Estudo do comportamento estrutural da flexão em vigas protendidas projetadas de acordo com as normas da ABNT e ACI

Abstract

Prestressing consists in the use of pre-elongated steel that turns possible to reduce cracks, to have better use of concrete compressive strength, larger spans and slender structures due to the reduction or even the elimination of tensile stresses. The non-adherent prestressing concrete is being widely applied in Brazil due to its constructive advantages. This study analyzes different recommendations of ABNT (2014) and ACI (2019) standards on the analysis, design and verification of bending in prestressed beams. The different recommendations for service and ultimate limit states, considerations regarding deflections and stress losses are studied and discussed. Isostatic and continuous beams with design beams profiles are checked against both bending standards, making use of a commercial software widely used for prestressed designs, aiming to assess which standard is more conservative. In addition to the comparison between standards, the beams will be evaluated with a nonlinear physical and geometric analysis formulation. The standards have similar recommendations, being the most conservative Brazilian with regard to the Ultimate Limit State (ULS) ultimate strength and the American in the Serviceability Limit State (SLS). One of the main factors for the differences found is the recommended load combinations. The nonlinear analysis presented satisfactory results, showing that the standard recommendations for ULS designs present significant safety. It was also possible to analyze the influence of passive reinforcement on the ULS, results showed that the use of the minimum bonded reinforcement creates a quite increase in the beam last strength.