Externally bonding of the carbon fibre reinforced polymer (CFRP) plate is a common method for flexural strengthening of steel beams. However, interfacial stress concentration at the CFRP plate end can easily cause premature debonding failure of strengthened beams. Consequently, the high performance of the materials will not be fully used, and in particular, the safety of the strengthened beams may be threatened. To this end, a simple C-shaped plate gripper is proposed for the strengthening of H-shaped steel beams which can improve the anchorage at the CFRP plate end. In this paper, four-point bending tests are carried out for strengthened beams and the reliability of the gripper is verified. The strengthening effects of specimens under the ratios of the length of the CFRP plate extended to the shear span to the length of the shear span and anchorage types are examined. The latter includes three types. The first type is that the CFRP plate is only bonded on the tensile face of the beam, the second type is that the CFRP plate is attached to the tensile face of the beam and a gripper is added to the end of the CFRP plate, and the third type is the combination of the above two. They are named by pure bonding, end anchorage and hybrid strengthening, respectively. It is found that the case with an anchorage at the CFRP plate end is very different from the case with pure bonding. As long as the failure doesn't occur first in the outer section of the CFRP plate, the strain and the utilization ratio of the CFRP plate and the strengthening effect will decrease as the length of the CFRP plate. For the strengthened beam with a CFRP length of 600 mm, the ultimate strain of CFRP is 27.3% higher than that of the case with a CFRP length of 750 mm. It is worthy to note that all of the hybrid strengthened beams debonded suddenly and degraded to be beams with only end anchorage in the later loading stage. There is no obvious improvement for the hybrid strengthening with comparison to the beams with end anchorage only and the reason may be due to the poor surface treatment of the beam. It is necessary to improve the quality of surface treatment in the future. Even so, compared with the cases of pure bonding, the flexural behavior is largely improved for the cases with end anchorage for hybrid strengthened beams since the grippers can successfully impede the debonding of the CFRP plate. Meanwhile, the debonding process is real-time detected by the piezoresistance method and the results can basically agree with the observations.
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