MANUAL OF NATO SAFETY PRINCIPLES FOR THE STORAGE OF MILITARY AMMUNITION AND EXPLOSIVES (May 2010)

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(d)

On sloping terrain when the stacks are contiguous line AC must pass through at least 1.0 m

barricade material or undisturbed natural earth.

(e)

On sloping terrain when two stacks are not contiguous but the quantity-distance between

them is less than 5 Q^1/3, the 2° rule is not applicable.

Stacks separated by at least 5 Q^1/3

When stacks, contiguous or not, are separated by the quantity-distance 5 Q^1/3 or more, barricade requirements

are assessed individually with respect to each stack.

Length of Barricade

The barricade length is determined by extending the barricade exclusive of the end slope to 1.0 m beyond lines

between the extremes of the two stacks of ammunition under consideration. These lines must pass through at

least 2.4 m of barricade material or undisturbed natural earth (see Figure 3-IV).

Distance from Stack to Barricade

The distance from a stack to the foot of a barricade is a compromise. Each case is considered

individually to achieve the optimum solution taking account of the following factors.

A barricade close to a stack results in smaller dimensions for the barricade to intercept high velocity

projections through a given solid angle. However, on sloping terrain the minimum separation may not

result in the smallest barricade.

A barricade further away from the stack results in easier access for maintenance and for vehicles, and

the possibility to site the barricade outside the predicted crater, when the PES contains ammunition

and explosives of Hazard Division

1.1. Avoidance of the crater is an advantage in some

circumstances, see subparagraph 2.3.3.3.c). The barricade must be sited so that the crater does not

undermine it more than one third of its thickness at ground level.

2.3.3.3.

Material for Earth Barricades and for the Cover of Buildings

Earth for barricades and for cover of buildings should be made of material as prescribed below. When concrete

or brick is used in conjunction with earth, either of these materials may be taken as equivalent to 4 times its

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thickness of earth with regard to the ability to stop fragments. The concrete or brick may be used to support the

earth or it may be those parts of the roof and walls of a building which intercept the high velocity projections.

There are two types of precaution which are necessary in the construction of earth barricades or the earth-cover

for buildings used for storage of ammunition and explosives. One type relates to the potential hazards to other

ammunition and to personnel in the event that the material is dispersed by an accidental explosion in the

contained building. The other type relates to the precautions necessary to ensure structural integrity of the earth

barricades or cover.

There is no need to consider the first type of precaution if it can be predicted that the material would not be

dispersed by the postulated explosion. This will be the case if the barricade is sited beyond the crater radius.

Scouring of the top surface by air blast can be neglected. The crater dimensions would be determined by the

geometry of the stored explosives, their height above ground or depth of burial, and the nature of the ground.

Unless the arrangement is particular asymmetrical, a good working estimate of the crater radius can be

calculated from the formula:

Crater radius (m) = ½ (NEQ (kg))^1/3

This radius is measured from the centre of the explosives. In certain soil conditions (saturated soil or clay) the

crater may be larger than calculated from the above formula (more complete information on cratering

phenomenology is given in paragraphs 2.5.6.1. and 2.5.6.2.). In such conditions consideration should be given

to increasing the Inter-Magazine Distances.

Where it is possible that the material would be dispersed by an explosion, precautions should be taken to

reduce the hazard of large stones causing initiation by impact upon ammunition or explosives in adjacent

storage sites. Where the storage site under consideration is near a densely occupied area, such as a group of

explosives workshops, consideration should also be given to the hazard to personnel from flying stones etc.

The selection of material and its use should be governed by the following prescriptions which represent a

reasonable compromise between undue hazards and excessive costs of construction:

Do not deliberately use rubble from demolished buildings.

Ensure that stones larger than 0.3 m girth (about the size of a man's clenched fist) are removed during

construction. Other deleterious matter should also be eliminated.

In climates where the ground becomes severely frozen, consideration should be given to the provision

of an impermeable cover over the material or drainage to keep out excessive moisture.

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The second type of precaution mentioned in subparagraph b) above, relating to structural integrity, applies in

all cases. For this purpose the material should be reasonably cohesive and free from excessive amounts of trash

and deleterious organic matter. Compaction and surface preparation should be provided as necessary to

maintain structural integrity and avoid erosion. Where it is impossible to use a cohesive material, for example

at a site in a sandy desert, the earth-works should be finished with either a layer of cohesive soil or an artificial

skin. On the other hand one should avoid solid, wet clay during construction since this is too cohesive and

would result in an excessive debris hazard.

2.3.3.4.

Walls as Barricades

A building without windows and with walls with a thickness of 45 cm reinforced concrete (70 cm of brick) or

its equivalent is acceptable as a barricaded building with regard to stopping fragments from an explosion in an

adjacent building or stack. However, consideration must be given to the necessary blast resistance of such

walls, see subparagraph 2.3.3.1.b)1). Furthermore account should be taken of the increased debris hazard from

such walls at a PES. A 23 cm brick wall protected by a 45 cm brick wall is preferable to a single wall of about

70 cm brick. These buildings need not necessarily have a protective roof.

