| Concrete-filled steel tubes (CFT), which combine the advantages of ductility generally associated with steel structures with the stiffness of concrete components, are useful and efficient structural members. However, connections to tubes are inherently difficult because the shape of the tube does not permit the use of traditional reinforcement concrete frame connection, and little research on CFT column-footing connection has been conducted until now, this requirement has been a primary limitation for the use of CFT. And also, when CFT column is used, stress in footing is different from that for footing sustaining reinforcement concrete columns, the effectiveness of footing designed following current design standard should be investigated. Moreover, previous research has shown that H-piles-to-footing connection designed following current designed standard could not develop the full-design ultimate tensile capacity, improved details should be adopted for securely anchoring the pile into the footing.(1) A total of two Bridge-Column-Pile-Footing models (BCPF) were designed, for which CFT column, RC footing and H-Piles were used. Column diameters considered were 360mm, with D/t ratio of 60.(2) Based on a quasi-static test of BCPF models, the bearing capacity, hysteretic characteristics, ductility and performance of plastic deformation, stiffness degeneration, the properties of seismic energy dissipation and failure of BCPF models are analyzed. Testing results show that the base connections are capable of transferring the full moment demand and sustaining the cyclic plastic rotation demand, BCPF models and CFT column have shown good seismic behavior.(3) On the basis of experimental study and theoretical analyses, analytical methods are developed to determine ultimate strength of CFT column with constant axial load, stress model is built up for design of CFT column-to-footing connection, and improvement has been made to current design standard for footing sustaining CFT columns. |
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