【摘要】：傳統(tǒng)的抗拔樁中上拔荷載是作用在樁身頂部的,隨著上拔荷載的增加,樁側摩阻力由淺及深地逐漸發(fā)揮作用。同時,在上拔作用下,樁身處于拉伸狀態(tài),由于泊松效應,樁徑會產生收縮,對樁側摩阻力的發(fā)揮產生負面影響;除此之外樁身拉應力過大還容易導致混凝土開裂,致使鋼筋暴露、腐蝕,進而影響到抗拔的承載力與使用壽命。本文提出了一種新型的抗拔樁受力結構——雙級受拉抗拔樁。其在普通的鋼筋混凝土樁中心位置增加一根上部與鋼筋、混凝土脫開的主筋,將部分上拔力直接傳遞至樁身中部,這樣在上拔荷載下樁側摩阻力會從兩個位置同時開始發(fā)揮作用,并且樁身的拉應力也將大大減小。本文主要進行了以下研究:(1)結合原位上拔試驗數據,對傳統(tǒng)樁頂單一位置受力條件下的抗拔樁在上拔荷載作用下的位移、軸力及側摩阻力特征進行了分析研究。(2)介紹了有限元分析的基本原理,利用FORTRAN語言對廣義雙曲線接觸模型進行程序化,然后將其接入到ABAQUS,并應用于抗拔樁數值模擬計算中,最后對比分析了試驗結果與數值模擬結果,驗證了數值模型的正確性。(3)利用ABAQUS中建立的數值模型,變更受力條件,使荷載分別作用在樁身不同深度,研究了不同受力位置條件下抗拔樁的變形及上拔特征。(4)在上述研究的基礎上,進一步改變模型受力條件,令上拔荷載按不同比例分別作用在樁頂與樁身中部或中下部,分析了樁頂-樁身中部(中下部)雙級受拉作用下,不同荷載分配比例時,雙級受拉抗拔樁的應力、變形、側摩阻力、樁身軸力、樁頂位移的特征及變化規(guī)律,研究了雙級受拉抗拔樁的變形及上拔特征。
[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.
【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU473.1

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