Estudo comparativo de modelos para dimensionamento ao cisalhamento de vigas de concreto armado de seção circular maciça

Abstract

In the shear design of reinforced concrete beams, it is necessary to calculate transverse reinforcement, which must combat the state of cracking caused by the main tensile and compressive stresses in the internal structure of the material. In the Brazilian scenario, NBR 6118 (2023) prescribes formulations that determine a ruin-resistant arrangement of the compressed and tensioned diagonals. Despite its value, this model is restricted to structures with rectangular cross-sections or those derived from this geometry. On the other hand, structures with circular cross-sections, subjected to bending and shear forces, have a reasonable range of applications in civil construction, such as excavation containment elements, road tunnel beams, street lighting poles, among others. Beyond the Brazilian regulatory context, foreign technical standards omit or lack precise methods for estimating the resistive capacity of reinforced concrete elements with circular crosssections. Currently, there is still no consensus in the literature on the best model for predicting the resistive capacity of circular elements. In view of the above, the aim of this study was to analyse and compare four models associated with the assessment of shear strength in the field of circular reinforced concrete beams. The comparative analysis between the models was carried out using computer implementations in Python, based on experimental data from 68 circular beams found in the literature. It was concluded that all the models lead to adequate values, with the individual accuracy being the difference observed between them. While the approximate models tend to underestimate the real resistive capacity of the circular elements, the advanced models, when the appropriate safety coefficients are applied, lead to successful values. These are equations that could already be contemplated or used to support formulations in technical design documents for structures.