Flexural Behaviour of Carbon Textile-Reinforced Concrete with Prestress and Steel Fibres
Four-point bending tests were adopted to investigate the influences of the number of textile layers, volume content of steel fibres, and prestress on the flexural behaviour of carbon textile-reinforced concrete (TRC). The failure mode of the specimen changed from debonding failure to shear failure, accompanied by the matrix-textile interfacial debonding with an increasing number of textile layers. The interfacial bonding performance between the textile and matrix improved with the addition of steel fibres in the TRC specimens. The presence of prestress or steel fibres improved first-crack and ultimate stresses of the TRC specimen. In comparison with the first-crack stress, a more pronounced enhancement in the ultimate stress was achieved by the addition of steel fibres. However, the effect of prestress on the first-crack stress was found to be more significant than on the ultimate stress. The prestress combined with steel fibres further improved the flexural behaviour of the TRC specimens. The prestressed TRC specimens with 1% volume content of steel fibres effectively avoided debonding. Thus, the utilization of the textiles could be improved.
Numerical Simulation of Steel Reinforced Concrete (SRC) Joints
This paper presents a three-dimensional finite element model to confirm experimental tests carried out on steel reinforced concrete joints. The nonlinear behavior of this concrete is simulated, along with its reduced capability to resist large displacements in compression. The aim was to obtain the plastic behavior of reinforced concrete beams with a numerical model in the same way as obtained experimentally, in which the reduction of strength in the post-critical stage was considered to simulate behavior until structures collapsed. To do this, a nonlinear calculation was necessary to simulate the behavior of each material. Three numerical models provide a moment–curvature graph of the cross-section until collapse. Simulation of the structural elements is a powerful tool that avoids having to carry out expensive experimental tests. From the experimental results a finite element model is simulated for the non-linear analysis of steel reinforced concrete joints. It is possible to simulate the decreasing stress behavior of the concrete until reaching considerable displacement. A new procedure is discussed to capture the moment-curvature diagram. This diagram can be used in a simplified frame analysis, considering post-critical behavior for future research.
Fabric structure and its reinforcing efficiency in textile reinforced cement composites
In polymer matrices reinforced with fabrics, the effectiveness of the reinforcement is reduced when the yarns do not maintain a straight geometry. In cement composites, this concept may not be adequate since the nature of the interaction between the cement matrix and the fabric and its individual yarns is more complex, as concluded from pullout tests. The present paper discusses the bulk properties and geometrical characteristics of textile fabrics that need to be considered in order to predict the performance of cement composites reinforced with textile fabrics. It was found that the geometry of a given fabric could enhance the bonding and enable one to obtain strain hardening behavior from low modulus yarn fabrics, due to the special shape of the yarn induced by the fabric. On the other hand, variations of the geometry in a fabric could drastically reduce the efficiency, resulting in a lower strengthening effect of the yarns in the fabric, relative to single yarns not in a fabric form. Therefore, in cement composites the fabrics cannot be viewed simply as a means for holding together continuous yarns to be readily placed in the matrix, as is the case in composites with polymer matrix.