Dual-Hazard Blast and Seismic Behavior of Concrete-Filled Double-Skin Steel Tubes Bridge Pier

The dual-hazard inelastic behavior of concrete-filled double-skin steel tubes (CFDSTs) is experimentally investigated as a substitute to reinforced concrete columns for bridge piers in multihazard applications. Results demonstrate that CFDSTs exhibit substantial toughness and ductility that can help achieve satisfactory performance when exposed to seismic and blast hazards. Under cyclic loading, for all specimens designed as part of this testing program, yielding of the section preceded buckling of the outside tube. The onset of local buckling of the outside tube was not observed until well beyond 4% drift, and failure of all the sections happened generally beyond 7% drift, even when compactness of the outside tube met only the AISC seismic provisions requirements for moderately ductile behavior. In the cyclic tests, although pinching of the hysteresis curve happened during the test, the curves remained stable. For the blast tests, all sections behaved in a ductile manner when subjected to near-contact charges; but for extreme conditions, sections having large voids in their cross section experienced significant denting. Overall, these tests validated the viability of CFDSTs in compliance with AISC compactness requirements for bridge columns in the dual-hazard application considered here. (C) 2017 American Society of Civil Engineers.