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

Considering the insufficient of current confined concrete and the excellent material characteristics of RPC,an innovative composite structure,named Concrete-filled RPC tube(CFRT),was presented in this thesis.In this system,high-strength stirrups are arranged in prefabricated reactive powder concrete(RPC)tube which made by the method of spun-cast concrete,and then concrete is cast in RPC tube.In order to explore the composite action of CFRT under axial load,total 30 large-scale columns were conducted axial compression test.22 CFRT specimens,6 high-strength stirrup confined concrete(HSCC)specimens and 2 hollow RPC tubes were conducted axial compression test.The internal concrete strength,the stirrup spacing in the RPC tube and the different internal and external reinforcement forms are the main factors in tests.The results show that RPC tube of CFRT column only occurs slightly cracking without any spalling when axial load approaches its peak value,That was obviously different from the High-strength stirrup confined concrete column.In terms of axial carrying capacity,the CFRt is significantly higher than HSCC,and the increase rate increases with the increase of stirrup spacing,For the CFRT column with the same stirrup ratio,the axial carrying capacity is basically the same,but the more dense the stirrup spacing in the RPC tube,the better ductility of the CFRT specimen.Based on the existing research results of the research group,Three classic strength models for confined-concrete columns are selected to predict the carrying capacity of the CFRT columns.Results of comparison show that those existing models are not fit to be used to evaluate the carrying capacity of the CFRT specimens.Based on Mander(1988)model and reasonable considering the damage of the RPC tube and confinement effect,introducing the RPC tube strength reduction coefficient kd and enhancement coefficient ks,axial carrying capacity model for CFRT columns is proposed.Compared with concrete-filled in steel tube(CFT)columns,the CFRT columns show the similar dead weight under the condition of the same axial carrying capacity.It suggests that from the index of capacity/weight,the CFRT is easy to construct as the CFT.