Cyclic behavior of strong beam–weak column joints strengthened with different configurations of CFRP sheets

Abstract

The current paper reports the results of experiments on deficient exterior reinforced concrete (RC) strong beam-weak column connections strengthened with carbon fiber-reinforced polymer (CFRP) sheets. Five RC-joint specimens with half-scale size were manufactured and tested subjected to constant axial and reversed cyclic quasi-static loads. These joints consisted of one control and four specimens retrofitted with FRP sheets used in different strengthening configuration. The study is mainly directed to the examination of the different anchoring methods for longitudinal FRPs at beam-column intersection including L-shaped anchorage or CFRP anchor fans as a modern anchorage technique. Furthermore, the efficiency of transverse CFRP sheets in the form of innovative corner strip-batten technique to improve the seismic performance of the weak column was compared with longitudinal sheets. The externally bonded reinforcement on grooves (EBROG) method was also used in all strengthening schemes to eliminate surface debonding of CFRP. Test results revealed that although all the retrofitting schemes used led to significant improvements of up to 80% in strength capacity, longitudinal FRP sheets applied through the EBROG method and anchored with CFRP fans were more effective in inducing a completely ductile behavior in the joints, while the plastic hinge was also relocated into the beam.

Experimental investigation on the compressive behaviour of FRP-confined rectangular concrete columns

“…The strengthening of concrete structures is the field of construction where composite materials made of FRPs (fibrereinforced polymers) are being introduced most quickly and with the greatest success [1,2], mainly due to their corrosion resistance, good mechanical properties and lightness that translates into ease and savings in the execution of works. Typical FRP applications include flexural strengthening [3], shear strengthening [4] or strengthening of beam-column joints suffering from both flexural and shear deficiencies [5].…”

An Improved Anchorage System for L-Shaped FRP Composites to Enhance the Seismic Response of Beam-Column Joints in a Low-Strength Substandard Reinforced Concrete (RC) Frame

“…The test concluded that the EBROG technique combined with the FRP anchors has successfully eradicated the debonding failure of the FRP composites and enhanced the seismic capacity of the BCJ. A similar study was conducted by Ilia et al [47] using the EBROG technique in combination with FRP anchors in the X-shaped layout to strengthen the deficient BCJ. It was concluded that the EBROG technique along with other combinations successfully eliminated the debonding of the FRP composites and improved the strength characteristics of the weak column-strong beam joints.…”

“…To assess the effectiveness of L-shaped CFRP sheets (LCS), only the BCJ of the ground floor slab was strengthened with LCS. To avoid debonding of the FRP composites, which is most likely to occur at the beam-column interface [24,47], a narrow opening in the slab adjacent to the beam along with complete wrapping around the L-shaped FRP sheets were proposed. The ACI 440.2R also suggests the superior performance of a complete wrapping around the perimeter of the strengthened section [51].…”

Experimental and numerical study on reinforced concrete beam-column joints with diagonal bars: Effects of bonding condition and diameter

“…Moreover, retrofitting of non-seismically designed BCJs faces challenges of debonding of the external layer, which requires special treatment such as grooving technique [6][7][8][9]. Consequently, proper detailing is required for BCJs to ensure their satisfactory performance.…”