Walls can often be used to divide a building into individual rooms or compartments in accordance with

subparagraph 1.3.2.2.b). The function of each dividing wall is to prevent, or at least delay substantially,

transmission of explosion between explosives on opposite sides of the wall. the main advantage is that

quantity-distances can then be based on the NEQ in one compartment instead of the aggregate amounts in the

building. A second advantage is that an accidental explosion is less likely to render unserviceable all the stocks

in the building. The specification of such a wall depends upon the quantity, proximity and type of ammunition

or explosives on each side. The design must take into account the likely blast loading, including the effect of

reflections, and the flame, ground shock, primary fragments and secondary missiles (spalling and scabbing

from the remote face of the wall). In order to achieve an efficient and economical design for a particular

situation, expert advice is essential. Information on the scope and state of the art of designing dividing walls is

given in the technical manual "Structures to Resist the Effects of Accidental Explosions, US Army TM 5 -

1300, June 1969" or a newer edition.

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Section IV - Lightning Protection

2.3.4.1.

Definitions

In addition to the definitions given in Part I, Chapter I, Section II the following definitions are used in

connection with protection against lightning.

2.3.4.2.

Air Termination Network

The part of a lightning protection system that is intended to intercept lightning discharges.

2.3.4.3.

Bond

A conductor intended to provide electrical connection between the protective system and other metal work.

2.3.4.4.

Down Conductor

A conductor which connects the air termination network with the earth termination network.

2.3.4.5.

Earth Termination Network

The part of the lightning protection system which is intended to discharge lightning currents into the general

mass of earth. All parts below the lowest test joint in a down conductor are included in this term.

2.3.4.6.

Joint

The junction between portions of the lightning protection system.

2.3.4.7.

Ring Conductor

The ring conductor is that part of the earth termination network which connects the earth electrodes to each

other or to the down conductors.

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2.3.4.8.

Test Joint

A joint designed and situated to enable resistance or continuity measurements to be made.

2.3.4.9.

Zone of Protection

The zone considered to be protected by a complete air termination network.

2.3.4.10.

General

This chapter covers the particularities of lightning protection for ammunition handling installations and

facilities. An effective lightning protection is part of the overall safety concept for the handling of ammunition

and explosives.

Lightning protection systems are to be designed and constructed in a way which ensures an effective and

long-term protection of the ammunition against lightning discharges. Lightning protection systems must be

constructed by specialist personnel and according to the state-of-the-art of lightning protection technology.

As a matter of principle, installations and facilities used for handling ammunition must be equipped with

lightning protection systems. Whether such systems can be omitted in individual cases is to be decided by the

nations. The hazard of lightning discharges and possible consequences are to be assessed within the scope of a

facility-related safety analysis.

A distinction must be made between "external" and "internal" lightning protection. External lightning

protection forms the basis of an effective lightning protection consisting of

air termination network,

down conductors, and

earth termination network.

For internal lightning protection a lightning protection equipotential bonding must be established between the

lightning protection system of a building and the metallic installations and electrical systems of the building.

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2.3.4.11. Lightning Protection Systems for Buildings

As a rule, buildings for the handling of ammunition and explosives (explosive workshops, magazines) are

equipped with two external lightning protection systems, one lightning protection system which is insulated

against the building and one lightning protection system for the building itself.

The insulated lightning protection system is designed to intercept high-current lightning discharges in order to

keep them away from the lightning protection system of the building itself.

The lightning protection system for buildings designed for ammunition handling is to be arranged in such a

way that an electro-conductive cage is established. This cage must surround the building on all sides (ceiling,

walls, ground). The design of the cage depends on the construction of the building.

2.3.4.12. Insulated Lightning Protection System for Buildings

As a rule, fixed air termination networks with a roof conductor in form of a mesh are applied in insulated

lightning protection systems.

The fixed air termination network is to be supported by supporting poles.

The poles shall be positioned at least 3 m from the building.

The mesh size must not exceed 10 m.

Roof edges, projections, etc. shall be located at a maximum distance of 0.3 m from the network.

Even if the network sags, the minimum distance from the roof of the building must be 1.5 m.

If vertical air termination networks are used, their height and zone of protection shall be such as to ensure that

the entire surface of the building will be situated within this zone of protection (see Figure 3-V). The vertical

air termination networks shall be positioned at least 3 m from the site. In case there should be a barricade, the

vertical air termination networks may be mounted thereupon.

Instead of vertical air termination networks trees may be used and equipped with air termination networks if

they are located in an appropriate position.

In buildings with a complete earth of at least 0.5 m, insulated lightning protection can be omitted; this applies

also to earth covers with vent pipes.

