Spall and Breach – Not All Blast Loads are Created Equally

Localized blast loading on structural and architectural systems can generate very different responses than more uniform “global” blast loads.  Spall or breach of a wall, column or other building member is the direct result of a typically close-in explosive or impact loading.  Threats at large standoff distances create a uniform load on a structure, but if the threat is close-in, the load becomes orders of magnitude higher in pressure and non-uniform in spatial application, generating completely different response mechanisms in the structure or architectural elements.  The shock wave from a close-in threat will propagate through the component several times before more global responses (shear or flexure) can take place.  This localized shock derived material response can manifest itself as front face (exterior) cratering or rear face (interior) spall or scabbing.  If the load is large enough, the front face cratering and the back face spall or scabbing will meet, causing a through thickness breach (hole) in the section.  In order to mitigate spall and breach, our engineers routinely work directly with the structural engineer and architect to harden the building components or create an esthetically pleasing standoff distance.  As little as 6-inches of standoff distance can be the difference between safety and failure.  With over 30 years of design experience, our engineers have performed tests, authored design procedures and specifications and provided practical design solutions with minimal impact on the architectural design.  We’d love the opportunity to discuss your next project.