Compressive behavior of concrete columns wrapped with hemp fiber reinforced polymer – an experimental study -

Abstract

Concrete confinement with fiber reinforced polymers is a method widely used for strengthening and rehabilitation purposes. The replacement of synthetic fibers used as external confinement (carbon, glass, and aramid) with natural fibers is a step to achieve a sustainable construction. In this research, an experimental study reports the efficacy of the use hemp fibers reinforced polymers as external confinement for concrete columns. This study, aimed at understanding the effect of different parameters that may affect the structural behavior of concrete columns confined with fiber reinforced polymers. The test variables are: the number of the confining layers, the columns slenderness ratio, the addition of transverse steel reinforcement. Uniaxial compression test was done for a total number of 36 specimens, 30 of which are made of plain concrete and 6 with added transverse reinforcement. The axial stress-strain curves, structural ductility measured by fracture energy and failure modes were analyzed. Also, the applicability of existing stress and strain models available in the literature is checked. It was found that the number of confining layers has a significant effect on the confinement effectiveness and ductility. Small numbers of confining layers lead to insufficient confinement. The column slenderness ratio also significantly affects the axial compressive strength and ductility of the confined samples. As the slenderness ratio increases, the confinement effectiveness and ductility decrease. The conjunction of transverse steel reinforcement with external confinement lead to a better confinement effectiveness. This study gave promising results vis-à-vis the use of natural fibers as external confinement despite the tensile strength of hemp FRP that are significantly lower than that of synthetic FRP.