Column Tests Of Dodecagonal Section Double Skin Concrete-filled Steel Tubes

Double skin concrete-filled steel (DSC) tubular columns consist of two concentric thin steel tubes with concrete sandwiched between them. DCS holds almost all the advantages of the concrete-filled steel tube (CFT) with its unfolding cross-section, higher flexural stiffness, lighter weight as well as better fireproof performance. It is no doubt that a beautiful prospect is out there for double skin concrete-filled steel tubular columns as a new form of structure. However, so far the research conducted experimentally or analytically mainly focused on the behavior of circular hollow sections and square hollow sections which has their own weakness. In addition, more studies of slender columns and full-scale or larger-scale columns should be carried out.This paper is devoted to investigate the behavior and strengths of dodecagonal section double skin concrete-filled steel columns. Moreover, local buckling of inner and outer steel tubes were also investigated. The major works through experiment and theory analysis are as follows:(1) By using12stub columns of dodecagonal section double skin concrete-filled steel tubes (DSC), experiments are conducted to discuss the observed phenomena and failure mode. The main experimental parameters in this part are dimension of the tubes as well as the thickness of the outer tube.(2) By using13double skin concrete-filled steel tubular slender columns, experiments are conducted to discuss the observed phenomena and failure mode. This part also analyzes the influence of the type of cross-section, thickness of the outer tube as well as the height on strength and ductility of the columns.(3) The test strengths are compared with the design strengths calculated using the AISC Specification, Eurocode for the design of composite structural members and the design method proposed by Han and Zhao. The differences between them are pointed out and the reasons are analyzed.(4) Large general finite element analysis software ABAQUS is used to simulate the test process. Good agreement with test results was achieved, verifying the feasibility and reliability of finite element analysis. Full-scale specimens are then simulated, and the results are compared with the design strengths calculated using the AISC Specification for the design of composite structural members.