Cálculo de deslocamentos em vigas de concreto armado no estado limite de serviço utilizando a mecânica do dano

Abstract

The present work deals with a proposal for the analysis of displacements in reinforced concrete beams using a constitutive model based on Continuum Damage Mechanics. It is known that in structural concrete elements, the preponderant mechanical phenomenon is the microcracking process. Even before any imposed request, this material already has small microcracks in its microstructure. However, according to NBR 6118 (ABNT, 2014) and ACI 318R (2014) regulations, it is possible to find a different conceptual determination, and for the estimates of vertical deflection in reinforced concrete beams, the stiffness of the section is homogeneously penalized, having the exclusion of the cracked region and, as a consequence, the non-linear mechanical behaviour of the concrete is not considered. That is, it does not present coherence with the theoretical essence about the microcracking process of the material, since the microcracks propagate by a gradual process. In this context, the proposal intends to fill this gap identified in the Brazilian and American standards, proposing a methodology for the calculation of vertical displacements in reinforced concrete beams in service regime using the Damage Mechanics. Among the objectives, we sought to evaluate the proposed methodology, for which 54 (fifty-four) experimentally tested beams of 31 (thirty-one) different works have been used, thus being able to identify the potentialities and limitations of the model. With the results of the numerical analyzes compared with those from the tests and standards, good results have been identified, essentially in domain 3. Then, an improvement of the studied methodology is developed, presenting a new hypothesis for the expression of a parameter of the model seeking to relate the reinforcement ratio of the beams with a constant evaluated from a parametric identification. In the same way, analyses have been carried out on the tested beams, comparing the numerical results provided by the model with the experimental and the standards ones. In the results, numerical answers have been found representative of the mechanical behaviour, evidencing the feasibility and applicability of the proposal, still relating a configuration corresponding to the service regime. Therefore, the proposal of the present work presents displacement responses in cracked reinforced concrete beams considering their non-linear behaviour via Damage Mechanics.