Behaviors of axially loaded circular concrete-filled steel tube (CFT) stub columns with notch in steel tubes

Compressive tests of the CFT stub columns with artificial notches in the steel tubes were conducted in this paper to investigate the effects of the material imperfections of steel tubes on mechanical performances of the CFT stub columns. The load-displacement responses, column strength and confining effects were discussed in detail. A parametric study, including the notch length, notch orientation, concrete strength and steel ratio, was also conducted. The results indicated that the notched CFT specimens had quite different failure modes from the intact CFT specimens. A notched CFT specimen might fail by cracking of the steel tube or closing of the notch, which was determined by the notch orientation. The results also showed that the notched CFT specimens had lower mechanical performance than those intact CFT specimens because the notch steel tube could not offer sufficient confining effect on the concrete core inside it. Based on the experimental results, an empirical equation for predicting the column strength of a notched CFT column was proposed.