2.3.4.13. Lightning Protection Systems for Buildings

Fixed air termination networks are to be arranged on the building with a mesh size not exceeding 10 m x 10 m.

Parts of the building made of nonconductive material which protrude from the network are to be equipped with

suspended air termination networks and pointed conductors. Superstructures made of metal are to be bonded to

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the suspended air termination networks. The air termination networks of the lightning protection system of the

building must be installed in the middle between the conductors of the insulated lightning protection system

(top view). Each building must have one down conductor for 10 m each of the circumference of the building

with four down conductors being the minimum number. Those down conductors should be positioned at least

0.5 m from windows, doors, and other openings. Aboveground pipelines leading up to the buildings are to be

bonded to the down conductor next to them. In the case of reinforced concrete buildings which have connected

reinforcing rods, these can be used as down conductors; these buildings only require air termination networks

but not separate down conductors. Reinforced concrete buildings without connected reinforcing rods are to be

equipped with air termination networks and down conductors. In any case the reinforcement is to be bonded to

the internal ring conductor at intervals not exceeding 10 m.

For earth-covered buildings (e.g. igloo) with an earth-cover of at least 0.5 m a fixed air termination network

having a mesh size not exceeding 10 m x 10 m and installed within or on the earth-cover is a sufficient

lightning protection (see Figure 3-VI). For buildings with a lateral length of less than 10 m two conductors in a

diagonal arrangement are sufficient. Those conductors are to be bonded to a ring conductor. Metal venting

systems which protrude from the earth-cover are to be equipped with down conductors which must be bonded

to air termination networks or the ring conductor. Venting systems made of non-conductive material must be

equipped with air termination networks and down conductors. In buildings made of reinforced concrete the

connected reinforcement can be used as down conductor; it must be bonded to the ring conductor in at least

two opposing locations. Suspended air termination networks are necessary here as well. Instead of a fixed air

termination network, a space screen (e.g. as alternative upgrading measure) may be inserted into the building.

The space screen consists of a network of band steel having a mesh size not exceeding 2 m x 4 m on which a

fine grid (5 cm x 10 cm) is installed. The space screen must surround ceilings, walls, and columns; it is to be

connected to the ring conductor.

2.3.4.14. Earth Termination Networks

Each lightning protection system must be grounded with an earth termination network. In most cases closed

ring conductors or grounding circuits are used for that purpose.

The total earth resistance of the earth termination network shall not exceed 10 ȍ for buildings or groups of

buildings.

The earth termination network and the lightning protection system are to be appropriately connected.

Earth termination networks of adjoining buildings within a radius of 20 m are to be connected underground.

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Ammunition and packaging containing ammunition are usually not grounded.

Test joints are to be integrated into the lightning protection system between down conductor and earth

termination network for test and measuring purposes. They are to be situated approximately 0.5 m above

ground; below the test joint only parts of the earth termination network are permissible.

2.3.4.15. Equipotential Bonding in Lightning Protection

All essential conductive elements of a building such as machines, equipment, radiators, pipelines as well as

large metal items (metal doors and windows, conductive floors) are to be bonded to the lightning protection system via

lines.

2.3.4.16. Lightning Protection Systems for Open-air Stacks of Ammunition

Ammunition stacks endangered by lightning, especially those containing mass-detonating ammunition, are to

be protected by a lightning protection system.

Ammunition stacks are particularly endangered by lightning discharge if they are situated.

on mountain tops, hills,

at the edges of woods, or

under isolated trees.

In general, four horizontal aerial conductors of a rectangular shape (e.g. zinc-coated steel rope with a cross

section of 50 mm² mounted on insulated supports (e.g. made of wood) at least 0.5 m above the upper edges of

the ammunition stack are sufficient to provide lightning protection. On each of the four corners one down

conductor which is to be bonded to the ring conductor shall be installed at least 0.5 m from the stack. The ring

conductor is to be buried at least 0.5 m below ground with a minimum lateral distance of 1 m round the

perimeter of the stack (see Fig 3 - VII). If the stacks are positioned on floor plates the latter are to be connected

with the ring conductor on the four corners of the stack.

For ammunition stacks established temporarily a makeshift lightning protection is sufficient which is arranged

as follows:

A zinc-coated steel rope of at least 50 mm² in cross section or a copper rope of at least 35 mm² in cross section

which is to be supported by 2 supports made of wood or metal is to be tensioned across the stack. Outside the

supports the rope is to be secured in the ground with metal stays.

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Additionally, each support has two stay wires with metal stays. The distance between the rope tensioned across

the stack and the supports to the stack is to be 3 m; in case of deviations it must be ensured that the complete

stack lies within the protected zone (see Fig 3 - V and 3 - VIII).

2.3.4.17. Lightning Protection Systems for Ammunition Bins

In ammunition bins made of concrete the reinforcement forms a conductive cage which is to be grounded using

two earth electrodes (50 cm deep into the ground).

