Note: Descriptions are shown in the official language in which they were submitted.
A8138325W0
MULTI-LAYERED PNEUMATICALLY SUPPORTED STRUCTURES
TECHNICAL FIELD
The present disclosure generally relates to protective structures. In
particular
the present disclosure relates to protective structures that comprises one or
two layers
with each layer comprising a plurality of inflatable air beams that are
configured to be
laterally abutting and where the two layers form at least an inner layer and
an outer
layer of the structure.
BACKGROUND
Explosive events generate blast waves that are often the cause of significant
injury to people. The types of human injuries that typically occur due to
explosions
may be divided into three categories: (i) primary injuries that result
directly from blast
overpressure and shock-wave effects; (ii) secondary injuries that result from
impacts
with airborne fragments, debris, structural deformations and the like; and
(iii) tertiary
injuries resulting from the people being physically propelled by the blast
wave. Blast
waves can also be transmitted from outside a structure to inside the structure
as a shock
wave, which can also cause injuries to the structure's occupants.
It is known to construct protective structures from a layer of air beams that
are
covered with a polymer sheet-material, which is referred to as a fly. These
protective
structures are designed to protect occupants from the effects of explosive
blast-loads.
The protective structures are inherently resistant to blast loading as a
direct
consequence of the flexible properties of the air beams and the fly. These
flexible
properties allow a significant but controlled flexure in the event of severe
blast-loads
where deformation of the protective structure absorbs aspects of the blast
loads, which
ultimately minimizes injury risk to occupants or damage to any material housed
within
the protective structure.
For example, protective structures that are made with a layer of air beams can
reduce the potential for primary, secondary, and tertiary injuries to
occupants. The
potential for primary and tertiary injuries is reduced by partial mitigation
of blast-pulse
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transmission to the interior of the structure. The possibility of secondary
injury is also
reduced in comparison to a rigid building that may lose structural integrity
and have
surfaces fragment or tear away, which can create further hazards.
However, the desirable flexible properties of the air beams may also limit the
ability to make pneumatically-supported protective structures beyond a given
size,
which may limit the applications of such protective structures. Furthermore,
even the
flexible properties of the air beams does allow some transmission of a shock
wave into
the interior of the protective structures.
SUMMARY
Embodiments of the present disclosure relate to a structure that comprises at
least one layer of air beams that define an interior space of the structure
wherein
laterally adjacent air beams are configured to abut each other.
Some embodiments of the present disclosure relate to a structure that
comprises
at least a first layer of a plurality of air beams and a second layer of a
second plurality
of air beams, wherein the second layer is positioned adjacent and interior to
the first
layer for defining an interior space of the structure.
Inflated structures are comprised of inflated air beams that arc made up of
fabric
the inflation pressure, tube radius, and material stresses are connected
through the
relationship:
S=pr
where:
= S is the fabric hoop stress (in units of Force/Distance vs. Engineering
Stress in
units Force/Rdistance)^21;
= p = tube inflation pressure; and
= r = tube radius.
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So that for air beams that are inflated at a constant pressure, the stress in
the
material increases proportionally with radius (likewise, for tubes of constant
radius,
stress increases proportional to pressure). As the clear span of the structure
increases,
the air beam diameter (and therefore radius) must be increased to withstand
the
additional loads ¨ especially snow loads and wind loads. As the radius
increases, with
constant inflation pressure, the stress in the fabric membrane containing the
air pressure
also increases. Eventually, as the span of a structure is increased, the
stress in the
fabric ¨ due to inflation pressure only, not due to other loading ¨ becomes
unacceptably
high. This may be due to one or more several concurrent constraints:
= Due to a complex response of textile fabric under load, the Factor of
Safety
(FoS) is commonly set quite high ¨ typically between 5 and 7 for fabric as
compared to about 2 for structural steel. The stress-strain characteristics of
fabrics are both nonlinear, and characterized by several discrete loading
regimes, in each of which the average modulus of elasticity is significantly
different. Therefore, in an effort to avoid troublesome loading regions, the
FoS
is usually set high.
= The seam strength for heat-fused coated fabrics is lower than the
strength of the
base material (unlike for steel where the welded connection is typically
stronger
than the steel) as the fabric stresses increase, the risk of (longitudinal)
seam
failure increases.
= As the radius of a tube increases, the weight of the air beams increases
(due to
more fabric being used).
= Increasing fabric stress can be compensated for with heavier fabric, but
this also
increases weight of the air beams.
At some point, the designer can no longer continue increasing the diameter of
the air beams. Without being bound by any particular theory, as the size of
the
intended structure increases using two or more layers of air beams may be
suitable
alternative to larger diameter air beams when one or more constraints prevent
increasing the diameter any further. This is primarily due to the fact that
the primary
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constraint on using two or more layers of air beams is that it requires twice
the material
of an equivalent single-layer structure.
