Axial compressive behavior of square concrete columns confined with CFRP strip ties using wet lay-up technique

Abstract

Pultruded fiber-reinforced polymer (FRP) bars used as confining reinforcement in concrete columns provide limited ductility and confinement efficiency due to the drastic reduction of strength at bend portions and premature bond slip failure at overlapping regions. In this study, complete close-type CFRP strip ties (C-S) with rectangular cross-section and fabricated using wet lay-up technique were proposed to overcome the shortcomings of pultruded FRP ties. Ten square concrete columns (300 × 300 × 900 mm), longitudinally reinforced with steel bars and confined with different types of ties such as steel, pultruded CFRP (C-P), and CFRP strip (C-S) ties, were tested to investigate their axial compressive behavior. Test results depicted that the columns confined with C-S ties exhibited improved confined concrete strength and ultimate axial strain in comparison with the columns confined with steel and C-P ties. Confined concrete strength and ultimate axial strain were increased up to 1.16 times and 3.5 times, respectively, by the replacement of C-P ties with the equal volumetric ratio of C-S ties.