Uniaxial Tensile Stress–Crack Width Relationship of 3D/4D/5D Steel-Fiber-Reinforced Concrete

Steel-fiber-reinforced concrete (SFRC), as a composite engineering material, exhibits excellent physical and mechanical properties, making it widely applied in civil engineering, construction, water conservancy, transportation, and port industries. To date, significant progress has been made in the research of plain and single-hook (3D) steel-fiber-reinforced concrete both domestically and internationally. With advancements in technology, multi-end hooked 4D and 5D steel fibers have emerged, offering more end hooks and a higher tensile strength. These fibers possess a stronger anchorage capacity with the matrix, and SFRC with multi-end hooked fibers exhibits superior tensile and flexural properties. However, research on multi-end hooked (4D and 5D) steel-fiber-reinforced concrete is still in its early stages, particularly regarding the axial tensile stress–crack width constitutive relationship. The accuracy and rationality of this constitutive relationship directly affect the reliability and precision of structural design. Therefore, in this study, a novel σ-w constitutive relationship model for steel-fiber-reinforced concrete and an axial tensile stress–crack width testing method for SFRC are proposed, based on 16 sets of uniaxial tensile tests. This model considers the comprehensive effects of the concrete matrix, fiber bridging, fiber volume fraction, fiber shape factor (effects of the number of hooked ends), aspect ratio, and crack width.