Behavior Of Rectangular RACFST Columns Subjected To Eccentric Compression

As a kind of green building material,recycled aggregate concrete(RAC)can produce great benefits to environmental protection,energy and economy through the reasonable utilization.Recycled aggregate concrete filled steel tube(RACFST)consisting of a steel tube and the in filled RAC is a new type of composite member,which can take full advantage of the merits of both materials and simultaneously overcome their own weakness.The existence of RAC can effectively delay or avoid the premature local buckling of steel tube.Meanwhile,due to the constraint and protection effect of external steel tube,the defects of RAC,such as low strength,low elastic modulus,large shrinkage and creep,can be significantly improved.The outer steel tube of rectangular RACFST column also has the constraint effect to the core concrete,and the joint between the rectangular RACFST column and the beam in the connection area is more simple and convenient.In engineering application,structural columns are often under eccentric loading condition due to the existence of both axial load and bending moment.Therefore,it is necessary to study the performance of rectangular RACFST columns under eccentric compression to provide theoretical basis for engineering practice.In this paper,combined with the test and simulation,the mechanical properties,working mechanism and design method of rectangular RACFST columns under eccentric compression are studied in depth.The main works are as follows:(1)Fifteen rectangular RACFST column specimens,with sectional length-to-width ratio,load eccentricity ratio,slenderness ratio and recycled coarse aggregate replacement ratio as the basic parameters,are prepared for eccentric compression tests.The failure patterns,load-deformation curves and bearing capacity of the specimens are recorded and analyzed.(2)On the basis of determining the constitutive relationship of steel and RAC,the software ABAQUS is used to establish the finite element analysis(FEA)model of rectangular RACFST columns under eccentric compression.The simulation results are in good agreement with the test results,which verifies the rationality and usability of the FEA model.(3)The influence of recycled coarse aggregate replacement ratio,sectional length-to-width ratio,load eccentricity ratio,slenderness ratio,steel ratio,yield strength of steel,strength of original concrete on the behavior and mechanism of rectangular RACFST columns subjected to eccentric compression are systematically investigated by using the FEA model.(4)The effect of various parameters on the stability coefficient and axial force-bending moment relationship of rectangular RACFST columns is analyzed using the FEA model,and the corresponding simplified calculation formulae are further suggested based on the regression analysis method.The simplified stability coefficient and bearing capacity of rectangular RACFST columns generally agree well with the FEA and experimental results.