Experiment And Research On Concrete Filled Steel Tubular Laced Columns Under Axial Compression

Concrete-filled steel tubular (CFST) laced columns are widely used in buildings and bridges. However, only a few of research works have been done on the mechanical properties of them up to now. The current design methods which were mainly derived from research results of concrete-filled steel tubes and steel laced columns are not verified neither analytically nor experimentally. Thus, it is necessary to investigate the performance of CFST laced columns. In this dissertation, the elastic stability, ultimate bearing capacity and shearing force of CFST laced columns under axial compression are analyzed in detail by means of specimen tests, numerical models and theoretical analyses. The subjects investigated comprise four (two)-legged and three-legged CFST laced columns with four different kinds of lacing arrangements. The main works and results are as follows:(1) 20 specimens of CFST laced columns (consist of 6 two-legged, 7 three-legged and 7 four-legged specimens) with slenderness ratio as main experimental parameter were tested under axial load to investigate the deformation behavior, deformation process, mechanical properties of CFST members and lacings, the influence of slenderness ratio on the ultimate bearing capacity. The results show that the CFST members are bearing eccentrical load with small eccentricity; the ultimate capacity reduces with the increasing of slenderness ratio, and it is also affected by imperfections.(2) Finite element models are established by finite element program ANSYS to analyze the elastic buckling and ultimate load carring capacity of CFST laced columns, and then the influence of core concrete and lacing bar's cross sectional shape on the limite capacity of steel laced columns are researched.(3) The elastic stability of CFST laced columns is studied with the equivalent continuing mechanical model. Subsequently, a formula is proposed to calculate the elastic buckling load of CFST laced columns with end shearing deformation restricted or free. (4) A parametric study is performed to investigate the axial bearing capacity of CFST laced columns with four (two) or three legs. Furthermore, based on an abundant finite element analysis results, an equation for determining the axial ultimate capacity is presented.(5) The shearing force of axial compression CFST laced columes is analyzed, and a formula for the force is derived.