Estimación del factor de intensidad de esfuerzo en una probeta wedge splitting bajo carga estática mediante el método de elementos finitos

El factor de intensidad de esfuerzos (SIF) es un parámetro suficiente para definir el campo de esfuerzos al cual está sujeto un cuerpo agrietado bajo los lineamientos de la mecánica de fractura lineal elástica (LEFM). El valor del factor de intensidad de esfuerzos SIF es una función del esfuerzo aplicado, la longitud de la grieta y la geometría general de la probeta. Existen varios métodos experimentales para calcular este factor de intensidad de esfuerzos, entre los que se destaca el Wedge Splitting Test (WST). En el presente trabajo se calcula el factor de intensidad de esfuerzos para una probeta de WST mediante la técnica de elementos finitos manteniendo una carga constante y realizando variaciones en la longitud de la grieta y la geometría del cuerpo. Los resultados obtenidos se comparan con una correlación numérica tomada de la literatura en donde se constatan resultados satisfactorios para la simulación.

Mechanical Performance and Environmental Assessment of Sustainable Concrete Reinforced with Recycled End-of-Life Tyre Fibres

The presented research’s main objective was to develop the solution to the global problem of using steel waste obtained during rubber recovery during the tire recycling. A detailed comparative analysis of mechanical and physical features of the concrete composite with the addition of recycled steel fibres (RSF) in relation to the steel fibre concrete commonly used for industrial floors was conducted. A study was carried out using micro-computed tomography and the scanning electron microscope to determine the fibres’ characteristics, incl. the EDS spectrum. In order to designate the full performance of the physical and mechanical features of the novel composite, a wide range of tests was performed with particular emphasis on the determination of the tensile strength of the composite. This parameter appointed by tensile strength testing for splitting, residual tensile strength test (3-point test), and a wedge splitting test (WST), demonstrated the increase of tensile strength (vs unmodified concrete) by 43%, 30%, and 70% relevantly to the method. The indication of the reinforced composite’s fracture characteristics using the digital image correlation (DIC) method allowed to illustrate the map of deformation of the samples during WST. The novel composite was tested in reference to the circular economy concept and showed 31.3% lower energy consumption and 30.8% lower CO2 emissions than a commonly used fibre concrete.

Characterization tests for predicting the mechanical performance of SFRC floors: design considerations

The paper presents an experimental program carried out to check the load bearing capacity of a steel fibre reinforced concrete (SFRC) floor in northern Italy. The extensive mechanical characterization focused on the suitability of 3 non-standardized test methods for quality control and tensile constitutive curve assessment was performed, this consisting of: uniaxial tensile test (UTT), double edge wedge splitting test (DEWST) and double punching test (DPT) to characterize the post-cracking mechanical properties of the material. The joint experimental programme, carried out at the Politecnico di Milano and at the Universitat Politècnica de Catalunya, included the flexural characterization of four shallow beams (1.5 × 0.5 × 0.25 m3) and six standard notched beams (0.55 × 0.15 × 0.15 m3). All the samples were produced from the same batch and with the same SFRC mix which was applied for the floor. After that, 192 cores were drilled from the shallow beams and subjected to either UTTs, DEWSTs or DPTs. The stress level, the scatter and the constitutive curves derived from the non-standardized tests were identified and analysed. The calculated constitutive curves were used to predict the behaviour of the shallow beams.