RC Columns Reinforced With FCCC-R:Axial Compressive Behavior And Seismic Performance

In the present dissertation,a noval FRP confined concrete core encased rebar(FCCC-R)is proposed.The FCCC-R is composed of the high strength internal steel bar,the filled high strength concrete and outside FRP tube.By equipping this component into RC columns,the axial compression ratio can be reduced and the ductility and load capacity of the hybrid column can be enhanced.Based on the proposed component FCCC-R and corresponding hybrid column,a series of studies have been carried out.For component FCCC-R,the mechanical behavior of internal steel bar under axial compressive load was firstly studied.The final failure mode,axial load-displacement relationship was figured out.For FCCC-R with proper section configuration,the internal steel bar can reach its yield strength under compression even with a relatively large slenderness ratio.Based on the principle that the yield of internal steel bar should be guaranteed,a simple design equation was proposed to calculate the minimum effective area ratio of FCCC-R.Secondly,the axial compressive behavior of FCCC-R was studied by experimental study,numerical simulation,theoretical calculation and simplified design methods.Main issues in this section include the modification of traditional FRP confined concrete model,the definition of 3-D model in finite element model,the influence of slenderness on compressive behavior of FCCC-R and the combination of section band method and Newmark method.And a simple calculation method based on the modified Euler equation was proposed in order to calculate the compressive behavior of FCCC-R.For RC columns reinforced with FCCC-R,the mechanical behavior of the hybrid column under cyclic axial compressive load and seismic load was studied experimentally.The failure mode,failure procedure and different mechanical performance(i.e.loaddisplacement relationship,hysteretic behavior,load capacity and ductility)were discussed.The buckling behavior of FCCC-R and the bond behavior of FRP-concrete interface illustrates great influence on the mechanical behavior of the hybrid column.Besides,based on the strain development of different components in the column,the contribution of different materials were figured out,Moreover,based on the numerical simulation of the hybrid column,influence of additional parameters were studied.Based on the mechanical behavior of FCCC-R and the hybrid column,the design equations were proposed in this dissertation.M-N relationship of the hybrid column could be obtained by the proposed design equations.Besides,two ultimate conditions were used in the design procedure which are corresponding to the ultimate condition of unconfined and confined concrete.Influence of FRP confined concrete and bond behavior of FRPconcrete interface was also considered.According to the design method,the reinforcement effect of FCCC-R on M-N relationship of RC columns was illustrated and discussed.