Experimental Research And Design Theory Of RC Beams Strengthened By Pre-Stressed FRP Sheet

Along with technical and economical development, the demands of structure reinforcement are improved year by year in all countries. To repair and strengthen existent structure has been becoming a branch domain of civil engineering day by day. Under the condition of no broken structure function, to search for high effective, simple and convenient, economic and applied technique of structure reinforcement become the supreme purpose of design and research engineer. Within the all methods of structure reinforcement, pre-stressed technique can adjust the internal force of original structure by active mode. It can also reduce former material stress, resume structure displacements, and relax the phenomenon of stress lag in new reinforcing material, bring the new material into play high effectively. So, while to choose the project of structure reinforcement, the pre-stressed method becomes the first one.FRP sheet has the great application foreground in engineering structure reinforcement by its high strength and good performance. But just ordinary to glue FRP to reinforce anti-curved strength of beam with no pre-stressed has the obvious shortcoming. The new material of reinforcement FRP does not participate to pull gradually until the reinforced structure is loaded again. The efficiency of reinforcement is too low. This method is not able to adjust the internal force of structure; it also improves the performance of structure using state very little. Up to now, the research of pre-stressed FRP technology is relatively less in the world, and the application of actual engineering is in minimum amount, reason that the key techniques of FRP anchorage and tension have not been solved better. The states of pre-stressed FRP technology affect its research and application greatly. In this article, a set of unique technique of FRP anchorage and tension device has been put forward, the experiments of beams and plates reinforced with this technique have verified its feasibility, and the every capability of this pre-stressed FRP technology has been studied roundly, and the theory of design and analysis has been constituted. It was applied in practice successfully at last. Now main contents introduction as follows:1. Research and development of the anchorage and tension facility in pre-stressed FRPAccording to the thought of to anchor FRP first and tension it transversely secondly, the new devices of pre-stressed FRP anchorage and tension clamp have been designed and developed. The experiments indicate that the devices could be able to anchor and tension FRP simply, conveniently and reliably. The CFRP sheet has been tensioned over 1600MPa of stress. Then combined this kind of new device of pre-stressed FRP, the thought of FRP stress control with the numerical value of torsion spanner has been bring forward. The function has been found that is the relationship of FRP stress, the position of tension device and the numerical value of torsion spanner. The sample table was designed and drawn that can be used in locale site. So this method of FRP stress control in locale site is very simple and convenient.2. Experiments and studies of FRP mechanical behaviourThe device that is able to test mechanical behaviour of FRP was designed. The mechanical parameters of used CFRP and GFRP have been tested. With the unique equipment, some of the experiments of FRP stress relaxation are put over. The reliability and feasibility are verified by the experiments. The results of FRP stress relaxation indicate that the phenomenon of stress relaxation occur visibly in GFRP, but not obviously in CFRP.3. Experimental study of RC beams strengthened with pre-stressed CFRPThe experiments on bending strengthen of 8 RC beams strengthened with pre-stressed CFRP have been put over, with the max pre-tension stress of 1070 MPa. The reliability of anchorage and tension clamp is verified by the experiments. The experiment results indicate that this strengthening technique of RC beam with pre-stressed CFRP can make the strengthened beam to bend reversely, delay cracking, increase beam rigidity.