Effects of Meso-scale Modeling on Concrete Fracture Parameters Calculation

Mechanical fracture brings about considerable financial and living costs to various communities. Since the early twentieth century, the issue has been scientifically under scrutiny. Hence, it is of necessity to explore the failure of various materials including concrete as one of the most widely used materials in the construction industry. In examining the concrete structures, while it is assumed that concrete is a homogeneous material, it consists of several components such as cement paste, an aggregate of sand, gravel, and air, and the components play an essential role in determining correct concrete behavior. Hence, in the present research, to calculate the concrete fracture parameters under the three-point bending experiment, 100 distributions of aggregates and cement matrix were considered, and fracture factor and integral J were investigated, and contrary to expectations, the second and third fracture modes were also created. Besides, energy release ratio distribution along the beam thickness becomes unsymmetrical, contributing to early failure and crack propagation

Seismic Retrofit of Defective RC Beam-Column Joints

Strong earthquakes always occur in countries with seismic risk and can potentially cause multiple deaths. This study investigates the seismic vulnerability of RC beam-column connections. Generally, it is impractical to simultaneously set up the molds of the concrete beam, ceiling and column and achieve a uniform concrete and this can cause numerous constructional deficiencies. Usually, these deficiencies can be instrumental in the failure of RC frames. Therefore, this study investigates the performance of a defective RC beam-column connection and provides a method to improve the behavior of the connection. The defective connection studied herein belongs to a high school in the city of Kermanshah, Iran. Many factors that affect the performance of the retrofitting designs are studied. Also, all of the parameters used in the analyses were obtained based upon the actual behavior of the material through core extraction and tensile tests. Finally, an optimal design is proposed

Analyzing the Edge Cracked Semicircular Disc under Uniform Compressive (ECSD(UD)) Load

In this study, by employing the edge cracked semicircular disc under uniform (ECSD(UC)) and calculating the shape factor, the toughness of brittle materials under uniform compressive load has been quickly evaluated. Samples, on the loading location and the support, under angle β changing from 0 to 10 degrees, with the crack length (a) changing from 1 to 29 mm and the thickness (t) changing from 1 to 30 mm were investigated. By taking into account the simultaneous effect of thickness and crack length, a relationship for the shape factor (F) of the ECSD(UC) was presented