A mechanical and simplified model for RC elements subjected to combined shear and axial tension

Very little is known about the shear behavior of elements, in particular those subjected to axial tension. The shear accompanied by tensile forces could cause premature failure of reinforced concrete, which is sudden with minimal warning. Therefore, understanding the shear behavior of reinforced concrete (RC) elements, including those subjected to axial tension, is an ultimate goal of the worldwide research community. In the current study, a new shear mechanical model for RC elements subjected to axial tension is developed, which makes physical sense and explains the behavior. The model is strain-based, inspired by the critical crack theory model (CSCT). In addition, the proposed model extended CSCT (ECSCT) quantifies the effect of axial tension forces on the shear strength in terms of reduction in the compression zone depth and increase in the longitudinal strain. Moreover, the nonlinear trend observed in the literature was implemented using nonlinear multi-variable regression. The ECSCT is validated and compared with available design methods with respect to an extensive database, including 180 elements tested under shear and tension from 18 different research investigations. The ECSCT provided an accurate and physically sound model yet safe to an acceptable extent. Last but not least, a simplified model for the purpose of design is proposed. The simplified model was chosen based on the mechanical model and calibrated using the extensive experimental database. The simplified model provided an accurate and simple model, yet safe to an acceptable extent.