If ammunition bins made of wood are to be equipped with a lightning protection system, they must be provided

with suitable suspended air termination networks and the conductive roof decks are to be included in the

lightning protection system.

2.3.4.18. Minimum Distances of Ammunition from Lightning Protection Systems

Ammunition and packaging containing ammunition are to be stored so as to prevent flash over the lightning

stroke from the lightning protection system to the ammunition or the packaging. Ammunition stacks in a

magazine or an explosives workshop are to be positioned at a distance to walls, support, ceilings, beams, metal

parts, and electrical installations which shall be:

10 cm at least if the lightning protection system is properly designed and meets the requirements of

this chapter,

50 cm at least if the lightning protection system does not meet the requirements of this chapter.

2.3.4.19

Testing of Lightning Protection Systems

Each lightning protection system is to be tested upon completion. The result shall be recorded. The established

values for the earth resistance are to be used as comparative values for future tests.

The proper condition of the lightning protection system is to be ensured by regular inspections and

measurements.

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CHAPTER 5 - DESIGN ENVIRONMENT CRITERIA

Section I - List of Symbols

SYMBOL

DIMENSION

DESCRIPTION

(m²)

Area

A_T

(m²)

Area of target

A_(x)

(m²)

Specifically defined area

A_f

(m²)

Projected area of a projectile/fragment

A_D

(m²)

Drag area

A_v

(g)

Maximum vertical acceleration (shock)

A_w

(m²)

Area of wall

A_v , A_h

(m/s²) . (g)

Maximum vertical/horizontal acceleration

(m/s²)

Acceleration

a_o

(m/s)

Speed of sound

(

^o)

Angle

B, B_x

(¥kg/m^7/6)

Mott constant for explosives

b_f

(m)

Fragment width

(-)

Pressure drop constant in Friedländer function

C_D

(-)

Drag coefficient

C_E

(-)

Equivalent load factor

C_L

(-)

Confidence level

C_P

(m/s)

Seismic velocity in the ground

(m)

Distance

(m)

Blast wave position at maximum loading of

structural element

(kg/m³)

Density/caliber density

(N)

Attenuation force

DIF

(-)

Dynamic increase factor

DLF

(-)

Dynamic load factor

D_a, D_t

(m)

Depth of apparent/true crater

D_v, D_h

(m)

Maximum vertical/horizontal displacement

D/L

(-)

Blast wave position factor

DOB

(m)

Depth of burst

(s)

Duration

d_i

(m)

Mean inner diameter of ammunition case

(J)

Energy

E, E_c, E_m, E_s

(Pa)

Modula of elasticity for concrete, masonry, steel

E_kin

(J)

Kinetic energy

E_cr

(J)

Critical energy

(-)

Exposed site

(N)

Force

F_D

(N)

Drag force

(Hz)

Frequency

f_r

(-)

Reflection factor

(kg/m³)

Ammunition storage building density factor

¥(2·E)

Gurney constant

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SYMBOL

DIMENSION

DESCRIPTION

GOF

Terrain surface

(9.81 m/s²)

Gravity acceleration

(m)

Height

H_s

(m)

Height of building

H_w

(m)

(Height of wall

HOB

Height of burst

(Ns)

Shock impulse

(m⁴)

Moment of inertia

I_s

(Pa-s)

Positive side-on impulse

I_r

(Pa-s)

Normally reflected positive impulse

I_q

(Pa-s)

Dynamic impulse

i_g

(Pa-s)

Gas impulse

i_s

(Pa-s/kg^1/3)

Scaled positive side-on impulse

i_r

(Pa-s/kg^1/3)

Scaled positive reflected impulse

(-)

Shape factor/ballistic density factor

(m)

Span of structural element under consideration

(m)

Length of flight path traveled after which the

fragment trajectory velocity drops to the (1/e)^th part

of the fragment departure velocity

L_^

(m/kg)

L related to the unity mass

L_H, L_L

(m)

Span in transverse/longitudinal direction

L_w

(m)

Blast wave length, positive phase

L_S

(m)

Width of structural element strip

L_w/L

(-)

Ratio between blast wave length and span of the

structural element under consideration

l_d

(m)

Length of debris (average value of sphere and cube)

(kg)

Mass

(kg)

Static/dynamic system mass

(Nm)

Moment

M_A

(-)

Fragment distribution factor

M_e

(kg)

Effective mass

M_ej

(kg)

Crater ejecta mass

M_ex

(kg)

Explosive mass

M_c

(kg)

Total mass of ammunition case

M_d

(kg)

Design fragment mass

M_f

(kg)

Mass of the fragment under consideration

M_o

(kg)

Average fragment mass

M_p

(kg)

Projectile mass

M_str

(kg)

Mass of structure/structural component

M_t

(kg)

Total fragment mass

max

(-)

Maximum

min

(-)

Minimum

(-)

Geometrical constant

N_f

(-)

Number of fragments with masses higher than M_f

N_t

(-)

