【作者】 杨萌；

【导师】 黄承逵；

【作者基本信息】 大连理工大学 ， 结构工程， 2006， 博士

【摘要】 纤维混凝土作为一种高性能混凝土建筑材料,在我国工程建设领域得到非常广泛的应用。为了适应纤维混凝土向高强度、高性能方向的发展和应用趋势,根据中国工程建设标准化协会的要求,中国土木工程学会纤维混凝土委员会委托大连理工大学为主编单位,经对原协会标准《钢纤维混凝土结构设计与施工规程》CECS 38:92进行全面修订,制定了新的标准《纤维混凝土结构技术规程》CECS 38:2004。在规程修订的前提下,本课题对钢纤维与高强砂浆的粘结性能,钢纤维高强混凝土的基本力学性能进行了系统的试验研究;深入分析了钢纤维与基体间的界面粘结机理,以及钢纤维对高强混凝土的增强、增韧作用;考虑钢纤维混凝土的韧性,提出了新的钢纤维混凝土工业建筑地面设计方法。 (1).通过进行钢纤维与高强度水泥砂浆粘结拉拔试验,联系现有文献的试验资料,系统地研究了5种钢纤维(其中有4种为异型钢纤维)与4种强度等级高强砂浆基体的粘结性能。分析了基体强度、钢纤维类型和自身强度对界面极限粘结强度、纤维破坏形态的影响,讨论了不同类型钢纤维适用的基体强度范围。同时发现,随着基体砂浆强度的升高,在钢纤维与基体间界面粘结剪力的各个组分中,沿钢纤维体长分布的粘着力和广义摩擦力的提高最为显著。比较了钢纤维形状和砂浆基体强度对粘结滑移曲线特征和粘结拔出功的影响,当纤维出现拔断现象时,其增韧效果会大大降低。通过试验数据回归得出了不同类型钢纤维与高强水泥砂浆基体间极限粘结强度计算公式。 (2).针对原有规程《钢纤维混凝土结构设计与施工规程》CECS 38:92适用强度等级偏低的问题,本文对钢纤维高强混凝土的抗压、抗拉、弯曲、抗剪等基本力学性能进行了详细的试验研究,分析了钢纤维形状和自身强度、基体强度、钢纤维掺量等因素对钢纤维高强混凝土基本力学性能的影响。对基于复合材料理论的SFRC基本强度计算公式进行了回归,研究了钢纤维高强混凝土轴拉、弯曲荷载-变形全曲线的特性,提出了统一的钢纤维混凝土韧性评价模式。给出了钢纤维高强混凝土劈拉强度、轴拉强度和弯拉强度的关系式。通过试验建立了钢纤维高强混凝土单轴拉伸曲线计算模型。给出了钢纤维高强混凝土弯拉初裂强度和弯拉极限强度的关系公式。并且提出了新的钢纤维混凝土抗剪强度的计算公式,公式的计算结果与实验结果符合较好。 研究发现,在使用钢纤维来改善混凝土受压性能时,宜选取大长径比、自身强度高、小直径的线状钢纤维;提高钢纤维掺量对高强混凝土抗拉强度的改善作用比对普通强度混凝土明显,而对于轴拉初裂强度的提高与对于普通混凝土的提高基本相同;更多还原

