Armadura de cisalhamento devido ao esforço cortante em seções retangulares: material didático para autoaprendizado

Abstract

This paper makes a bibliographic review of the calculation of shear reinforcement due to shear force according to the recommendations of ABNT NBR6118 (2014). Continuing the learning in the disciplines of Reinforced Concrete Structures, the study elaborates a table, with the help of Microsoft Excel® software presenting the calculation of cross-sectional reinforcement due to the shear force for calculation models I and II, according to the normative requirements. The user is allowed to follow the variation of the values of all parameters involving the calculation of cross reinforcement for a defined rectangular cross section and the concrete and steel materials, with the input of the shear force (Vsd). The computational simulations revealed that, for Calculation Model I, with the inclination of the compressed connecting rods at a constant angle of 45°, there is a linear variation of the results of the calculation of the reinforcement between the extreme limits (minimum shear reinforcement, corresponding to the minimum shear force and maximum shear reinfrcement for crush shear, VRd2). Also, for this calculation model, the minimum shear force value is fixed. However, for Calculation Model II, the study shows that there is no fixed value for minimum shear force, because the value of Vc (portion of the shear force resisted by concrete) is variable (dependent on the request level, Vsd). Graphs were plotted presenting this variation. In the same line of reasoning as was completed for Calculation Model I, we sought a way to calculate the shear reinforcement for Calculation Model II through a linear interpolation, and the work was successful in finding this answer. The linearization proposal helps to understand the results and the proposed simplification is compared with the values calculated with the fundamental expression of reinforcement calculation, without presenting differences. The results and graphs confirm the relevance of the proposed simplification. The spreadsheet produced can be used in Active Methodologies, such as Flipped Classroom for the teaching-learning process.