Influence of plastic hinge models on the displacement capacity assessment of a reinforced concrete frame

This work investigates the influence of using three different plastic hinge Finite Element (FE) models on the assessment of the displacement capacity/demand ratio of a Reinforced Concrete (RC) frame, in accordance with the Italian Building Code. The considered plastic hinge models include: the fiber model, which is based on the use of nonlinear stress-strain diagrams for the materials and the definition of the plastic hinge length, and two models based on moment-rotation diagrams. One of the last two models considers the dependence of hinge behavior on axial force, while the other does not. Moreover, the flexural elastic stiffness of the structural elements used in these two models is different. The displacement capacity, displacement demand and the displacement capacity to demand ratio of the considered RC frame, obtained from the three FE models, are provided. The minimum ratio, equal to 0.79, is obtained from the model that does not account for the dependence of hinge behavior on axial force and where the flexural elastic stiffness of the structural elements is reduced to account for cracking effects. Conversely, the maximum displacement capacity to demand ratio, equal to 1.24, is obtained from the FE model with fiber plastic hinges. The third model, which is the most compliant with the Code’s requirements, provides a ratio equal to 0.92.