Experimental Research On The Flexural Performance Of The RC Beam Strengthened The Negative Capacity With CFRP Sheets

As a new structural engineering material, continuous carbon fiber sheet has many advantages such as excellent mechanical strength and deformation property, convenience in use, low weight, non-dimensional increase, and immunity to corrosion. The CFRP-strengthening technique has attracted many researchers and engineers in the world. CFRP is one of the high-tech materials which is the earliest applied in the civil engineering, the most well-rounded in the technique and the largest in the amount, compared with other FRP material.At present, most of the studies carried out all over the world were mainly about the rehabilitation in the positive moment area , but few researches focused on the rehabilitation in the negative moment area . The difficulty of the rehabilitation in the negative moment area is how to anchor FRP to the surface of the member firmly. In this study ,two kinds of anchorage have been considered which are outer anchorage and inner anchorage . The ultimate bearing capacity ,the deflection and ductility of the beams are investigated to decide which one is more efficient.Although there are a great amount of experimental studies on flexural performance of RC beams strengthened with FRP, most of the test members are strengthened under initial state without crack , there is a great difference with the actual structural members. Therefore it has a practical significance to study the flexural performance of RC members strengthened with FRP which simulate the practical state .Through the experimental and theoretical analysis, the conclusion can be summarized as follows.1) Beams strengthened in the negative moment area can improve the ultimate capacity, which is the same as beams strengthened in the positive moment area.;2) It is proved that the outer anchorage is more efficient than the inner anchorage3) The initial load hardly influence the flexural bearing capacity of CFRP-Strengthened RC beams;4) The analytical results of ultimate capacity are not consistent with the experimental results very well, which might be contributed to the fact that concrete in the anchorage area cracked which lead to decrease in stiffness,5) The deflection formula deduced by the hypothesis agrees with the test results before crack ,while it is not consistent with the test results of ultimate deflection verywell.