Are You Positive About Negative Phase?

摘要

Explosions in air create both an initial overpressure load (i.e., positive phase) and a subsequent underpressure load (i.e., negative phase), before conditions ultimately return to equilibrium. The positive phase load has traditionally been the focus of blast design efforts. While the magnitude of the exterior peak positive pressure is always higher than the subsequent negative pressure, the effect on loaded structural and facade components may not be fully represented by considering only positive phase blast loads. In addition, there are cases when negative phase infill loads may be significantly higher than positive phase infill loads. Design professionals need to understand negative phase blast loads and their corresponding impact on structural response. Herein we provide a brief review of airblast wave characteristics for high explosives (HE), discuss the impact of negative phase both analytically and based on explosive testing, and review typical design practices. Based on this review, we present key recommendations for design professionals and researchers in consideration of negative phase in testing, analysis, and design.