Novel Multiaction Model for Shear Strength Prediction of Reinforced Concrete Beams: Development and Application to Elements with FRP Bars and FRC

The behavior of concrete structures subjected to shear forces involves the contribution of several shear force transfer actions, such as aggregate interlock, dowel action, concrete residual tensile along the fracture process zone, and transfer through the uncracked concrete. While the contribution and interaction between these actions dependt on the shape and kinematics of the critical shear crack, the prediction models available either do not consider all these actions or are based on linear or bilinear shapes for the critical crack. In this context, this paper presents a multiaction model in which the shear actions are considered in the equilibrium of forces and moments based on the shape and kinematics of the critical shear crack. The crack shape, represented by a quadratic Bézier curve, was obtained from an optimization process using a genetic algorithm. The results obtained from the model include the location, shape, and kinematics of the critical crack and the final shear strength and the contributions of each mechanism. The outcomes of the proposed approach were compared with experimental results reported in the literature for beams without stirrups and made with fiber-reinforced concrete (FRC) and fiber-reinforced polymer (FRP) or conventional steel bars. The experimental behavior was accurately simulated, especially for the critical shape and shear strength, which presented relative errors of around 1% and 7%, indicating good agreement. In addition, the model revealed that the residual tensile stress resulting from a discrete fiber action had the highest impact on the load-bearing capacity, following the same observations as the reference studies. The proposed model represents a promising methodology to predict the shear behavior of reinforced concrete beams with various combinations of materials.