Compressive behavior of concrete confined by CFRP and transverse spiral reinforcement. Part A: experimental study

This study presents the results of an experimental investigation of 18 short concrete columns confined by carbon fiber-reinforced polymer (CFRP) and transverse spiral reinforcement (TSR) under uniaxial compression. Longitudinal rebars are not installed in the specimens in order to eliminate their confinement effect to concrete which affects the analysis of 3-D compression of concrete. The paper only consider for FRP and spiral reinforcement confinement in transverse direction. Two key experimental parameters were investigated: the thickness of the CFRP tube (0.167, 0.334, and 0.501 mm) and the spacing of the TSR (25 and 50 mm). The failure mode, axial and transverse stress-strain relationship, confinement effectiveness, Poisson's ratio and dilatation performance of the specimens were discussed. Test results show that the ultimate strength of concrete has a linear proportional enhancement with an increase in the FRP layer in each TSR category and a decrease in the TSR spacing in each FRP layer category. The ultimate load carrying capacity of the confined concrete depends on the confinement pressure during failure in terms of ultimate strength and axial strain.