T-stiffener On Rectangular Concrete-filled Steel Tube Column With Large Width-to-thickness Ratio

Due to the high axial rigidity and bearing capacity, good ductility and stability, also simple construction and relatively joint structure is easier than concrete-filled circular steel tube column, concrete-filled rectangular steel tube column are widely used in high-rise and super high-rise buildings. At present, the standard of our country-<technical specification for concrete-filled steel tube structure> [1] on the design method of rectangular concrete-filled steel tube column had made some clear rules,and made a strict limit to width-to-thickness ratio of steel tube: 60 235 yb t ￡f.Therefore, in order to prevent the kind of rectangular concrete-filled steel tube column wall buckling occurs while the width-to-thickness ratio of steel tube over specification limits, set T stiffening rib on the tube wall is a new kind of effective method.From the economic consideration of concrete-filled steel tube column, the steel tube wall thin, the less consumption of steel, the more economic. Although after the steel tube filled concrete can enhances the critical buckling stress of steel tube, but when the width-to-thickness ratio of cross section of steel tube beyond a certain limit,concrete-filled steel tube would still inevitably arise local buckling phenomenon, thus reduce the bearing capacity of concrete filled steel tubular member. Xue-yi Fu professor put forward a design concept that setting T-stiffener in tube wall for large cross-section rectangular steel tube concrete column to improve the buckling performance. Compared with strip stiffener, T-stiffener’s bending stiffness is bigger than the type of strip stiffener. In addition, T-stiffener’s flange is wrapped by the internal concrete, the bending capacity would significantly enhanced; therefore, in order to prevent the kind of rectangular concrete-filled steel tube column wall buckling occurs while over the specification limits, set T-stiffener in the tube wall is a new kind of effective method.The provisions at home and abroad about the width-to-thickness ratio of rectangular concrete-filled steel tube wall were introduced in this paper, and obtain various calculation formulas of the steel tube wall buckling stress under different boundary conditions. In addition, on the basis of previous studies, the effects of T-stiffener that wrapped by the core concrete on steel tube wall on plate buckling performance was investigated. As a result of the existence of T-stiffener flange, when tube wall arising convex buckling, the core concrete would interactions with T-stiffener(prevent tube wall convex buckling), more effective inhibits the trend of buckling. Using finite element analysis software ABAQUS [2], to modeling ribbed tube wall which considered the concrete, using static analysis(considering the initial defects) and buckling analysis, observe corresponding buckling stress changes, load-displacement curve and stress nephogram in parameter(area ratio, stiffness ratio of stiffener to tube wall, etc.) changes, analysis the mechanism of T-stiffener which wrapped by internal concrete, perfecting T-stiffener design method.