Liao, Han and He 2011
Experimental Study, Results and Discussion
A total of 21 specimens were tested with axial loading and bending moment in order to determine the influence on gap type, gap ratio, and failure mode. Typically, in CFT’s, there are many imperfections in both the concrete filling, and steel tube, known as gaps. These gaps can either be circumferential which is caused by concrete shrinkage, or spherical-cap, which occurs in horizontal tubes and begins during the construction phase. The short columns had pinned-ended support conditions, and strain gages were placed on the outer steel surface, and measured both longitudinal and transverse strain. A four-point bending rig was used to measure bending. All of the specimens displayed outward buckling, and it was seen that the spherical-cap gap specimens displayed similar failure to that of the normal columns without a gap. It was seen that as the axial displacement increased, there was more severe local buckling. Furthermore, the larger the gap ratio, the compressive strain decreases. The beams that were tested all failed in terms of ductility.
Liao, F., Han, L., He, S. (2011). “Behavior of CFST Short Column and Beam with Initial Concrete Imperfection: Experiments.” Journal of Constructional Steel Research, 67(12), December, pp. 1922-1935. doi:10.1016/j.jcsr.2011.06.009