The use of vehicle bombs by terrorists to attack building structures has become of increasing concern to structural engineers since the bombing of the marine barracks in Beriut (1982). This is particularly true following attacks on the Murrah building (1995). Due to increasing threat of vehicle bomb attack, structural engineers have developed methods of design and analysis to protect against blast loads. However, the behavior of structures under blast loads is difficult to understand. Current design for air blast loads generally uses simplified analysis procedures that were developed in the late 1950’s [19]. More recent modeling and computation capabilities can readily be used to provide a more exact estimate of the structural behavior under these extreme loads. It has been suggested that buildings designed for strong ground motions will also have improved resistance to air blast loads. As an initial attempt to quantify this behavior, the responses of a three story and ten story steel building, designed for the 1994 building code, with lateral resistance provided by perimeter moment frames, are considered. An analytical model of the building is developed and the magnitude and distribution of blast loads on the structure are estimated using available computer software that is based on empirical methods.

To obtain the relationship between pressure, time duration, and standoff distance, these programs are used to obtain an accurate model of the air blast loading. A hemispherical surface burst for various explosive weights and standoff distances is considered for generating the air blast loading and determining the structural responses. Linear and nonlinear analyses are conducted for these loadings. Air blast demands on the structure are compared to current seismic guidelines. These studies present the displacement responses, story drifts, demand/capacity ratio, diaphragm analysis and inelastic demands for these structures.