Test of seismic performance of earthquake damaged reinforced concrete columns strengthened with sprayed FRP

Based on the tensile strength tests of 12 groups of 72 pieces of sprayed fiber reinforced polymer (FRP) specimens, the effects of factors such as fiber type, resin matrix material, fibers volume fraction, hybrid ratio of fibers and fiber length etc. on the properties such as tensile strength, elastic modulus and elongation at break etc. of sprayed FRP were investigated. The seismic performance of earthquake damaged reinforced concrete (RC) columns specimens strengthened with sprayed basalt fiber reinforced polymer (BFRP) and hybrid basalt-carbon fiber reinforced polymer (BF-CFRP) was investigated by the quasi-static test of 8 RC columns, and the influences of the thickness of sprayed FRP layer, hybrid ratio of fibers, pre-damage degree of columns and the axial compression ratio of column etc. on the ultimate load capacity, lateral deformation resistance, degradation characteristics of stiffness and hysteresis properties of the strengthened specimens were analyzed. The test results show that the cooperative working performance of glass fiber and vinylester matrix is the best, and basalt fiber can be used as a favorable succedaneum of glass fiber because of its excellent performance of high durability, good ductility and good cooperative working performance with vinylester matrix; hybrid basalt fibers with small amount of carbon fibers used as reinforcement for resin matrix can effectively increase the tensile strength and deformation performance of sprayed FRP; earthquake damaged RC column can almost be rehabilitated to its designed ultimate load capacity before the earthquake damage by strengthening with sprayed FRP, and both the ductility and the ability of energy dissipation can be effectively enhanced. This strengthening technique can fast strengthen the earthquake damaged RC column in seismic area and effectively hinder the collapse of whole structures exposed to the aftershock and other heavy damages.