INTERNAL FORCE ANALYSIS AND EXPERIMENTAL INVESTIGATIONS OF WIDE-GAP CONCRETE BEAMS STRENGTHENED WITH NEARSURFACE MOUNTED CARBON FIBER REINFORCED PLASTIC BARS

The internal force analysis was made on three media of the carbon fiber reinforced plastic (CFRP) bar, adhesive and concrete and two interfaces including the CFRP to adhesive and concrete to adhesive interfaces of wide-gap beams strengthened with near-surface mounted carbon fiber reinforced plastic bars. The findings show that the shear stress is the main part of the stress in the CFRP bar-adhesive-concrete interfaces. It is more convenient to obtain the interface strength by destruction tests of wide-gap concrete beams strengthened with near-surface mounted (NSM) CFRP bars. A CFRP bar under forces is equivalent to a cylinder that bears shear stress and normal stress on the surface. The shear stress was provided by the bonding force, and the effects of normal stress can be ignored. The average shear stress on the surface of a CFRP bar can be obtained by strain gages in the wide gap. The analysis results are in good agreement with the experimental results. The distribution of cross-sectional normal stress of the carbon fiber reinforced plastic bar is non-uniform and exhibits a power distribution along the length, which leads to certain differences about the deformation between the center and the edge of the cross section of the CFRP bar. The adhesive cohesive body after solidification inside the groove is a column section circle that can be approximately assumed as a thick wall cylinder. The glue cohesion in the tangential and radial stress has almost no effect on the shear deformation of the adhesive cohesive body. Interfacial debonding damage occurred in the concrete near the interface. The concrete strength will significantly affect the performance and the peel bond strength.