ABSTRACT
To understand the effects of the factors dening the axial strength of laterally con-ned concrete, we start by examining a sample result from a series of tests of columns under axial compression by Richart et al. (1929). The column measured 10 in. around by 40 in. long. It had no longitudinal reinforcement, but had spiral reinforcement (Figure 8.1a) or helical reinforcement* on the outer surface of the test column. The spiral reinforcement had a diameter of 0.19 in., and its spacing was 1 in. The cylinder strength of the concrete in the column was 2640 psi. The spiral reinforcement developed 61 ksi in tension at a strain of 0.005. Figure 8.1 shows the variation of the measured axial and radial strains in the concrete core with increase in axial stress.
