Estimation of the Impact of the Forces from an External Explosion to Building Faces on the Responses of a 3D Frame Structure

Surface explosions resulting from terrorist attacks will produce a hemispherical shock wave in the air, which, upon release, can affect five faces of the building which is in front of it. Given the fact that conventional buildings are usually exposed to such explosions, this study examined the effect of pressure to each face of a building on the responses of the structure and has compared different relevant scenarios. This study, which includes the following two steps, was conducted as a case study on earthquake resistant RC buildings, with the help of UFC guideline and using the software SAP2000. In the first step, responses of loading on each face were separately calculated so that they were compared with the responses from overall loading on all faces. The sensitivity of the responses and their ratio to the variables considered were evaluated in the second step. Accordingly, an outline was formed on the explosion hazards considered for these types of buildings. 1. Introduction Following the increased terrorist attacks in the past decade and consequently many human and financial losses to the international community, extensive studies are underway on the phenomenon. Structural engineering is a field that has entered into this arena to reduce losses and examine the nature of the phenomenon and its effects on buildings where people gather and are the target of such attacks. In addition to these studies, some researches have been conducted on issues related to nonterrorist and accidental explosions as well as side phenomena of explosion. In studies close to the subject of our research, which were conducted in recent years to evaluate the vulnerability and damage to an RC frame building affected by the explosion, it was found that a combination of global and local analyses are needed to evaluate the effect of explosions on structures; the former to determine the critical and more damaged members and the latter to evaluate the extent of damage and the behavior of members [1]. In addition, a study about the effect of seismic design on the behavior of an RC frame building against internal and external explosions showed that, although seismic criteria do not provide sufficient structural robustness against blast scenarios, they cause more strength and less displacement in the building [2]. The results of a study focused on the residual strength of RC building columns which show that the use of seismic design can significantly reduce the extent of direct damage from the explosion and subsequent collapse [3]. Another study on concrete buildings also indicates