摘要
多层建筑与地基基础共同作用是把上部结构、基础与地基三者看成一个整体，并要满足地基、基础与上部结构三者在接触部位的变形协调和力的平衡条件。利用共同作用分析三者的内力和变形的方法就称为共同作用分析方法。多层建筑与地基基础共同作用课题的研究，涉及到上部结构、基础和地基三者本身特性的结合，由于影响因素很多，互相结合成一个整体进行研究，确实相当复杂和困难。
本文以某多层结构为例，采用共同作用与常规作用相比较，利用数值分析软件模拟了两种工作机理情况下，比较基础的沉降、基础应力分布的差别，为工程实践提供理论基础。
通过综合对比分析：
（1）在应用常规设计方法与共同作用设计方法时，比较上部结构的水平位移与框架柱内力的差异，以便为结构设计的安全和经济提供一定的参考。
（2）在分别只改变上部结构、基础、地基刚度时，分析上部、基础、地基的受力特性。
（3）在只改变上部结构、基础、地基的刚度或者只增加结构的竖向荷载、层数、跨度的情况下，分析弹塑性地基上筏板基础的沉降变形。
关键词：上部结构；筏板基础；地基；共同作用原理；内力
I
Abstract
The interaction theory of the space superstructure-base-soil has made great progress， since it is developed to this day. And that，using this analysis theory， we can afford to improve the level and quality of foundation design and gain more economic effect. Firstly， effectively making use of the stiffness of superstructure， we can reach the scantling of structure of foundation to the least possible degree； if superstructure and foundation are considered as a whole， the height of coffer foundation，the thickness of raft foundation and the quantity of pile in piled raft foundation are diminished greatly. Secondly，for a main building and annex， that their layers and construction configurations are different from each other， usually， we select different configurable foundations， cautiously contrast them with interaction analysis and connect the base of a main building and annex with superstructure as a complete thing， to fulfill requirements in architecture function. Thirdly， taking advantage of interaction analysis to design soil and foundation rationally， reduce the internal force，settlement and cost of foundation to the smallest possible degree. As a design method of structure，interaction analysis should be made a study because its theory analysis and engineering practice are still in the primary stage.
Based on serially discussing method of calculation of soil，foundation and superstructure and by the background of the Building Block ，the mechanics analysis model of the nonlinear whole finite element is established by the authors，and the model is calculated and analyzed largely in the method of simulation by finite-element program “ANSYS”. According to the theory of the interaction among superstructure， foundation and soil， the subsoil， foundation and upper structure are researched and meshed as a whole in this paper. By the comparative and comprehensive analysis， we will reduce，
II
（1）degree that conventional design method is different from interactional one in level displace of superstructure and internal force of frame column，to supply references to safety and economy of structural design，（2）that characteristic under stress of superstructure，soil and foundation is analyzed with respectively changing the stiffness of each one，（3）that settlement deformation of raft on elasto-plastic base is assayed with the condition of merely transforming stiffness of superstructure，soil and foundation and increasing vertical load，number of floor and span.
Key words： superstructure；raft foundation；soil；theory of interaction；internal force
III
目录
摘要................................................................................................................................ I Abstract ......................................................................................................................... II 目录.............................................................................................................................. IV 第1章 绪论.................................................................................................................. 1
1.1 课题背景与研究意义...................................................................................... 1 1.2 国内外研究现状.............................................................................................. 2 1.3 本文研究的主要内容...................................................................................... 6 第2章 结构与土共同作用的原理.............................................................................. 7
2.1上部结构刚度对基础受力状况的影响........................................................... 7 2.2基础刚度对基底反力分布的影响................................................................... 8
2.2.1绝对柔性基础......................................................................................... 8 2.2.2绝对刚性基础......................................................................................... 8 2.2.3半刚性基础............................................................................................. 9 2.2.4基底反力分布的一些定性规律........................................................... 10 2.3地基条件对基础受力状况的影响................................................................. 11
2.3.1地基土的压缩性及其分布的影响....................................................... 11 2.3.2基础与地基界面处的边界条件及其影响........................................... 12 2.4上部结构、基础和地基共同作用的概念..................................................... 12 第3章 共同作用的分析模型.................................................................................... 13
3.1 引言................................................................................................................ 13 3.2上部结构的子结构分析方法......................................................................... 14 3.3地基计算模型................................................................................................. 17 3.4筏板计算理论................................................................................................. 19
3.4.1概述....................................................................................................... 19 3.4.2中厚板计算理论................................................................................... 20
第4章 工程实例与分析............................................................................................ 26
4.1 工程概况........................................................................................................ 26 4.2 有限元模型的建立........................................................................................ 27
4.2.1 单元的选择.......................................................................................... 27 4.2.2地基土模型建立................................................................................... 27 4.2.3框架模型............................................................................................... 28 4.2.4 加载及网格划分.................................................................................. 28 4.3 共同作用结果分析........................................................................................ 30
4.3.1 刚度对各部分受力性能的影响.......................................................... 30 4.3.2 各参数对基础的沉降变形的影响...................................................... 38 4.3 小结................................................................................................................ 43 第5章 考虑共同作用的结构设计............................................................................ 45
5.1 引言................................................................................................................ 45 5.2 上部结构的水平位移的差异........................................................................ 45 5.3 框架柱内力的差异........................................................................................ 48 5.4 小结................................................................................................................ 55
IV
第6章 结论与展望.................................................................................................... 57 参考文献...................................................................................................................... 60 致 谢............................................................................................................................ 68
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