Experimental Study On Axial Compression Behavior Of Square Steel Tububar Concrete Columns Filled Spatial Steel Frame

The tests show that core concrete is constrained better by square steel tubular or spatial steel frame,so the strength and deformation properties of core concrete can be improved.Based on these studies,a new theory of composite column named square steel tubular concrete columns filled spatial steel frame is proposed which spatial steel frame is embedded into square steel tubular concrete column.As a result,the core concrete is constrained not only by square steel tubular but also by spatial steel frame.On account of experiments of axial compression and nonlinear finite element analysis,we explore behavior of square steel tubular concrete columns filled spatial steel frame and put forward calculation methods of ultimate bearing capacity.These conclusions can provide some theoretical basis for engineer application of the column.By changing the width-to-thickness ratio of external pipe and the spacing of internal transverse lacing bar,5 square steel tube concrete columns filled spatial steel frame and 1square steel tubular concrete column was designed and produced..The test of axial compression showed spatial steel frame obviously improve the deformation of core concrete of square steel tubular concrete column because spatial steel frame constrained core concrete.When the specimen reaches the peak load,the bearing capacity attenuates delay.It shows good deformation ability.With the increased of external pipe thickness and decreased of the spacing of internal transverse lacing bar,the peak load and deformation of square steel tubular concrete columns filled spatial steel frame is increased.Based on the nonlinear finite element analysis software ABAQUS,finite element models for square steel tubular short columns filled spatial steel frame was established.By the simulation analysis of the experiment,the result shows the simulation results agree with the actual results.On the basis of verifying the accuracy of the models,8 specimen models are designed by changing the length of internal steel angles,the width of internal transverse lacing bar,the strength of concrete and the external and internal forms of steel skeleton.The peak load and deformation of double spatial steel frame is better than square steel tubular short columns filled spatial steel frame and.The peak load and deformation of double square steel tubular short columns is worst.On the basis of experiments and finite element analysis,2 calculation method of ultimate bearing capacity of square steel tubular short columns filled spatial steel frame concrete columns were proposed using superposition method.The result shows that thecalculated value is in good agreement with the experimental value and simulated value.