建筑抗震中单桩摩阻力动力效应分析

研究了地震发生时单桩摩阻力动力.为揭示摩擦桩与土体在考虑基本地震荷载作用下的耦合响应规律,采用拉格朗日数值分析方法建立桩与土体计算模型,通过施加地震荷载,分析桩周摩阻力、桩体轴力以及土体的变形在不同地震历时下的情况,得到:1)桩周负摩阻力从桩顶向下呈先增大后减小的态势,在桩长0.35倍范围内出现负摩阻力;2)由于地震荷载的作用,桩侧摩阻力和轴力均不断变化,当地震时间为3s时,桩侧摩阻力和轴力达到最大值;3)随着地震的持续进行,桩体和土体之间的相对位移的变化导致中性点位置发生往复变化;4)由于地震荷载的作用,土体的位移明显增大.在地震历时0~10s范围内,地表沉降迅速增大;在地震历时10~15s时,地震沉降增加的速度明显减慢;当地震历时持续到15~20s时,地表沉降逐渐减小.

Analysis for the Dynamic Effect of Friction Forces of Single Pile

In order to study the response of the single pile and soil under dynamic loading, the numerical calculation method was adopted to establish the pile soil interaction model considering the basic seismic intensity, then the pile friction force, pile axial force and surface settlement with the change of earthquake duration were analyzed. The results show that 1) negative friction of pile shows the trend of first increase then decrease, and the negative friction mainly appears in the range of 0.35 times the pile length; 2) under the dynamic loading, the pile friction force and axial force are constantly changing, when the earthquake time is 3 s, pile side friction and axial force reach their peak value; 3) as the earthquake continueds, the change of the relative displacement between pile and soil leads to the change of neutral point position; 4) as a result of the dynamic loading, the settlement of the soil increases obviously. Within the scope of the earthquake lasting 0 ~ 10 s, surface subsidence increases rapidly, the earthquake lasting 10 ~ 15 s, the surface subsidence increases slower. When the earthquake lasts until 15 ~ 20 s, the surface subsidence decreases.