STUDY ON THE ECCENTRIC COMPRESSIVE BEARING CAPACITY OF POLYGONAL MULTI-CELL CONCRETE FILLED STEEL TUBULAR COLUMNS

Based on the giant columns of Goldin Finance 117 tower in Tianjin, 11 eccentric compressive test specimens of polygonal multi-cell concrete filled steel tubular columns were designed and fabricated at a scale of 1/20. Mechanical behavior of the specimens was studied through the eccentric compression test. The failure mode, the load-lateral deformation curve and the load-strain curve were investigated. The influence of the steel wall's thickness, slenderness ratio, eccentricity and concrete strength on the ultimate bearing capacity of the specimens were analyzed by using the software package ABAQUS. The results show that the eccentric compression specimens mainly demonstrated a flexible buckling failure; the ultimate bearing capacity of the specimen increased with the increase in the strength of concrete or steel wall's thickness; the late bearing capacity and ductility of the specimen could be increased notably by the reinforced cage in the specimens. When the slenderness ratio increased from 24 to 70, the ultimate bearing capacity decreased by 38.6%. When the eccentricity ratio increased from 0.2 to 1, the ultimate bearing capacity decreased by 54.1%. Based on the results from the finite element analysis and the subsequent calculations about the bearing capacity of the columns, a calculation formula of the bearing capacity for hexagonal six-cell and pentagon four-cell concrete filled steel tubular columns was developed which can be used as a reference for practical engineering implementation.