Experimental and numerical investigation on the seismic performance of reinforced concrete columns retrofitted with basalt FRP composites

초록

A basalt fiber composite-fiber-reinforced polymer (BFC-FRP) system is proposed to improve the cyclic deformation capacity of reinforced concrete (R/C) columns with shear- or flexure-controlled behavior. Seven columns with cross-sectional dimensions of 350 × 350 mm and a clear height of 1.5 m were fabricated: three shear-controlled speci mens and four flexure-controlled specimens. The specimens were subjected to reversed cyclic lateral loading under a constant axial load ratio of 0.10. The strengthening variables were the strengthening length (end-region or full-surface) and the arrangement of prefab ricated BF sheets and FRP panels. Nonlinear quasi-static cyclic finite element analyses based on the disturbed stress field model were also conducted. For the shear-controlled columns, full-surface BFC-FRP strengthening increased the ultimate strength by approxi mately 1.5 times and the displacement at ultimate strength by 2.0–2.6 times relative to the unstrengthened specimen. For the flexure-controlled columns, the ultimate displacement increased by approximately 1.4 times, the ductility ratio nearly doubled, and the energy dissipation capacity increased by approximately 2.4–2.5 times. The numerical results re produced the load–displacement and energy-dissipation responses with average deviations of approximately 10%. These results demonstrate that the proposed BFC-FRP system can improve the deformation and energy-dissipation capacities of shear- and flexure-controlled R/C columns within the tested conditions.