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7/31/2019 A Blast and Ballistic Resilient Air-beam Shelter System
1/14
A BLAST AND BALLISTIC RESILIENT AIR-BEAM SHELTER
SYSTEM
D.V. Ritzel1, S.A. Parks
2, J. Crocker
3, H.A. Warner
4
1Dyn-FX Consulting Ltd., 19 Laird Ave. North, Amherstburg, Ontario N9V 2T5, Canada;2ORA Inc., 71 Commerce Pkwy, Suite 107, Fredericksburg, Virginia 22406, USA;
3Martec
Ltd., 1888 Brunswick St., Suite 400, Halifax, Nova Scotia B3J 3J8, Canada;4Dynamic Air
Shelters Ltd., 220 4441 76 Ave. S.E., Calgary, Alberta T2C 2G8, Canada
ABSTRACT
Lightweight temporary shelters such as tents and work-trailers are sometimes required by armed forces, civil
authorities, or emergency responders in areas at risk from enemy action, terrorist attack, or accidental explosions.
An extensive program of full-scale trials, computational modelling, and component testing has been conducted todevelop and validate a novel deployable shelter system based on air-beam technology having high resilience to
blast and ballistic threats. The shelter has no hard framing, paneling, or shear connections in its construction but
is self-supporting by means of air-beam arches of large diameter polyester-fabric tubing which are lightly air-
pressurized. Free spans to 40m can be enclosed. Such a structural system flexes and rebounds when subjected
to blast, impact, or seismic action ultimately taking loads as membrane and tensile stresses for which the
materials are inherently strong. The mode, rate, and extent of wall deflection can be largely controlled by flexing
lateral supports. An optional self-supporting geotextile curtain-wall can be incorporated with the shelter which
has been designed to provide high ballistic protection using minimal local soil fill. The integration of the air-
beam structure, flexural support system, and ballistic curtain-wall is the basis for the Integrated Blast Resilient
Shelter (IBRS) concept. The IBRS design is modular to meet a range of requirements and constraints.
Due to the highly responsive nature of the fabric surfaces under blast, computational modelling of the blastencounter requires an approach using fluid-structure interaction (FSI). FSI modeling which links the FE code
LS-DYNA with the blast CFD code CHINOOK has been applied to analyze the complex response dynamics and
optimize the IBRS design. Full-scale blast field trials including the use of instrumented manikins have validated
the blast resilience and occupant protection of the current IBRS prototype to blast levels of 40kPa x 36ms. Field
trials have proved the standard geotextile curtain-wall will withstand the combined blast/fragmentation from155mm artillery at 5m standoff as well as military 50-cal rounds using only 300mm thickness of soil fill.
INTRODUCTION
Lightweight relocatable shelters (LRS) include a wide range of both soft- and hard-skinned
structures such as trailers, tents, and various pre-fabricated field-assembled structures
intended for expedient environmental protection of personnel or materiel during temporary
deployments. Such shelters are used extensively at expeditionary military camps, industrial/
commercial sites under construction or maintenance, and during emergency response
operations. LRS are applied in wide-ranging roles including accommodations, offices,
workshops, messing, vehicle-bays, and stores; specially adapted units are used for field
hospitals or housing specialized equipment including aircraft. Large tents, such as those ofthe pavilion style, are also used for social functions or displays at public venues.
In historical military applications, LRS were intended for use behind lines beyond risk of
combat threats; in general, such shelters are deployed with the primary consideration being to
provide expedient environmental protection during short-term operations. However, in
modern applications LRS are often required in areas at risk from explosions, ballistic impacts
including military small-arms fire, accidental impact from industrial equipment or vehicles, or
seismic actions. For the military, even homeland bases can no longer be considered behind-
lines from terrorist attack. Military expeditionary camps are at risk from attack by enemy
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explosive munitions or insurgent truck-bombing; such camps also have risks from explosive
accidents at their own ammunition or fuel-storage compounds. Emergency response
operations require LRS for field hospitals, accommodations, and stores; however, in the
aftermath of a terrorist attack, these shelters may be vulnerable to second hit bombing or
small-arms attack specifically targeting responders. In deployments to earthquake-stricken
areas, temporary shelters are at risk from after-shocks.
