Experimental Research on Influence of Loading Method on Behavior of CFST Long Columns and Mid-long Columns under Axial Loads

Experimental research on influence of four types of loading methods on behaviors of CFST long columns and mid-long columns subjected to axial loads is carried out.The comparison between stubs and long columns is presented.Analyses results indicate that the loading methods influence the cross-section stresses of long columns slightly and the stiffness and stability limit load-carrying capacity significantly.The effects of initial stresses on load-carrying capacity of long columns are serious than for short columns.When loading is applied only on steel tubes,the load-carrying capacity of the long columns is larger than that of the short columns.With the increasing of the slenderness ratio,the influence of the loading method on the hooping effect and mechanical behavior of the members are decreased.The influence of the loading method on mid-long columns lies between long columns and stub columns,and it appears more close to latter ones.Finally,the estimating method of the load-carrying capacity of CFST long and mid-long columns under different modes of axial loading is discussed.