This study developed 3D finite element (FE) models using calibrated cohesive zone material (CZM) law to predict debonding under single and mixed mode loading. The validity of the proposed approaches is first evaluated by modelling four beams documented in the literature and then applied to the case of CFRP-concrete joints extracted from 57-year-old bridge elements exposed to severe subzero environmental conditions. The comparison between the developed FE models and the experimental results demonstrates that the proposed models effectively capture the debonding process for both concrete members strengthened with pristine materials and concrete specimens tested from a deteriorated concrete bridge, with a maximum difference of 12% in the peak strain at failure. An increase in out-of-plane displacement from 1 mm to 2.5 mm , 5mm and 10 mm led to reduction in the maximum CFRP strain of approximately 3.1 %, 7.2 % and 11.6 % respectively, relative to pure shear loading.
Fowai et al. (Mon,) studied this question.