Experimental Study On The Concrete Beams Strengthened With Segment Bonded And Prestressed CFRP Laminate

As a kind of new materials, CFRP has many good qualities, such as small density, strong ability, corrosion resistance, good durability, and so on.So it has more and more widely used in the reinforcement and restoration project for building and bridge structure. In recent years, more and more research on prestressed CFRP reinforcement technology are carried on, have being the hotspot in the field of reinforcement.The reinforcement effect of prestressed CFRP depends on two aspects, on the one hand, rely on the reliable anchorage at the end of the beam, on the other hand, rely on the good bonding interface between carbon fiber plate and the beams. In engineering practice, however, due to the bonding surface failed to clean up(such as carbide layer no clean, etc.), or because of a shortage of the durability of adhesive glue, lead to adhesive capacity degradation, and so on, this can cause the prestressed carbon fiber plate may be partial unbonded or all unbonded. In the case of all unbonded, engineers can completely accord to the unbonded prestressing system assessment for evaluation. But the partial unbonded situation may be much more complex, and there have no people to do this research.For this, through daubing glue to the local place of carbon fiber plate, we can form the partial unbonded prestressed carbon fiber plate reinforcement, with reliable anchorage measures, our team conduct the experiment to study the flexural performance of the concrete, geting the following conclusions:① Bonded in the pure bending zone and no bonded in the shear bending area, the final failure pattern of reinforcement is having the too widen crack, the insufficient flexural bearing capacity(concrete on the top has a tendency to crush).This phenomenon shows that at the moment of unbonded in smaller moment area(bonded in larger), beam’s ultimate destruction zone may completely change. The phenomenon also explains that because of no bond, the carbon fiber plate can not fully participate in the component bending, and the strengthening effect can reduced significantly.② Unbounded in he pure bending zone and bonded in the shear bending area, the final failure pattern of reinforcement is the concrete crushing on the top, the strain of the carbon fiber plate of unbonded area and the steel bar within the bonded beam are not synchronized, and the situation of the cracks is different with the beam all bonded, this show that the carbon fiber board with unbonded part cannot collaborative force with the original structure.③ The analysis of the data shows that the carbon fiber plate in unbonded area are not synchronized with the steel bar within the bonded reinforcement beam, and the development of cracks is different with the beam bonded, this show that the carbon fiber plate in unbonded part cannot coordinate together with the original structure,the mechanical behavior of the prestressed carbon fiber plate in unbonded area are similar to the unbonded prestressed system.The results of the above research further proved that the effective treatment to the interface can help improve the strengthen effect of the prestressed carbon fiber plate reinforcement, this have good practical value to engineering.