Compression Tests on Hoop-Reinforced Concrete

Forty-eight concrete prisms of square section were studied under monotonically increased axial compression up to maximum load. The two variables in the study concerned the provision of transverse reinforcement in the form of closed square hoops. One variable was the spacing of hoops and the other was the area of cross section of the hoop. Center-to-center spacings varied between 3/4 in. and 6 in., and three areas of hoop cross section were considered. Results clearly showed that the increase in strength, over that for plain concrete, was proportional to the cross-section area of the hoop and to the reciprocal of the hoop spacing. The axial contraction at the maximum load appeared to be similarly related to those two parameters. A semi-empirical equation for the strength of concrete confined by rectangular hoops proposed by Blume, Newmark and Corning was shown to predict the strength of the speicmens with satisfactory accuracy.