Approach to Developing Design Charts for Quantifying the Influence of Blast Wave Clearing on Target Deformation

If a structural component is located close to the free edge of a building, clearing of the blast wave around the target edge may significantly influence the temporal characteristics of the applied pressure. Because of this, traditional analysis methods assuming a linear decaying load may not be valid, particularly if the blast event imparts a relatively large impulse from the negative phase. Treatment of this phenomenon is brief in the literature, and its influence is usually neglected. This article presents an approach to quantifying the influence of clearing on target deformation, through rigorous analysis of elastic–perfectly-plastic equivalent single-degree-of-freedom (SDOF) systems. The cleared load is evaluated for structural components situated at various distances from the free edge of a reflecting surface using the Hudson acoustic approximation. The results from the SDOF analyses are then used to draw up design charts for determination of the likely influence clearing may have on the design of blast-resistant structural components. Four regions are identified: areas where clearing is beneficial, where clearing has no effect, where clearing is acting adversely, or where clearing is acting highly adversely. The method presented herein provides clear demarcation of these regions.