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ABSTRACT： Structural tests were performed to investigate the structural performance of concrete-filled steel tube column using different strength steels in their flange and web with high-strength steel HSA800 and mild steel SM490, respectively. The test parameters included the strength of column flange and infill concrete, and effect of concrete infill.Connection between different grade steels were welded using the electrode appropriate for mild steel and verified its performance. To evaluate the behavior of test specimens, eccentric loading tests were performed and the results were compared with the prediction by current design codes. Axial load and moment carrying capacity of test specimens increased with the yield strength of compression flange and weld fracture occurred after the specimen shows full strength. The prediction result for axial load-bending moment relationship and effective flexural stiffness gave good agreement with the test result.

Concrete filled steel tube has been consistently used in tall buildings as it represents excellent structural performance and economical efficiency compared with other structural systems. The use of high strength steel in concrete filled steel tube can reduce the column size and increase the effective space in the buildings. But, the limit of width-to-thickness ratio to prevent local buckling is an obstacle to applying the high strength steel as it considerably decrease following to the strength increase. This paper addresses the effect of steel plate slenderness limit on the compression behavior in 800 MPa Grade steel. Four short column specimens were tested under axial compression. Main test variables were width-to-thickness ratio and shape of section. Test results were analyzed in the viewpoint of local buckling strength, yield strength, maximum strength and plastic deformation capacity of specimens. The experimental results showed that all specimens exceeded the maximum strength of calculated value by design code and represented similar deformation capacity regardless of width-to-thickness ratio. So, the limit of width-to-thickness ratio in high strength steel could be amended less strict.