Influence of Carbon Fiber-Reinforced Ropes Applied as External Diagonal Reinforcement on the Shear Deformation of RC Joints

Abstract

The use of the innovative material of Carbon Fiber-Reinforced (C-FRP) ropes as external near surface mounted reinforcement for the strengthening of reinforced concrete beam-column joints is studied. The ropes are diagonally applied forming external X-type reinforcements on both sides of the joint body. The efficiency of the technique is mainly based on the assumption that the confinement of the joint body due to the applied X-shaped ropes and the contribution of the ropes as shear reinforcement are efficient enough to reduce the shear deformations observed in the joint core during the seismic excitation. Thereof the experimental measurements of the shear deformations of nine full scale beam-column joints tested in cyclic deformations are elaborated and presented herein. The specimens are sorted in two groups. Specimens of group A have been designed in the way that damage is mainly expected in the beam. On the other hand, in order to investigate the efficacy of the use of the ropes for substandard joints the group B specimens have been designed in the way that cracks and some damages are expected to develop in the joint body. Systematic and extended comparative presentations for specimens with and without ropes proved in all the examined cases that the externally mounted C-FRP ropes kept the joint body intact and substantially reduced the shear deformations especially in high drifts. Moreover, the influence of the externally mounted X-shaped C-FRP ropes on the seismic behaviour of these specimens is also examined in terms of the developing principal tensile stresses inside the joint body. From the comparisons of the principal stresses developing in specimens with and without X-form C-FRP ropes it became quite obvious that the ropes kept the joint body intact and allowed the development of higher values of principal stresses comparing with the stresses developing in specimens without ropes.

Seismic Tests of Full Scale Reinforced Concrete T Joints with Light External Continuous Composite Rope Strengthening—Joint Deterioration and Failure Assessment

“…The second step is the application of a two-component epoxy resin in the notches as an adhesive substance between the ropes and the concrete. Instead of cutting the rope in two different layers (see [ 35 , 37 , 38 , 46 , 47 ]), here the continuous flexible rope is cut for the total length of the two layers and for the self-anchorage length and is resin-impregnated. The anchorage of the rope started at the point where the two diagonals intersect and was anchored after two laps and at the corresponding intersection point of the opposite face of the joint.…”

“…Full scale RC beam column joints subjected to cyclic loading and comparing different FRP rehabilitation methods, such as CFRP sheets and CFRP ropes placed in an X shape in the joint region alone, or in combination with beam or/and column retrofit, have been investigated [ 37 , 38 ]. The external CFRP rope technique has revealed in all cases the versatility and suitability for demanding retrofits of RC joints, being embedded inside grooves and being able to go through transverse RC members if needed.…”

Efficacy and Damage Diagnosis of Reinforced Concrete Columns and Joints Strengthened with FRP Ropes Using Piezoelectric Transducers

“…External corners of the notch lines had to be rounded to a radius of at least 20 mm, based on the manufacturer’s recommendations [ 48 , 49 ]. The existing conventional steel reinforcing bars and stirrups had to be protected from unintentional damage during notch formation and further attention was essential to ensure and secure each C-FRP rope anchorage [ 51 , 52 ].…”

Experimental Verification of the New Models Applied to Glass Fibre Reinforced Concrete (Gfrc) Confined With Glass Fibre Reinforced Polymer (Gfrp) Composites

“…It also has properties that prevent shrinkage, breaking, freezing, and corrosion. Steel fibres [7][8][9], carbon fibres [10][11], polypropylene fibres [12][13], basalt fibres [14][15], glass fibres, [16][17] and vegetal fibres [18][19] are just some examples of the fibres that can be utilised. According to these research studies, the fibre type should be carefully chosen depending on the job's specifications.…”