Investigation On Flexural Performance Of RC Beams Using A Partially Bonded CFRP Plate Anchored With Inclined U-Jackets

Fiber Reinforced Polymer/Plastic（FRP）has the advantages of light weight,high strength,corrosion resistance and good designability.In recent years,it has been widely used in the reinforcement of existing reinforced concrete structures.It has become the mainstream of composite reinforcement technology to increase the ultimate flexural bearing capacity by attaching FRP materials to the bottom of reinforced concrete beams.The bearing capacity of the cross-section of FRP-strengthened reinforced concrete beams is usually controlled by Intermediate crack induced debonding and Concrete cover debonding.When these two debonding types occur,the maximum tensile strain of FRP plate is only20%-40% of its ultimate tensile strain,which limits the high-strength properties of FRP materials.Various anchoring measures have emerged at the historic moment,among which the inclined FRP U-jackets at the end is the most convenient and effective one.On the other hand,there is a significant difference between the externally attached FRP and the steel bars embedded in the concrete,concretely speaking,the bond strength will no longer increase significantly after the bond length exceeds the effective bond length.Based on this,this research proposes a technology for strengthening concrete beams with inclined FRP Ujackets at the ends with locally bonded CFRP plates.This technology significantly saves the strength of the FRP pasting surface treatment and the amount of paste glue through local pasting,thereby saving reinforcement costs;On the other hand,the adoption of the inclined FRP U-jackets ensures the full utilization of the tensile strength of the FRP bottom plate.In this paper,a series of full-size reinforced beams（width: 200mm;height: 450mm;span: 4000mm）are tested to verify the effectiveness of the proposed new reinforcement technology.The main test variables are the width of the FRP bottom plate（the same amount of FRP）,the bonded length and the bonded method of the inclined FRP U-jackets.The test results show that:（1）The use of inclined FRP U-jackets significantly improves the utilization rate of the tensile strength of the FRP plate.The maximum tensile strain of the FRP plate when failure occurs is 12316 με,which is about 93% of its ultimate tensile strain;（2）Partially bonded FRP plate can reduce the surface treatment area up to 80% in this paper,at the same time,the ultimate bearing capacity of the reinforced beam was only reduced by7.1%.（3）When the amount of CFRP plate is the same or close,the bonding width of FRP plate has little effect on the ultimate bearing capacity of the reinforced beam.At the same time,this paper uses the large-scale general finite element software ABAQUS to carry out the finite element simulation work on the actual situation of the test beam reinforcement.By extracting the relevant data,the load-displacement curve,the bearing capacity and the mid-span deflection of each stage,and the strain distribution of the carbon fiber board are carried out.The comparative analysis finally proved the validity of the established finite element model.