Size effect in shear for fiber reinforced concrete members

大量的研究已经建立了钢筋混凝土无腹筋构件的剪切尺寸效应，其中破坏时的剪应力随着构件深度的增加和/或骨料尺寸的减小而减小。研究还表明，用轻骨料建造的构件和高强度混凝土的抗剪能力都有所下降。钢或聚合物纤维的加入将有助于减少裂纹宽度，控制裂纹间距，并提供一种替代的剪切力传递机制。与没有纤维的类似构件相比，这些优点有望缓解纤维混凝土(FRC)的剪切尺寸效应。拟议的项目将利用当地可获得的水泥和集料，开发几种含纤维和不含纤维的普通和高强度混凝土混合料。将考察FRC在压缩、间接拉伸和直接剪切下的本构响应的尺寸效应。使用选定的混合料，没有常规腹板加固的剪切临界梁试件将在早期开发的材料模型的基础上进行研究，以表征构件在剪切中的响应。在这项研究的每个阶段，将使用1：4(或更高)的几何比例因子来评估尺寸效应。将对结果进行分析，以制定FRC受弯和受剪构件的分析模型和设计准则。这项研究将在阿尔伯塔大学与加拿大水泥协会和NSERC加拿大公司合作进行。

Considerable research has established a size effect in shear for reinforced concrete members without web reinforcement, where the shear stress at failure decreases with an increase in the member depth and/or a drop in the aggregate size. Research has also shown a decrease in the shear capacity for members constructed with lightweight aggregates and, for high strength concrete. The addition of steel or polymeric fibers into the matrix will help reduce crack widths, control crack spacing and provide an alternate shear force transfer mechanism. These benefits are expected to mitigate size effects in shear for fiber reinforced concrete (FRC) in comparison with similar members without fibers. The proposed project will develop several normal and high strength concrete mixes with and without fibers, using locally available cements and aggregates. Size effects will be examined for the constitutive response of FRC in compression, indirect tension, and direct shear. Using selected mixes, shear-critical beam specimens without conventional web reinforcement will be studied to characterize member response in shear, building upon the material models developed earlier. In each phase of this study, geometrical scale factor of 1:4 (or higher) will be used to assess the size effect. The results will be analyzed to develop analytical models and design guidelines for FRC members subjected to flexure and shear. This study will be conducted at the University of Alberta, in collaboration with the Cement Association of Canada and NSERC Canada.