ANALYTICAL STUDY OF CONCRETE-FILLED DOUBLE SKIN STEEL TUBULAR COLUMNS UNDER INTERACTION OF BENDING MOMENT AND AXIAL LOAD

Concrete Filled Double Steel Tubular columns are from the concrete filled tubular columns’ (CFT) family formed of two steel walls with square or circular sections. They are assembled concentrically and the space between the two walls is filled with concrete. Since CFDST columns do not need concrete casting and are easy to assemble and carried and are well protected against damages، they have some advantages over other columns. They are generally used in offshore structures، piers of the bridges with large openings، and nuclear canals in power plants. They have recently been used in the frames of high rising buildings in Japan as well. The present study attempts to investigate the behavior of these new columns under axial pressure forces and bending moment through finite element method and ABAQUS 6. 10 program. In order to make sure the finite element modeling is correct، the results of numerical analyses of CFT columns were compared to the laboratory results and the results were satisfying. The present study also investigated the effects different parameters of column thinness، the cross section’s geometric features، and characteristics of strength of materials and found that these columns’ capacity for load is more than CFT columns and are lighter and more economical compared to them.