Suggested empirical models for the axial capacity of circular CFT stub columns

In this paper, a total of 250 experimental tests of axially loaded circular concrete-filled steel tube (CFT) stub columns, published in the literature was summarized. The applicability of the current design codes such as ACI, Australian Standards, AISC, AIJ, Eurocode 4, DL/T and some available empirical models proposed by various researchers for calculating the axial capacity of circular CFT stub columns was examined using these experimental data. Based on the investigations, four new empirical models for predicting the axial capacity of circular CFT stub columns are proposed. The comparisons between the experimental results and the predictions of these models show that the proposed empirical models provide a direct, compact, and efficient representation of the ultimate strength of circular CFT stub columns made with not only normal strength but also high strength steel tubes and concrete. Finally, the limiting values of the maximum effective length, the compressive strength of concrete, the yield strength of steel tubes and the diameter-to-thickness for circular CFT stub columns with respect to the present empirical models are suggested. It is expected that engineers can easily use the present empirical models to estimate the axial capacities of circular CFT stub columns for engineering designs.