Experimental study with DIC technique on the bond failure of structural concrete under repeated reversed loading with different amplitude

The bond between deformed steel rebar and concrete plays a critical role against seismic action, thus it is important to capture the dynamic bond loss and establish the bond-slip model with cyclic loading. To explain the macroscale performance such as bond-slip relationship and establish the bond strength model, it is meaningful to capture the mesoscale and local behaviors between ribs and concrete. In this paper, pull-out specimens with rebar embedded in concrete and small windows excavated in the cover concrete are adopted with DIC technique to monitor the strain variation and crack development along the interfaces under static and reversed loading of different amplitude. From the test, it is found that DIC is an effective approach to obtain the localized characteristics including the normal and shear deformations. Through parametric study, the effects of concrete cover depth and the existence of stirrups on bond deterioration in terms of both global and local behaviors are studied. Interestingly, the global slip and local crack-width show synchronically increase under the pulling-out action, which demonstrates that the macroscale behaviors could be clarified from mesoscale measurement with the aid of DIC technique.