| The thickness of special-shaped reinforced concrete columns can be designed to be same with those of walls, which avoids edges and corners of columns and displays an architectural function. However these columns are sensitive to the direction of lateral loads and also with a low ductility. It is therefore demanded a large of link ratio and limited the maximum value of longitudinal load ratio. At the same time, the confinement in special-shaped concrete-filled steel tubes (CFST) is not effective due to the local buckling. To solve the problems of these two kinds of columns, an innovative special-shaped concrete-filled steel tube, adding a set of reinforcement ribs in the conventional CFST, is designed in this paper. It is expected that this new kinds of special-shaped CFST has a higher performance over the previous members through which the ribs delay the tubes'local buckling and improve the overall ductility. The mechanical behavior of T-shape and cross-shape concrete-filled steel short columns is researched theoretically and experimentally. In particular, the local buckling is studied. The research can be divided into three contents as follows:1. The mechanical behaviors of CFST with and without reinforcement ribs are respectively investigated using the finite element package ABAQUS. Material and geometrical nonlinearity, initial geometrical deformation and post-buckling are taken into account and their influences are discussed. A set of appropriate construction for reinforcement ribs is put forward.2. Two T-shape CFST specimen, having reinforcement ribs and without, are tested. Their longitudinal load versus displacement relationship curves are measured and the failure modes is also observed and analyzed. The functions by reinforcement ribs are studied concerntrately.3. A finite element analysis model is developed using ABAQUS and validated by the test results. The confinement between concrete and steel tubes in the T-shape and cross-shape CFST is then studied. The parameters including steel ratio, steel yield strength, concrete strength are analyzed to the mechanical behavior of special-shaped CFST. |