Although LRS are usually designed for some nominal wind or snow-load capacity, theirprimary design criteria focuses on transportability, breakdown size/weight, and the ease and
speed of setup. Therefore, such structures are typically highly vulnerable to blast since they
present large surface areas relative to their lightweight, low-rigidity framework in
combination with weak ground fixity. A weak incident blast of 10kPa overpressure, which
would not inflict serious ear-drum injury to personnel in the open [1], will impart peak
reflective loading exceeding 10-fold that from a 200km/hr wind and cause serious damage to
LRS. Even with the benefit of continuous full-sized framing elements and rigid fixture to
concrete foundations, standard steel-framed light industrial buildings will typically fail
catastrophically when subjected to long-duration blasts of 25kPa [2], hence blast failures for
LRS can be expected at a fraction of this level. Extensive defence-research studies conducted
in the US [3] and Canada [4] investigated the blast response dynamics and injury risk to
occupants for a range of military LRS designs and confirmed this vulnerability. Figure 1
shows a typical deployment of tents at a military encampment and frames from internal high-
speed imaging of the response dynamics to low-level blast [4].
Figure 1. (Upper) Typical deployment of tent accommodations at a military expeditionary
camp. (Lower Left and Right) Blast effects within a military tent installed with manikins and
fittings typical of habited shelters (1: clip-on fan; 2: clip-on lamp; 3: helmet; 4: circuit panel;
5: lamp fixture; 6: 5KW heater). The deflecting framework, projected items and whipping
wires present a significant injury risk to occupants (from [4]).
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Typical LRS framing is not designed for severe side-loading, especially applied as a shock or
step function, and frame members often fail at their fixtures or joints if not buckled or
broken outright. Blast-induced deflections, break-up and projection of structural elements or
wall attachments, and ultimately structural collapse will usually present far greater injury risk
to occupants than had they been exposed to the blast in the open. Whereas humans can
survive a free-field blast exposure of about 100kPa overpressure [1], standard hard-framed
LRS structures such as tents or work-trailers are typically destroyed at blast conditions 1/5th
that level. This injury risk became tragically highlighted by the casualties of the Texas City
petrol-chemical blast accident in 2005 blast in which all 16 fatalities and seriously injuries
were inflicted on occupants of work trailers within the blast-hazard zone [5].
Similarly, by virtue of their primary basis for design, standard LRS are intrinsically
vulnerable to ballistic threats. Although appliqu ballistic panels have been proposed for
LRS [6], these are typically expensive, limited in protection to non-military threats, and in
fact can increase injury risk and damage form blast. When deployed to areas at risk of
significant ballistic threats, LRS will usually be enclosed by a separate ballistic barrier wall of
concrete segments or earthworks such as shown in Fig. 2 which demand considerable
resources and time for their installation and ultimately for dismantling or relocation.
INITIAL STUDIES
The recognition that injuries to LRS occupants from blast events were inflicted primarily by
the impact or projection of the hard framing or hard sheathing of the shelter itself led to the
investigation of a novel alternative air-beam shelter for deployments having blast risks,
effectively a soft-framed soft-sheathed structure. Figure 2 shows two models as
commercially available at the onset of the study in 2007 designated as the DSI-10 and DSI-19.
As shown in the figure, the structures are formed from large columns of reinforced vinyl
tubing formed into arches and lightly pressurized by low-power air blowers. The system of
arches is tied together by cross-cabling and the entire assembly is enclosed by a tough fly
covering. Although the shelter is self-supporting, guy-lines run from hug-straps around the
girth of each column at various points along each arch to ground stakes in order to providelateral restraint from wind action. In fact, the shelter is stabile in winds exceeding 100km/hr
using ground stakes at the column base alone. The DSI shelters have been well-proven in
industrial applications including extended performance in arctic conditions.
Figure 2. The original DSI-10 and DSI-19 air-beam shelters.
