Theoretical evaluation equation for capacities of beam action in shear resistance mechanisms of rc beams reflecting dowel action of main reinforcements

This study proposes a theoretical evaluation equation for the capacities of beam action in reinforced concrete (RC) beams. The equation reflects the dowel action of the main reinforcements for the development of rational evaluation methods for the shear capacity. To verify its accuracy, a static loading experiment and finite element (FE) analyses were conducted for the beams with 2.1 to 9.4% of the main reinforcement ratio. The fundamental equation that reflects the dowel action of the main reinforcement was developed using the equilibrium condition of the free body in beam action. The decrease in crack width by the main reinforcement, which was required to calculate dowel force, was derived by the assumption of perfect bonding between concrete and rebars. The governing equations were formulated to derive the experimental values of the contributing forces of arch action and beam action in RC beams with cross sections of multilayered rebars. The calculated values indicated that changes in load-carrying mechanisms could be explained from the equation. The accuracies of the proposed equation and evaluation equations of shear strengths based on design codes were compared against the capacities of beam action based on the analytical results. As a result, for the values based on the proposed equation, the coefficient of variation was 7.7% and the highest accuracy was observed in all the cases examined. It was confirmed that the proposed equation accurately reflected the dowel action of the main reinforcements and guaranteed rationality owing to its theoretical background.