This research is carried out to investigate the effects of scale on bond strength of deformed bar using lap-splice and pull-out specimens with and without stirrup. The bar diameters are17.4 mm, 34.8 mm and 52.2 mm. This research also verifies the effect of rib shape on bond strength, using 2 kinds of rib shape. As a result, the effect of scale on both lap-splice and pull-out specimens with stirrup is smaller than those without it. Especially large scale-effect is observed in the pull-out specimens without stirrup and with thin cover concrete, where the bond strength is proportional to about-0.5 power of bar diameter. In the case of lap-splice specimens, the bond strength is proportional to about-0.2-0.3 power of bar diameter. Furthermore, a Larger confinement-effect due to stirrup is observed for pull-out specimens than lap-splice specimens, which results in the larger effect of rib shape on lap-splice specimens is larger than pull-out specimens.
