超高強度鉄筋コンクリート柱の圧縮特性の寸法効果

Abstract

A series of uniaxial compression tests of reinforced ultra-high strength concrete (RC) columns were carried out to examine the size effect on their compressive behavior. Experimental factors include the section size of specimen (b×b, b=9.7,15,20 and 25cm), the type of bar arrangement (shape of hoops are : ([figure]), pitch (S=∞, b/4,b/6 and b/8) and yield strength of hoops (σy≒3000,5000 and 15000kgf/(cm)^2 level). The strength (Fc) of concrete was set to be about Fc=1000kgf/(cm)^2. Based on the test results, discussion is carried out mainly on the relation between the type and yield strength of hoops and the size effect on the compressive failure of the RC columns. Following statements can be drawn from the test results. 1) The compressive strength of large specimens with b=25.0cm is smaller than that of small specimens with b=9.7cm by about 25%, almost regardless of the shape, pitch, and yield strength of hoops. 2) Compressive toughness (area under stress-strain curve) gradually decreases with increasing size of specimen. It should be noted that the shapes of stress-strain curves in softening range are rather obtained from various size of specimens, i. e. size effect in the stress-strain curves is mainly due to the size effect in the peak stress point.