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，纺织网格对纺织钢筋混凝土（TRC）在压缩下的承载性能的影响是不可忽略的。除了纺织品的影响外，试验表明，即使是手工层压的制造过程也会对铸件的最大强度产生负面影响。此外，层与荷载方向的朝向对混凝土强度有显著影响。分层制作的未加筋试件的各向异性材料性能更强。在这里，纺织平面方向的变化甚至导致了不同的失效模式。如果纺织品与加载方向平行排列，则会发生脆性破坏。另一方面，纺织品与加载方向的垂直对齐将导致相当的延性行为。这些差异可能是由两种相反的机制造成的。一方面，纺织品作为一个不连续，因为他们不能传递任何压应力垂直于他们的纵向。这会导致试样应力场的偏移。这些干扰诱导混凝土产生额外的拉应力，从而导致加速破坏。另一方面，织物在加载过程中产生侧向约束，稳定试件。这些机制支配着材料的行为和失效模式，特别是当纺织品垂直于加载方向排列时。层间距、纱线直径、网目尺寸或纺织品层间距的不同，对TRC材料在压缩下的性能有不同的影响因素。所有试验结果表明，随着层间距的增大，单一参数对强度和各向异性的影响减小。尚待解决的问题是已取得的成果的发现是否可转移到实际组成部分。解决方案的第一步是在项目的第二阶段进行，通过调查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，暴露在剪切或扭转载荷下。计划的试验应主要研究以下参数的影响：纺织增强材料的种类、制造工艺和不同的应力比。单轴和双轴试验的结果应作为数值材料模型的基础，对梁或柱等大型混凝土构件进行虚拟参数研究。数值计算的目标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，但对于在第三个资助期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.