混凝土细观数值模拟及尺寸效应研究

发布时间：2018-04-17 07:31

本文选题：混凝土短柱 + 有限元　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：混凝土具有价格低廉、来源广泛、易于施工等优点,是世界上运用最为广泛的建筑材料。同时,混凝土作为一种准脆性材料,其力学性能存在尺寸效应,最典型特征为抗压强度随尺寸的增大而降低。然而目前各国混凝土结构设计规范均根据小尺寸试件确定混凝土强度,无法准确反映大体积混凝土构件的真实强度,进而导致不同尺寸混凝土构件可靠度不一致,为混凝土结构设计埋下了安全隐患。现阶段对混凝土尺寸效应研究多局限于试验手段,且试件尺寸一般较小。尺寸效应经典理论在大尺寸范围内的有效性缺乏验证。混凝土细观数值模拟作为一种新的混凝土性能分析方法,突破了试验条件的限制。将其运用于混凝土尺寸效应分析将大大降低试验量,获取更多有效数据,同时也更为方便从细观角度分析混凝土尺寸效应机理。本论文工作主要包含以下三方面内容:(1)细致梳理了代表性国家和地区(包括美国、欧洲、加拿大、中国)的混凝土以及约束混凝土(FRP约束混凝土、钢管混凝土)结构设计规范中混凝土设计强度确定方法和思路,分析各国混凝土结构设计规范对混凝土尺寸效应的考虑;广泛收集了以往文献中混凝土、FRP约束混凝土和钢管混凝土短柱轴压承载力试验数据,将各规范确定的设计值与所收集试验数据对比,进一步考察混凝土尺寸效应对现行各国规范设计值可靠度的影响。(2)在细观层次上将混凝土看作是由粗骨料、水泥砂浆基体和二者之间的过渡界面层所组成的非均质三相复合材料,编写随机骨料生成程序,并建立随机骨料有限元模型;采用随机骨料细观有限元模型进行混凝土的单轴压缩破坏性试验,分析试件破坏形态。(3)基于细观混凝土随机骨料模型,探究有效模拟混凝土尺寸效应的方法,结合试验数据验证采用数值方法研究尺寸效应的可行性,最后在模型有效的基础上进行参数分析;探究主动约束力对同一级配混凝土力学行为的作用,并进一步探索其对混凝土尺寸效应的影响,为FRP约束混凝土、钢管混凝土的细观数值分析奠定基础。
[Abstract]:Concrete is the most widely used building material in the world because of its low price, wide source and easy construction.At the same time, as a kind of quasi-brittle material, the mechanical properties of concrete have size effect, and the most typical characteristic is that the compressive strength decreases with the increase of size.However, at present, the concrete strength is determined according to the small size concrete structure design codes, which can not accurately reflect the real strength of mass concrete members, and lead to different reliability of concrete members of different sizes.The hidden danger of safety is buried for the design of concrete structure.At present, the research on the size effect of concrete is limited to the test method, and the size of the specimen is generally small.The validity of the classical theory of size effect in large scale range is not verified.As a new method of concrete performance analysis, meso-numerical simulation of concrete breaks through the limit of test conditions.Applying it to size effect analysis of concrete will greatly reduce the test quantity and obtain more effective data. At the same time, it is more convenient to analyze the mechanism of size effect of concrete from a mesoscopic point of view.This paper mainly includes the following three aspects: 1) combing the concrete of representative countries and regions (including the United States, Europe, Canada, China) and confined concrete FRP confined concrete.In the design code of concrete filled steel tube (CFST) structure, the concrete design strength determination method and train of thought are analyzed, and the size effect of concrete is considered in the concrete structure design codes of various countries.The experimental data of axial compression capacity of FRP confined concrete and short steel tubular columns in previous literatures are collected extensively. The design values determined by each code are compared with the test data collected.Further study on the effect of concrete size effect on the reliability of design values in current national codes. (2) the concrete is regarded as coarse aggregate at the meso level.The heterogeneous three-phase composite composed of cement mortar matrix and the interfacial layer between them is composed of random aggregate generation program and the finite element model of random aggregate is established.Based on the random aggregate meso finite element model, the uniaxial compression destructive test of concrete is carried out, and the failure pattern of the specimen is analyzed. Based on the random aggregate model of meso concrete, the effective method to simulate the size effect of concrete is explored.According to the experimental data, the feasibility of using numerical method to study the size effect is verified. Finally, the parameter analysis is carried out on the basis of the effective model, and the effect of active binding force on the mechanical behavior of the same grade concrete is explored.Furthermore, the influence on the size effect of concrete is further explored, which lays a foundation for the meso-numerical analysis of concrete confined by FRP and concrete filled with steel tube.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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