Constructing a protective structure with at least two layers of air beams may
provide a stiffer structure as compared to a structure that is constructed
from a single
layer of air beams. A stiffer structure can be built to larger dimensions with
larger
interior spaces. These interior spaces may be sufficiently large to enclose an
already
constructed building or structure. Furthermore, when the protective structures
have at
least two layers of air beams and the air beams within each layer are
laterally abutting
each other, the protective structure can defeat the transmission of a shock
wave through
the at least two layers. Defeating the transmission of a shock wave may reduce
the
primary, secondary and tertiary injuries that can occur when a shock wave is
transmitted inside a structure.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the present disclosure will become more apparent
in
the following detailed description in which reference is made to the appended
drawings.
FIG. 1 is an isometric view of one embodiment of the present disclosure that
relates to
a structure;
FIG. 2 is a series of different views of the structure shown in FIG. 1: FIG.
2A is a front
elevation, midline, cross-sectional view of the structure shown in FIG. 1;
FIG. 2B is a
top plan view of a section of the structure shown in FIG. 2A; FIG. 2C is a
bottom plan
view of the section shown in FIG. 2B; and FIG. 2D is a side-elevation view of
the
section shown in FIG. 2B;
FIG. 3 is a schematic illustration of embodiments of the present disclosure
that relate to
= various configurations of air beams: FIG. 3A shows a first configuration;
FIG. 311
shows a second configuration; FIG. 3C shows a third configuration; and FIG. 3D
shows
a fourth configuration;
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FIG. 4 is a schematic illustration of embodiments of the present disclosure
that relate to
various further configurations of air beams: FIG. 4A shows the first
configuration; FIG.
4B shows the second configuration; FIG. 4C shows a variation of the second
configuration; FIG. 4D shows another variation of the second configuration;
FIG. 4E
shows a variation of the fourth configuration; FIG. 4F shows another variation
of the
second configuration; FIG. 4G shows another variation of the fourth
configuration; and
FIG. 4H shows another variation of the second configuration;
FIG. 5 shows an example of a shock-tube assembly and example configurations of
target samples tested therein: FIG. 5A is a side elevation, midline schematic
of a shock-
tube assembly that was used for acquiring data from a target sample; and FIG.
5B is a
top plan schematic of the example configurations of air beams and flys that
were used
as target samples within the shock-tube assembly;
FIG. 6 is a line graph that shows an example of overpressure vs. time data
that was
captured within a shock-tube assembly without a target sample;
FIG. 7 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
test-sample was present;
FIG. 8 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
different test-sample was present;
FIG. 9 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
different test-sample was present;
FIG. 10 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
different test-sample was present;
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FIG. 11 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second scnsor and a third sensor within the shock-tube assembly
when a
different test-sample was present;
FIG. 12 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
different test-specimen was present;
FIG. 13 is a line graph that shows an example of overpressure vs. time data
that was
acquired at a second sensor and a third sensor within the shock-tube assembly
when a
different test-specimen was present;
FIG. 14 is a bar graph that compares the peak overpressure data from the data
provided
in FIG. 6 through to FIG. 13;
FIG. 15 is an isometric view of a schematic of one example of a shear control
system
according to embodiments of the present disclosure;
FIG. 16 is an isometric view of a schematic of another example of a shear
control
system according to embodiments of the present disclosure;
FIG. 17 is an isometric view of a schematic of another example of a shear
control
system according to embodiments of the present disclosure;
FIG. 18 is an isometric view of a schematic of another example of a shear
control
system according to embodiments of the present disclosure;
FIG. 19 is a dot plot that shows an example of experimental data that compares
the
collapse load ("breakpoint") of air beams in bending, using various shear
control
systems;
FIG. 20 is a combined side elevation view and isometric view of a schematic of
an
example of a connection system according to embodiments of the present
disclosure;
FIG. 21 is a top plan view of two parts of the connection system shown in FIG.
20;
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FIG. 22 is a top plan view of the connection system shown in FIG. 20; and
FIG. 23 is a top plan view of the connection system shown in FIG. 20 for use
with
multiple air beams in two layers.
DETAILED DESCRIPTION
Unless defined otherwise, all technical and scientific terms used herein have
the
same meaning as commonly understood by one of ordinary skill in the art to
which this
disclosure belongs.
As used herein, the term "about" refers to an approximately +/-10% variation
from a given value. It is to be understood that such a variation is always
included in any
given value provided herein, whether or not it is specifically referred to.
Embodiments of the present disclosure relate to a structure that can be
rapidly
deployed proximal a site of interest. The structure may at least partially
protect the site
of interest from an explosion. Alternatively, or complimentarily, the
structure may be
large enough to provide a large interior space with various commercial uses,
industrial
uses, recreational uses and combinations thereof. The structure comprises
multiple air
beams that may also be referred to as fabric beams, pneumatic beams, pneumatic
columns, pneumatic arches or pneumatic tubulars. The air beams may be arranged
in
one or more configurations to form ribs of the structure with multiple ribs
forming a
frame of the structure. A fly that is made of a sheet material may be
incorporated into
or on top of the ribs to enclose the frame. Connection systems may also be
employed
to connect the air beams to each other to form the structure and optionally to
incorporate the fly. The configuration of the air beams determines the type of
protection the structure provides to the site of interest and the overall size
that the
structure can be.
