Shear behavior of RC beams without transverse reinforcement: An analysis of crack kinematics and transfer mechanisms based on stereophotogrammetric measurements

This paper presents an evaluation of the shear capacity of reinforced concrete beams without transverse reinforcement by comparing the theoretical background with the experimental investigation. It is well known in the research community that the various shear transfer mechanisms contribute to the shear capacity. However, there are ongoing discussions regarding the critical shear crack kinematics that affect the relationship between the contributions of these mechanisms. In this study, 16 RC beams without transverse reinforcement were tested and their shear strength was compared with the predictions of existing codes and mechanical models. The shape of the critical crack was tracked using 3D stereophotogrammetric measurements. To analyze the crack kinematics, its shape was idealized by an optimized polyline with the newly proposed discretization degree. Based on stereophotogrammetric measurements with a sampling frequency up to 25 Hz and using available physical models, the detailed analysis of different shear transfer mechanisms is conducted for 4 tested beams, emphasizing the contribution of aggregate interlock. By comparing the experimental results with the calculated contributions to the shear resistance of each mechanism, a reasonable agreement was obtained. However, the measurements showed that most of the available physical models for the aggregate interlock contribution overestimate both the normal and shear stresses developing across the critical shear crack. Thus, with adequate data acquisition and analysis, digital image correlation has proven to be a viable tool for performing detailed real-time measurements of crack shape and kinematics.