Title: Flexural Strengthening of Reinforced Concrete Beam- Column Joints Using Innovative Anchorage System

Author(s): Davood Mostofinejad and Alireza Akhlaghi

Publication: Structural Journal

Volume: 114

Issue: 6

Appears on pages(s): 1603-1614

Keywords: anchor fan; beam-column joints; debonding; EBROG; fiberreinforced polymer composites; flexure; grooving method; reinforced concrete; seismic rehabilitation; strength

DOI: 10.14359/51700953

Date: 11/1/2017

Abstract:
Application of fiber-reinforced polymer (FRP) composites to enhance the flexural strength of members in the expected plastic hinge regions of ductile reinforced concrete (RC) moment frames for resisting seismic loads are stipulated in the current construction codes and guidelines. The main issues of concern in these documents include provisions for appropriate anchorage details for FRP composites at the beam-column interface, debonding of FRP composites off the concrete substrate, and the effect of cyclic load reversal on FRP reinforcement. The present experimental study was conducted to gain insight into the effectiveness of an innovative FRP anchor fan at the beam-column joint interface flexurally strengthened with carbon FRP (CFRP) sheets. To avoid any likely debonding of FRP composites off the concrete substrate, surface preparation of the test specimens was performed according to a recently developed grooving method (GM) in the form of externally bonded reinforcement on grooves (EBROG). For the purposes of this study, seven half-scale RC beam-column subassemblies, including a control specimen and six rehabilitated ones, were tested under constant axial and reversal cyclic lateral loadings. The primary test variables were the FRP sheet length along the beam and fiber volume in the CFRP anchor fan. The results indicated that the adopted rehabilitation strategy enhanced the lateral strength of RC joints up to 80% compared to the control one. It was also found that deformation-controlled classification action could be justified for strengthened specimens under specific circumstances.