Total number of fragments

N_d

(-)

Number of fragments with masses higher than M_d

NEQ

(kg)

Net explosives quantity

NEQ_TNT

(kg)

Net explosives quantity; TNT equivalent

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SYMBOL

DIMENSION

DESCRIPTION

PES

(-)

Potential explosion site

P_o

(Pa)

Peak overpressure

P_so

(Pa)

Peak side-on overpressure

P_s

(Pa)

Side-on overpressure

P_a

(Pa)

Atmospheric pressure; ambient pressure

P_a,s

(Pa)

Atmospheric pressure at standard sea level

P_r

(Pa)

Peak reflected overpressure

(Pa)

Pressure

P_(t)

(Pa)

Time-Dependent pressure

P_i

(Pa)

Pressure inside of building

(%)

Probability

Q, Q_exp

(kg)

Charge mass

Q_TNT

(kg)

Equivalent TNT charge mass

Q_o

(kg)

Reference charge, usually expressed at TNT

equivalent

Q_o

(-)

Total number of fragments per unit solid angle

emitted in target direction by ammunition item

Q_x

(kg)

Actual charge mass, usually expressed as TNT

equivalent

(Pa)

Dynamic pressure

q_o

(Pa)

Peak dynamic overpressure

(kW/m²)

Thermal radiation flux/radiation density

q_f

(1/m²)

Fragment density

(m)

Separation/radius/distance

R_a, R_t

(m)

Radius of apparent / true crater

R_e

(m)

Effective projection distance

R_f

(m)

Fragment distance

R_G

(m)

Ground distance

R_m

(N)

Maximum resistance of system

R_o

(m)

Reference distance from center of charge Q_o, for a

defined overpressure or dynamic pressure

R_x

(m)

Distance from center of charge Q_x (kg) at which the

explosion of the charge Q_x produces the same

pressure as that caused by the reference explosion

with the parameters R_o and Q_o

(Pa)

Unit resistance

rho

(kg/m³)

Soil density

rho

(kg/m³)

Air density

(-)

Position index/center of element strip

SGZ

Surface ground zero (point of burst)

T_AG

(s)

Arrival time of ground shock wave

T_o, t_o

(s)

Duration of positive air blast phase

t_of

(s)

Fictitious duration of positive airblast phase

T_a, ta

(s)

Arrival time of shock front

T_a

(

^oC)

Ambient temperature

T_a,s

(

^oC)

Ambient temperature at standard sea level

T_c, t_c

(s)

Clearing time of blast wave at target

T_o

(K)

Temperature

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SYMBOL

DIMENSION

DESCRIPTION

T_r, t_r

(s)

Time of load increase

(s)

Time

t_w

(s)

Duration of loading

t_a,a

(s)

Arrival time of blast wave

t_a,s

(s)

Arrival time of direct ground shock wave

t_c

(m)

Mean thickness of ammunition case

t_c

(s)

Clearing time

t_s

(s)

Time at point of intersection between reflected

pressure and combined side-on / drag pressure

t_r

(s)

Duration of reflected pressure

(m/s)

Shock front velocity

(m/s)

Particle velocity behind shock front

V_a, V_t

(m³)

Volume of apparent/true crater

(m/s)

Velocity

V_cr

(m/s)

Critical velocity

V_f

(m/s)

Final velocity of projections

V_m

(m/s)

Mean impact velocity

V_o

(m/s)

Departure/initial velocity

V_r

(m/s)

Residual velocity

V_s, V_i

(m/s)

Impact velocity

V_v, V_h

(m/s)

Maximal vertical/horizontal velocity

(N)

Weight

(J)

Work

W_f

(N)

Fragment weight (mass)

(m)

Width of structure

X, x

(m)

Deformation

(-)

Position index

X_el, X_p

(m)

Elastic/plastic deformation

Y_el

(m)

Elastic deformation of system

Y_m, Y_p

(m)

Plastic deformation of system

(m/kg^1/3)

Scaled distance

Z_A

(m/kg^1/3)

Scaled normal distance

Z_G

(m/kg^1/3)

Scaled distance above ground

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Section II - General

2.5.1.1

Introduction

This chapter deals with the effects of an accidental explosion or fire in an aboveground ammunition storage

site on persons or surrounding buildings and other engineering works. The magnitude of the effects constitute the

design environment criteria.

2.5.1.2

General Principles

Design Environment Criteria

The design environment criteria serve the purpose of …

. . . preparing risk analyses;

. . . designing and dimensioning ammunition storage facilities;

. . . defining quantity distances;

. . . determining hazard parameters in terms of quality and quantity;

Note:

The quantity distances are based on design environment criteria, threat spectrum as well as performance and

safety requirements.

. . . verifying design drawings and detail specifications for facilities of a particular site in

order to assure compliance with the safety regulations;

. . . modifying buildings originally constructed for other purposes to ammunition storage

buildings and explosives workshops;

. . . planning damage control, fire-fighting and rescue operations.