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The initial investigation of the blast response of air-beam shelters and the development of
concepts leading to the current Integrated Blast Resilient Shelter system have been described
in previous reports [7,8,9,10], but will be summarized here for completeness.
Although the original DSI shelters had not been designed for blast, an exploratory full-scale
blast trial was conducted in September 2007 to test the DSI-10 for blast response dynamics.
The shelter was subjected to the blast from a 2000kg TNT-equivalent charge at 100m
standoff, yielding an incident blast wave of 30.6kPa amplitude, 45ms positive-phase duration,and 570kPa-ms impulse. From previous studies it was known a blast of this severity would
have catastrophically damaged a conventional LRS design. As reported in detail in [7], the
shelter performed remarkably well and rebounded fully from the blast after deflecting in a
mode of elastic buckling action; the air-beam columns intruded 14% into the primary
habitable internal space at their maximum deflection. The wall deflection would not have
inflicted serious impact injuries, although occupants in the path of the air-columns would
certainly have been knocked to the ground. A diminished and distorted pressure wave was
transmitted into the interior space of lesser severity than had been measured for tents [4].
The main conclusions from the exploratory trial were as follows:
The DSI air-beam shelters demonstrated strong potential for further developmenttowards a military-grade blast-resilient LRS
Certain components required upgrading to survive the high-acceleration conditionsimparted by the blast loading in most cases involving elimination of stress
concentrations, distributing loads, or introducing shock-absorbing connections
Significant revision of the tethering system was required to control the mode, rate, andextent of wall deflection and reduce the required ground footprint
New measures would be required to ensure ballistic protection for the shelter as wellas ensure a safe-fail backup capacity to support the arches in some diminished mode
even if all pressurization was lost
Modular component design was required such that levels of blast and ballisticprotection can be adjusted depending on particular user requirements and constraints.
Due to the highly responsive nature of the fabric surfaces, an FSI (fluid-structureinteraction) approach was required in the computational modeling by which thesolution for the structural response dynamics is coupled in time with that for the
compressible gas-dynamics of the blast-wave flow
Since the structure rebounds from blast through actions of elastic buckling andirregular flexure, a new performance criteria was required to assess designs based on
injury potential rather than one based on traditional structural or material failure
INTEGRATED BLAST RESILIENT AIR-BEAM SHELTER SYSTEM
Following the initial exploratory blast trial, an intensive 3-yr R&D program was initiated to
develop an advanced Integrated Blast Resilient Shelter (IBRS) system to meet the objectives
identified above. Aided by the development and application of specialized FSI modeling [7],working prototypes of the necessary upgrades were developed and validated in full-scale blast
and ballistic trials and use of large-scale blast simulator facilities.
In the development and appraisal of various design upgrades both from computational and
experimental studies, a new performance criteria or measure-of-effectiveness was required
as noted in the last item of the previous section. That is, since the structure largely responds
elastically and ultimately rebounds despite sometimes large irregular deformations, traditional
engineering design criteria based on limiting rotation of shear connections, beam deflection,
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or material failure are inappropriate. Since injury risk to personnel or damage to housed
materiel is affected most by the extent and rate of wall deflection into the occupied space, a
performance criteria based on the maximum cross-sectional area intrusion of the deflecting
wall into the primary habitable space was adopted as depicted in Fig. 3. This criteria was
also used to define the iso-damage curves for the P-I diagrams generated from the
computational studies; that is, rather than having a pass/fail iso-damage curve, a family of
curves was generated by which any user can define an unacceptable level of elastic intrusionof the air-beam columns. The three primary upgrade developments are described in the
following subsections with regard to their incorporation in baseline DSI-19 model. However,
all concepts can be applied equally well to both larger and smaller DSI shelter models.
Tethermast
The key upgrade for the IBRS involves an entirely revamped tethering system including the
use of a line of tethering masts or tethermasts along the wall of the shelter as shown in Fig.
