Research On Flexural Behavior Of The Damaged Reinforced Concrete Beams Strengthened By Prestressed Steel Wire Rope And UHPC

Through combination of Prestressed Steel Wire Rope(PSWR)strengthening method and Ultra-High Performance Concrete strengthening method,PSWR-UHPC flexural strengthening method for damaged RC beams was developed in this paper.Four-point bending tests as well as analytical and numerical analyses were carried out to investigate this method systematically.Dominent work and conclusion are as follows:(1)Through conducting four-point bending tests on 14 test beams,the impacts of number of PSWR,prestressing ratio of each PSWR,concrete strength,damage level of RC beam and the material of covering layer on the failure mode,crack resistance,deformation performance and ultimate bearing capacity of PSWR-UHPC strengthened RC beams were studied.Test results show that the failure mode of all test beams is the reinforcing layer rupturing,tensile rebars yielding and the normal concrete on the top of specimens crushing subsequently which is similar to the typical failure mode of ideally reinforced beam.The UHPC-RC interface showed a satisfactory bonding performance during tests with no debonding phenomenon,and the main UHPC crack develops into RC beam and becomes the main crack at the end of one test.The crack resistance and flexural stiffness of test beams are significantly increased by PSWRUHPC strengthening but PSWR-mortar.Because of the unaccuracy of prestress,the ultimate bearing capacity of some test beams is not increased,in addition to these beams,the maximum increase of bearing capacity is 36%.The test beams with higher original damage level,more steel wire ropes,lower prestressing ratio and lower normal concrete strength are strengthened more efficiently.(2)Based on the test results and existing specifications,the formulas of UHPC/RC cracking load,UHPC/RC crack width-0.2mm load and steel wire rope rupturing load were proposed with consideration of the strain hardening and softening of UHPC and the brittle failure of steel wire.Most of the analytical results agree well with test results except for the UHPC crack width 0.2mm load which exceeds test results by 12% in average.(3)Based on the test results and analytical analyses,ABAQUS was utilized to develop the numerical models of test beams,and the numerical results are in acceptable agreement with test results.Based on the validated numerical models,the impacts of the area of single steel wire rope,strengthening way,depth of RC beam,and reinforcement ratio of RC beam on strengthening effect were studied numerically.Numerical results show that the larger the cross-sectional area of steel wire rope,the smaller the depth of the RC beam and the smaller the reinforcement ratio of the RC beam,the better the strengthening effect of PSWR-UHPC.Besides,directly strengthened beams have the highest cracking load and the lowest steel wire rope rupturing load,while load-bearing strengthened beams have the opposite trend.