Fiber-reinforced concrete has a wide application in practice, and many fields of research are devoted to it. In most cases, this is a specific problem, i.e., the determination of the mechanical properties or the test method. However, wider knowledge of the effect of fiber in concrete is unavailable or insufficient for selected test series that cannot be compared. This article deals with the processing of a comprehensive test study and the impact of two types of fibers on the quantitative and qualitative parameters of concrete. Testing was performed for fiber dosages of 0, 40, 75, and 110 kg/m3. The fibers were hooked and straight. The influence of the fibers on the mechanical properties in fiber-reinforced concrete was analyzed by functional dependence. The selected mechanical properties were compressive strength, splitting tensile strength, bending tensile strength, and fracture energy. The results also include the resulting load–displacement diagrams and summary recommendations for the structural use and design of fiber-reinforced concrete structures. The shear resistance of reinforced concrete beams with hooked fibers was also verified by tests.

This article focuses on the analysis and numerical modeling of a concrete slab interacting with subsoil. This is a complex task for which a number of factors enter into the calculation, including the scope or dimension of the model, the non-linear solution approach, the choice of input parameters, and so forth. The aim of this article is to present one possible approach, which is based on a non-linear analysis and a three-dimensional computational model. Five slabs were chosen for modeling and analysis. The experiments involved slabs of 2000 × 2000 mm and a thickness of 150 mm, which were tested using specialized equipment. The slabs included a reinforced concrete slab, a standard concrete slab, and three fiber-reinforced concrete slabs. The fiber-reinforced slabs had fiber volume fractions of 0.32%, 0.64%, and 0.96%, which corresponded to fiber dosages of 25, 50, and 75 kg/m3. A reinforced concrete slab was chosen for the calibration model and the initial parametric study. The numerical modeling itself was based on a detailed evaluation of experiments, tests, and recommendations. The finite element method was used to solve the three-dimensional numerical model, where the fracture-plastic material of the model was used for concrete and fiber-reinforced concrete. In this paper, the performed numerical analyses are compared and evaluated, and recommendations are made for solving this problem.

This article focuses on researching the interactions of fiber concrete slabs with subsoil. The experimental series includes four slabs made of fiber concrete with different dosages of fibers, from 0 to 75 kg/m3. The slabs were exposed to a loading test on a specialized loading frame. The laboratory tests for detailed descriptions of the fiber concrete’s mechanical properties were also an integral part of the experiments, including tests of the compressive strength, the modulus of elasticity, and split and bending tensile strength. Each slab’s deformation in a particular load step was evaluated in two-dimensional (2D) sections based on data measured with displacement sensors and in three-dimensional (3D) charts with the use of interpolation.

AbstractThe article deals with the interaction of a reinforced concrete slab with subsoil. The paper contains a non-linear analysis based on an experiment of reinforced concrete slabs with dimensions 2000 x 2000 mm and thickness 150 mm. A steel mesh with a diameter of 8/100 mm was used as reinforcement. The calculations and analysis are complemented by a comparison with EC2 design approaches. The research area combines the design of concrete structure and geotechnical tasks. The real behavior of the concrete structure with subsoil is considered for the analysis for advanced design. The selected computational approach of nonlinear analysis allows to capture the change of stiffness after the creation of cracks and modelling the shear punch failure of the slab - the collapse of the structure. The paper focuses on comparing the experiment with the numerical model in select loaded states for various input parameters of subsoil. Based on the experiment and numerical analysis the failure mechanism was determined. It was the punching of the slab. The calculations and the experiment verified that the critically controlled perimeter is at a distance of 1d. The effect of the modulus of elasticity on the slab punch mechanism was verified. In case of low modulus of subsoil, the load-bearing capacity of the slab is significantly reduced. The punching mechanism is influenced not only by the mechanical properties of the concrete but also by the properties of the subsoil. The performed parametric study also verified the influence of the size the nominal cover reinforcement depending on the modulus of elasticity of the subsoil. The deformation variant finite element method and a 3D computational model were used for numerical modelling. Nonlinear analysis was based on the Newton-Rapson method.

AbstractThe paper deals with the determination of mechanical properties of fiber reinforced concrete in dependence on various dosages and recipe of concrete. The mechanical properties were determined for the default recipe of concrete, where the individual variants differ in the amount of fibers. The fibers dosing was 0, 25, 50 and 75 kg/m3. At the highest dosage of 75 kg/m3, the recipe is optimized with regard to the microstructure of the concrete. In the experimental program were determined compressive strength, modulus of elasticity, split tensile strength, flexural tensile strength and load-displacement diagram. The flexural tensile strength was determined based on a three-point and four-point bending test. Based on the evaluated data, the uniaxial tensile strength and the functional dependence for the resultant recipe of concrete with a dosage of 75 kg/m3 is with respect of the increasing importance and application of numerical modelling of building structures, the analysis is performed using non-linear calculation. The aim was to simulate the performed laboratory test and appropriately approximate the specific input parameters of the fiber reinforced concrete for nonlinear analysis.