3. The tethermast has several critical roles in the enhanced capabilities of the IBRS. The
exact design and materials for the tethermast to optimize its performance under blast load
when coupled to the air-beam column are IPsensitive (Intellectual Property) and will not be
detailed here. In the computational simulations shown, the tethermasts are external to the
shelter wall and in-line with the air-beams; however, this is only one option for the tethermastarray and convenient for illustration purposes. For most installations the tethermasts will be
set between the columns and beneath the fly such that they are within the profile and normal
architectural lines of the shelter as shown in Fig. 4. The introduction of tethermasts to replace
the original ground guy-lines greatly improves the effectiveness and control of wall deflection
as well as reducing the ground footprint of the shelter installation.
The line of tethermasts allows incorporation of an auxiliary curtain-wall for the shelter which
serves as a barrier for blast and fragmentation protection. Although the design details and
materials of the revised tethering system and curtain-wall are proprietary, Fig. 3 shows that
blast deflections can be reduced by factors of 5-fold by the upgrades; the pressure wave
transmitted to the interior is also greatly diminished in severity compared to the case without
the curtain-wall. The tethermasts are modular and can be broken-down to five componentsfor ease of shipping and handling. Each of the primary components, such as the base-flexure
unit, has variants or adjustments which can be substituted to meet particular performance,
cost, or weight constraints.
A final optional role for the tethermasts is to allow a safe-fail mode for suspension of the
arch roof in the unlikely event of total loss of pressure to the entire system. Although each
air-beam column is independently pressurized and incorporates a check valve, it is possible
(for reasons not evident at this time) that all air-beam arches might abruptly and
simultaneously lose pressure. In such an event, the deflating air-beam arches will be
restrained from total collapse by the use of cross-cables spanning the width of the shelter as
shown in Fig. 4. For the configuration shown, the cross-cable acts as a catenary between the
tethermasts across the shelter and will maintain head-room of over 2m at the centre of the
shelter to nearly 3m at the inner wall. The internal cross-cables also allow the option ofsuspending lightweight partitions to divide work-spaces within the shelter interior.
Air-Beam Restraint
The original method of tether attachment and lateral restraint of the air-beam columns had
been by means of the hugstrap connection described from Fig. 2. This attachment is in fact
extremely ineffective for load transfer under impulsive forces in particular. The hugstrap
restraints were revised to a hugsheet arrangement as shown in Fig. 5.
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Figure 3. Computational modelling of maximum air-beam shelter deflections subjected to a
20kPa blast of 100ms duration, comparing results for standard ground tethering, tethermast
support, and tethermast with fabric curtainwall.
Figure 4. Sketches of optional configurations for tethermasts set between the air-beam columns
for the cases without and with external geotextile curtain-wall. The curtain-wall option
provides ballistic shielding or ballast as required.
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Curtain-Wall
As described previously, the line of tethermasts allows incorporation of an optional geotextile
curtain-wall to provide ballistic protection, enhanced blast mitigation, as well as stabilizing
ballast for deployments not having other means of secure ground fixture. The same curtain-
wall design can be configured in various modes to meet a range of performance specifications.
Although specialized curtain-walls are being devised for requirements such as protection from
rocket-propelled grenade attacks, the standard design has a tapered side profile with a nominal600mm base, 300mm width at the top, and height of 2400mm. Although generally intended
to be a geotextile wall, that is, filled with local soil, gravel, or crushed stone as available, the
simple fabric curtain-wall provides a high degree of ballistic protection against severe non-
military threats such as tornado-borne debris. Figure 6 shows an image sequence from testing
of the empty curtain-wall conducted to validate protection level for the highest kinetic-energy
threat specified in ASTM E1886 for tornado-borne debris.
Figure 6. Impact of a 6.8kg steel bar at 35m/s on an unfilled prototype curtain-wall as part of
testing to validate protection from explosion-borne debris due to accidental explosions at
petrol-chemical sites. The projectile is highlighted in the first frame as it was launched by
means of a specially designed gun-barrel. No damage was inflicted to the curtain-wall in this
test due to the combined membrane action of the fabric and flexure of the supports.
Figure 5. Revision of the air-beam restraint from hugstrap to a hugsheetconfiguration such
that the columns are restrained as if in a lateral sling. The line-of-action of the forces and
the load distribution at the connection reduce stresses over 1000-fold as depicted at right.
