Study On The Axial Compression Performance Of Square Steel Tube Recycled Ceramics Coarse Aggregate Concrete Short Column

This paper proposed to pour the recycled ceramic coarse aggregate concrete into the steel pipe to form a square steel pipe recycled ceramic coarse aggregate concrete composite structure.In view of this,11 sets of recycled ceramic coarse aggregate concrete cube and prism test blocks were designed.And uniaxial compression tests were carried out.Based on the test results of recycled ceramic coarse aggregate concrete,18 square steel pipe recycled ceramic coarse aggregate concrete short columns were designed.And axial pressure comparison test was carried out,the influence of ceramic coarse aggregate substitution rate on the axial pressure performance of the specimens were analyzed.The applicability of recycled ceramic coarse aggregate concrete in steel pipe was explored through finite element simulation analysis and six specification ultimate bearing capacity formulas and test results.The ultimate bearing capacity formula based on multiple linear regression was established to provide a theoretical basis for engineering applications.The main research work of this paper is as follows:(1)The 11 groups(a total of 66 test pieces)test groups were designed according to the water absorption rate and free water-cement ratio of ceramic coarse aggregate as the design methods.The uniaxial compression test of recycled ceramic coarse aggregate concrete cube and prism was completed.The influence of the substitution rate of ceramic coarse aggregate on its mechanical properties were analyzed from the perspectives of failure process and morphology,compressive strength,stress-strain,elastic modulus and Poisson’s ratio.Through the test data fitted,the conversion formula between the compressive strength ratio and the substitution rate between the recycled ceramic coarse aggregate concrete prism and the cube were obtained;The formula for calculating the elastic modulus of recycled ceramic coarse aggregate concrete were proposed;A conversion formula between Poisson’s ratio and substitution rate of recycled ceramic coarse aggregate concrete were proposed.At last,the compressive constitutive equation of recycled ceramic coarse aggregate concrete was fitted through the stress-strain curves of the obtained prism specimens.(2)Eighteen square steel pipe recycled ceramic coarse aggregate concrete short columns were designed,which were divided into three groups according to the different steel content,each group had one square steel pipe ordinary concrete short column and five square steel pipe recycled ceramic coarse aggregate concrete short columns,and to analyse the axial pressure comparison test.Through the test,the stress process and failure form of the specimens were observed,the load-deformation relationship curves and the load-strain relationship curves were obtained;The effects of the replacement rate of ceramic coarse aggregate on the ultimate bearing capacity,peak strain,secant stiffness,stiffness degradation,damage,ductility and energy dissipation of the specimen were analyzed.(3)ABAQUS finite element software was used to simulate the axial pressure performance of square steel pipe recycled ceramic coarse aggregate concrete.The failure morphology and stress-strain curves of the simulated specimens were compared with the test results.At the same time,the load distribution of the steel pipe and the core concrete in the axial compression process of the specimens were discussed.The longitudinal stress of the core concrete and the longitudinal stress of the steel pipe of the span section were analyzed.Finally,combined with ABAQUS’ Python interface,the parametric automatic modeling of the specimens were realized.(4)The ultimate bearing capacity of the axial compression short column of steel pipe recycled ceramic coarse aggregate concrete was calculated by unified strength theory,conversion theory and superimposed strength theory.The test results were compared and analyzed.The results show that the calculation results of the unified strength theory were in best agreement with the experimental results.At the same time,on the basis of the above formula,the five factors affecting the bearing capacity of short columns(the width-thickness ratio of steel pipe,the yield strength of steel pipe,the standard value of axial compressive strength of concrete,the constraint effect coefficient and the replacement rate of ceramic coarse aggregate)were analyzed by multiple linear regression method,and the ultimate bearing capacity formula based on multiple linear regression was established.