推扭荷载下群桩基础承载机理及计算理论研究

发布时间：2018-04-15 22:07

本文选题：桩基础 + 耦合效应　；参考：《长沙理工大学》2015年硕士论文

【摘要】：近年来,大型建(构)筑在复杂的工作环境中的工作性状与破坏形态受到了广泛关注。与常规环境不同,复杂环境下结构物所受的组合荷载更为特殊,如风荷载或船舶撞击等引起的扭转荷载与水平荷载的耦合。工程上已有由于船舶撞击而导致上部结构突然破坏,以及风载引起建筑物永久变形的案例。因此,对推扭耦合条件下群桩基础的承载机理及相关计算理论进行研究十分必要。本文为此展开了一系列的研究,主要工作如下:(1)结合国内外研究现状,在已有的研究成果的基础上,对推扭荷载下群桩基础的荷载分配、位移模式以及破坏模式进行了初步的分析;(2)结合屈服接近度概念,分别对推扭荷载下单桩地表及桩中桩周土在荷载下的应力路径进行分析,由结果可知:扭转荷载下桩周土应力通常沿某一?平面上向屈服面接近;水平荷载下桩周土应力路径与?平面呈一定角度;而推扭耦合作用会导致两种应力路径的组合。其应力路径分析有助于定性分析推扭耦合效应对桩基水平和扭转特性的影响;结合三维数值分析方法,对推扭荷载下桩基础的响应特征及耦合效应进行分析,分析表明,土质以及偏心距的大小均对群桩基础的受荷性状有影响;水平荷载与扭矩荷载存在耦合效应,水平荷载对群桩扭转刚度有增强的作用,扭矩荷载对群桩的水平向刚度有减弱的作用。(3)首先在分析推扭荷载下群桩基础工作机理的基础上,根据静力平衡条件建立了以转心为参照点的各基桩位移及转角普适方程。其次,采用p-y曲线法以及单桩扭转刚度计算理论分别确定各基桩的水平刚度与扭转刚度,并提出了各计算参数的取值方法。然后,建立了推扭荷载群桩内力与位移的解算流程,编制了相应的计算程序,与试验数据的对比表明,本文方法计算结果与实测结果吻合较好,且计算过程简单,具有工程实用性。最后,采用计算程序对推扭耦合作用下群桩基础进行了失稳破坏分析,结果表明:当荷载偏心距变大时,同等量级荷载下群桩转角即随之增大,偏心距对承台转角的影响更明显;而影响群桩水平位移的主要因素则是水平荷载及桩头水平刚度。(4)在对桩基础基本设计原则、桩型选择方法以及一般设计步骤进行初步总结分析的基础上,建立了推扭荷载下群桩设计验算流程。
[Abstract]:In recent years, extensive attention has been paid to the working characteristics and failure patterns of large-scale construction in complex working environment.Different from the conventional environment, the combined loads of structures in complex environments are more special, such as the coupling of torsional loads and horizontal loads caused by wind loads or ship impacts.There have been cases of sudden damage to superstructures caused by ship impact and permanent deformation of buildings caused by wind loads.Therefore, it is necessary to study the bearing mechanism and related calculation theory of pile group foundation under the condition of push-torsion coupling.In this paper, a series of studies have been carried out, the main work is as follows: (1) combined with the current research situation at home and abroad, based on the existing research results, the load distribution of pile group foundation under push-torsional load is discussed.The displacement mode and failure mode are analyzed preliminarily. Combined with the concept of yield approach, the stress paths of the ground surface and the soil around the pile under the load are analyzed, respectively.From the results, it can be concluded that the stress of soil around pile is usually along a certain one under torsional load.The stress path of the soil around the pile under horizontal load and the stress path of the soil around the pile are close to the yield surface on the plane.The plane is at a certain angle, and the coupling of push and torsion will lead to the combination of two stress paths.The analysis of stress path is helpful to qualitatively analyze the influence of the coupling effect of push and torsion on the horizontal and torsional characteristics of pile foundation, combined with the three-dimensional numerical analysis method, the response characteristics and coupling effect of pile foundation under push-torsion load are analyzed, and the results show that,Soil quality and eccentricity influence the behavior of pile group foundation, the coupling effect of horizontal load and torque load exists, and horizontal load can enhance the torsional stiffness of pile group.Firstly, on the basis of analyzing the working mechanism of pile group foundation under push-torsion load, the universal equations of pile displacement and rotation angle with reference point of rotation center are established according to the static equilibrium condition.Secondly, the horizontal stiffness and torsional stiffness of each pile are determined by the p-y curve method and the calculation theory of torsional stiffness of single pile.Then, the calculation flow of the internal force and displacement of the pile group under push-torsion load is established, and the corresponding calculation program is worked out. The comparison with the experimental data shows that the calculated results of this method are in good agreement with the measured results, and the calculation process is simple.It has engineering practicability.Finally, the instability failure analysis of pile group foundation under the coupling of push and torsion is carried out by using the calculation program. The results show that when the eccentricity of load increases, the rotation angle of pile group increases under the same order of magnitude.The influence of eccentricity on pile cap angle is more obvious, and the main factors influencing the horizontal displacement of pile group are horizontal load and horizontal stiffness of pile head.Based on the preliminary summary and analysis of the selection method of pile type and the general design steps, the flow of pile group design verification under push-torsion load is established.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1

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