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Once filled as a geotextile barrier, the curtain-wall has been designed to provide maximum
ballistic protection for its thickness of fill using a simple but effective new technique to
restrict the cavity growth from high-speed projectiles. Due to the incorporation of the curtain-
wall with the tethermast supports, the combined system is highly resilient to the synergistic
effects of combined blast and ballistic loading from close-proximity detonations of military
munitions. As shown in Fig. 7, arena tests proved the performance of the standard curtain-
wall against near-field explosions of military munitions to the severity of a 155mm artilleryshell at 5m standoff. NATO STANAG 4569 specifies qualification testing for fragmentation
from 155mm shells at 25m standoff, since it is generally not expected that ballistic panels also
perform well in blast resilience. In separate tests, 50-cal BMG rounds (Federal American
Eagle XM33C, 42.8gm, steel-core) fired at 30m standoff with nominal muzzle velocity
884m/s were successfully stopped by the curtain-wall; this performance significantly
surpasses STANAG 4569 Level 3 ballistic protection intended to cover Russian AK rounds.
As previously noted, this level of ballistic protection is afforded by the standard geotextile
curtain-wall tested at its minimal 300mm thickness. A double-wall barrier with burster-screen
is being developed to defeat the shaped-charge warhead of a rocket-propelled grenade
including follow-through effects of its spent motor casing.
BLAST TESTING
12RQ Full-Scale Field Trials
By arrangement with the Suffield laboratory of Defence R&D Canada (DRDC), a full-scale
configuration of a prototype blast resilient shelter system was deployed in blast field trials
being staged under the DRDC 12RQ Defence Research program. The blast trials were
conducted on the Experimental Proving Ground of DRDC Suffield in Alberta September-
October 2009 under direction of the 12RQ program manager Dr. J. Anderson.
A series of three tests of escalating blast intensity were conducted subjecting the prototype
shelter to the blast conditions summarized in Table 1. The instrumentation layout for the
trials is depicted in Fig. 8 and included both H-III and H-II ATDs (Anthropomorphic Test
Devices). The H-III was fitted sensors for assessment of head/neck injury due to impact of the
air-beam columns, while the un-instrumented H-II was used to assess gross motions from air-
beam impact. At the time of the trials, a complete prototype curtain-wall was not ready for
deployment around the shelter, hence a crude simulation of its effect was made by suspending
Figure 7. Arena tests of the prototype standard curtain-wall have verified protection against
the combined blast/fragmentation effects of the munitions as shown. The specifications
shown are nominal values for design as provided in US DoD manuals [11]; the asteriskdenotes that the designated wall thickness relates to protection against ballistic penetration
without consideration of blast effects.
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the equivalent layers of fabric material from the tethermasts as shown in Fig. 8. Therefore, it
was not possible in these trials to assess the full efficacy of the curtain-wall for blast
attenuation, including its optimal soil-filled (geotextile) mode.
Key results from the trials are shown in Figs. 9-11 for which the incident blast, transmitted
overpressure, and wall deflection into the internal space are presented for each trial. Being the
case of most severe blast, further detailed results from Trial 3 are presented in Figs. 12 &13.The main conclusions from the trials were as follows:
The response of the prototype shelter met or exceeded expectations for controlled walldeflection and minimized injury risk to occupants. For Trial 2 (20kPa x 40ms), the
maximum extent of air-beam intrusion was less than 1% of the habitable space; for
Trial 3 (40kPa x 36ms), the maximum intrusion was 4% of the habitable space. The
shelter fully rebounded from all blasts, although several non-structural seams and
connections of the covering fly were torn in the final test. It should be considered that
the same structure was exposed to all blasts in succession without intermediate repairs,
hence incipient damage was likely accumulated from the prior tests.
In both tests yielding measurable wall deflection, only the zone immediately adjacentto the wall was affected such that personnel, or their furnishings they occupy, would
have to be abutted directly against the air-beam column for any significant effects.
Partly due to the yielding nature of the air-beam impact, a seated manikin in a chair
with its back abutted to the wall was imparted an average velocity less 0.7m/s.
