Study On Axial Compressive Mechanical Properties Of Hybrid Aggregate Concrete Filled Steel Tubes

Due to the advanced mechanical properties(especially excellent compressive properties),concrete filled steel tube(CFT)has been widely used in the construction industry.However,with the demand of filled concrete,billions of tons of aggregates are produced and used worldwide every year,which not only means that a considerable quantity of natural aggregate is consumed rapidly,but also makes a negative effect on the environment.Additionally,the heavy self-weight or cost of traditional structure is another problem that cannot be ignored.Therefore,this paper presents the research and utilization of hybrid aggregate concrete filled steel tube(HACFT).In hybrid aggregate concrete(HAC),the lightweight aggregate(LWA)is introduced as the partial substitute of natural crushed stone to reduce the natural aggregate consumption,self-weight as well as overall cost.On the experimental research of HAC’s physical properties,it can be found that the mechanical properties of HAC remain a good level with the increase of LWA content.Moreover,it is more deformable in lateral expansion than the common concrete.Using the the model parameters such as the peak strain,initial and peak secant modulus of elasticity,a numerical formula is finally proposed to describe the stress-strain relation of HAC.On the structure,the overviews of the bearing capacity of CFT are undertaken.Meanwhile,with the volume content of LWA and the thickness of steel tube as the key parameters,and combine with the study results of Poisson effect of HAC,an experimental research on behaviors of HACFT under axial compression are performed.The results show that the bearing capacity of HACFT columns is influenced by the compressive strength and Poisson effect of LWAC in dual-facets.With a rational LWA volume fraction,the bearing capacity of HACFT columns is not lower than that of common CFT.Furthermore,by using statistics,the research to study stochastic model of confining stress is put forward.It is found that the probability distribution model is similar to that of Rayleigh distribution,which means when the thickness is comparatively thick,the specimens not only have strong confining effect,but also show great dispersion.Considering the influence of Poisson effect and D/t ratios on the confining stress,a formula for predicting compressive strength of HAC confined by circular steel tube is proposed.Finally,the study about whole-process nonlinear analysis of specimens is carried with CSBNLA software.In addition,using the volume content of LWA as the variable,a numerical model is suggested to predict the bearing capacity of HACFT columns.It is demonstrated that the calculated results with the suggested formula agree with the experimental ones well.This model can be referenced potentially in design of HACFT structure in practice.