Ductility Analysis of RC Beams Considering the Concrete Confinement Effect Produced by the Shear Reinforcement: a Numerical Approach

Abstract

In this paper, a simplified numerical approach to study the influence of the confinement effect provided by transversal reinforcement on the ductility behavior of RC beams in bending is proposed. A unidimensional FEM mechanical model coupled to the Mazars' damage model to simulate concrete behavior was adopted to assess ductility curvatures at the ultimate limit state. The confinement effect was incorporated to the numerical model through a calibration process of the damage internal parameters, based on the Least Square Method and an analytical law proposed by Kent and Park (1971). Several numerical analyses were carried out considering different designs of RC beams according to a parametric study varying the neutral axis position, concrete compressive strength and the volumetric transversal reinforcement ratio. The obtained results showed the importance of the amount of transversal reinforcement on the ductility behavior, increasing the ductility factor even for the cases with inappropriate neutral axis position.

Prestressing Effects on Full Scale Deep Beams with Large Web Openings¨: An Experimental and Numerical Study

“…When the concrete resistance increases, the amount of longitudinal reinforcement required to maintain the same ductility also increases. Therefore, a direct dependence between the ductility factor and the longitudinal reinforcement rate was observed [18].…”

The Threshold for Under-Reinforced Concrete Sections Proposed by ACI 318, EC 2 and BS 8110

“…According to the graph in Figure 3, the coefficient α increases from 0.60 to 0.80 when ε cu increases from 0.003 to 0.008. α is constantly 0.5 according to BS 8110 code, and 0.45 for ordinary concrete according to EC2. Therefore, α is calculated accurately based on equation (2) which is obtained from the linear strain distribution over RC cross-sections. α proposed by BS 8110 code is less accurate than that of ACI 318-19 but more accurate than that of EC2.…”

“…The ductile behavior of reinforced concrete (RC) cross-sections has always been desirable for building codes and standards. However, the threshold to distinguish ductile and brittle behavior of RC cross-sections proposed by building codes has yet to be evaluated [1][2][3][4]. This behavior mainly depends on the type of RC cross-section whether it is under-or over-reinforced.…”

New design model of reinforced concrete beams in bending considering the ductility factor

“…However, several important mechanisms that interfere on the general behaviour of reinforced concrete beams are not considered in an explicit way, like damage evolution and cracking as the loads act in the structure; the confinement effect of the compressed concrete given by the stirrups and the concrete's tensile contribution between cracks (tension stiffening). Different researchers have studied ductility in reinforced concrete elements, and also the plastic hinge capacity in collapse situations, using empirical or numerical models that consider the effects described previously (Teng et al [15]; Oehlers [11]; Panagiotakos e Fardis [14]; Lopes et al [9]; Oehlers et al [13]; Nogueira e Rodrigues [10]). Regarding numerical analysis, the results has been considered trustworthy and with good representation of the experimental answers, especially in the case of regular beams in bending, once the phenomenological behaviour of the materials and the structural elements have been modelled with good precision (Oehlers et al [12]; Nogueira e Rodrigues [10]; Nogueira et al [17], Pituba e Lacerda [18]; Pereira Junior et al [19]).…”

“…Different researchers have studied ductility in reinforced concrete elements, and also the plastic hinge capacity in collapse situations, using empirical or numerical models that consider the effects described previously (Teng et al [15]; Oehlers [11]; Panagiotakos e Fardis [14]; Lopes et al [9]; Oehlers et al [13]; Nogueira e Rodrigues [10]). Regarding numerical analysis, the results has been considered trustworthy and with good representation of the experimental answers, especially in the case of regular beams in bending, once the phenomenological behaviour of the materials and the structural elements have been modelled with good precision (Oehlers et al [12]; Nogueira e Rodrigues [10]; Nogueira et al [17], Pituba e Lacerda [18]; Pereira Junior et al [19]). Models of material behaviour based on Continuous Damage Mechanics (Lemaitre e Chaboche [20]) have been frequently used on the numerical analysis of reinforced concrete structures, since they are capable to represent well the damage evolution as a penalizing magnitude for stiffness of reinforced concrete elements.…”