Retrofit strategies to protect structures from blast loading

Structural retrofits to buildings can be implemented to increase the protection level to occupants from potential terrorist bombing attacks. Retrofit strategies discussed in this paper can be categorized into three groups: (i) strengthening concepts, (ii) shielding concepts, and (iii) concepts to control hazardous debris. Strengthening concepts such as span reduction and increasing member sections are considered in this paper for three common construction systems including steel, concrete, and masonry. Shielding concepts are intended to prevent structural members from being fully loaded by blast forces and range from local area applications to entire building coverage. Examples of shielding concepts include a new section of wall that shields a vulnerable portion of the building or a new structure built over an entire building. Examples of concepts to control hazardous debris include arresting or deflecting failed cladding away from critical areas with "catch systems" or internal shield systems. This paper is intended to discuss typical building retrofit strategies for primary structural members (load bearing) and secondary structural members (nonload bearing) through strengthening, shielding, or controlling hazardous debris.