PERFORMANCE ADVANCEMENT OF RC COLUMNS BY APPLYING BASALT FRP COMPOSITES WITH NSM AND CONFINEMENT SYSTEM

Basalt fiber reinforced polymer (BFRP) composites are regarded as promising structural strengthening material due to their environmental friendly and superior mechanical and chemical properties. In order to enhance the overall seismic performance of RC columns, a strengthening system is developed by applying BFRP composites with both near surface mounted (NSM) and confinement approaches. The variables taken into account consisted of the diameters and anchorage lengths of BFRP bars, as well as the confinement amounts of BFRP sheets. A total of eight column specimens including one control were tested subjected to simultaneous axial compression and cyclic bend. The structural performance such as load capacity, displacement, ductility, stiffness degradation, energy dissipation capacity, curvature and post-yield stiffness were investigated. The test results indicate that the combination of NSM and confinement techniques contributes to the comprehensive performance enhancement of RC columns, which lies in (1) constantly enlarging diameters of BFRP bars increases the yield and peak loads, the ultimate displacement, the initial and post-yield stiffness as well as the ductility, whereas it has no obvious influence on the yield displacement; (2) longer bonding length results in higher seismic performances although it makes no changes to the yield displacement, the post-yield stiffness, and the degradation of strength and stiffness as well; (3) the adoption of BFRP confinement significantly improves the ductility and the strength degradation performance; (4) the largest post-yield stiffness can be achieved by enlarging diameter to 12 mm, whereas the ductility and the strength degradation characteristics deteriorate due to the weakness of interfacial bonding between BFRP bars and concrete.