Shear-Transfer Mechanisms and Strength Modeling of RC Continuous Deep Beams

Based on experimental results including the crack pattern and maximum applied strut stress, as well as on stress states obtained using a nonlinear finite-element analysis, it is identified that the typical critical shear crack of continuous deep beams is a web-shear crack, which has a large effect on shear-transfer mechanisms of deep beams. By theoretically considering the influence of the web-shear crack on the diagonal strut in a strut-and-tie model (STM) of continuous deep beams, a cracking strut-and-tie model (CSTM) has been developed. Shear-transfer mechanisms including aggregate interlock action, dowel action of longitudinal bars, and tension of web reinforcement are rationally considered. By comparing with a large database including 90 tests, the CSTM is verified to well predict the effect of main parameters including shear span-to-depth ratio, longitudinal reinforcement ratio, stirrup ratio, concrete compressive strength, and effective depth on the shear strength. Moreover, the proposed model is simplified to be used in the practical shear design, which shows a better prediction than the STM of a current standard.