【Abstract】 As a kind of high-performance construction concrete material, fiber reinforced concrete (FRC) has been widely used in the domain of engineering construction. High strength and high performance become the developing and application trend of FRC today. According to the instruction of China Association for Engineering Construction Standardization, the compilation group organized by Dalian University of Technology make a wholly adaptation to the "Specification for Design and Construction of Steel Fiber Reinforced Concrete Structures (CECS 38:92)". Therefore, the "Technical Specification for Fiber Reinforced Concrete Structures (CECS 38:2004)" is compiled. As a part of the revisal project, a special study on the bond-slip characteristics between steel fiber and high-strength mortar, as well as on the mechanical properties of high-strength SFRC, is performed with experiment. This paper analyzes the bond mechanism on the interface between steel fiber and matrix. The strengthening and toughening function of steel fiber on high-strength concrete is also studied. Furthermore, a new designing method of SFRC industrial ground floors is suggested, taking the toughness of steel fiber reinforced concrete into account.(1) A serials of pullout tests of steel fiber from high-strength mortar of 4 strength grades are accomplished. 5 kinds of fiber are used in these tests, thereinto 4 kinds were profiled. Based on the test data, the bond-slip characteristics between steel fiber and mortar matrix are analyzed. The effects of several parameters, such as the matrix strength, the fiber type and the fiber strength, on the bond-strength and failure form are studied. The applicability of a kind of steel fiber to certain matrix strength is suggested. During the analysis, it is found that the effects of the rising of matrix strength on adherence and generalized friction are higher than on the other components of bond stress. The influences of fiber aspect and matrix strength on the pullout curves and pullout works are studied. When fiber breaks, the toughnees of the bond between matrix and steel fiber is rapdly reduced. Formulas of bond strengths between high-strength mortar and different kinds of steel fiber are statistically regressed with test data.(2) To enlarge the application scope of concrete strength grade of the former Specification (CECS 38:92), large quantities of experiments have been carried through to analyze the behaviors of steel fiber reinforced high-strength concrete under compression, tension, flexure or shear. The effects of fiber aspect, fiber strength, fiber content and matrix strength on the mechanical properties of high-strength SFRC are analyzed. On the base of thecomplex material theory, the ultimate strength formulas of SFRC under the stress conditions mentioned above are statistically regressed. The load-displacement curves of SFRC under uniaxial tension and flexure are analyzed, and a unitized model to evaluate the toughness of SFRC is given. Relational expressions between split strength, tensile strength and flexural strength are educed. With the statistically regressing of the test data, a constitutive equation of SFRC under uniaxial tension is educed. Furthermore, an expression is given to quantify the relationship between flexural crack strength and flexural ultimate strength. A new formula is educed to calculate the shear strength of SFRC, and the formula 1 value well fits the test date.Some conclusions have been draw during the analysis. When be used in construction members to bear compression, steel fiber with large aspect ratio, high strength and minor diameter may be more effective. It is more effective of increasing fiber content on improving the tensile strength of high-strength concrete than on that of common -strength concrete. But as matrix strength rising, the ratio of tensile crack strength of SFRC with certain content of fiber is almost unchanged. The flexural crack strength of SFRC is hardly influenced by fiber type, but the flexural ultimate strength is strongly influenced by fiber type. Through comparing several methods for evaluation criterion of the flexural toughness of SFRC. one of them is selected. The method is not only objective and accurate, but also be easy to calculate. So it is compiled into the "Technical Specification for Fiber Reinforced Concrete Structures (CECS 38:2004)". Another point to notice, the shape parameters of the cross section of steel fiber has much influence on the shear strength of SFRC.(3). Based on the pullout tests, the bond-slip mechanism on the interface between steel fiber and matrix is particularity analyzed. On the base of Cox shear lag theory, SFRC is analyzed as a three phase complexes (reinforcing phase, reinforced phase and interface phase). With refined mechanical deducing, a new bond-slip model between profiled steel fiber and high-strength mortar is educed. Combined with the mechanical property tests and bond-slip model deduced above, strengthening and toughening mechanism of profiled steel fiber on high-strength concrete is systematically analyzes on the base of complex material theory. Finally a new constitutive model of bond-slip between steel fiber and matrix is built.(4). Aim at the vacancy of the design theory on SFRC industrial ground floors in our country, a new design method is given which takes the toughening function of steel fiber into account. This method is based on Meyehoff yield line theory of slab on elastic ground base and "Code for Design of Building Ground Engineering (GB 50037)", refer to the "Concrete Society Technical Report 34: Concrete Industrial ground floors" of the concrete society of England. The formula for SFRC floor slab thickness under many kinds of load conditions are given in this method, in which the effect of the toughness of SFRC after crack is adequatelyconsidered. This content has been compiled into the 10th chapter of the "Technical Specification for Fiber Reinforced Concrete Structures (CECS 38:2004)".更多还原