Blast and Impact Loading and Response of Structures
Full Session with Abstracts
Blast-resistant analysis, design, and testing frequently use blast pressure and impulse for defining the load environment and associated basis-of-design for components and structural systems. In the past, a number of blast-resistant criteria utilized established peak pressure and impulse values associated with a pre-determined design-basis explosive charge weight and standoff distance. As blast-resistant analysis and design has evolved, these standard pressure and impulse definitions have been employed less, and instead, acceptable limits of response are provided in connection with a site-specific design-basis explosive threat and standoff. However, many times these design-basis-threats are security-sensitive, and as a result not shared with product vendors or designers of structural components or cladding. However, design-basis pressure and impulse values are often still communicated in the form of performance-based specifications, conventional construction standoff distances, and in some cases even “equivalent” static design loads. When blast loads are defined solely in terms of pressure and impulse, a linear equivalent function is often assumed. However, geometric variation of the loads over an area of structure, negative phase, clearing, and other factors can all contribute to the dynamic response of structural components subjected to blast loads based on the facility’s size, geometry and location. Hence, it is important for designers to understand how these factors can affect designs prepared from ‘blind’ performance-based specifications and limitations on simplified load definition, particularly for designs whose inherent features may be subject to more complex load environments. A review is provided of the effects of various load definitions on design outcomes using linear-equivalent loads, static-equivalent loads, pressure-impulse diagrams, standoff distance limits, dynamic load histories, and performance of windows, components and cladding, and structural members. Recommendations are provided for designers in the development of design-basis loads and performance specifications to facilitate proper coordination of delegated design items.