피복두께에 따른 초고강도 콘크리트에 매립된 철근의 부착특성

Abstract

An experimental study was conducted to evaluate the bond characteristics of reinforcing bars embedded in ultra high-strength concrete. The Major variables are bar diameter(19㎜, 22㎜, 25㎜) and concrete cover(30㎜, 40㎜, 50㎜). The concrete compressive strength was kept equal strength(150㎫) at each specimen and confining of bar space effect were not taken into account. Nine specimens subjected to uniaxial tension were tested under hypothesis uniform bond stress distribution along the reinforcing bar embedded in concrete. The test results obtained show that the bond strength increases in proportion to compressive strength. It shows that the produced steps of the critical slips on each variable are not constant. And as the bar diameter was smaller and smaller, maximum bond strength was bigger and bigger. Therefore the concrete cover has affected to the bond strength. The Bond strength of specimens with 40㎜ concrete cover has a higher strength than 30㎜. Furthermore, when the ratio of concrete cover(C/db) is below the 2.0, splitting failure should not be disregarded. After comparing with ACI, Zsutty and test results, Zsutty's theory is more appropriate to the experiment result by 1.29 times of the result.