【作者】 柏巍；

【导师】 彭刚； 姜袁；

【作者基本信息】 三峡大学 ， 岩土工程， 2008， 硕士

【摘要】 钢纤维混凝土作为一种新型复合材料,已广泛的应用于建筑、桥梁、隧道、水利等工程中。目前,对于钢纤维混凝土的低应变速率静力试验以及高应变速率冲击试验已有较多研究成果,但对于地震荷载作用下中等应变速率范围内(10-4 /s~10-2 /s)的试验研究还有待深入,混凝土材料的动态特性是抗震研究中的薄弱环节[1-3]。为此,本文系统地进行了钢纤维混凝土在中等应变速率响应范围内的6种纤维含量(0%、1%、1.5%、2%、2.5%、3%)、4种周围压力(0MPa、8MPa、16MPa、24MPa)、2种基体强度(C40,以SFCA表示;C30,以SFCC表示)的单轴、常规三轴的单调与重复加卸荷等多种动态压缩试验,累计完成252个试件的加载试验。同时,利用医用CT扫描技术得到了混凝土内部细观数据图像,结合图像数字处理技术对混凝土内部细观结构进行了重建,并在此基础上进行了混凝土材料的有限元数字劈拉试验。具体工作内容如下。(1)研究了单向应力状态下各种钢纤维含量和强度等级的钢纤维混凝土在应变速率为10-3 /s时的强度特性和变形特性。(2)系统地分析了三向应力状态下各种钢纤维含量、围压和强度等级的钢纤维混凝土在应变速率为10-3 /s时的峰值应力、峰值应变、应力-应变曲线、弹性模量、泊松比、韧度比、八面体应力空间的分布等多种指标参数,得出了各种指标参数与纤维含量、围压大小、强度等级等相互的影响关系。(3)采用等应变增量的重复完全加卸荷试验,并对其应力-应变曲线的包络线特征、峰值应力、峰值应变、卸载曲线特征、残余应变、再加载曲线特征、横向应变特征、共同点轨迹线特征等进行了分析。(4)根据地震时程曲线的特征,进行了钢纤维混凝土两种不同频率的非等幅循环荷载试验,比较了不同频率循环荷载下的强度特性和变形特性。(5)基于CT扫描得到的图像,结合图像数字处理技术,对混凝土的真实细观结构进行了重建,并将其导入有限元软件之中,建立了更能准确表征混凝土细观非均质性的二维数值试件,进行了几种不同情况的劈裂对比试验;采用对CT扫描的DICOM格式原始数据调用的方式,建立了混凝土或钢纤维混凝土真实细观结构的三维模型,较好的体现了混凝土的非均质性,为进一步在细观层次上研究混凝土内部的破坏机理奠定了一定的基础。更多还原

【Abstract】 Steel Fiber Reinforced Concrete(SFRC) is a new compound material which widely used in buildings, bridges, tunnels and other projects. Currently, a lot of the static tests and high strain rate impact tests of steel fiber reinforced concrete have taken, but the intermediate strain rate tests are rare.According to this curent reasearch, this paper completed six kinds of different steel fiber contents, four kinds of different ambient pressures, two kinds of different strength grades uniaxal and triaxial dynamic compressive tests. The main work as follows.(1) The uniaxial dynamic properties of SFRC about different steel fiber contents and different strength grades were investigated in the strain rate 10-3/s, peak stress and peak strain were investigeted.(2) The triaxial dynamic properties which include peak stress, peak strain, stress-strain curve, young’s modulus, poisson ratio, toughness ratio, octahedral stress distribution, were investigeted.(3) According to equidifferent strain cyclic loading tests, cyclic stress-strain relaationships were gained, and the properties of envelope line, peak stress, peak strain, unload curve, residual strain, reload curve, lateral strain, common point path line were analyzed.(4) Based on actual seismic time history curve, two kinds of different frequencies of inconstant cyclic loading tests were taken to farther investigate the dynamic properties of SFRC.(5) A 2D finite element model of concrete meso-level structure, which was more approaching to the actual concrete, was reconstructed by Digital Image Processing with CT scanning image. Three different models of concrete indirect tensile test contrast indicated that the heterogeneity and the voids tremendously influenced the computed result. A concrete and SFRC 3D meso-level structure were reconstructed according to deal with the CT original data. The result showed that the steel fiber, cobblestones, mortar and pore space were clear, and can describe the heterogeneity of concrete more accurately.更多还原