Analysis of the bond stress when using GFRP bars

Abstract

For most of the structural solutions, the construction industry in Brazil is based on the use of conventional reinforced concrete elements composed of concrete and steel bars. However, problems related to this traditional structural system, such as the corrosion of metallic bars exposed to aggressiveness environments, motivate the study of new materials to be used as a replacement of conventional bars. In this context, FRP (Fiber Reinforced Polymers) bars can be viable due to their good mechanical properties and resistance to aggressive environmental agents. Thus, the main objective of this paper was the evaluation of the bond stress of GFRP bars using pullout tests. Thus, twenty specimens were analyzed with two concrete compressive strengths of 30 MPa and 60 MPa and two different GFRP bar diameters of 9.5 and 16.0 mm. According to the test results, it was verified a high variability of the adhesion between the GFRP bar and the concrete. Concerning the statistical analysis of pullout tests performed and considering the methodology proposed to analyze the quality control, the variation coefficient varied from 13.71% to 20.17%, classifying the pullout tests performed as medium or poor. These results demonstrate that the response of the GFRP bars obtained in the pullout tests was not reliable, demonstrating the need for new research to obtain adhesion coefficients and anchoring lengths for use in structural designs with such materials.