Strength evaluation of steel columns significantly deformed due to manmade or natural disasters

It is not uncommon to encounter substantially deformed steel columns, which are not yet collapsed. Such columns can be observed in buildings or bridges, impacted by out-of-control vehicles, derailed subway or rail trains, or boats or debris carried via flooded water, or damaged by blast loads. One of the greatest concerns and interests about the deformed columns is whether or not the columns can sustain full service loads, required by building code. The damages on the columns can result in global or local deformations, which could undermine column stability and strength. The column strength subject to global deformations and subsequent secondary moments could be analyzed by established methods, such as the P-delta analysis or the second order analysis method of the AISC Specification. However, the local deformations, where flanges are flared or web is swollen, cannot be addressed in these methods. The purpose of this study is to investigate the effects of the local deformations on steel columns, permanently damaged by manmade or natural disasters. Focus has been made on steel columns subjected to close-range detonations, in which local deformations prevail, such as flange flaring or web swelling. Explicit dynamic FEA is performed to apply static service loads first, followed by close-range detonation pressures to investigate the combined effects for a series of wide flange steel columns. Attempts are made to come up with relationships between the level of local deformations and the level of sustainable service loads depending on a local stiffness of the columns.

Learning Objectives:
What happens when service loads are applied directly to an end of a column in an explicit dynamic FE analysis without damping?

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