Flexural cracking behavior of RC beams confined with PVC-CFRP in compression zone

Although regional confinement in compression zone is proven to improve flexural ductility of the beam members, its influence on flexural cracking behavior remains insufficiently understood. In this study, based on the four-point flexural tests of 16 reinforced concrete (RC) beams confined with PVC-CFRP in compression zone and 3 RC control beams, the flexural cracking behavior of the RC beams confined with PVC-CFRP in compression zone under various reinforced forms, including under-reinforced, balanced-reinforced and over-reinforced were evaluated, the design parameters such as the tensile rebar ratio, CFRP strip layers, rebar ratio and concrete strength of the confined zone were considered. The results indicated that, within the tested range, regional confinement in the compression zone had negligible influence on the cracking behavior of under-reinforced specimens, whereas its crack-control effect was more evident in balanced-reinforced and over-reinforced specimens. Increasing the tensile rebar ratio reduced both the mean crack spacing and maximum crack width. In contrast, increasing the CFRP strip layers, rebar ratio and concrete strength of the confined zone mainly reduced the maximum crack width, in particular, increasing the concrete strength of the confined zone from C30 to C50 reduced the maximum crack width by up to 29.23% under the same loading level. Lastly, the applicability of the standard equation for mean crack spacing and maximum crack width was assessed, and a modified approach was proposed for maximum crack width prediction by considering the confined unit in compression zone, which showed improved agreement with the test data.