| The brittleness of ceramic recycled concrete prepared by replacing the traditional coarse aggregate such as gravel with waste ceramics can be significantly reduced by placing it in double-skin tubes and subjecting it to lateral passive constraint under compression.It also has the advantages of easy joint connection,large bending stiffness and good seismic performance.To study the mechanical behaviour and influencing factors of ceramic recycled aggregate concrete-filled double-skin square steel tubular(CRACFDSST)columns under eccentric compression,the experimental study was carried out first.In addition,A finite element(FE)model was established on the basis of experimental research.Based on test and FE analysis,a simplified formula was proposed to predict the bearing capacity of CRACFDSST columns under eccentric compression.The main contents of this paper are as follows:(1)16 columns,with changing coarse aggregate type,slenderness ratio,eccentricity and hollow section ratio parameters,were tested,and the coarse aggregate types are waste ceramics and natural gravel respectively.The test results indicated that all specimens exhibited elastic?plastic instability failure.No cement-based materials attached to the ceramic glaze surface were observed at the crushed position.The ultimate bearing capacity and flexural rigidity of specimens decreased with the increase of the slenderness ratio and load eccentricity.Furthermore,the ultimate bearing capacity of CFDST specimens is higher than that of ordinary CFST specimens.Additionally,the ultimate bearing capacity of ceramic recycled concrete specimens is close to that of ordinary concrete specimens,and CRACFDSST columns had good ductility and bearing capacity.(2)The constitutive relationship of ceramic recycled concrete constrained by the square steel tube was adopted to establish FE models,which considered the plastic damage of concrete.The FE calculation results,such as failure modes,the load?deflection curves at the mid-span and the load?longitudinal strain curves,agreed well with the experimental results.(3)The ceramic recycled concrete and the ordinary concrete members under eccentric compression were modelled by the FE method for comparative analysis.The results indicated that the mid-span deflection corresponding to the peak load of the ceramic recycled concrete member was more significant than that of the ordinary concrete member.The constraints of the outer steel tube on the concrete were mainly concentrated in the corner,and the interaction between the inner steel tube and the concrete was relatively small.Furthermore,the loads were mainly carried by the concrete.At the corner of the compressive side,the mid-span deflection corresponding to the maximum contact stress between the outer steel tube and the concrete was higher than that of the ordinary concrete member.In addition,at the corner of the tensile side,the development trend of the contact stress of the two kinds of members was generally consistent.(4)A total of 310 FE models were used for parameter analysis,which showed that the coordinate values of the characteristic equilibrium point of the N/N_u-M/M_u curve increased with increasing concrete strength and the diameter-to-thickness ratio of the inner steel tube and decreased with increasing yield strength of steel,replacement rate of the ceramic coarse aggregate,hollow section ratio,nominal steel ratio and slenderness ratio.Moreover,with increasing slenderness ratio,the effect of the replacement rate on the N/N_u-M/M_u curve first increased and then decreased.(5)A simplified formula is proposed to predict the bearing capacity.The predictions of the simplified model agree well with the measured results and numerical predictions,which could provide a reference for related engineering practice. |
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