Experimental Study On Flexural Behavior Of Reinforced Concrete Beams Strengthened With Steel Plate Enveloped By BFRP

Fiber cloth and steel plate are commonly used as flexural reinforcement materials for concrete beams.In this thesis,the strengths and weaknesses of two kinds of sheets were analysed,and a method of external flexural strengthening using fiber enveloped steel plate(FESP)as composite plate was proposed.Through the static load test of 7concrete beams,the feasibility of FESP flexural reinforcement was verified,the influence of various factors on the mechanical properties of specimens is discussed,and the characteristic load of FESP flexural reinforcement concrete beams is calculated and analyzed.The research content and main achievements of this thesis are as follows:(1)A new type of composite plate(FESP)formed by fiber cloth and steel plate with the aid of binder and its corresponding new method of strengthening is proposed.The steel plate can provide large stiffness and good deformability for the reinforced beam,and the steel plate wrapped with FRP can inhibit the corrosion of steel plate and improve the durability after strengthening.(2)The surface treatment of the pasting area of concrete beam was carried out by longitudinal slotting method,and the pasting technology of external pasting FESP strengthening method was explored and clarified.Because FESP itself has a certain stiffness,it is easy to cause the bond layer to be empty if only impregnated adhesive is used.It is recommended to use repair adhesive to fill the groove and plaster the adhesive surface at the same time,and then use impregnated adhesive to paste FESP.(3)A series of flexural reinforcement tests of concrete beams was completed,the results show that the ultimate bending moment of reinforced concrete beams is increased by 16.46%～41.21%.The failure mode and bearing capacity of reinforced concrete beams are related to the length and thickness of FESP.When thin FESP is adhered,with the lengthening of FESP,the location of peeling is transferred from the end to the middle,and the ultimate load and ductility are significantly improved.Although the middle peeling occurs in the specimen with long FESP,both ends of FESP are always well bonded,and the load can continue to increase until it approaches the theoretical load limit with concrete crushed.When the length of FESP is equal but the steel plate thickness is doubled,the end of FESP is detached earlier,which leads to the decline of the bearing capacity and ductility.(4)The formula of cracking load and yield load of reinforced concrete beam reinforced with FESP is derived,and the thickness of composite plate is discussed by using the existing calculation method of stripping load.Compared with the test results without bonding defects,the calculated values of the above characteristic loads are in good agreement.