Shear strength evaluation of RC D-Regions based on Single-Panel Strut-and-Tie model

In existing shear test databases of reinforced concrete D-regions (discontinuity or disturbance regions), most data points are concentrated in parameter ranges of high main reinforcement ratio, small overall dimensions, or low concrete strength. Based on regression analysis of these databases, large model errors in effective coefficients of strut compressive strength (hereafter referred to as strut coefficients) for strut-and-tie models (STMs) have been obtained. In this study, a uniformly distributed (or unbiased) large-scale shear database is generated through a mechanics-based cracking strut-and-tie model (CSTM), which has been validated against extensive test results. Then a strut coefficient with a simple form and comprehensive consideration of various design parameters is proposed through regression analysis. On the other hand, the traditional STM presents a tedious design procedure and uncertainty in structural reliability caused by the subjectivity in geometric modeling. In order to simplify the design procedure and eliminate the uncertainty, a unified shear design equation based on the strut coefficient is proposed for D-regions that the single-panel STM can well simulate. The accuracy of the unified equation is verified by an extensive shear test database consisting of simple and continuous deep beams, corbels, squat shear walls, and short coupling beams.