Flexural Retrofit of Support Regions of Reinforced Concrete Beams with Anchored FRP Ropes Using NSM and ETS Methods under Reversed Cyclic Loading

Abstract

Many studies have been carried out on enhancing the positive moment capacity of the midspan areas of RC beams with fiber-reinforced polymer (FRP) reinforcement under monotonic increasing loads. The present study focuses on retrofitting of beam support regions under reversed cyclic loading conditions representing seismic conditions. The tests were conducted on seven full-scale RC beam-column-slab subassemblages with a part of transverse beams perpendicular to the main beam. The specimens were divided into three series that represented different geometrical characteristics of beams and columns in frames such as wide beam–narrow column, narrow beam–wide column, and beam and column of equal widths. One reference specimen in each series was tested as is, while the remaining four specimens were tested after being retrofitted with near surface–mounted (NSM) carbon fiber–reinforced polymer (CFRP) ropes. Two different retrofitting details in terms of anchorage of CFRP ropes at the support region were applied [NSM and embedded through-section (ETS)] and their effectiveness is investigated. Furthermore, the validity of design code formulations currently available for near surface–mounting method is investigated and a modification is proposed to consider the effects of cyclic loading conditions. The results show that the retrofitted beams achieved an enhancement in the moment capacity but it could not be sustained at large deformations due to weakening of bond between concrete and adhesive under cyclic actions and localization of cracks at the maximum moment zone.