单桩-土-结构振动台试验模型数值计算分析

Numerical analysis of single pile-soil-structure shaking table test model

为研究地震荷载作用下桩基-土-核电结构的抗震性能及土结动力反应规律,对拟开展的地震模拟振动试验模型进行数值计算分析。核电工程结构上部质量大和刚度大,试验模型不同于一般的工程结构,为检验振动台试验模型设计、传感器布设方案,对试验模型进行了数值模拟。数值模拟以单端承桩为研究对象,计算了上部结构质量和刚度变化时,在脉冲荷载及基于RG1.60谱人工合成地震动作用下桩身的地震反应规律。数值模拟表明:在水平地震动作用下,桩身剪力和弯矩包络线呈“X”状分布,桩底和顶处剪力弯矩较大;上部结构质量越大,桩身的剪力与弯矩越大;上部结构的刚度越大,桩身的剪力与弯矩越小;随着上部结构质量的增大和刚度的减小,反弯点逐渐向桩顶移动。桩顶发生最大位移时所对应的桩身挠度随着上部结构质量的增加而增大并且随着上部结构刚度的增大而减小。土层分界面处,桩身内力发生突变。此外,在脉冲荷载输入下,桩身反弯点位置与输入荷载的周期有关。计算结果为振动台试验模型设计提供了理论依据。

In order to study the seismic performance of pile foundation-soil-nuclear power structure and the dynamic response law of soil-structure interaction under the action of seismic load,the numerical simulation analysis of the planed shaking table test is carried out.The upper part of the nuclear power structure has large mass and rigidity,therefore the test model is different from the general structures.In order to verify the design of the shaking table test model and the sensor layout scheme,the numerical simulation of the test model is performed.The numerical simulation takes the single-end bearing pile as the research object,considering the changes of superstructure mass and stiffness,and calculates the seismic response of the pile body under the impulse load and artificially synthesized ground motion based on the RG1.60 spectrum.Numerical simulations show that under horizontal ground motion,the pile body shear and bending moment envelopes are distributed in an“X”shape,and the pile bottom and top shear and bending moments are larger.The greater mass of the upper structure leads to greater pile body shear.The greater stiffness of the superstructure leads to the smaller shear force and bending moment of the pile body.As the mass of the superstructure increases and the stiffness decreases,the reverse bending point gradually moves towards to the top of the pile.When the maximum top displacement of the pile occurs,the deflection of the pile body increases with the increase of the mass of the superstructure,and decreases with the increase of the stiffness of the superstructure.At the soil interface,the internal force of the pile suddenly changes.In addition,under the impulse load input,the position of the inflection point of the pile body is related to the period of the input load.The calculation results in this paper provide a theoretical basis for the design of the shaking table test model.