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Reinforced concrete (RC) flat slabs without transverse reinforcement are commonly used in RC buildings. Despite their appeal and widespread use, these slabs are susceptible to brittle shear failure. While most previous research has focused on estimating the punching shear strength (PSS) of RC flat slabs, accurately identifying their failure modes is crucial for effective design and reinforcement. This paper presents an analysis of ensemble neural network and ensemble deep neural network models, including bagging neural network (BaggingNN), model averaging (MA), separate stacking (SS), and integrated stacking (IS) algorithms, to develop a predictive model for failure mode identification. The results of this new model are compared with those of earlier studies. To evaluate how variables such as concrete strength and reinforcement ratio impact the failure modes of RC flat slabs, the model's prediction process is examined using the SHapley Additive exPlanation (SHAP) method. The findings indicate that the IS algorithm outperformed the BaggingNN, MA, and SS algorithms, as well as models from prior research.

Materials’ fracture mechanics are crucial because they can predict how a material will break before it really happens. An extended finite element 2D numerical model implemented in the finite element ABAQUS software was used to investigate the initiation and propagation of pre-existing frictional cracks in rock material. The material used in this study was Coconino sandstone. First, a single pre-existing crack in a rock medium was modeled using a displacement method to determine the Stress Intensity Factor (SIF) at the tips of the crack. To validate the modeling methodology, the SIF derived using this approach was compared to a closed-form solution. Then, the size effect of a single flaw was studied. Results of the verification show that the relative error between the numerical and theoretical solutions decreases and eventually approaches a constant value as the plate size ratio to the flaw length increases. Hence, the effects of the boundary condition on SIF are negligible, and the medium can be assumed as infinite. Then, two pre-existing frictional cracks were modeled. The slip distribution along flaw length was obtained for these pre-existing cracks. The results show that slip distribution is zero at the flaw tips and maximum at the middle part of the flaw length. Additionally, increasing the pre-existing crack's friction coefficient causes an increase in the flaw's surface strength and a decrease in the slip distribution along the flaw's length. Finally, it was examined how the size of the rock mass model affected the uniaxial compressive load and SIF. The findings reveal that increasing the flaw length to model dimension leads to a decrease in uniaxial compressive strength on the rock mass model, but there is no significant change in SIF until the ratio is greater than 0.33, however after the ratio of 0.33 significant variation occurs.

Discontinuities are an integral part of the rock masses, and fewer rocks are found in nature which are intact. These discontinuities control mechanical properties of rocks, and lack of attention to their growth and interaction results in reduced rock structure's useful lifespan. The research to date has tended to focus on single cracks rather than crossover cracks. In recent years, there has been an increasing interest in V shaped cracks. In this study, initiation and propagation of V-shaped cracks, the nature of the cracks, failure mode, and failure stress in the specimen of Brazilian disks on a rock-like material was experimentally investigated. The cracks were studied in this study are the open type with the thickness of 1 mm and created by thin steel shims shaped as V, with five different angles. Fifteen different types of crack geometries, with different angles and length, have been investigated in specimens of Brazilian disks with 100 mm diameter and 30 mm thickness performing 45 Brazilian tests. The variables that have been considered are the angle between the two cracks and the length of each crack. With the results of Brazilian tests, it was observed that the predominant mode of failure in the V-shaped cracks is tensile. It also showed that the effect of crack length on the fracture process from the angle between the two cracks is much higher. Another important finding was that the angle of 45° reaches failure in minimum tension, so this angle is critical. In some specimens, one tip from three tips of V-shaped crack remains inactive which appears to be the asymmetric failure pattern in intact Brazilian disks. A possible explanation for this might be that stress distribution in the sample, and the possible existence of the low difference between lengths of these two cracks may be responsible for this phenomenon.