بررسی تاثیر اندرکنش لنگرخمشی ونیروی برشی بررفتارتیرهای بتن مسلح

Reinforced or prestressed concrete beams are commonly subjected to complex loading conditions that simultaneously induce shear forces and bending moments. In order to accurately evaluate the structural behavior of these members, it is essential not only to assess the individual effects of shear and flexure but also to consider their interaction. The flexural capacity and shear resistance of reinforced concrete elements are strongly interdependent, and a thorough understanding of this relationship is vital for achieving safe and efficient structural designs. Despite this, current design codes such as ACI and CBC typically treat flexural and shear capacities as independent phenomena, disregarding their mutual influence. This decoupled approach can lead to considerable discrepancies between analytical predictions and actual structural responses, potentially resulting in non-conservative designs that fail to reach full flexural capacity under combined loading scenarios. To address this issue, the development of accurate predictive models that incorporate the influence of shear on flexural behavior is critically important. These models can assist engineers in determining the optimal amount and configuration of shear reinforcement required to ensure the full development of flexural strength. Integrating such models into numerical simulation platforms improves the reliability of design and assessment methodologies, especially for members subjected to critical loading conditions. Furthermore, the mechanical behavior of reinforced concrete structures is significantly affected by the initiation and propagation of cracks that occur during the loading process. Experimental investigations into crack behavior are often limited by practical challenges, high costs, and the potential for measurement inaccuracies. In contrast, finite element simulations offer a powerful and cost-effective tool for analyzing crack development in greater detail. In this study, a comprehensive numerical simulation was conducted using ANSYS software to investigate crack patterns in reinforced concrete beams. A fragmental modeling approach was adopted, where zero-thickness interface elements were inserted between all solid elements to realistically simulate crack initiation and growth. Furthermore, the cohesive zone model (CZM) was applied to describe the relationship between stresses and crack widths, and to identify the formation and propagation of new cracks. This method allows for a more accurate representation of discontinuities and failure mechanisms in concrete structures. The study focuses on evaluating the effects of several key parameters—namely the shear span-to-depth ratio (a/d), longitudinal reinforcement ratio, and concrete compressive strength—on the shear–flexure interaction in reinforced concrete deep beams. Various failure modes, including pure shear failure, flexural failure, and combined shear–flexure failure, are systematically analyzed through the simulation results. Additionally, the influence of shear force on flexural behavior, the contribution of flexure-induced shear resistance, and the resulting crack paths are examined. Based on the simulation outcomes, a physically informed mathematical model is proposed to predict the shear–flexure interaction in deep beams. This model captures the actual behavior observed in the finite element simulations and aligns closely with experimental trends reported in the literature. The insights gained from this research contribute to a better understanding of complex failure mechanisms in reinforced concrete members and provide a basis for enhancing current design procedures, aiming to improve both the accuracy and safety of structural systems under combined loading conditions.