, the peak acceleration, pile top relative displacement and pile bending moment of near-fault bridge pile foundation are larger. Affected by the seismogenic fault and the characteristics of bulk materials in the fault fracture zone, the semi-infinite properties of the soil around the pile are changed, and the peak acceleration of the pile top of the near-fault pile foundation lags behind. the time history response curve of pile bottom acceleration is closer to the input ground motion, but the amplitude of pile top acceleration time history curve is much larger than that of pile bottom, and the peak occurrence time obviously lags behind the pile bottom and input seismic wave. The time history response of pile top acceleration and relative displacement of near fault pile foundation has a large amplitude at about 10s, and the displacement response begins to attenuate at 30s, during which the dynamic response characteristics of pile foundation are most obvious. the maximum bending moment of near fault pile foundation does not exceed its bending ultimate bearing capacity, and has a surplus of 20.36% to 28.41% bending bearing capacity. The basic frequency of near-fault pile foundation does not change, which shows that it meets the requirement of seismic fortification intensity VIII. To sum up, in the seismic design of near-fault bridge pile foundation, the influence of the difference of seismic wave spectrum characteristics on the structure should be considered, and the change law of dynamic time-history response should be paid more attention to. Seismic analysis and checking calculation of near-fault bridge pile foundation are carried out according to various types of seismic waves.