Using grooving and corner strip-batten techniques for seismic strengthening of square reinforced concrete columns with fiber-reinforced polymer composites

This study represents the results of an empirical program investigating the behavior of square reinforced concrete (RC) columns retrofitted using longitudinal carbon fiber-reinforced polymer (CFRP) composites under simulated seismic loading. The main challenges to tackle are the premature buckling and the debonding of the longitudinal FRP composites on the tension and compression sides of the columns, respectively. To postpone both, the two versions of the grooving methods (GM), that is, the externally bonded reinforcement on grooves (EBROG) and the externally bonded reinforcement in grooves (EBRIG), were employed and the results were compared with those obtained under the traditional externally bonded reinforcement (EBR) procedure. Another aspect of the study involves investigating the influence of the recently developed corner strip-batten (CSB) method on confining column specimens. For these purposes, seven half-scale RC columns strengthened using FRP sheets were subjected to reversal cyclic loading. Experimental results exhibited that using the EBRIG and EBROG methods simultaneously with CSB technique could prevent altogether the debonding and buckling of longitudinal CFRP sheets. It was also found that the application of FRP strips utilizing the GM and CSB methods could produce an important increment in the performance of the RC columns in different terms such as ductility and lateral strength.