Research On Bending Performance Of RC Beams Strengthened With RPC Reinforcement Mesh Under Load

At present,reinforced concrete(RC)structure still plays a major role in the structural forms used.However,in the service process,due to the increase of the service life of materials,the structure will be damaged,aged,the use function will change and can not bear the new design load,resulting in the continuous reduction of the ultimate bearing capacity,stiffness and durability of the structure,and various engineering safety problems.RC beam is a common horizontal load-bearing member in concrete structure,and its failure mode is usually flexural failure.In order to solve the deficiency of bending resistance of existing RC beams,a reinforcement material using reactive powder concrete(RPC)reinforcement mesh is proposed.This material is a reinforced composite material with reinforcement mesh as reinforcement and a new cement-based material of reactive powder concrete with excellent properties such as ultra-high strength,low brittleness and high impermeability as matrix.Using the composite material to reinforce RC beams with thin layers on all sides can effectively improve its flexural performance.The reinforcement of concrete components is mostly carried out on the basis of one-time forming or under the condition of unloading,which is not consistent with the engineering practice.Therefore,considering the stress condition of the reinforced members in the load state in the actual project,this paper makes an experimental study and numerical analysis on the flexural performance of RC Beams Strengthened with thin layers wrapped around RPC reinforcement mesh under secondary stress.The main work contents and achievements of this paper are as follows:(1)Six concrete beams were designed and fabricated,of which five were reinforced with RPC reinforcement mesh and one was not reinforced as a comparative test beam.Through the bending test,the effects of the specification of reinforcement mesh and the initial load on the test results are studied,and the failure mode and crack trend of the test beam,the load deflection curve in the middle of the span,the strain development law of each material and so on are analyzed.The test results show that RPC steel mesh thin-layer composite reinforcement material has good reinforcement effect.When it is used in the reinforcement of concrete flexural beams,it can significantly improve the flexural performance of RC beams.(2)On the basis of the test,the finite element models of six test beams are constructed.The stress nephogram,load deflection curve and plastic damage diagram of each material of the model beam are compared with the test beam.It is obtained that the finite element simulation results are in good agreement with the test results.Based on the accuracy of the model,several specimens are established by using the same modeling method,and further parameter expansion analysis is carried out to explore the influence of other variables on the flexural performance of the strengthened beam.(3)Referring to the existing relevant literature and code requirements,two formulas for calculating the flexural capacity of RC Beams Strengthened with RPC reinforcement mesh under load are proposed and compared with the experimental values.The data results show that the bearing capacity obtained by the two different methods is close to the test results,and the calculated value is slightly less than the test value,indicating that the proposed calculation formula has good safety and reliability.