Blast Resistance of Steel and Composite Bridge Piers and Decks
Professor Abolhassan Astaneh-Asl, University of California, Berkeley
Doctoral Graduate Student Jin Son, Univ. of California, Berkeley
Post-doctoral researcher Marcus Rutner

Abstract:

The main objectives of this research and development program were: (a) to investigate performance of steel bridge piers and roadway decks of elevated freeways and major long span bridges subjected to blast loads and (b) to develop economical technologies that can limit the damage to these bridge components to a minimum during the blast and can prevent progressive collapse of the bridge after the blast.  The analyses consisted of building realistic non-linear models of typical bridge piers and roadway deck systems and subjecting the model to realistically simulated blast effects using MSC.Dytran software of MSC Software Corporation. The blast load levels used in the study were

representative of various levels of car bombs. The paper focuses on comparing behavior of typical steel bridge components and their hardened versions subjected to the same amount of explosives  without disclosing the amount of explosive in the paper.  The bridge pier sections studied were single cell steel hollow box and multi-cell steel box sections. To study hardened versions of these steel sections, two composite cross sections were proposed by the authors and were included in the studies.  The deck types studied were typical steel orthotropic deck system as well as traditional reinforced concrete deck slab supported on steel plate girders.

The study indicated that  the most important parameter for blast resistance of steel and composite bridge components  is ductility of material and not the strength.  For orthotropic decks, steel with medium range strength and high ultimate strain performed much better than the deck with a very high strength steel but less ultimate strain. . For composite decks, the deck with normal strength concrete slab performed much better and had much less damage than the deck with high strength concrete. 

The steel single cell and multi-cell piers with medium level of yield strength performed much better than the piers with very high strength steel. The composite piers, proposed by the authors as a measure of economical hardening of steel piers, performed extremely well. In these composite piers, the steel portion of the pier sustained very limited damage from the blast while some of the concrete elements were crushed by the blast and acting as “sacrificial” elements provided very valuable and needed energy dissipation and absorption capacity to the section. 

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