Dynamic Effects on Steel Frames with Concrete Slabs under a Sudden Edge-Column Removal Scenario

Abstract

The dynamic effect of structures under column removal scenarios is investigated by conducting comparative experiments on two identical steel frames with concrete slabs. One frame suffers from a static edge-column loss, while the other is subjected to a dynamic column loss that is simulated by imposing an impact on a three-hinged column. The vertical deflections at the column-removal location of the two frames are reported and compared. The stress measurements at key locations of the frame in the static test are also presented. Numerical models are created and validated against experimental results. To quantify the dynamic effect of structures under a sudden edge-column loss, a dynamic amplification factor (DAF) is analytically determined based on the principle of energy conservation and is verified against validated numerical analyses. Parametric studies are also conducted on DAFs for various deflections and stiffness ratios. The experimental results suggest that the two orthogonal steel beams intersecting at the column-removal location deform linearly. The double-span beam after column loss suffers more external loads than the cantilever beam perpendicular to it. The positive yield lines diagonally distribute at the slab bottom, extending from the column-removal location to the corners of the slab. It is found that, owing to the dynamic effect, the ultimate bearing capacity of the frame in the test decreases by approximately 25.6% under a sudden edge-column loss scenario. The discrepancies between the dynamic and static deflections are intensified when the initially imposed gravity loads increase. The DAF at the ultimate limit state of composite frame structures due to a sudden edge-column loss can range from 1.15 to 1.4. Ignoring the enhancement of membrane and catenary action to the resistance can result in an underestimation of the dynamic effect of frames at large deflections. The method for calculating DAFs proposed by Department of Defense is not conservative in practical safety design since a monotonously decreasing value is designated.