Experimental Study On The Flexural Behavior Of RC Damaged Beams Strengthened With Side-near-surface Mounted CFRP Plates

Near-surface mounted CFRP is a new reinforcement method.Near-surface mounted CFRP is a reinforcement method to advance on the surface of the components that need to reinforce the slot,and then put the CFRP strips into slots to improve the mechanical performance of the component.Compared with the surface stick method,near-surface mounted CFRP has the advantages of low dosage of materials,corrosion resistance,applicable to the uneven surface of the component,and more effective component force,suffers accident load is not easy to damage,etc.Considering that there are cracks on the concrete and walls and pipers on the bottom of the beam,there is no way to strengthen the beam on its bottom.So in this paper,Near-surface Mounted CFRP is used to strengthen 6 damaged test RC beams.According to the result and analysis of the experiment of these test beams,the mechanical performance of strengthened beams is studied.Here are the researches and conclusions:1.Experimental ResearchTo study the anchoring ability between the CFRP plate and concrete and the reinforcement effect of the Near-surface Mounted CFRP plate,3 parallel longitudinal grooves must be first notched and on the vertical direction of the longitudinal grooves,transverse grooves are also notched.And mount the CFRP plates as the anchoring components.On the WJ2-1(2,3)beams,the longitudinal grooves spacing is designed to be 50mm(75mm,100mm),and the transverse grooves spacing is designed to be 400 mm.And as for the WJ5-1(2,3)beams,the transverse grooves spacing is designed to be 200mm(400mm,600mm),and the longitudinal grooves spacing is designed to be 50 mm.From that,we can study the influence of longitudinal and transverse grooves spacing on the anchoring ability,the development and numbers of cracks,flexural stiffness,etc.Based on the experimental research,the calculation method of bending bearing capacity and mid-span deflection is derived.The study shows:(1)Until these test beams are damaged,the concrete cover is still in a good condition.The bonding between longitudinal and transverse mounted plates is very well.And the longitudinal CFRP plate has certain influence on the anchoring effect of the transverse plate.The longitudinal CFRP plate and the concrete form a whole.The section of the beam fits the plane cross-section assumption.(2)Because of the strength of longitudinal CFRP plates,the development and amount of cracks are well controlled and the flexural stiffness and bending bearing capacity are also improved.(3)With the increase of the longitudinal grooves spacing of the CFRP plate,the section of longitudinal plate moves up,the tension decreases.And that can lead to the decrease of bending bearing capacity and flexural stiffness,besides,the width of the main bending fracture increases.Considering the efficiency of the bond and strengthen between the CFRP plates and concrete,the longitudinal grooves spacing is advised to be 50 mm,and the transverse grooves spacing is advised to be 60 mm.2.Theoretical ResearchThe bonding between longitudinal and concrete is very well and they form a whole.The section of the beam fits the plane cross-section assumption.Without considering the damage of bonding,the calculation method of bending bearing capacity and mid-span deflection is derived.The formula can be used as reference because the calculated result of load-mid-span deflection and flexural capacity matches with the surveying data,...