This paper summarizes a research program undertaken to develop cost-effective solutions aimed at protecting new and existing bridge column bents against multiple natural and manmade treats such as earthquakes and blast. Concrete-Filled Double Skin Tube (CFDST) column and Modified Steel Jacketed Column (MSJC) designs were proposed and tested for new bent construction and retrofit, respectively. While CFDSTs maintained their cross-section geometry in dissipating energy under cyclic loading, under severe blast loading, they deformed locally to dissipate the applied impulse and have enough residual strength to prevent collapse. MSJC, on the other hand, were developed to eliminate a deficiency observed in the form of direct shear failure near the top and/or the bottom of the jacket for steel jacketed column (SJC) subjected to blast loading. The proposed modification increases direct shear resistance in the shear-deficient areas and does not interfere with the ability of the jacketed columns to resist earthquake loading.
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