Bond behavior between concrete and steel rebars for stressed elements

Earlier research efforts related to concrete-to-steel rebar bond behavior predominantly focused on common parameters such as concrete strength, rebar diameter, bonded length and concrete cover, disregarding the actual/real state of concrete that comprises tension cracked regions. This investigation aims to study the concrete-steel rebar bond behavior through bending stressed specimens, in order to evaluate the influence of concrete cracking coupled with other parameters to achieve a realistic simulation. Accordingly, beam-end specimen(s) have been modified to yield the possibility of conducting pull out testing under certain bending stress level. In this study, ten test specimens were prepared and tested to cover some parameters including concrete strength, rebar diameter, bonded length, concrete cover thickness and confining stirrups in conjunction with bending stress level. Test results proved remarkable influence for stress level on bond behavior whereas, unstressed specimens showed higher bond strength than partially and fully stressed specimens by 40 and 63%, respectively. New models are proposed to predict bond strength and describe bond stress-slip behavior for stressed members. The proposed models demonstate adequate agreement with the experimental results.