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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... 相似文献
84.
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。 相似文献
85.
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. 相似文献
86.
87.
高强混凝土立方强度尺寸效应的分析计算 总被引:1,自引:0,他引:1
王岩 《数学的实践与认识》2006,36(8):144-147
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. 相似文献
88.
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. 相似文献
89.
Behavior of concrete cylinders confined by carbon-composite tapes and prestressed yarns 1. Experimental data 总被引:1,自引:0,他引:1
V. Tamuzs R. Tepfers Chi-Sang You T. Rousakis I. Repelis V. Skruls U. Vilks 《Mechanics of Composite Materials》2006,42(1):13-32
The results of a comprehensive test program for the mechanical behavior of round concrete specimens confined by carbon-fiber
epoxy tapes and prestressed carbon yarns are reported. Five different concrete batches of compressive strength from 20 to
100 MPa and the confinement of various thickness and pretension level were investigated. The specimens, which were subjected
to monotonic or repeated compressive loadings, showed a nonlinear stress-strain behavior with a significant ductility and
increased ultimate strength, in contrary to the brittle behavior of plain concrete. The limit of linearity on the stress-strain
diagrams of the confined concrete roughly coincided with the ultimate strength of plain concrete. Above this limit, the damage
accumulation and plastic deformations proceeded in the confined specimens. This fact was evidenced by the increasing slope
of deformation diagrams in unloadings and repeated loadings and by the pronounced residual strains. The limit of linearity
could be raised significantly by pretension of the carbon yarns during their winding.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 21–44, January–February, 2006. 相似文献
90.
Changes in the elastic and viscoelastic (creep) characteristics of polymer concrete and its structural components (polyester resin, unfilled or filled with diabase flour) during a long-term exposure to water at 20°C were studied. Modeling the structural changes in polymer concrete with time showed an increase in the relative volume content of pores filled with water and a decrease in that of unfilled pores. Based on the free-volume concept and the data on swelling due to moistening and shrinkage due to physical aging of the binder, a rather accurate estimate of the time-moisture reduction function for polymer concrete was obtained. The function was found to be nonmonotonic: the interval of increase was followed by an interval of decrease. 相似文献