Wang, Han and Hou 2013

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Experimental Study and Results

In this paper, 22 CFTs were tested with axial loading and lateral impact, with the main parameters being load applied, constraining factor, and impact energy. The concrete tubes were cold-formed with vibration, and fixed-sliding end conditions were applied. In order to apply impact loading, a mass of 229.8kg was applied, and the impact energy was changed by changing the drop height of the hammer. The hammer was lifted to the designated height, and released in order to come into contact with the mid-span of the column. From the test, it is shown that as the impact velocity increased of the lateral impact, with no additional axial load, the deflection increased. Furthermore, the larger the impact energy, the greater the local buckling and fracture occurs. With the increase of height and velocity, the peak impact force and load duration also increase. The specimens that were tested with axial force, in addition to constant impact loading could display a decrease in residual lateral deflection. Cracking of the concrete occurs at both the top of the support ends and the mid section, however no major shear failure was observed.


Analytical Study and Discussions

A finite element analysis was performed using the ABAQUS module in which both the steel and concrete components of the tubes, as well as the hammer were simulated using 4, 8, and 4 node shell elements, respectively. The yield strength and ultimate strength of the steel under certain strains could then be calculated using the Cowper-Symonds model. The test results of the concrete under the impact loading displays an increase of compressive strength with an increase of strain rate, as well as the relationship between tensile strength and strain rate can be modeled with the CEB-FIP code. The FEA proved that it can predict buckling and deformation of the CFST, in addition to the cracking of concrete.


References

Wang, R. Han, L., and Hou, C. (2013). “Behavior of Concrete Filled Steel Tubular (CFST) Members under Lateral Impact: Experiment and FEA Model.” Journal of Constructional Steel Research, 80, January, pp. 188–201. doi:10.1016/j.jcsr.2012.09.003