Effect of Pitch and Shape of Hoop on Size Effect of Stress-Strain Curve of Confined Concrete and Confined Microconcrete

In the present study, the effects of specimen size on stress-strain behavior of confined concrete and confined microconcrete prism are examined. Experimental factors include the section size of specimen (bxb, b=9.7,15,20 and 25cm), the pitch of hoops (proportional pitch and fixed pitch), and the type of hoops (rectangular hoop and rectangular hoop with cross type subtie). The maximum sizes of aggregate are 15mm for normal concrete, and 12,9 and 6mm for microconcrete. Following statements can be drawn from the test results. 1) For the same lateral reinforcement ratio, size effect on the strength of confined concrete with fixed pitch of hoop (S=1.6cm, rectangular hoop) is smaller than those of large specimen with proportional pitch of hoop (S=b/6,S=1.6cm for b=9.7cm), but the size effect on the stress-strain behavior is still rather remarkable. 2) The Size effect of stress-strain curves of confined microconcrete are observed, as well as that of normal concrete