Shear strengthening of RC 3D exterior beam-column joints with CFRP sheets an experimental and numerical study

The present article presents the numerical and experimental investigations carried out on CFRP shear strengthening of full-scale RC 3D exterior beam-column joints lacking transverse rebars at their joint core and subjected to a combination of gravity and reversed lateral loads. For this purpose, one non-strengthened beam-column joint used as control and two strengthened with given patterns of single-layer and three-layer CFRP sheets were prepared. In the next step, cyclic load–displacement, failure mode, ductility, energy dissipation, energy absorption, and secant stiffness curves were derived for all the specimens and compared. The experimental specimens were then modeled in ABAQUS using the finite-element method and subjected to non-linear analysis; the analytical results thus obtained were finally verified against the experimental ones. In another phase of the study, changes were made in such parameters as beam longitudinal tensile reinforcement ratio, concrete specific compressive strength, and compressive axial force applied to the column to create eight simulated numerical specimens, which were then subjected to non-linear analysis and compared. The results indicate that the strengthened specimens not only prevented shear diagonal failure at the rear of the column-transverse beam joint but also increased lateral load capacity by 11 to 15%, energy absorption by 10 to 20%, and energy dissipation by 2.2 times when compared with the same parameters of the control. Moreover, it was observed that increasing concrete specific compressive strength from 12 to 30 MPa led to an average increase of 31% in lateral load capacity and one of 46% in absorbed energy, while a twofold increase in applied axial force led to an average reduction of 11% in lateral load capacity.