Han, Hou, Zhao, and Rasmussen 2014

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Experimental Study, Results and Discussions

A combination of 12 CFTs and hollow steel tubes for reference were tested in a drop hammer rig subject to transverse impact loading. The main parameters were length of specimen, and mass and height of drop hammer. A combination of circular and square columns were tested, with varying end conditions. The tests concluded that CFTs have high ductility and resistance under impact load. In order to test the impact energy of the Chromium drop hammer, a laser was used to measure the initial velocity. All of the CFTs displayed flexural deformation, and local buckling was observed around the top of the mid-span, and at the bottom of the fixed-fixed columns. Fracture occurred at the area of welding, and led to greater deflection. The hollow columns displayed much more deflection, and the test concludes that the CFT’s are much ductile. The pinned-pinned specimens display the largest deflection, while the fixed-fixed specimens undergo the smallest.

Analytical Study

A FEA model was used to analytically determine the impact behavior prior to the experimental study. This study proved that the deformation of CFT’s under impact loading can be accurately predicted using the FEA. Both the deflection, and impact force vs time graphs generally agreed with the experimental study. This study was also utilized to analyze the full-range behavior of the CFT under impact load including failure mode, internal force distribution, stress, strain, and the section moment vs. longitudinal strain curve. A simplified model was then determined using a parametric study, which proved that yield stress, steel ratio, sectional diameter, and impact velocity are main parameters that influence flexural capacity.

References

Han, L., Hou, C., Zhao, X., and Rasmussen, K. (2014). “Behaviour of High-Strength Concrete Filled Steel Tubes under Transverse Impact Loading.” Journal of Constructional Steel Research, 92, January, pp. 25–39., doi:10.1016/j.jcsr.2013.09.003