The pressure transmitted to the interior was significantly diminished in effect asquantified by its amplitude, impulse, and rise-time. The degree of amplitude reduction
increased with blast strength to 50% for the strongest blast; impulse reduction
decreased with incident blast strength from 38 to 28%. Very importantly, in all cases
Table 1. Summary of 12RQ blast field-trial test conditions.
Trial Charge Incident Blast Conditions
P (kPa) Duration (ms) Impulse (kPa-ms)
1 165kg TNT Eq 12.4 24 150
2 500kg TNT Eq 20.7 40 330
3 1000kg TNT Eq 40.6 36 690
Figure 8. Instrumentation layout for the 12RQ blast trials.
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the shock front of the incident blast became diminished to a less-injurious compression
or set of staggered shocks spanning about 4ms of rise-time.
Although not affecting occupants, unexpected damage was sustained by someequipment due to the significant upward rebound of the shelter well after the passage
of the blast itself (~ 200ms). Ultimately, much of the elastic energy stored from the
blast encounter with the shelter is recovered as a powerful upward rebound of the air-
beam columns. Straightforward measures were identified to secure the column bases
against this action, as well as introduce shock absorption, flexure, and reduced mass of
attachments at the base of the air-columns.
Component Testing
Certain components, fittings, and seams were identified from the most severe 12RQ blast test
of 40kPa as warranting further assessment and possible modification. Although not damaged
by the blast itself, the heavy and rigid blower fitting attachments to the base of the air-beam
columns were damaged by the powerful and abrupt late-time vertical rebound action of the
columns. The blower bulkhead assembly was redesigned to minimize its mass and stiffness
and allow for flexing action with its various connections. In addition, a check-valve wasintroduced such that in the event of a failure of the blower attachment or any rupture of
external feed lines, pressure is not lost from the columns. The revised blower assembly was
subsequently re-qualified in tests using a large-scale blast simulator as shown in Fig. 14.
Figure 9. Summary of key results from 12RQ Trial 1, 12.4kPa x 24ms blast. (Upper left
and right) Overview of the trial layout showing the fireball shortly after detonation and
comparison of incident blast and transmitted overpressure waveforms. (Lower left and
right) Interior view of the shelter immediately prior to blast arrival and at time of maximum
air-beam deflection at 36ms. The seated and propped manikins shown abutted to air-beam
columns were unaffected by the blast.
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Figure 10. (Upper left and right) Overview of the Trial 2 layout showing the fireball shortly
after detonation and comparison of incident blast and transmitted overpressure waveforms.
(Lower left and right) Interior view of the shelter immediately prior to blast arrival and at
time of maximum air-beam deflection at 37ms. The seated manikin shown abutted to the
air-beam column was unaffected by the blast.
Figure 11. (Upper left and right) Overview of the Trial 3 layout showing the fireball shortly
after detonation and comparison of incident blast and transmitted overpressure waveforms.
(Lower left and right) Interior view of the shelter immediately prior to blast arrival and at
time of maximum air-beam deflection about 80ms after blast arrival. The manikin shown
seated in the chair abutted to air-beam columns slid from the chair at about 0.7m/s.
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Figure 12. Deflection of the inner wall of the
central air-beam column during the first 100msof the blast encounter. The initial shape is
shown in blue with the deformation tracked at
10ms intervals. In the final stages of the
response, the base of the columns rebounded
backwards and upwards. The general mode of
elastic buckling closely followed computational
predictions as previously shown in Fig. 3.
Figure 13. Prostrate manikin on cot
abutted to air-beam column in Trial 3comparing positions pre- and post-blast
(upper and lower respectively). The
manikin itself was not displaced,
although the cot was shifted about
15cms beneath it by the action of the
air-beam column on its frame.
Figure 14. 1.8m Blast Tube facility used to qualify IBRS components such as the
revamped air-blower configuration and air-beam check valves. From lower-left to right:
installation of the test column and blower fittings; setting of the concrete-wall closure; and
view from inside the Tube after the test column has been strapped to the reflecting wall.
