Strengthening of defected beam–column joints using CFRP

Abstract

This paper presents an experimental study for the structural performance of reinforced concrete (RC) exterior beam–column joints rehabilitated using carbon-fiber-reinforced polymer (CFRP). The present experimental program consists of testing 10 half-scale specimens divided into three groups covering three possible defects in addition to an adequately detailed control specimen. The considered defects include the absence of the transverse reinforcement within the joint core, insufficient bond length for the beam main reinforcement and inadequate spliced implanted column on the joint. Three different strengthening schemes were used to rehabilitate the defected beam–column joints including externally bonded CFRP strips and sheets in addition to near surface mounted (NSM) CFRP strips. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and the developed ultimate strain in the reinforcing steel and CFRP were considered and compared for each group for the control and the CFRP-strengthened specimens. The test results showed that the proposed CFRP strengthening configurations represented the best choice for strengthening the first two defects from the viewpoint of the studied failure criteria. On the other hand, the results of the third group showed that strengthening the joint using NSM strip technique enabled the specimen to outperform the structural performance of the control specimen while strengthening the joints using externally bonded CFRP strips and sheets failed to restore the strengthened joints capacity.

Determination of Mechanical Properties of Methyl Methacrylate Adhesive (MMA)

“…shear connections and these zones are the failure initiation areas [9]. Common failures of adhesive layers due to the stress concentrations in joints of strengthened RC and masonry structures showed the need for research on the influence of adhesive stiffness on the load-bearing capacity of the strengthened elements [1,10].…”

Seismic Performance of Exterior RC Beam–Column Joints Retrofitted using Various Retrofit Solutions

“…It is noted that in this study only one specimen strengthened with CFRPs was tested. In fact, many other strengthening layouts of FRPs, in particular, at the corners between columns and beams were investigated and showed good retrofit effect (Del Vecchio et al 2014;Mahmoud et al 2014). Figure 5 shows the details of specimen J-H, which was strengthened with haunch elements made by steel plates (SS400) having a thickness of 16 mm and specified yield strength of 400 MPa.…”

A review of FRP strengthened concrete structures under extreme loading

“…It makes little difference for the initial stiffness of the joint but leads to a more gradual stiffness degradation after the appearance of the first crack in the joint (Mahmoud et al 2014, Del Vecchio et al 2015, Hadi and Tran 2015. The application of an appropriate anchorage system can delay or prevent the premature FRP debonding failure and this significantly improves the effectiveness of FRP strengthening Chua 2009, Sasmal et al 2014).…”