Experimental investigation of fatigue bond behavior between deformed steel bar and concrete

Abstract

Bond degradation induced by fatigue loading may affect the serviceability and even safety of reinforced concrete (RC) structures. To investigate fatigue bond behavior between rebar and concrete, three sets of eccentric pull-out tests were carried out, especially on specimens with a thinner concrete cover. Based on monotonic tests of nine specimens with different cover thicknesses, a bond stress-slip model was developed for specimens with splitting failure. According to the tested monotonic bond strength, repeated loadings with different amplitudes and cycles were applied to 15 specimens to fail. Failure mechanism of different fatigue bond failure modes was analyzed. Relative slip develops in three stages under repeated loading and it can be well predicted by a power function model. To investigate the effects of fatigue loading history, five specimens were subjected to a certain number of cycles of repeated loading before undergoing monotonic tests. Test results show that fatigue loading history has little influence on bond strength but leads to increased bond stiffness and peak slip. An empirical unified model for splitting failure was finally proposed to describe the bond stress-slip relationship of specimens under monotonic and repeated loading.