Behaviors Of Slender Concrete-filled Elliptical Hollow Section Columns Subjected To Combined Compression And Bending

The concrete-filled steel tubular(CFST) column possesses high load-bering capacity, easy construction and good seismic performance, and has been widely applied in practice now. Concrete-filled elliptical steel tubular(CFEST) column possesses the advantages of CFST. And its cross section has major axis and minor axis, the aspect ratio can be changed according to the load conditions and then the structural efficiency can be maximised. The oval cross section also has advantages of small fluid resistance and has high flexural capacity. This thesis intends to investigate the behaviour of the CFEST slender columns under combined compression and bending experimentally. The main contents are as follows:(1) A total of eleven specimens were tested, including five specimens under axial compression and six specimens under eccentric compression. The considered parameters were slenderness ratio, load eccentricity, and buckling about major axis or minor axis. Experimental results shows that the load-bearing capacity decreases with the increase of slenderness ratio and load eccentricity. Amd the load-bearing capacity of columns buckling about major axis is much higher than buckling about minor axis.(2) Finite element models were developed to study the behaviours of the CFEST slender columns under axial compression, combind compression and bending and pure bending, using software ABAQUS. The FE model was validated by tests in this study and relative test data. And then parametric studies were conducted, including the slenderness ratio, the aspect ratio, the steel yiled strength, the concrete strength, the steel ratios and the load eccentricity ratio. The results show that the slenderness ratio, the load eccentricity and the buckling axis about major or minor axis have significant effects on the load-bearing capacity.(3) The design methods for CFEST columns in code GB50936-2014 and the design methods for CFST columns in code EC4 were used to predict the specimens in this study and relative tests. It was found that the method specified in GB50936-2014 can reasonablely predict the N-M interaction curve of the CFEST columns. And the method for CFST columns in EC4 also can be applied for CFEST columns.