双级受拉抗拔桩变形及上拔特性研究

发布时间：2019-01-17 17:42

【摘要】：传统的抗拔桩中上拔荷载是作用在桩身顶部的,随着上拔荷载的增加,桩侧摩阻力由浅及深地逐渐发挥作用。同时,在上拔作用下,桩身处于拉伸状态,由于泊松效应,桩径会产生收缩,对桩侧摩阻力的发挥产生负面影响;除此之外桩身拉应力过大还容易导致混凝土开裂,致使钢筋暴露、腐蚀,进而影响到抗拔的承载力与使用寿命。本文提出了一种新型的抗拔桩受力结构——双级受拉抗拔桩。其在普通的钢筋混凝土桩中心位置增加一根上部与钢筋、混凝土脱开的主筋,将部分上拔力直接传递至桩身中部,这样在上拔荷载下桩侧摩阻力会从两个位置同时开始发挥作用,并且桩身的拉应力也将大大减小。本文主要进行了以下研究:(1)结合原位上拔试验数据,对传统桩顶单一位置受力条件下的抗拔桩在上拔荷载作用下的位移、轴力及侧摩阻力特征进行了分析研究。(2)介绍了有限元分析的基本原理,利用FORTRAN语言对广义双曲线接触模型进行程序化,然后将其接入到ABAQUS,并应用于抗拔桩数值模拟计算中,最后对比分析了试验结果与数值模拟结果,验证了数值模型的正确性。(3)利用ABAQUS中建立的数值模型,变更受力条件,使荷载分别作用在桩身不同深度,研究了不同受力位置条件下抗拔桩的变形及上拔特征。(4)在上述研究的基础上,进一步改变模型受力条件,令上拔荷载按不同比例分别作用在桩顶与桩身中部或中下部,分析了桩顶-桩身中部(中下部)双级受拉作用下,不同荷载分配比例时,双级受拉抗拔桩的应力、变形、侧摩阻力、桩身轴力、桩顶位移的特征及变化规律,研究了双级受拉抗拔桩的变形及上拔特征。
[Abstract]:The uplift load of the traditional uplift pile is acting on the top of the pile body. With the increase of the uplift load, the friction on the side of the pile is gradually exerted from shallow to deep. At the same time, under the action of uplift, the pile body is in the state of tension, because of the Poisson effect, the diameter of the pile will shrink, which will have a negative effect on the exertion of the friction on the side of the pile. In addition, the excessive tensile stress of the pile can also lead to cracking of concrete, which leads to the exposure and corrosion of steel bar, and then affects the bearing capacity and service life of pull-out. In this paper, a new type of mechanical structure of pull-out pile, two-stage tensile pile, is presented. At the center of the ordinary reinforced concrete pile, it adds an upper part of the steel bar to the steel bar, and the main bar separated from the concrete is transferred directly to the middle of the pile body by the partial pull-out force. In this way, the frictional resistance of the pile will start from two positions and the tensile stress of the pile body will be greatly reduced under the uplift load. The main works of this paper are as follows: (1) the displacement of the uplift pile under the load of uplift under the condition of single position stress on the top of the traditional pile is studied in combination with the data of in-situ uplift test. The characteristics of axial force and lateral friction are analyzed. (2) the basic principle of finite element analysis is introduced. The generalized hyperbolic contact model is programmed by FORTRAN language, and then it is connected to ABAQUS,. Finally, the test results and numerical simulation results are compared and analyzed to verify the correctness of the numerical model. (3) using the numerical model established in ABAQUS, the stress condition is changed. The deformation and uplift characteristics of the uplift pile under different stress positions are studied. (4) on the basis of the above research, the stress conditions of the model are further changed. The uplift load acts on the top of the pile and the middle or lower part of the pile body according to different proportions. The stress and deformation of the two-stage tensile uplift pile with different load distribution ratio under the action of the pile top and the middle or lower part of the pile body are analyzed. The characteristics of lateral friction, axial force of pile body and displacement of pile top are studied in this paper. The deformation and uplift characteristics of two-stage tensile uplift pile are studied.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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