Enhancing Constructability and Reducing Construction Costs of Reinforced Concrete Blast Cells
Wi
lliam H. Zehrt, Jr., P.E.; US Department of Defense Explosives Safety Board; Alexandria, VA, USA
Keywords: explosives safety, protective construction, blast design, close-in detonation, detailing, constructability
Abstract
Within the US Department of Defense, “DoD Ammunition and Explosives Safety Standards” (DoD 6055.09-M) is
applied to manage risks associated with DoD-titled ammunition and explosives (AE). These standards provide
protection criteria to minimize serious injury, loss of life and damage to property from an accidental detonation.
Typically, DoD 6055.09-M protection requirements are satisfied by maintaining minimum default separation
distances between AE and exposed personnel and property. If these distances aren’t available, protective
construction may be designed in accordance with “
Structures to Resist the Effects of Accidental Explosions” (UFC 3-340-02)
to provide equivalent protection.
UFC 3-340-02’s blast analysis and design procedures were developed from detonation tests in typical Service
explosives operating and storage rooms. While UFC 3-340-02’s reinforced concrete design procedures are based on
the ACI 318 Building Code, more rigorous requirements are applied, when needed, to ensure adequate performance
under blast loading. These requirements may produce severe reinforcing bar congestion, particularly at element
intersections.
In this paper, UFC 3-340-02’s blast design requirements for continuously supported walls and slabs will be
reviewed, focusing on applications to typical DoD explosives operating and storage rooms. Potential
constructability impacts will be examined, and recommendations will be provided for mitigating them, thereby
reducing construction costs.
Introduction
UFC 3-340-02 classifies protective structures into three categories – shelters, barriers and containment structures.
• Shelters protect personnel and property from an external detonation. They are usually sufficiently separated
from potential explosion sites to satisfy the default DoD 6055.09-M separation distances for thermal hazards.
Accordingly, the exterior walls and roof of a shelter are typically designed to protect occupants and property
from blast overpressures and fragmentation hazards.
• Barriers are designed to prevent the propagation of an explosives detonation.
• Containment structures mitigate the blast effects from an internal detonation to acceptable levels. Containment
rooms/cells may be designed to protect areas within the building in which an accidental detonation occurs or to
protect other buildings sited within its applicable default separation distances. As a general guideline, UFC 3-
340-02 recommends that the W/V ratio in a well vented cell be less than 0.15 where W is the effective
explosives weight in pounds TNT and V is the interior room volume in cubic feet.
UFC 3-340-02 applies more stringent blast design requirements to structural elements that may be placed in tension
under blast loading or that may be exposed to a close-in detonation. In UFC 3-340-02, a close-in detonation is
defined by the distance from the center of the explosives charge to an element (in feet) divided by the charge’s
TNT equivalent weight (in pounds) raised to the one-third power. To illustrate, AE with an effective charge weight
of 8-lbs TNT located 3-ft from a wall would be located at a scaled stand-off distance of 3-ft/(8-lbs)
1/3
or 1.5 from
the
wall. UFC
3-340-02 applies close-in requirements when the scaled stand-off distance is less than 3.0.
CLEARED
For Open Publication
Department of Defense
OFFICE OF PREPUBLICATION AND SECURITY REVIEW
