Análise numérica dos parâmetros que exercem influência sobre resistência à força cortante em lajes maciças de concreto armadas em duas direções

Abstract

The slabs can be subjected to shear force, which causes shear stress in the structural element, as occurred in the structural system in which slabs are supported directly on columns, without the use of beams to mediate the transmission of forces between these two elements. In this context, there are factors that contribute to the increase in shear strength in concrete structures without shear reinforcement, such as cross-sectional height, longitudinal reinforcement ratio, crack size and concrete compressive strength. Some studies sought to analyze the influence of these factors on the shear strength gain in slabs reinforced in two directions. Therefore, the present work aimed, through numerical analysis, to understand the influence of three main parameters such as slab thickness, concrete compressive strength and longitudinal reinforcement ratio on shear strength in the reinforced concrete two-way slabs without shear reinforcement, in addition to defining the parameter that has the greatest contribution. For that, two numerical models were elaborated: the first numerical model did not present representative results of the experimental models, besides not bringing a good reproduction of the behavior of the slabs; with Model II it was possible to reach results close to those of the experimental models. Thus, Model II was used to carry out the simulations with the variation of the parameters under study. With the results, analysis of variance was used to determine the most relevant factor on the increase in shear strength. Finally, it was verified that for slender slabs the factors considered in the research do not present great significance on the shear strength, being necessary the definition of new variables to define the most relevant factor. For the group of thick slabs, the longitudinal reinforcement ratio was determined as a relevant factor, being the parameter that exerts the greatest influence on the gain in shear strength.