Stability of Steel Columns Subjected to Near-Field Detonations

Blast attacks are no longer uncommon threats to modern society. For steel columns subjected to far-field detonations, several design approaches have been developed by government agencies and organizations. However, there are no design provisions for steel columns subjected to near-field detonations, which do not necessarily cause bending, but often cause breaching of a section instantaneously. The reduced cross-section can be the weakest part of the column, where a premature buckling failure can be precipitated. Recently, provisions were developed for steel bridge towers subjected to near-field detonations. Although bridge towers and building columns are major structural members to support vertical loads similarly, the same approach as bridge towers cannot be applicable to steel columns, due to the differences in geometry and in the order of magnitudes in charge weights and stand-off distances. The purpose of the present study is: first to identify all possible failure modes of standard wide-flange steel columns subjected to near-field detonations, second to evaluate column performance with lost or deformed components, and third to suggest practical mitigation design methods to save columns. Additional protective layers are considered, such as steel plate and reinforced concrete layers around columns, for more efficient and practical mitigation designs. Extensive parametric studies are performed using non-linear explicit finite element analysis for various sizes, charge weights, stand-off distances and protective layers. The results are then used to develop simple design approaches that can be used by practicing engineers. The numerical approaches are validated through experiments by others.

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