Basic Data

There is further basic research to be done in order to complete the technological basis required for exploiting

all conceivable uses of explosives and ammunition storage buildings. The technological developments with

respect to ammunition types, building materials as well as design and dimensioning make it necessary to

constantly improve the relevant data and knowledge base. For the economical handling of the problem fields,

special data banks with constant updating are required. Carefully prepared scaled model and full-scale tests

will provide these data, constitute the basis for realistic risk analyses and help saving costs.

2.5.1.3

General Design Aspects

Design Principles

To ensure compliance with the safety requirements for exposed sites, the design methods applied must be

selected according to the following basic conditions.

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(1)

No Design Environment Criteria Available (Standardized Construction)

When no design environment and performance criteria are given, the building shall conform to a

standard construction which, in former explosion events, has proved to be satisfactory for a given

Net Explosives Quantity (NEQ) at a specific distance or has been proof-tested, preferably in full-

scale tests.

With this approach, additional design calculations are not required, and deviations from applicable

construction specifications and quantity distance requirements are not permitted since the

consequences are not predictable.

Note:

This method is inflexible and does no longer constitute a state-of-the-art approach.

(2)

Limited Design Environment Criteria Available

In case only a few quantity distance values are available as design environment criteria, design and

construction will be based on analytical calculations supported by model or full-scale tests. The

construction may be safely used over the full range proved by the calculations. Appropriate

consideration of design criteria (e.g. specified quantity distance) provided, modifications to the

original construction are permissible since consequences of such modifications can be predicted to a

large extent.

Note:

This method constitutes a compromise between empirical and analytical approaches.

(3)

Complete Design Environment Criteria Available

When design environment criteria are available as continuous functions of net explosives quantity

and distance from the Potential Explosion Site (PES), there is complete freedom to choose both the

distance and the type of construction in order to obtain the most economical solution. Design and

construction are based on analytical calculations supported by model or full-scale tests. The

construction may be used over the full range proved by the calculations. Modifications may be made

provided the design environment criteria are taken into account.

Note:

This is the ideal case giving complete freedom with respect to design and modifications.

When seeking the optimum combination of construction type, required quantity distance, and degree

of protection, the following parameters shall be taken into account:

Availability of land for building purposes;

Costs of land;

Construction costs;

Value of ammunition and explosives stored in the Exposed Site (ES) which would become

unserviceable in case of an explosion in the potential explosion site.

For ammunition storage facilities exceeding the minimum strength and blast resistance requirements the

quantity distances may be reduced provided qualified evidence has been furnished.

When designing a building for the storage of ammunition, in almost all cases the donor/acceptor

conflict has to be solved.

A building with donor function should be of lightweight in order to minimize the size and

mass of projections.

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The degrees of protection are distinguished as follows

Degrees of

Hazard

Protection Criteria Remarks

Protection

Division

Virtually

1.1

Against:

Practically instantaneous propagation of explosion by

Complete

ground shock, blast, flame and high velocity projections.

Protection

Result:

Immediate sympathetic detonation not to be

expected.

Stored items largely remain serviceable.

Individual evaluation required for sensitive

stored items.

1.2

Against:

Immediate or subsequent fires and explosion caused by

blast, flame, firebrands protections and lobbed

ammunition.

Result:

Immediate or delayed sympathetic detonation not

to be expected.

Stored items probably remain serviceable.

1.3

Against:

Immediate or subsequent fires among the contents of an

ES by flame, radiant heat, firebrands, projections and

lobbed ammunition.

Result:

Immediate or delayed burning, deflagration or

explosion of stored items not to be expected.

Inflammation of burnable external parts of the

building.

No propagation of fire to stored items.

Degrees of

Hazard

Protection Criteria Remarks

Protection

Division

High Degree

1.1

Against:

Practically instantaneous propagation of explosion by

of Protection

ground shock, blast, flame and high velocity projections.

Result:

High protection against immediate sympathetic

detonation.

Delayed fire and sympathetic detonation to be

expected.

Bulk of stored items probably remains

serviceable.

1.2

Against:

Immediate propagation of explosion by blast, flame and

projections.

Result:

High protection against immediate sympathetic

detonation.

Delayed fire and sympathetic detonation to be

expected.

Loss of stored items depends on effectiveness of

fire fighting.

1.3

Against:

Immediate propagation of fire to the contents of as ES by

flame, radiant heat, firebrands, projections and lobbed

ammunition.

Result:

Delayed burning, deflagration or explosion of

stored items cannot be excluded.

Inflammation of burnable internal and external

parts of the building.

Stored items may catch fire.

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Degrees of

Hazard

Protection Criteria Remarks

Protection

Division

Limited

1.1

Against: Practically instantaneous propagation of explosion by

Degree of

ground shock, flame and high velocity projections.

Protection

Result:

Immediate sympathetic detonation to be

expected.