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DISCUSSION AND CONCLUSION
Lightweight relocatable shelters such as tents, trailers, and pre-fabricated huts are intended for
rapid deployments with the primary role of providing weather protection for personnel or
equipment during temporary operations spanning weeks to a few years. However, in many
applications these shelters are at risk from severe loadings such as due to blast or ballistic
threats including terrorist bombings or small-arms attacks, accidental explosions, extreme
winds, or seismic action such as earthquake aftershocks. Ironically and tragically, it is mostoften the shelter in these events which inflicts the gravest of injuries to occupants in
comparison to personnel being exposed to such threats in the open. Whereas the traditional
design approach for blast or ballistic protection of structures usually involves the hardening,
thickening, or stiffening of components, this is not feasible for lightweight deployable
shelters. In this regard a novel approach has been taken to allow significant but controlled
flexure in the event of severe loads where this deformation is readily absorbed by the
materials and can be exploited to maximize the overall resilience of the system and ultimately
minimize injury risk to occupants or damage to materiel being housed.
The development of the Integrated Blast Resilient Shelter system has been described
involving a comprehensive 3yr R&D program involving advanced computational modelling
full-scale field trials, and component testing. The basis of the design is an underlying low-pressure air-beam structure with flexing lateral supports such that shock and impact loads are
taken by membrane and tensile stresses for which the materials are inherently strong and
energy-absorbing. The air-beam arches allow open spans of 40m to be enclosed offering
large working areas for equipment or as required for assembly areas such as lunchrooms. In
the case of blast loading, although some degree of intrusion of the air-beam wall into the
internal space is incurred, this deflection can be tailored to present very low injury risk to
occupants. Overpressure is transmitted to the interior, although the amplitude, impulse, and
rise-time of the transmitted wave are greatly mitigated; all blast levels of consideration here
are non-lethal to personnel in the open.
A geotextile curtain-wall is incorporated into the shelter system which has been specially
designed to maximize performance of local soil as fill for ballistic protection. The standardcurtain-wall of nominal 300mm thickness has been field-tested against a range of munitions
including 155mm artillery detonation at 5m standoff and 50-cal rounds; the ballistic
protection can be readily increased as required. The curtain-wall is also functional as a
separate rapidly deployable stand-alone barrier to protect other structures or areas. The
combined shelter system meets all the normal criteria for a lightweight deployable shelter yet
has many attributes of traditional hardened bunkers including blast protection exceeding
35kPa overpressure and ballistic protection greatly exceeding NATO STANAG 4569 Level 3.
R&D continues at this stage to provide optional overhead protection and defeat of special
threats such anti-armour weapons including rocket-propelled grenades with shaped-charge
warheads.
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REFERENCES
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Effects of Air Blast, Progress Report DASA-2113, Defense Atomic Support Agency, US Dept. of
Defense, Washington, DC.
[2] Glasstone S., and Dolan, P.J., (Eds), 1977, The Effects of Nuclear Weapons, Chapter V: Structural
Damage from Air Blast, 3rd Ed., US DoD and the Energy R&D Administration, Washington, DC.
[3] Stevens, D., Marchand, K., Young, L.A., Moriarty, R., Cropsey, L., 2003, Evaluation of Structural
Response and Human Injury in Shock-Loaded Expeditionary and Temporary Shelters, Proc. 11th
Intl Symp. on the Interaction of the Effects of Munitions with Structures, Mannheim, Germany.
[4] Ritzel, D.V., Crocker, J., 2006, Blast Response of Hemi-Cylindrical Tents, 19th Intl Symposium
on Military Aspects of Blast and Shock (MABS19), Banff, Alberta, Canada.
[5] US Chemical Safety and Hazard Investigation Board, 2007, Final Investigation Report: BP Texas
City Refinery Explosion and Fire, Report No. 2005-04-1-TX.
[6] Horak,K.,Quigley, C., Devine, R., 2009, Ballistic Protection for Tentage,Logistics, US Army
Natick Soldier RD&E Center, pp.56-60, Natick, MA.
[7] Ritzel, D.V., 2008, Blast Response of an Air-Beam Shelter, Dyn-FX Contract Report CR040801
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