EXPERIMENTAL INVESTIGATION ON THE SHEAR BEHAVIOR OF RC COLUMNS STRENGTHENED WITH CFRP GRID REINFORCED HIGH DUCTILE CONCRETE

Reinforced concrete (RC) columns are vulnerable to shear failure under severe earthquake loading when the axial load ratio is high and when the stirrup ratio and span-depth ratio are low. To improve the shear performance of RC columns, CFRP grid reinforced high-ductile concrete (HDC) jacket was proposed to strengthen the RC columns. Six RC columns were designed. The effects of the strengthening methods, the layers of carbon meshes and axial load ratio were studied under low cyclic loading tests. The failure modes, ductility performance and energy dissipation capacity of the specimens were analyzed. The experimental results show that: the shear strength, ductility and energy dissipation were improved obviously, indicating that the CFRP grid reinforced HDC strengthening method was very effective; with the increase of the number of CFRP grid layers, the shear strength was increased slightly, but the ductility and deformation capacity were significantly improved; with the increase of the axial load ratio, the shear strength was increased slightly, but the displacement ductility and energy dissipation capacity of the specimens were decreased; the strengthening effect of increasing the number of CFRP grid layers on the columns with high axial load ratios was basically the same as that on the columns with low axial load ratios. Based on the truss-arch model, a method of predicting the shear strength of the strengthened columns was proposed. The calculated results agreed well with the test results.