Stored items severely damaged and

unserviceable.

1.2

Against: Immediate or subsequent fires among the contents of an

ES by flame, radiant heat, firebrands, projections and

lobbed ammunition.

Result:

Limited protection against immediate

sympathetic detonation.

Fire and sympathetic detonation to be expected.

Loss of stored items in case of ineffective fire

fighting.

Due to the high costs involved, virtually complete protection will only be reasonable, if the net explosives

quantity is small or if the total quantity of the items stored inside the building is divided by walls into smaller

portions thus avoiding immediate sympathetic detonation.

Protection Against Sympathetic Detonation

Ammunition storage buildings shall be designed in such a way as to reliably prevent sympathetic detonation of

stored explosives.

Thus, the primary design objective must be to prevent destruction or collapse of the building.

Plastic deformation of structural parts shall be acceptable as long as the stability of the building is not

impaired. Deformation, however, shall be less than the separation distance between the deformed part

and the stored items so that no shock propagation is possible.

Proper design of the exposed site and adequate quantity distance from the potential explosion site are essential

factors to prevent immediate sympathetic detonation which may be initiated by high-energy projections,

spalling, torn-off structural parts (e.g. pillars, doors etc.), or by the collapse of the building.

Degree of hazard, type of stored items, design, and environment of the ammunition storage facility are critical

parameters for the evaluation of the sympathetic detonation load case.

It is impossible to specify quantity distances which provide complete safety from sympathetic detonation,

damage or injury. Economical and internal operational reasons may temporarily justify a calculated risk to

personnel and material. It also may be necessary under certain circumstances to deviate from regulations due to

tactical requirements. Design measures should be taken to prevent spalling inside the building. This applies

primarily to buildings which are not earth-covered. Tests have demonstrated that spalling velocities are usually

overestimated except when caused by contact detonations. Dangerous spalling effects are not to be expected

with earth-covered buildings.

Lobbed ammunition may explode upon impact. The explosion of ammunition with a caliber of more than 155

mm impacting close to the wall or on the roof of an exposed storage building may cause a sympathetic

detonation.

Ammunition storage buildings shall provide full protection against projections of any kind, such as fragments,

structural debris, lobbed ammunition and spalling. The limits for spalling, below which no firing of packaged

initiating devices will be caused, are specified in AASTP-1, 2.3.3.2.

According to this paragraph, for the different spalling velocities the following criteria shall apply

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(-->> Table [5.27]) . . .

For velocities ≥ 50 m/s the kinetic energy shall be E_kin ≤ 2500 Js

For velocities ≤ 50 m/s the impulse

shall be I ≤ 100 Ns

Penetration by projections shall only be acceptable if the residual velocity (V_r) of the penetrating projectile is

below the critical velocity (V_cr) at which sympathetic detonation is induced.

For V_r ≤ 50 m/s

V_cr

100 / M_p

(m/s)

For V_r ≥ 50 m/s

V_cr

¥ (5000/Mp)

(m/s)

Loads / Design Loads

As a rule, ammunition storage buildings should be individually designed according to local design

environment criteria. Existing design formulations and data will allow the sufficiently safe determination of the

various loads to be expected.

An accidental explosion or fire in an aboveground ammunition storage site constitutes a hazard to personnel,

buildings, facilities, and other material due to airblast, fragments, structural debris, shock and thermal

radiation. These effects, which occur almost simultaneously, define the design environment criteria for

planning and designing ammunition storage buildings. The design loads for an exposed building or structural

part of a building are functions of these effects as well as of geometrical and material conditions at the exposed

site.

(1)

Rebound of Closure Components

An airblast acting on closures, such as doors and gates, will produce extreme rebound loads on the

latches and hinges. In order to ensure security of building closures, the ability of the construction to

withstand these rebound loads must be mathematically proven.

The parameters of a blast wave due to an accidental explosion depend upon the complex conditions at the

explosion site.

These include:

Distribution of explosives at the storage site;

Loading density;

Types of explosives;

Explosives content of the stored ammunition;

Mass and type of earth cover and building;

Constructional stability of the building.

Design Details

(1)

Aboveground Ammunition Storage Buildings

For a storage site with earth-covered or detached uncovered aboveground ammunition storage

facilities (e.g. igloos), the most straightforward and safe quantity distances will result if the storage

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area has a rectangular shape, the axes of the ammunition storage buildings are parallel to each other,

and all doors face in the same direction.

An arrangement with the front walls of the buildings facing each other should be avoided for

economical (area required) and safety reasons.

Due to its type of design, an earth-covered ammunition storage building (igloo type) will effectively

withstand external effects such as airblast, fragments, and exploding lobbed ammunition, provide

protection of the stored items and prevent sympathetic detonation.

