Experimental Study On Fatigue Behavior And Failure Mode Of RC Beams Strengthened With Prestressed Steel Wire Under Different Parameters

The strengthening technique using prestressed high-strength steel wire has proven to be an effective method and has been widely is widely used in the field of building structural reinforcement.Due to the difference of the bridge and the building structure,the reinforcement technology has problems in applicability and effectiveness in bridge reinforcement.In particular,there are few studies on the fatigue performance of RC beams strengthened by steel wire,which limits the promotion and application of the reinforcement methods in the field of bridge reinforcement.It is urgent to carry out related research work.Therefore,it is of great engineering significance to study the fatigue performance of RC beams strengthened with high-strength steel wire.In this thesis,the reinforcement technology of“new prestressed steel wire reinforced RC beam”is studied in depth.The main research work is as follows:New prestressed steel wire reinforcement technology adopts distributed anchoring method which constructed by the end angle steel and the eyebolt to complete the rapid application of the prestress and the end anchoring,and design two box steel in the mid-span for distributed anchoring,so that the steel wire can work with beam better.In this thesis,the prestressing control technology and prestress loss research are carried out,and the change of prestress in the construction stage is mainly monitored.The result shows that the loss of prestress value of the wire is relatively fast in the first 12 hours,and then tends to be stable.So In the project,the loss of prestress can be reduced by over-tensioning.In this thesis,a reinforced beam was tested under the static load first to verify that the method can improve capacities and stiffness of the beam and provided mechanical parameters for the fatigue test.On the basis of the static test,the three reinforced beams were subjected to fatigue test.The prestressing degree??=0.25?0.35?and the maximum stress ratio(p_max^f/p_u=0.25?0.5)were used as analytical variables.The mechanical properties of each beam,including ultimate flexural capacity,ductility performance,The rigidity change,failure process and corresponding mechanism,etc.Are derived and the stiffness degradation formula and residual deflection development formula are derived.The test results show that:?1?The prestressed steel wire reinforced beam withstands 2 million times of fatigue load without obvious fatigue damage,which can meet the engineering requirements.?2?The anchoring performance of the distributed anchorage was excellent during the test,and no obvious fatigue damage and bond slip occurred.The reliability of the distributed anchorage under fatigue load conditions was verified.?3?In the initial stage of fatigue loading,the stiffness degradation,crack and residual deflection develop rapidly,and the later stage tends to be stable.The study of the fatigue load ratio shows that the increase of the fatigue load will accelerate the crack,stiffness degradation and residual deflection development.The ABAQUS finite element simulation of the specimens shows that the reinforced beams have similar mechanical characteristics during the test process and the simulation process.And the parameters of the reinforced beams under different prestressing degrees are extended to study the mechanical properties of the reinforced beams.The results can provide reference for engineering applications.