【作者】 刘彬；

【导师】 郑山锁；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2010， 硕士

【摘要】 混凝土材料由于具有原料丰富、耐久性好等优点,在建筑结构中得到广泛的应用。与钢材等各向同性均质材料不同,混凝土作为一种复合材料具有多相性、多孔性和非均质性,在宏观上反映为其力学性能的离散性和随机性,对建筑结构的受力性能及抗震性能产生的影响较为复杂。相对于普通混凝土,高强高性能混凝土中水泥浆强度较大,甚至与骨料强度相当。所以高强高性能混凝土脆性较强,也可认为其均匀性较强,其力学性能随机性和离散性减弱。针对混凝土材料的上述力学性能,本文进行了如下研究：配制了三组不同强度的超高强高性能混凝土,分析了水泥标号、胶凝材料种类、粗骨料级配、砂率、减水剂以及水胶比等参量对混凝土力学性能的影响。对3组共15个超高强高性能混凝土试件进行了单轴受压试验,分析了超高强高性能混凝土受压的损伤机理及组成材料对损伤性能的影响；对受压损伤过程中的弹性模量进行了阶段性检测。将损伤指数定义为损伤破坏过程中混凝土弹性模量的变化量与初始弹性模量的比值。基于试验所得损伤指数变化规律,建立了双参数函数以反映混凝土损伤演化发展规律。基于Yu Liu的弹簧摩擦块模型和李杰的弹簧模型,建立了混凝土随机损伤细观模型。该模型由两个弹簧、一个滑移块及摩擦块组成。运用能量守恒原理,建立了超高强高性能混凝土(UHSHPC)及普通混凝土的静力单轴受拉随机损伤本构关系。在上述细观模型中引入质量块,建立了UHSHPC和普通混凝土动力损伤细观模型,进而建立了UHSHPC和普通混凝土单轴拉压动力随机损伤本构关系。与试验结果及其它研究结果对比表明,本文所提出的一系列损伤本构模型能够较为准确地反映混凝土的损伤演化规律。本研究为超高强高性能混凝土的应用提供了一定的理论基础,有助于工程技术人员对混凝土内部组份之间的作用机理进行认识和理解,将为进一步研究混凝土在多轴应力作用下的力学性能提供参考。更多还原

【Abstract】 Concrete material is widely used in the building structures, for its characteristics of obtaining material easily and good durability. Different from the isotropic homogeneous materials (e.g. shaped steel) the concrete is a kind of composite material with properties of heterogeneity, porosity and anisotropy, which reflect as stochastic and discreteness on the macro-mechanical properties of concrete. Stochastic and discreteness will have an influence on mechanical properties and the seismic performance of concrete structure. Compared with normal concrete, strength of cement paste in ultra-high strength and high performance concrete (UHSHPC) is close to, or even greater than that of coarse aggregate.First of all, three kinds of concretes with various strength levels are made in this paper. The influence of the cement grade, cementitious materials, coarse aggregate gradation, sand ratio, superplasticizer and water-cement ratio on the mechanical properties of concrete are analyzed. Uniaxial compression tests on 15 specimens, which are divided into 3 groups, are performed to research the damage and failure mechanism of UHSHPC. The elastic modulus of concrete is measured in the process of compression periodically. The damage index is defined as the ratio of variation of elastic modulus in the process of damage to initial elastic modulus. A double parameters damage function is established to research the damage evolution rules, based on study about variation of damage index obtained from the tests. A uniform mesoscopic model made up by two springs, one slipper and one displacement constraint element is proposed, based on Yu Liu’s spring-friction model and Li Jie’s spring model. The stochastic damage constitutive relationships are established for normal concrete and UHSHPC under uniaxial tension, for the energy conservation principle in the damage process. A mass block is introduced to the model above to establish the dynamic damage model, which is applied to normal concrete and UHSHPC. Consequently, the dynamic stochastic damage constitutive relationship of normal concrete and UHSHPC are found. Comparison between theoretical and experimental results of ordinary concrete and UHSHPC have verified that the constitutive relationship established in this paper can describe the failure mechanism of concrete well.The results of this study provide a theoretical foundation for wider application of HSHPC, and a profound knowledge and understanding about the mechanism of each component of concrete for engineers. This study provides some references for the further study of concrete mechanical properties subjected to multiaxial stress.更多还原