【作者】 罗章；

【导师】 李夕兵；

【作者基本信息】 中南大学 ， 安全技术及工程， 2004， 博士

【摘要】 钢纤维混凝土（SFRC）是由细骨料、粗骨料、乱向分布的钢纤维和水泥浆所组成的一种混凝土材料。本文首次较系统地从理论与实验两方面研究了中应变率下SFRC的本构关系。论文的主要工作可概述如下： 1．第一章，给出了SFRC本构模型一个综合性纵览，评述了现今有关SFRC动力性能研究的最重要的成果与存在的问题，介绍了选择本课题的工程背景。 2．第二章，介绍了基于Instronl342液压伺服材料实验机，经辅助改装的动态测试系统的基本情况，以及实验方案、试件制作及实验步骤。得到SFRC在中应变率范围内的抗拉（四点弯拉、劈拉）全过程应力应变曲线。 3．第三章与第四章，详细分析了中应变率下SFRC抗拉实验结果，研究表明：中应变率区不同应变率下SFRC的应力应变曲线基本形状是相同的，峰值应力、峰值应力对应的应变与弹性模量（割线模量）随着应变率增加，均有不同程度的提高。当应变速率从1.38×10^-4s^-1增大到0.532×10^-1s^-1时，SFRC的抗拉强度提高30％左右，峰值应力对应的应变提高10％左右，动态拉伸弹性模量提高20％左右。中应变率下，当钢纤维掺量从0％增加到4％时，SFRC的抗拉强度提高1.3倍左右。 4．第五章，系统研究了中应变率下SFRC的本构理论。基于能量原理，推导出水泥基材料的非线性超弹性本构模型的一般形式；通过对实验结果的综合分析，首次研究了用数理统计方法中的典型分布密度曲线表述SFRC的应力-应变关系，阐述了这一新方法的基本原理。通过将数理统计方法与SFRC非线性超弹性本构模型结合，只要知道了材料破坏的局部应力-应变信息，就可以预测SFRC的应力-应变全过程曲线。基于弹塑性力学的有关理论，推导出SFRC弹塑性本构方程的一般形式。并采用分析的方法研究了SFRC的有效弹性模量，这一方法充分考虑了乱向分布的钢纤维的边壁效应与重力效应及混凝土基体孔洞的影响。基于一系列理论与实验分析，建立了一个四相复合材料模型用于计算SFRC的有效弹性模量，应用该方法，得到了一些用于预测SFRC有效弹性模量的简单、明确的理论公式；然后，在此基础上，进一步完善了SFRC弹塑性本构模型。最后，用实验结果校核了文中构建的率相关型SFRC弹塑性本构模型与SFRC非线性超弹性本构模型的正确性。中南大学博士学位论文中应变率下钢纤维混凝土的本构关系5.第六章，为了更好地了解SFRC在荷载（包括动力载荷）作用下的断裂行为，采 用理论分析方法讨论了SFRC的增强机理与裂纹尖端微裂区的力学行为;基于一 系列理论分析与实验观察，提出了一个新的SFRC材料断裂破坏的力学模型.同 时，阐述了基于损伤演变一断裂力学的SFRC破坏理论的基本思想。6.第七章，给出了全文的主要结论。更多还原

【Abstract】 Steel fiber reinforced concrete (SFRC) is concrete made of hydraulic cements containing fine aggregate, coarse aggregate, and with randomly oriented steel fibers. The constitutive relationship of SFRC under intermediate strain rate is studied from different analysis of theory and experiment in mis dissertation. The main work of this dissertation is summarized as following:1. In chapter 1, a comprehensive survey of constitutive models of SFRC is presented. Some of the most important aspects of the research on dynamic performances of SFRC are reviewed. Some main issues of which remain to be solved are outlined. The engineering background about the thesis selecting is introduced.2. In chapter 2, the basic information of a self-developed SFRC dynamic test system matching with Instron 1342 materials testing machine is given. The scheme of experiment, the specimen fabricating, the processes of both loading and measuring are introduced in detail. The complete process of SFRC under tension (four-point flexure, cleavage ) with different strain rate from 1.0x 10-4 s-1 to 1.0x10-1s-1 has been investigated. By this system, the complete stress strain curve for SFRC under intermediate strain rate is obtained.3. In chapter 3 and chapter 4, the experimental results of SFRC under intermediate strain rate are analyzed. The results indicate that the stress strain curves in the process with different strain rate are somewhat similar, with the peak stress and peak strain corresponding to peak stress and elastic modulus (secant modulus) increasing in different degree when the strain rate increases. While the strain rate increases from 1.38 X 10-4s-1 to 0.532 X 10-1s-1, the tensile strength of SFRC increases around 30%, the peak strain of under peak stress increases 10%, the dynamic tensile elastic modulus increases 20%. Under intermediate strain rate (e=1.0x10-4s-1 ~1.0x10-1s-1), while the contents of steel fiber increases from 0% to 4%, the tensile strength of SFRC increases around 130%.4. In chapter 5, the constitution theory of SFRC under intermediate strain rate is studied in detail. Based on energy theory, the general form of nonlinear hyper-elastic constitution equations for cement-matrix materials is got. Based on the comprehensive analysis of the experimental data, some statistics curves ofmathematical statistics method are used to describe the stress-strain relationship of SFRC under intermediate strain rate. The basic theory of the new method is introduced. After combining mathematical statistics method with the nonlinear hyper-elastic constitution model for SFRC, the complete stress-strain curve of SFRC may be prognosticated by using a part of the data of stress- strain. At the same time, based on the theory of elastic-plasticity mechanics, the general form of a rate-dependent’s elastic- plasticity constitution equations for SFRC is got. An analytical method has been used to determine the effective elastic modulus of SFRC with randomly distributed steel fibers. The influence of boundary effect and gravitation effect of randomly distributed steel fibers and concrete matrix porosity are taken into account in this method. Based on a series of theoretical and experimental analysis, a four-phase composite model has been proposed to calculate the effective elastic modulus of SFRC. By this approach, some simple, explicit formulae are derived for estimating the effective elastic modulus of SFRC. Based on the analytical results, the rate-dependent’s elastic- plasticity constitution model for SFRC is improved. And finally, the rate- dependent’s elastic-plasticity constitution model and nonlinear hyper-elastic constitution equations for SFRC are validated by experimental data.5. In chapter 6, for a better understanding of the fracture behavior of SFRC composite materials under loading (including dynamic loading), the theoretical analysis method has been used to discuss the reinforcing mechanism and the mechanical behavior of crack in micro-crack zone of SFRC. Based on a series of theoretical anal更多还原