Study On Eccentric Compressive Performance Of Recycled Big Aggregate And Self-compacting Concrete Filled Steel Tubular Short Columns

In order to solve the problem of reusing waste concrete,this paper produced recycled large aggregate which can save cost and energy,adopts the construction method of rock fill concrete,which fills the large aggregate stacked in the steel pipe,and uses the large aggregate recycled in the steel pipe to form the structural form of self compacting concrete(referred to as composite column).Eleven composite column specimens were made with recycled aggregate strength,recycled aggregate particle size,self compacting concrete strength,steel tube wall thickness and eccentricity of axial loading as variables.The mechanical behavior of composite column specimens under eccentric compression load was studied by combining experiment and finite element simulation.The main research contents and conclusions are as follows:(1)The eccentric compression test of recycled large aggregate self compacting concrete filled steel tube was carried out.According to the test results,it is found that the composite column has good working performance,and the failure mode is local buckling failure of steel tube,which belongs to strength failure.According to the test data,the load deflection curve,load strain curve,lateral deflection curve and Poisson’s ratio curve are drawn to compare the changes of mechanical properties of composite columns under eccentric compression with different parameters.It is found that the strength of recycled aggregate,Confirmed strength,thickness and abnormal locality are key factors affecting the mechanical properties of the composite column,However,due to the particularity of concrete reactor construction method,the effect of aggregate fraction recycling is not obvious.After exceeding the limit load,the load decreases slowly due to the good restraint capacity of the steel tube,showing good ductility of the specimen,which is concentrated in the compression zone.The lateral deflection curve of the composite column is in good agreement with the sine half wave fitting curve.(2)Taking Wu Bo formula as the core strength formula of concrete-filled composite column,the eccentrically loaded bearing capacity of composite column structure is calculated according to six related formulas used to calculate concrete-filled steel tubular structure.The results show that all the six formulas can reflect the variation of mechanical properties of composite column members,and the accuracy of CAI Shaohuai formula and Zhong Shantong formula is the highest.(3)A composite column of digital model is created by using ABAQUS software and a limited number of elements The data confirmed the feasibility of the finite element model.The constitutive relation,the interaction between the materials and the parameters needed to be input in the modeling are given.The results show that the contact stress on the surface of core concrete is very small at the initial stage of loading,and the steel tube and core concrete are basically in an independent state.It is not until the elastic-plastic stage that the steel tube plays an obvious restraining role.According to the resistance coefficient,five comparable models are designed,The influence of pressure coefficient on the mechanical properties of the sample is analyzed,and the experimental application is supplemented.When the restraint effect coefficient increases to 0 To a certain extent,the load deflection curve will not decline,or even rise slowly.