钢筋混凝土浅基础底板抗剪、抗冲切问题探讨

发布时间：2018-04-12 11:06

本文选题：柱下独立基础 + 梁板式筏形基础　；参考：《长安大学》2014年硕士论文

【摘要】：现行地基规范关于钢筋混凝土浅基础的冲切和剪切计算，存在一些不明确之处，本文主要针对GB50007-2002《建筑地基基础设计规范》和GB50007-2011《建筑地基基础设计规范》两版规范中关于柱下独立基础冲切和剪切计算中存在的较大差异问题进行算例分析，并与欧美规范进行对比，得到影响柱下独立基础冲切和剪切计算的因素和各因素对冲切和剪切计算的影响规律，并提出相关建议；针对梁板式筏基底板冲切和剪切受力规律及其底板的单双向板划分问题，进行有限元模拟计算研究，得到梁板式筏基底板在均布荷载作用下，板格的变形和内力分布规律及单双向板的划分界限。方便了工程设计，为地基规范的进一步完善提供了参考。本文针对独立基础冲切、剪切破坏问题，，做了如下工作并得到相关结论：（1）对我国新旧《建筑地基基础设计规范》中关于独立柱下基础冲切和剪切公式，进行算例分析，得到：当基础底面短边尺寸小于或等于柱宽加两倍基础有效高度时，新规范的抗剪验算算得基础底板厚度要比旧规范按冲切算得的厚度大很多，新规范变化较大；（2）分析并得到了基础底面宽度、长度和有效厚度对新旧规范扩展基础冲剪验算的影响规律。通过数据分析得知，底板长厚比可以很好的反应旧规范冲切力和新规范剪切力之间的关系，当长厚比大于4.0时，剪冲比值接近2.0，建议按新规范来进行验算。当长厚比小于4.0时，新旧规范计算差异较大，建议对新规范的抗剪验算进行进一步的研究；（3）对中美欧三国规范中混凝土柱下独立基础抗剪验算进行了大量的算例分析，找出影响受剪承载力和剪力效应的因素。得到了基础长度、宽度、有效厚度、配筋率、验算截面位置对各国规范抗剪承载力和剪力效应的影响规律，并对我国规范提出相应建议。本文针对梁板式筏基底板冲切、剪切受力规律及其单双向板划分问题做了如下工作：通过ABAQUS有限元分析软件对梁板式筏基进行建模，模拟实际状态下梁板式筏基的内力分布与变形，通过数据的分析讨论，得到梁板式筏基板格内力分布规律，提出梁板式筏基单双向板的划分建议。相关结论如下：（1）板格支承边单元截面上的内力在角部趋于0，随着向跨中靠近内力快速增大，在达到离板格角部1.6m处时，内力趋于稳定并达到峰值，内力方向与截面有一个角度，在靠近跨中时接近45°；（2）通过大量数据的分析和讨论，本文建议，选取长宽比ly/lx=3.0作为梁板式筏基底板单双向板的划分界限，明确了当ly/lx3.0时应全部按双向板设计；当ly/lx≥3.0时可按单向板设计，但应在垂直于受力的方向布置构造钢筋，构造筋的配筋率不宜小于长支承截面配筋率的15%。
[Abstract]:In the current foundation code, there are some ambiguities in the calculation of punching and shearing of shallow reinforced concrete foundations.In this paper, a numerical example is presented to analyze the large differences in the punching and shearing calculation of independent foundation under columns in GB50007-2002 Code for Design of Building Foundation and GB50007-2011 Code for Design of Foundation of Building Foundation.Compared with the European and American codes, the factors that affect the punching and shearing calculation of the independent foundation under the column and the law of the influence of each factor on the calculation of the punching and shearing under the column are obtained, and the relevant suggestions are put forward.In view of the punching and shearing force law of beam-slab raft foundation floor and its single and bidirectional slab partition problem, the finite element simulation calculation is carried out, and the results show that the beam-plate raft foundation floor plate is under uniform distribution load.The distribution law of deformation and internal force of plate lattice and the dividing limit of single and two-way plate.It is convenient for engineering design and provides a reference for the further improvement of foundation code.Aiming at the problems of punching and shearing failure of independent foundation, this paper has done the following work and obtained the relevant conclusions:1) by analyzing the formula of punching and shearing of foundation under independent columns in the new and old Code for Design of Building Foundation in China, it is obtained that when the size of short edge of foundation bottom is less than or equal to that of column width and twice the effective height of foundation,The thickness of the base plate calculated by the new code is much larger than that of the old code by punching, and the new code changes greatly.2) the influence of the width, length and effective thickness of the foundation bottom on the checking calculation of the expanded foundation of the new and old codes is analyzed and obtained.When the ratio of length to thickness is less than 4.0, the difference between the new code and the old code is great.3) A large number of examples are given to check the shear resistance of concrete columns under concrete columns in the codes of China, America and Europe, and the factors affecting the shear bearing capacity and shear effect are found out.The influence of the length, width, effective thickness, reinforcement ratio and section position of foundation on the shear capacity and shear effect of each country's code is obtained, and the corresponding suggestions are put forward for the code of our country.In this paper, the following work has been done on the punching and shearing law of beam-slab raft foundation floor and its single and bidirectional plate partition problem:The internal force distribution and deformation of beam-slab raft foundation are simulated by ABAQUS finite element analysis software, and the internal force distribution law of beam-slab raft foundation lattice is obtained by analyzing and discussing the data.The partition suggestion of single and bidirectional slab of beam-plate raft foundation is put forward.The conclusions are as follows:(1) the internal force on the section of the edge element of the plate lattice tends to be 0 at the angle, and increases rapidly with the internal force near the middle of the span. When reaching 1.6 m from the corner of the plate, the internal force tends to stabilize and reach the peak value, and the direction of the internal force has an angle with the section.Close to 45 掳near the middle span;However, the reinforcement should be arranged in the direction perpendicular to the force, and the reinforcement ratio of the structural reinforcement should not be less than that of the reinforcement ratio of the long bearing section.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU471.15

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