Response of roof beams in buildings subject to blast loading: Analytical treatment

Among the lateral loads that a building structure may experience is that produced by blast from an explosion. The analysis of the response of building structure to blast loads is traditionally carried out on a member-by-member basis. The magnitude and variation of blast load with time depends on the position of the member being considered in the building. The nature of such loads is different for the front face, the side faces, the roof, and the rear face of the building. In particular, loads for the roof and side face members that span in a direction perpendicular to the shock front vary both spatially and temporally in a complicated manner. In the current practice, such loads are represented by an equivalent load that is spatially uniform but varies with time. The roof or the side face member along with the load acting on it is then converted to a single-degree-of-freedom system, whose analysis provides the desired response parameters, such as deflections and stresses. It is shown in this paper that the current methodologies provide widely differing results whose accuracy is suspect. A method that provides a better representation of the load variations and a more accurate procedure of analysis is presented. The implementation of the method is carried out through a computer program developed for the purpose and it is demonstrated that the entire process is as simple as the present techniques based on a single-degree-of-freedom representation.