DIRECT OBSERVATION OF BOND FAILURE OF FATIGUE PULL- OUT TEST WITH LIQUID WATER BY USING DIC

摘要

A part of reinforced concrete structures are always subjected to dynamic repeated loading and simultaneously subjected to liquid water from an external source such as rains. These structures, especially the old ones, have numerous surface cracks that allow water to penetrate concrete and reach steel-concrete interface and subsequently affect the bond between concrete and steel bars. Against this issue, a fatigue pull-out test was carried out with supplying of water to investigate experimentally the bond behavior between the concrete and a deformed bar by using digital image correlation technique (DIC).A fatigue pull-out test was applied to a deformed steel bar which was embedded in a concrete specimen. The specimen had a trapezoidal “window,” which allows full continues observation and measurements of concrete or cement paste displacements and subsequently strains by recording high-resolution digital video which was later analyzed by DIC software. The experiment focuses on the failure mechanism of the deformed bar from the concrete and the mechanism of the sludge's formation in the vicinity of the deformed bar. The results show that the actual deformations of concrete in case of fatigue test were captured well in both positive and negative direction of loading by using the DIC technique and they matched the past results. Also, the experimental results show that the pull-out failure of the deformed bar occurred due to the failure inside the concrete, not through the interface between the concrete and the deformed bar.