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Flexural cracking behavior and calculation approach of reinforced highly ductile fiber-reinforced concrete beams

100%

Zhang M. , Deng M. , Wu Z. , Pan J.

tom Vol. 21, no. 4

320--333

Highly ductile fiber-reinforced concrete (HDC) is a class of cementitious composites reinforced with polyvinyl alcohol (PVA) fibers and exhibits strain-hardening behavior and multiple fine cracks under tension. This study aims to evaluate the cracking behavior and propose a simple calculation approach of the crack width and crack spacing of reinforced HDC (RHDC) flexural members. The four-point bending tests were conducted for RHDC beams with a different ultimate tensile strain of HDC and tensile reinforcement ratio. The flexural cracking performance of beams was mainly analyzed. The results showed that the width, spacing, height of flexural cracks of RHDC beams was significantly smaller compared with those of reinforced concrete (RC) beams. An increase in the ultimate tensile strain of HDC decreases the crack width and crack height while has little influence on the average crack spacing of RHDC beams. The effect of the tensile reinforcement ratio on the crack width is notable for RHDC beams with a higher ultimate tensile strain of HDC. The increasing of the tensile reinforcement ratio decreases the average crack spacing and crack height of RHDC beams. Furthermore, theoretical formulas for the average crack spacing, average crack width, and maximum crack width of RHDC beams were proposed based on the bond interaction between rebars and HDC and the fiber bridging stress. The predicted values have good agreement with the experimental values, indicating that the proposed method is reliable to evaluate the crack behavior of RHDC flexural members. Based on an accurate validation, the effect of cover thickness, HDC strength, and rebar diameter on the crack behavior of RHDC beams was conducted and found consistent with the law of RC beams.

Influence of textile grid forms on tensile mechanical behaviors of carbon textile-reinforced composites with polyethylene (PE) short fibers

75%

Wu Z. , Deng M. , Tian T. , Dong Z. , Sun Y. , Zhang W.

tom Vol. 23, no. 2

art. no. e103, 2023

Textile-reinforced composite (TRC) is a new material composed of finely grained cement-based concrete and textile grids, which can be a substitute for fiber-reinforced polymer (FRP) in strengthening applications. The diversity of the textile grid results in a difference in bond behaviors at the textile-matrix interface, which influences the tensile properties of TRC. Several researchers have investigated the tensile behaviors of TRC, mainly concentrating on the matrix strength, the content of short synthetic fibers, and the number of textile grids; discussions on the textile grid geometry, especially the coupling effect between the textile grid form and matrix category, remained limited. Therefore, this paper focuses on the effects of three carbon textile grids on the tensile behavior of TRC through a uniaxial tensile test; the design parameters also include the textile reinforcement ratio and matrix category. Twenty-seven groups of tensile samples were manufactured to investigate the effect of each variable on the crack distribution, failure pattern, stress-strain curve and characteristic parameter. The test results showed that flattening the roving diameter and especially thinning the coating depth ameliorated the matrix-to-textile permeability, and consequently improved the tensile mechanical properties of TRC. The enhancement level of tensile strength by increasing the textile reinforcement ratio was lower than that by optimizing textile grid form. In terms of different textile grid forms, the effect of the matrix category on the tensile performance of TRC showed significant differences. Finally, an analytical model is presented to forecast the stress-strain behavior of TRC with textile rupture failure.