纤维网格高延性混凝土加固RC柱抗剪性能试验研究

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

箍筋配置不当、剪跨比较小和轴压比较大的钢筋混凝土(RC)框架柱在地震作用下通常发生脆性剪切破坏。为提高框架柱的抗剪性能,提出采用碳纤维(CFRP)网格和高延性混凝土(HDC)复合加固RC柱。设计了6个RC柱试件,通过低周反复荷载试验,研究加固方式、纤维网格层数和轴压比对加固柱破坏形态、受剪承载力、延性及耗能能力的影响。结果表明:采用HDC和CFRP网格复合加固,可显著提高柱的抗剪承载力,明显改善其延性、变形性能和耗能能力;提高加固层的网格层数,对抗剪承载力影响较小,但加固柱的延性和变形能力得到较大改善;轴压比增大,复合柱的抗剪承载力稍有提高,但试件的延性、变形能力和耗能能力均降低;增加网格层数对高轴压比加固柱的增强效果和对低轴压比柱基本一致。最后基于桁架-拱模型,提出加固柱的抗剪承载力计算公式,计算结果与试验值吻合较好。

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.