考虑钢筋屈服和混凝土损伤的桩基础水平承载特性分析

发布时间：2018-06-04 00:21

本文选题：桩基础 + 水平承载力　；参考：《鲁东大学》2017年硕士论文

【摘要】：随着国民经济的发展,高层建筑、码头、跨海桥梁、海上钻探平台、海上风机等建筑物的数量急剧增加,桩基础在其中得到十分广泛的应用。桩基础不仅需要承受由上部建筑和桩身自重引起的竖向荷载,而且还需要承受由地震作用、风浪作用、车辆制动作用、上部结构起拱等引起的水平荷载。对于桩基础水平承载特性的探讨,国内外专家学者已作大量相关工作,但是考虑钢筋屈服和混凝土损伤情况的探究相对较少。在水平荷载较大且影响十分显著的工程中,水平荷载甚至成为控制性因素,因此,合理的考虑钢筋屈服和混凝土损伤对水平承载特性的研究具有很大的理论和现实意义。本篇文章在已有的桩基础水平承载原位荷载实验的基础上,利用大型有限元分析软件ABAQUS建立数值分析模型,其中土体采用摩尔库伦模型,混凝土采用弥散开裂本构模型,钢筋采用基于Mises屈服准则的理想弹塑性本构模型。通过分析数值模拟与试验所得的桩顶位移曲线、桩身位移曲线以及混凝土和钢筋的应力应变曲线等,可知该模型可准确的反映桩基础在水平荷载作用下的受力特性。在较大横向荷载水平作用下,不考虑混凝土的损伤和钢筋的屈服将导致桩的受力性状和实际情况不符,这也表明了在桩的水平承载特性分析中考虑钢筋屈服和混凝土损伤的必要性。在此基础上系统分析了土体参数、桩体参数和荷载条件对桩基础水平承载特性的影响,其中包括土的不排水强度、土体弹性模量、土体内摩擦角、桩径、配筋率、桩长、竖向荷载水平等。结果表明:(1)对于桩周土体,在其他条件都不变的情况下,增大土体内摩擦角可显著改善桩基础水平承载特性,增大极限承载力;增大土体弹性模量可在一定程度上改善桩水平承载特性,在土刚度很大情况下,桩头的侧移量仅取决于桩体自身的变形特性;增大桩周土体不排水强度也可一定程度上改善桩基础的水平承载特性。(2)对于桩身性质方面,配筋率较低的桩,水平承载力容许值主要受桩身开裂控制,而对于配筋率较高的桩,水平承载力容许值受桩头水平位移控制;增大桩径可显著改善桩基础的水平承载特性。(3)由上部结构传递下来的竖向荷载有利于桩头水平位移的减小,但同时会增大桩身最大弯矩,总结分析可以认为竖向荷载在达到竖向极限荷载的0.4-0.6倍之间为最优竖向荷载水平。根据实际工程的群桩基础形式,利用有限元数值分析软件,建立起群桩数值分析模型,探讨了不同桩数对群桩基础水平承载特性的影响,并得到相应的桩顶承台侧移曲线,结果表明增加群桩数量可改善桩基础水平承载特性。
[Abstract]:With the development of the national economy, the number of high-rise buildings, wharfs, cross sea bridges, offshore drilling platforms, offshore wind turbines and other buildings have increased dramatically. The pile foundation has been widely used in it. The pile foundation not only needs to bear the vertical load caused by the weight of the upper building and the pile body, but also needs to be subjected to earthquake action, wind and waves. The horizontal load caused by the braking action of the vehicle and the arch of the superstructure. For the study of the horizontal bearing characteristics of the pile foundation, a lot of relevant work has been done by experts and scholars at home and abroad, but the exploration of the condition of steel yield and concrete damage is relatively less. It is a controlling factor, so it is of great theoretical and practical significance to consider the reinforcement yield and concrete damage to the horizontal bearing characteristics. On the basis of the existing pile foundation horizontal loading in situ load test, a numerical analysis model is established by the large finite element analysis soft ABAQUS, in which the soil is used. In the Moore Kulun model, the concrete is used in the dispersion cracking constitutive model, and the reinforcement is based on the ideal elastoplastic constitutive model based on the Mises yield criterion. By analyzing the pile top displacement curve, the displacement curve of the pile and the stress-strain curve of the concrete and steel, it can be found that the model can accurately reflect the pile foundation. Under the action of horizontal load, the damage of concrete and the yield of reinforced bar will not conform to the stress behavior of the pile and the actual situation. It also shows the necessity of considering the reinforcement yield and concrete damage in the analysis of the horizontal bearing characteristics of the pile. The influence of soil parameters, pile parameters and load conditions on the horizontal bearing capacity of pile foundation, including soil undrained strength, soil elastic modulus, soil friction angle, pile diameter, reinforcement ratio, pile length, vertical load level, and so on. The results show: (1) the soil friction angle can be increased under the condition that other conditions are invariable. The horizontal bearing capacity of pile foundation can be improved and the ultimate bearing capacity is increased. The elastic modulus of soil can improve the bearing capacity of the pile to a certain extent. Under the condition of large soil stiffness, the lateral displacement of the pile head only depends on the deformation characteristics of the pile body itself, and the increase of the pile foundation level can also be improved to a certain extent by increasing the non drainage strength of the soil in the pile. Bearing characteristics. (2) for pile body property, pile with low reinforcement ratio, the allowable value of horizontal bearing capacity is mainly controlled by pile body cracking, and for piles with high reinforcement ratio, the allowable value of horizontal bearing capacity is controlled by the horizontal displacement of pile head, and the increase of pile diameter can significantly improve the bearing capacity of pile foundation. (3) vertical load transferred from superstructure. It can reduce the horizontal displacement of the pile head, but at the same time it will increase the maximum bending moment of the pile. It can be concluded that the vertical load is the optimal vertical load level between the 0.4-0.6 times of the vertical limit load. The influence of different pile number on the horizontal bearing capacity of pile group foundation is discussed, and the corresponding displacement curve of pile cap bearing platform is obtained. The result shows that increasing the number of pile groups can improve the horizontal bearing capacity of pile foundation.
【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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