Blast and Earthquake Resistant Bridge Pier Concept: Retrofit and Alternative Design Options Pierre Fouché 1 , Michel Bruneau 2 , Vincent Chiarito 3 and Jared Minor 4 1 Department of Civil and Structural Engineering, University at Buffalo, Buffalo, NY, USA 2 Department of Civil and Structural Engineering, University at Buffalo, Buffalo, NY, USA 3 Vincent Chiarito, MSc, US Army Engineer Research and Development Center, Vicksburg, Mississippi, USA 4 Jared Minor, Eng., US Army Engineer Research and Development Center, Vicksburg, Mississippi, USA ABSTRACT 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. INTRODUCTION There is a growing concern that bridges already prone to earthquakes actions may become targets for terrorists seeking to inflict psychological and economic woes on this nation. This concern is justified as threats have been received against bridges across the nation. In this context, highway bridges seem more accessible and vulnerable than landmark bridges which are closely monitored. In many instances, the destruction of a highway bridge can have profound effects on the economic circuit those infrastructures support. Protecting those critical components of the nation’s infrastructure requires a new paradigm for the design of bridges exposed to natural and manmade hazards. One that relies on a system approach in which a single structural concept is used to provide protection against all credible hazards is proposed in this study. Such a concept should accommodate consistent demands imposed by the hazards and provide satisfactory performance for conflicting demands. Because of their inherent structural qualities, ranging from higher strength, substantial toughness and ductility and their applicability to situations requiring accelerated constructions or repairs, CFDST and MSJC are proposed as candidate concepts in that approach.