Experimental Study on the Load Bearing Behaviour of Textile Reinforced Concrete under Uniaxial Compression – Phase II: Influence of Lateral Compression and Tension

申请人的调查表明，织物格栅对受压织物增强混凝土（TRC）的承载性能的影响不可忽略。除了纺织品的影响，测试表明，即使是手工层压的制造工艺也会对铸件的最大强度产生负面影响。此外，层的加载方向的取向对混凝土强度有显着的影响。无筋试件的各向异性材料行为，这是逐层制造，甚至更强的TRC试件。这里，织物平面的取向的变化甚至导致不同的失效模式。如果织物平行于加载方向排列，则发生脆性破坏。另一方面，织物与负载方向的垂直对齐将导致相当的延展性行为。这些差异可能是由于两种相反的机制。一方面，纺织品充当不连续性，因为它们不能传递垂直于其纵向方向的任何压缩应力。这会导致试样中的应力场发生转移。这些扰动会在混凝土中产生额外的拉应力，从而加速混凝土的破坏。另一方面，织物引起侧向约束，并在加载过程中稳定试样。这些机制主导材料行为和失效模式，特别是当纺织品垂直于加载方向排列时。不同参数的变化，如层间距，纱线直径，网孔尺寸或使用的纺织品层位于彼此偏移显示了各种影响因素的TRC压缩下的材料行为。所有试验的结果是，单一参数对强度和各向异性的影响随着层间距的增大而减小。解决方案的第一步将在项目的第二阶段进行，通过研究TRC在压缩-压缩和压缩-拉伸载荷下的双轴材料行为，因为在大多数结构构件中，存在多轴应力状态，例如在梁处，其暴露于剪切或扭转载荷。计划的试验应主要研究以下参数的影响：织物增强体的种类、制造工艺和不同的应力比。单轴和双轴试验的结果应该是一个数值材料模型进行虚拟参数研究的基础上的大型混凝土构件，如梁或柱。数值计算的目的是减少对这些混凝土构件的测试次数，这些测试非常复杂和昂贵，但在第三个资助期内验证工程模型是必要的。

Investigations of the applicant show that the influence of textile grids on the load-bearing behaviour of textile reinforced concrete (TRC) under compression is not negligible. In addition to the impact of textiles, the tests showed that even the manufacturing process by manual lamination affects the specimen’s maximum strength negatively in regard to casted ones. Furthermore, the orientation of the layers to the loading direction has a significant influence on the concrete strength. The anisotropic material behaviour of unreinforced specimens, which were manufactured layer by layer, is even stronger for TRC specimens. Here, the variation of the orientation of the textile plane leads even to different failure modes. If the textiles are aligned parallel to the loading direction, a brittle failure occurs. On the other hand, a perpendicular alignment of the textiles to the loading direction will cause a quite ductile behaviour. These differences are probably due to two opposing mechanisms. On the one hand, the textiles act as a discontinuity, because they cannot transfer any compressive stresses perpendicular to their longitudinal direction. This causes diversions in the stress field in the specimen. These disturbances induce additional tensile stresses into the concrete, which lead to an accelerated failure. On the other hand, the textiles cause a lateral constraint, and stabilize the specimens during the loading process. These mechanisms dominate material behaviour and failure mode especially if the textiles are aligned perpendicular to the loading direction. The variation of different parameters, like layer spacing, yarn diameter, mesh size or the use of textile layers located offset from each other showed the various impact factors on the material behaviour of TRC under compression. A result of all tests is that the influence of the single parameters on the strength and the anisotropy decreases with a taller layer spacing.What is open is the question of the transferability of the findings of the obtained results to practical components. A first step towards the solution is to be carried out in the second phase of the project by investigating the biaxial material behaviour of TRC under compression-compression and compression-tension loads, because in most of the structural members, there is a multiaxial stress state, e.g. at beams, which are exposed to shear or torsional loads. The planed tests should mainly investigate the impact of the following parameters: kind of textile reinforcement, manufacturing process and different stress ratios. The results of the uni- and biaxial tests are supposed to be a basis for a numerical material model to conduct virtual parameter studies on large-scale concrete members, like beams or columns. The goal of the numerical calculations is to reduce the number of test on such concrete members, which are quite complex and expensive, but necessary for validation of an engineering model in a 3rd funding period.