强震区近断层桥梁桩基础时程响应振动台试验

Shaking Table Test of Time-history Response of Bridge Pile Foundation Near Fault in Strong Earthquake Area

为进一步探明强震区近断层桥梁桩基础动力时程响应规律,依托海文大桥实际工程,采用1g振动台模型试验,开展0.35g不同类型地震波作用下,无断层及近断层桥梁桩基础加速度、桩顶相对位移、桩身弯矩动力时程响应及其差异与桩基损伤分析。结果表明:受发震断层及断层破碎带散体材料特性等因素的影响,改变了地基土半无限体性质。由于断层破碎带相较于地基土结构性较差,强度较弱,断层破碎带–地基土相互作用对地震波的放大效应较为明显,导致近断层桥梁桩基础的动力响应特征相较于无断层桩基础更为明显,其桩基加速度峰值、桩顶相对位移及桩身弯矩均较大,且加速度峰值出现时刻早于无断层桩基,平均提前0.44~3.18 s,近断层桩基础的桩顶加速度及桩顶相对位移时程响应在10 s左右振幅较大,位移响应在30 s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,且基频没有发生变化,表明海文大桥桩基础满足抗震设防烈度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桩基础产生的影响,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,并进一步增强近断层桩基础的抗震能力。

Based on the Haiwen Bridge,a 1g shaking table model test was adopted to further explore the dynamic time history response law of near-fault bridge pile foundations in strong earthquake areas.Under the action of 0.35g different types of seismic waves,the pile foundation acceleration,pile top relative displacement,pile bending moment dynamic time history response and its difference,and pile foundation damage analysis of non-fault and near-fault bridge were carried out.The results show that due to the influence of seismogenic fault and bulk material characteristics of fault fracture zone,the properties of the semi-infinite body of foundation soil are changed.Because the structure of the fault fracture zone is worse and its strength is weaker than that of the foundation soil,the amplification effect of fault fracture zone-foundation soil interaction on seismic waves is more obvious.As a result,the dynamic response characteristics of near-fault bridge pile foundations are more obvious than those of non-fault pile foundations,and the peak acceleration of the pile foundation,the relative displacement of the pile top,and the bending moment of the pile body are larger.And the peak acceleration appears earlier than that of non-fault pile foundation,with an average advance of 0.44 to 3.18 s.The time history response of pile top acceleration and relative displacement of near-fault pile foundation is larger at about 10 s.The displacement response begins to attenuate in the 30 s.During this period,the dynamic response characteristics of pile foundations are the most obvious.The maximum bending moment of near-fault pile foundation does not exceed its ultimate bending bearing capacity,and there is a surplus of 20.36%~28.41%bending bearing capacity.The fundamental frequency of the near-fault pile foundation does not change,which indicates that the pile foundation of Haiwen Bridge meets the requirement of seismic fortification intensityⅧ.To sum up,the influence of the difference in seismic wave spectrum characteristics on pile foundations should be considered in the seismic design of near-fault bridge pile foundations.The seismic analysis and checking calculation of near-fault bridge pile foundations should be carried out according to various types of seismic waves,and further enhance the anti-seismic capacity of near-fault pile foundations.