Analytical and modeling studies on discontinuity regions in reinforced concrete elements: review article

Abstract Traditional section design theories for reinforced concrete (RC) elements are widely used and generally provide safe solutions, particularly in cases with minimal shear or torsional stresses. However, in regions where there is a sudden change in geometry or where high shear stresses are present—such as deep beams, corbels, beams with openings, and beam-column joints—these conventional bending theory assumptions may no longer be valid. Relying on them in such areas can result in inaccurate assessments and potential failure. To address the behavior of these disturbed regions (D-regions), alternative approaches such as the strut-and-tie model (STM), nonlinear finite element modeling (FEM), and the two-parameter kinematic theory (2PKT) have been developed. These methods provide a more accurate representation of the stresses distribution in D-regions compared to traditional design approaches. This review examines the application of these methods to various D-regions in RC elements, referencing both international design codes and existing research. Many international codes already incorporate STM and FEM as reliable tools for D-region analysis, offering clear guidance on selecting appropriate STM configurations for specific scenarios. The 2PKT, while showing promise—especially in the analysis of deep beams—is still in a developmental stage and requires further research and application to be broadly adopted across various D-regions. More recently, a funicular-based approach has been proposed to enhance understanding of D-region behavior. Drawing on the form-finding principle of hanging chains, this method uses the natural force path within a structure to create a funicular arch that directly determines the optimal design shape. This technique simplifies the design process, offering accuracy comparable to the STM, FEM, and 2PKT, while requiring fewer calculations and less software support. In conclusion, this review aims to provide practical guidance for structural engineers working with D-regions in RC elements, as well as a comprehensive overview for researchers seeking in-depth analysis and extensive literature in this field.