Experimental Study On Concrete-filled RPC-FRP Tube Under Axial Compressive Loadings

Marine structure is facing the challenge of harsh marine environment.At present,there is no good way to overcome this problme in traditional reinforced concrete structures.Based on the domestic and abroad researchs of reactive powder concrete(RPC)and fiber reinforced polymer(RPC)bar,a new composite structure suitable for marine engineering,called concrete with seawater and sea sand filled RPC-FRP tube(SCC-RPCT)was propsed in this thesis to address the problems existing in the marine structures.In this structure,CFRP hoops are arranged in prefabricated reactive powder concrete(RPC)hollow thin-wall tube and then sea water and sea sand concrete is cast in RPC tube.To study the mechanism properties and lap splices of CFRP hoops,axial tensile tests were carried out on 18 CFRP hoops' basic mechanical test specimens and 48 lap splices test specimens.In order to explore the composite action of SCC-RPCT under axial load,total 15 large-scale columns were conducted axial compression test.Total 18 specimens of basic mechanical properties of 3mm diameter CFRP bar and 6mm diameter CFRP bar were designed and made,and the axial tensile tests were carried out to study the influence of the length of different casing anchorage and the surface with or without sand,and the basic mechanical parameters of the CFRP bars were calculated by the test results.The test result shown that,the larger the anchorage length is,the easier to occur effective failure mode,and the surface with sand can improve the ultimate tensile strength of the specimens.Total 48 lap splices test specimens including 3mm diameter CFRP bar and 6mm diameter CFRP bar were designed and made,and the axial tensile tests were carried out to study the influence of the different types and length of lap splice on the mechanical properties of the lap splice.The test result shown that,the larger the lap length is,the greater the tensil strength of the lap splice.The tensil strength are different when the type of lap splice are different.12 SCC-RPCT specimens and 3 FCC(CFRP hoops confined concrete)specimens were conducted axial compression test.The stirrup spacing in the RPC tube and types of lap splice of the CFRP hoops are the main variable in this test.And the result shown that,unlike the FCC columns,RPC tube of SCC-RPCT spcimens only occurs slightly cracking without any spalling when axial load approaches its peak value and the axial compression bearing capacity of the SCC-RPCT columns are by far higher than FCC columns with the same stirrup spacing.SCC-RPCT columns have higher bearing capacity with their stirrup spaceing smaller,and while the three types of lap splices have little influence on the mechanical properties of SCC-RPCT when the spacing of the stirrup is same.Mander model which is widely used steel confined concrete model,Afifi model a new CFRP stirrups confined concrete model and two kinds of CFRT(Concrete-filled RPC tube)model were adopted to predict the bearing capacity of the SCC-RPCT columns.Results of comparison show that those four models are not suit to evaluate the bearing capacity of the CFRT specimens.An innovate axial bearing capacity model was proposed by this thesis based on the above models and reasonable considering the damage of the RPC tube by introducting a reduction coefficient.Compared with the experimental results,the proposed SCC-RPCT model can accurately predict the axial compressive strength of SCC-RPCT specimens.