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Canadian Long Span Earth Covered Magazines – Design Challenges
H. (Vaidy) Vaidyanathan, P.Eng., Senior Structural Engineer;
Department of National Defence, Ottawa, Canada.
David D. Bogosian, P.E, Senior Principal Engineer;
Baker Engineering and Risk Consultants Inc, El Segundo, California, USA
Abstract
Canadian Long Span Earth Covered Magazine (CLSECM) has unique structural dimensions such as large column-
free span of about 17 m. This poses considerable design challenge in that the inter-magazine distance (IMD) and the
blast load have to be adjusted, as the design is governed by the long span roof and not the headwall/door assembly,
as usually observed in ECMs with lesser spans. Blast loads have to be determined from test results based on specific
IMD, instead of the standard 7bar/3 bar load criteria for standard IMD spacing, as listed in NATO and other
publications. Customized IMD and the associated blast load ensures achievement of an optimum blast hardened
CLSECM design, without undue compromise on real estate acquisition for siting of the CLSECM cluster (rear-front
and side-side configuration). The initial design, done in late 80s, was based on SDOF analysis using decoupled
components of CLSECM. Recent evaluation of the design, completed in 2016, is based on modern Finite Element
tool like LS-DYNA using integrated components of CLSECM, and demonstrates the conservatism inherent in the
simplified approach that required many assumptions. Regardless of the structural adequacy of the CLSECM in its
current configuration, it has also been evaluated for the classification of 7bar/3bar ECM standard, since this
classification is employed for Quantity-Distance criteria for siting and licensing purposes, a demand worth proper
examination from blast engineering design perspectives.
Keywords: Earth Covered Concrete Magazine, Long Span Concrete Roof, Blast Load Design, Single Degree of
Freedom Analysis, Finite Element Analysis (LS DYNA), Earth Covered Magazine Bar Rating, Earth fill overlap
Introduction
Ammunition storage facilities in the Canadian Forces Ammunition Depots (CFADs) date back to the days of the
Second World War. Most of these magazines for storing Ammunition and Explosives (A&E) were found to be
deficient in many respects and did not meet the requirements of safety, security, shelter, operation and long term
warehousing. Consequently, in the early 1990’s, the Department of National Defence (DND) embarked on a
magazine replacement program with the development of standard magazines to accommodate the long term
warehousing requirements, maximize storage efficiency and improve safety & operations. The following design
requirements were prescribed for the development of standard Earth Covered Magazine (ECM), to allow for varying
storage capacity with minimal design/construction adjustments. This led to the development of Canadian Long Span
Earth Covered Magazine (CLSECM), designed by departmental engineers. These were then site-adapted later by
external Consultants at various locations, as required. However, it must be emphasized that the DND inventory still
continues to accommodate other types of less structurally glamorous storage magazines, which are planned to be
assessed under the Ammo Safety Compliance Program.
Design/Construction Requirements
CLSECM design/construction features meet the following requirements:
Safety
The structure should resist all normal loads such as its own weight, earth, snow and live loads on roof and
lateral earth pressures on walls.
An accidental explosion within one magazine i.e. the donor (Potential Explosion Site – PES) should not
result in propagation of detonation in adjacent magazines i.e. the acceptors (Exposed Site – ES). The PES is
not expected to survive the internal accidental explosion. In addition, there is no specific requirement to
protect or limit the level of damage to the ES, except to prevent sympathetic detonation of its explosive
contents.
