Crack based bond strength model of externally bonded steel plate and CFRP laminate to predict debonding failure of shear strengthened RC beams

Shear cracking can have significant effects on interfacial bond strength of externally bonded (EB) plates, and thus development of a bond strength model considering effects of cracking is vital to predict debonding failure of shear strengthened reinforced concrete (RC) beams. The main aim of this study was to develop bond strength models of EB steel plate and CFRP laminate, considering effects of cracks, to predict debonding failures of shear strengthened RC beams. In the experimental program, forty-eight RC prisms were fabricated and strengthened using steel plate and CFRP laminate; all prisms in this category were tested using a special indirect pull out test to incorporate cracks. To validate the models, four full-scale RC beams were shear strengthened using EB steel plate and CFRP laminate. Based on the results of cracked prisms, interfacial bond strength models of EB steel plate and CFRP laminate have been developed. The proposed models showed that the presence of cracks reduced the interfacial bond strengths of EB steel plate and CFRP laminate significantly, and the bond strength was also reduced because of increased length and width of EB steel plate and CFRP laminate. As compared to existing models, the proposed models showed lower interfacial bond strength of EB plates. The predicted debonding failure loads of steel plate and CFRP laminate shear strengthened RC beams using the proposed models were 3.4% and 4.7% differences when compared to experimental results, respectively. However, the models from existing research had shown significantly higher debonding failure loads as compared to those of experimental results.