Blast and seismic resistant concrete-filled double skin tubes and modified steel jacketed bridge columns
Fouche, Pierre P.
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A proposed paradigm in engineering of bridges prone to the effects of multiple hazards calls for designing and detailing new bridges, as well as retrofitting existing bridges, so that an integrated structural concept provides protection against all credible hazards. This multi-hazard approach is believed to lead to structural systems that are optimal and offer a more uniform level of safety against various credible relevant hazard scenarios. Toward this objective, research was conducted to develop and experimentally validate two proposed structural concepts capable of achieving the objective of multiple hazard protection for highway bridges, namely Concrete Filled Double Skin Tube (CFDST) and Modified Steel Jacketed Columns (MSJC). CFDST is proposed as seismic and blast resistant column for new bridge multi-column bent. MSJC, on the other hand, is a "retrofit-of-the-retrofit" concept which adds blast protection to the capability of Steel Jacketed Column (SJC) already known to provide seismic resistance. Performance of CFDST is investigated both under cyclic pushover and blast tests whereas MSJC is tested under blast loading only using &frac14; scale column prototypes. The energy dissipation of CFDST under cyclic loading was found to be excellent. Under credible blast scenario, CFDST deform in bending without significant loss in capacity to carry load. For near-contact explosion, another energy dissipation mechanism is engaged in the form of cross-section deformation. In both credible and near contact blast explosion, MSCJ is found to be able to develop large flexural deformations which are not achievable with non-modified SJC that are usually prone to direct shear failure. Equations are also presented to help designer predict the behavior of CFDST under blast and earthquake loads. Comparison to the experimental data generated in this research as well to data available in the literature shows that those analytical results are accurate, and in some instances conservative.