(2)

Ammunition Stacks

Exploding ammunition stacks in the open or inside storage buildings may produce highly effective

projections, such as fragments, structural debris, and lobbed ammunition, which may penetrate into

a storage facility and immediately ignite the stored explosives and ammunition. Ceilings, doors, and

closures must be designed in such a way as to intercept projections of any kind or reduce their

velocity to a safe residual value. As an additional safety measure, barricades may be retrofitted,

which, however, will provide no protection against projections from above.

(-->> AASTP-1, 1.4.6.1. to 1.4.6.10.)

(3)

Walls

The minimum thickness required for wall and ceiling slabs affording adequate protection against

fragments, structural debris, detonating lobbed ammunition and firebrand, will depend upon the type

of the stored ammunition.

Table

[5-1] contains reference values for various construction materials related to selected

ammunition types.

(-->> Ref [1], [2])

(4)

Roofs and Ceilings

Roofs and ceilings may be designed such as to perform the following functions:

Contain fragments and prevent emission of projections.

Provide shielding against airblast, projections, and lobbed ammunition.

(5)

Pressure Relief Walls

An explosion in an asymmetrical ammunition storage building with a weak wall or roof (frangible

cover) will produce directed effects (airblast, flames, projections).

Pressure relief walls

(frangible covers) as well as doors and other closures shall be designed

fragment-proof and debris-proof. With standard earth covers, there will be no problems except in

case of a contact hit.

In case of not earth-covered ammunition storage buildings, the conflict between pressure relief and

fragment resistance requirements has to be solved. These requirements lead to contrary design

solutions. An approach to this problem is the erection of barricades to shield the pressure relief

component against fragments and debris.

(-->> AASTP-1, 2.3.2 and 2.3.3)

(6)

External Walls

Experience has shown that for not earth-covered buildings two-leaf external walls provide a high

degree of protection against airblast, fragments and debris. The outer leaf which is considerably

thinner must be separated from the inner main leaf by an air gap of approximately 0.10 m. The outer

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leaf, which serves to absorb the airblast, should consist of lightly reinforced concrete or masonry

with a thickness of at least 0.10 m.

(-->> AASTP-1, 2.3.3.)

(7)

Internal Walls and Dividing Walls

Structures required to contain fragments, debris and lobbed ammunition necessitate a more

sophisticated design than dividing walls to prevent sympathetic detonation. A double-leaf

construction should always be taken into consideration.

(8)

Doors and Gates

Doors and gates constitute weak points in terms of safety. As they have to be relatively large and

must be movable in addition, their design tends to become very complex to ensure adequate

resistance to explosion effects.

Doors and gates should be single-piece structures.

If a door is not part of a so-designed structural weak wall (frangible cover), it shall resist the airblast

to be expected and be fragment-proof and debris-proof.

The following essential criteria shall be considered for the design of doors . . .

Dynamic design with respect to airblast loading;

Assessment of rebound loads and appropriate design of door hinges and latches;

Proof of resistance to fragments;

Proof of resistance to high impulse loads due to impact of debris;

Ease of use.

(9)

Barricades

Barricades are structures suitable to intercept directed projections and to a limited extent to constrain

the effects of airblast and flames.

Above all, barricades reduce the effects of fragments and other projections ejected out of openings.

Note:

Efficiency of protection and employment range of barricades are described in detail in

AASTP-1, 1.4.6.

Details on the design of effective barricades are given in AASTP-1, 2.3.3.

An earth-covered building may be considered equivalent to a building with barricades if, for

example, the thickness and slope of the earth cover comply with the requirements of AASTP-1,

1.4.6, or meet the other criteria stated there.

Natural terrain features, such as wood, elevations, soil etc., may be regarded as "natural barricades"

if they have proven to provide the required protection. It must be considered, however, that the

natural environment and thus the protection it provides may change in the course of time.

(10)

Ventilation

When designing the ventilation system, preference should be given to natural ventilation for

economical reasons. The ventilation system must be designed such as to prevent ingression of

airblast, primary and secondary projections as well as thermal radiation and flames or reduce their

effects to a safe level.

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Construction Materials for Ammunition Storage Buildings

Basically, fire-resistant or at least fire-retardant materials should be used.

Typical materials for the construction of aboveground ammunition storage buildings are concrete, reinforced

concrete, masonry, corrugated steel liners or steel arches. In addition, soil material with a special consistency is

normally used for the earth covers.

Exposed parts made of iron, steel, aluminum or aluminum alloys, which might come into contact with

explosives, shall not contain more than 1 % of magnesium.

The walls and floors of rooms intended for the storage of chemical agents shall be lined with chemical agent-

repellent material at least up to the height of the stacks. Adequate ventilation of the storage area shall be

ensured.

2.5.1.4

References

Essential references -->> Section VIII

Ref

[1], [2], [3], [4], [76], [77], [78], [79], [83], [89], [102]

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MANUAL OF NATO SAFETY PRINCIPLES FOR THE STORAGE OF MILITARY AMMUNITION AND EXPLOSIVES (May 2010) - page 9