Experimental study on the ultimate load-carrying capacities of concrete filled steel tube battened columns

Concrete filled steel tube (CFST) built-up columns have been widely used as building columns, bridge piers and arch ribs in civil engineering. Much research progress has been made on them; however, attention was just focused on CFST laced columns, not on CFST battened columns. In this paper, experiments on 29 CFST battened columns are carried out. The test parameters are load eccentricity, slenderness ratio, chord spacing and batten spacing. The whole loadbearing process, the failure modes and the ultimate load-carrying capacities of the specimens are analyzed. The studies show that the eccentricity and slenderness are the two main parameters independently affecting the load-carrying capacities of CFST battened columns. Therefore, the partial safety factor to predict the reduction effect in DBJ/T code for CFST laced column is suggested to be used for CFST battened column. However, the CFST battened column has lower resistance to shear than that of the CFST laced column, the calculation method of equivalent slenderness ratio for the CFST laced columns cannot be applied directly for the CFST battened columns. The magnifying factor K for steel battened column, which is called M-K method, is introduced to calculate the equivalent slenderness ratio for CFST laced columns.