Proposta para cálculo da tensão de cisalhamento em vigas de concreto armado com estribos

Abstract

The present work discusses, through experimental and statistical analyzes, to estimate and evaluate behavior of reinforced concrete beams with stirrups. First, the research presents the main models of shear stress in beams and NBR 6118 (2014) and ACI 318 (2014) that adopt the Ritter-Mörsch lattice as a basis for design and evaluation of the ultimate stresses. However, restrict the compressive strength between 50 MPa and 69 MPa and the steel flow stress between 500 and 420 MPa and become conservative because they exclude several preponderant parameters from the estimation of the ultimate loads in beams, such as size effect, longitudinal reinforcement rate, mode load and aggregate gearing, causing inaccuracy in the verification of parts in their ultimate limit state. Based on an extensive literature, a database of beams that broke through diagonal traction shear (19 authors and 170 pieces) was created. Estimating through univariate regressions, a method that inserts the parameters neglected in the norms. To consolidate the efficiency of this methodology, experimental and theoretical tensions values were compared with the objective of statistically evaluating the methodologies, relating the accuracy and accuracy of the results. For the second stage, an experimental program was proposed with the purpose of verifying and evaluating the estimates of ZSUTTY (1971), RUSSO et al. (2013), the norms and the proposed model. Composed of 07 beams duly sized to shear rupture, the tests followed from 01 reference beam that served as comparative model between 03 groups with 02 beams each being these groups varying the transverse reinforcement ratio, width and useful height. Consequently, the results had a conservative relationship, determined by the greater area mobilized between the interfaces of the shear plane, besides the model to better express the experimental estimates, relating accuracy, accuracy and appropriate safety