Energy path of circular concrete-filled steel tube stub columns under axial compression

A clear understanding of the interaction mechanism between concrete and steel tube of concrete-filled steel tube (CFST) columns is essential for accurate load-bearing capacity modeling, which have been the main concern in the field of structural engineering. In this study, the interaction mechanism between the concrete and steel tube will be investigated from an energy relations perspective for the first time. An energy path is proposed to represent the variation trajectory of the relative energy relationship, which signifies the change of force and deformation state of different components during the loading process. Two quantitative metrics are introduced to characterize the energy path of the loading process. The interaction mechanism between the concrete and steel tube is analyzed from the perspective of energy paths. Experiments were performed on seven sets of CFST stub columns under whole section loading, and the energy paths for each set were obtained from measured data. The effect of the ratio of column width to steel tube thickness, steel strength, and concrete strength on the energy path was studied parametrically. The interaction mechanism is further explained by comparing the energy path of CFST column and stress path of confined concrete. Finally, a confined concrete strength model and a loadbearing capacity model of CFST columns based on the analysis of the energy relation were developed and the accuracy of the models was verified.