杆弹侵彻钢纤维混凝土实验研究

采用DOP实验方法,进行了35CrMnSiA杆弹对不同钢纤维体积含量的钢纤维混凝土的侵彻实验.分别研究了杆弹着速和钢纤维体积含量对钢纤维混凝土杭侵彻性能的影响.实验表明,随着弹速增加,不同钢纤维含量的钢纤维混凝土侵彻深度都会增加,但钢纤维混凝土中弹体便深增加较素混凝土缓慢;而钢纤维能增强混凝土的抗侵彻性能,且随钢纤维体...     

应用声发射技术的钢筋与混凝土粘结滑移特性研究

为研究钢筋与混凝土间的粘结滑移特性,分别对不同粘结长度的钢筋混凝土试件进行了拉拔试验,同时对粘结长度相同而钢筋外形不同的试件进行了比较试验.利用声发射技术采集相应波形信号,并对采集信号进行了小波去噪和Gabor小波时频分析.结果显示,各试件受力全过程均可分为完全粘结、局部脱粘、非线性滑移及残余粘结四个阶段;不同粘结长度...     

混凝土三维细观接触面模型数值模拟与CT试验验证

对混凝土三维随机骨料模型进行了改进,在骨料和砂浆之间加入了"面-面接触单元"模拟两者的接触特性,编制了相应的命令程序,称新模型为混凝土接触面模型.采用双折线损伤演化模型进行计算,对数值模拟结果进行了分析研究.从混凝土破坏过程图和荷载-位移曲线图两方面与CT试验结果进行了比较,表明试件破坏时裂纹的萌生、扩展过程与CT试验...     

钢筋混凝土轴心受压构件的非线性稳定性

采用我国混凝土规范GB50010-2002规定的混凝土应力一应变关系,考虑混凝土强度、构件长细比及混凝土徐变,从构件的非线性理论出发对钢筋混凝土轴心受压构件的承载力进行了研究,给出了混凝土构件临界状态时的构件边缘应变和纵向弯曲系数的计算公式。研究表明,徐变对轴心受压构件的承载力有很大影响。当不考虑混凝土徐变时,按本文公...     

三向受压混凝土的动态特性研究

为探究混凝土在三向受压状态下的动态特性,利用自行研制的大型多功能三轴材料试验机,进行不同应变速率(10^-5/s、10^-4/s、10^-3/s、10^-2/s)下混凝土不同定侧压比(1:1、2:1、3:1、4:1)的动态真三轴抗压试验,研究了混凝土在动态抗压下的强度和变形特性。结果表明:混凝土在三向受压状态下表现出明显的应变率效应,峰值应力随着应变速率的增加先减小后增大,峰值应力减小最大幅度为5.42%而后开始增大,最大增幅为18.22%。而峰值应力随着侧压比的增大而增大,到达3:1时应力速率敏感性降低。混凝土的峰值应变在低侧压比(1:1和2:1)时随着应变速率的增加而减小,而在侧压比较高(3:1和4:1)时先减小再增大。随着应变速率的增加,裂纹开始从骨料处产生,塑性应变增大,导致峰值应变增大;在动态加载条件下,峰值应变随着侧压比的增大有先增大后减小的趋势。较高侧压比时混凝土的弹性模量随着应变速率的增加具有增大的趋势,最大增幅为240.66%。应力-应变曲线上升段随着应变速率增大越来越陡峭。试件的破坏形态随着侧压比的增大从柱状破坏变为斜剪破坏。     

基于修正压力场理论的再生混凝土梁抗剪承载力计算方法研究

基于修正压力场理论分析有腹筋再生混凝土梁的剪切破坏机理,建立了更接近有腹筋再生混凝土梁实际受力的抗剪模型,并通过考虑再生骨料有效粒径和受箍筋作用下的裂缝宽度与构件裂缝处应力的联系,分析了再生骨料咬合力对梁斜截面抗剪性能的影响,提出了再生混凝土梁极限抗剪承载力的计算方法。此外,本文将理论结果与课题组自制的6根再生混凝土梁的抗剪承载力试验结果进行了对比,理论值与试验值吻合较好,验证了本文方法的有效性,从而为设计人员提供了一种预测再生混凝土梁极限抗剪承载力的计算方法。     

Determination of Chloride Content in Different Types of Cement Using Laser-Induced Breakdown Spectroscopy

The characterization and accurate determination of the chloride content in cement/concrete is very important for the assessment of the durability and safety of a concrete structure. The available analytical techniques are relatively expensive and time consuming. In this study, a laser-induced breakdown spectroscopy (LIBS) system was used for determination of elemental composition in three different types of cement samples. The plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm on the cement samples. The concentrations of different elements of significance for structural stability in cement samples were determined. The evaluation of the potential and the capabilities of LIBS as a rapid tool for characterization of cement samples is discussed. The optimum LIBS setup and experimental conditions to detect and measure chloride in building materials are reported. The LIBS results were compared with the results obtained using a standard analytical technique such as inductively coupled plasma emission spectroscopy (ICP–ES). The limits of detection were determined, and calibration curves were measured. The results of this investigation indicate the reliability of LIBS to characterize different cement samples and to assess the chloride content in these cements.     

冲击作用下的摩擦力效应实验研究

针对摩擦力效应产生的机理, 本文设计了三种不同尺寸的试件进行SHPB实验, 得到了摩擦力效应对实验的定量影响, 在此基础上对混凝土的DIF进行了修正研究, 为混凝土抗冲击工程设计提供了参考依据. 关键词： 冲击 混凝土 SHPB 摩擦力     

高强混凝土立方强度尺寸效应的分析计算

对55组高强混凝土立方强度实测数据作了分析,并给出了计算公式.表明高强混凝土立方强度尺寸效应不同于普通混凝土.     

Behavior of concrete cylinders confined by a carbon composite 3. Deformability and the ultimate axial strain

Results of an experimental investigation into the mechanical properties of concrete cylinders confined by a carbon-epoxy composite wrapping are presented. It is shown that, for all the con fined con crete spec i mens tested, the loading paths in the normalized stress space follow a single master curve, what ever the concrete strength and confinement intensity. At stresses in the confined concrete exceeding the strength of plain concrete, the tangent modulus was found to depend on the slope angle of the master curve and the asymptotic value of the differential Poisson ratio (the first derivative of the lateral strain with respect to the axial one). Formulas for predicting the ultimate axial strain and the tangent modulus are derived and compared with the corresponding fib (fédération internationale du béton) recommendations. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 433–448, July–Au gust, 2006.