Behavior of Centrally Loaded Concrete-Filled Steel-Tube Short Columns

A 5 year research on concrete-filled steel tubular (CFT) column system was carried out as a part of the fifth phase of the U.S.–Japan Cooperative Earthquake Research Program, and the tests of centrally loaded short columns were finished. The objectives of these tests were to clarify the synergistic interaction between steel tube and filled concrete, and to derive methods to characterize the load–deformation relationship of CFT columns. A total of 114 specimens was fabricated and tested in the experimental phase of investigations on centrally loaded hollow and CFT short columns. Parameters for the tests are as follows: (1) tube shape, (2) tube tensile strength, (3) tube diameter-to-thickness ratio, and (4) concrete strength. In determining the range of parameters, the emphasis was placed on obtaining a wide range of test data for establishing a generally applicable design method of CFT column systems. Design formulas to estimate the ultimate axial compressive load capacities are proposed for CFT columns with both circular and square sections based on tests results described in this paper.