| A new method for strengthening RC frame joints by prestressed closed wire ropeunits was proposed to overcome disadvantage of traditional seismic strengthening forRC frame joints, by prestressing and anchoring steel wire-ropes looped aroundcolumn reasonably, the shearing performance and deformation performance of jointscan be improved effectively. Steel wire-rope surrounded the core area of jointscrossing over the beams in this technology, which could overcome the obstacles offrame beams. Meanwhile, stress lagging existing in traditional strengthening methodscould be surmounted with prestress technology, which could improve reinforcedeffect effectively. Following studies were carried out in this paper.Experiment of anchorage performance of lapped steel wire-rope was taken toprove the feasibility of this reinforcement method. The results show.(1) By tighteningwire line hitchs installed at both sides of the ropes can clamp wire ropes which areprestressed.(2) The method of horizontal pressure injection after sealing pore channelcan make sure that pore’s filled up with glue.(3) The inserted bar glue used inexperiment was anchorage reliability, steel wire ropes were broken without obviousslippage in a short anchorage length (150mm).Seven joints strengthened with prestressed closed wire rope units and twocontrastive joints were tested under cyclic loading and the parameters includedstrengthening quantity, prestress degree, setting of the polymer grout, forms of jointsand site for anchorage. Test results show.(1) The shear capacity of joint core area wasincreased while the failure mode of specimens was converted from shear failure ofjoint core to flexural failure of beams.(2) Anti-seismic performance is improvedbecause of prestressed closed wire rope units. Strengthened joints dissipated moreenergy during latter loading, while with the increase of strengthening quantity thetotal hysteretic energy increased. Strengthened joints got gentler decrease both ofskeleton curves and strength deterioration. The ductility were better than contrastiveones too.(3) Prestressed closed wire rope units can constraint shear deformation ofjoint core effectively. Joint shear deformation’s contribution to story drift of strengthened joints reduced.(4) Raising of the prestress degree was propitious toconfine the developing of cracks in earlier stage.(5) Anchorage location has littleeffect on the reinforcement effect, which can be choosen according to the actualsituation.An analytical model for shear bearing capacity of RC frame joints strengthenedwith prestressed closed wire rope units was presented based on Attaalla’s model. Theshear bearing capacity was calculated using the equilibrium equation and geometricequation. Furthermore, this model for shear bearing capacity was simplified based onprevious studies.Construction technology of prestressed steel wire-rope units strengtheningmethod for RC beams and RC joints was summarized in this paper according to thestrengthening work of specimens and actual demand. Those main points and detailsof this strengthening method can provide the gist for the engineering practice. |