Embodiments of the present disclosure relate to a structure that is made up of
at
least two layers of air beams. Each layer comprises a plurality of air beams
that
substantially abut a laterally adjacent air beam so that a plurality of
abutting air beams
within a layer form part of or all of a wall of the structure. One layer of
air beams
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forms an inner layer and one layer of air beams forms an outer layer. Some
embodiments of the present disclosure relate to structures with more than two
layers of
air beams that comprise an inner layer, an outer layer and one or more
intermediate
layers therebetween.
Embodiments of the present disclosure will now be described by reference to
FIG. 1 to FIG. 14.
FIG. 1 shows one example of a structure 10. The structure 10 may include one
or more doors 200 to provide access to an interior space 12 of the structure
10 (shown
in FIG. 2A). While FIG. 1 shows a specific arrangement of four doors 200, this
is
provided merely as an illustrative example and it is not intended to be
limiting. For
clarity, the structure 10 is shown in FIG. 1 without a fly 218, which is
discussed further
herein below.
FIG. 2A shows a midline cross-section of the structure 10 that is taken
perpendicular to the longitudinal axis of the structure 10 (the direction of
the
longitudinal axis is shown as line X in FIG. 1). The structure 10 comprises as
least a
first layer 10A and a second layer 10B. Each layer 10A, 10B comprises one or
more
air beams 14, with air beams 14A forming the first layer 10A and air beams
1413
forming the second layer 10B. The air beams 14 are made of a fluid tight
material so
that a desired volume and pressure of an inflating fluid, such as air or other
mixtures of
gases, can be contained within each air beam 14.
As shown in the non-limiting depiction of the structure 10 in FIG. 2A, one or
more air beams 14 may extend from one side of the structure 10 to the other
side to
form a rib 15, which may also be referred to as an arch. Multiple ribs 15 are
arranged
in an abutting relationship to form a frame of the structure 10 in the shape
of a barrel
vault. Alternatively, multiple air beams 14, of successively smaller span, may
be
connected with each other to enclose the open ends of the barrel vault portion
of the
structure 10 in a manner similar to that shown in the region of rib 15. In
some
embodiments of the present disclosure, a first portion (shown as X2 in FIG.
2A) of the
structure 10 may be defined by one or more air beams 14 that extend away from
the
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ground upon which the structure 10 is deployed. In some embodiments of the
present
disclosure the structure 10 may be constructed without a first portion X2. In
some
embodiments of the present disclosure the structure 10 may be tethered to the
ground
by various approaches, including a tethermast and/or a frag wall, as described
in the
Applicant's patent application WO 2011072374 entitled Tethermast and Frag
Wall, the
entire disclosure of which is incorporated herein by reference. In some
embodiments of
the present disclosure, the rib 15 includes the first portion X2. In some
embodiments of
the present disclosure, the ribs 15 are dimensioned to provide a total span
(shown as Y1
in FIG. 2B) of about 200 meters. In some embodiments of the present
disclosure, the
ribs 15 are dimensioned to provide a span that is selected from a group of
about 175
meters, about 150 meters, about 125 meters, about 100 meters or less. In some
embodiments of the present disclosure the ribs 15 are dimensioned to provide a
span
that is between about 35 meters to about 125 meters. In some embodiments the
total
span may be smaller or larger than the range provided above. The peak height
(shown
as X1 in FIG. 2A) of the structure 10 may fall between a range of 2 and 100
meters. In
some embodiments the peak height may be smaller or larger than the range
provided
above.
In some embodiments of the present disclosure, the structure 10 may define a
large enough interior space 12 so that another building or structure will fit
therein. In
this fashion, the structure 10 could be deployed about an existing building,
either as a
temporary protective-structure or as a longer-term protective structure or for
providing
a large enough interior space 12 so that various commercial, industrial and/or
recreation
activities can occur therein. As described further below, when the structure
10 is
constructed with at least two layers 10A, 10B, the ribs 15 arc sufficiently
stiff enough
to support the large spans. Furthermore, the at least two layers 10A, 10B
provide
further protection from blast waves and transmitted pressure waves when
compared to
when similar structures are constructed of a single layer of air beams and
subjected to
similar blast waves.
The air beams 14 within and among the layers 10A, 10B may be similar to each
other, or not. In some embodiments of the present disclosure the air beams
14A, 1411
can be filled with a fluid, such as air, to a range of desired pressures. An
air beam 14
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may have a diameter between about 0.01 meters and about 2.5 meters or other
broader
ranges.
Within the embodiments of the present disclosure that are shown in FIG. 2B
and FIG. 2C, there are three air beams 14A with each air beam in an abutting
relationship with a laterally adjacent air beam 14A of the first layer 10A.
While in an
abutting relationship with a laterally adjacent air beam, there is
substantially no gap
between the adjacent air beams. In this abutting relationship, the laterally-
adjacent air
beams may be direct contact with each other and they may be physically coupled
together by a connection system, or not. In other embodiments of the present
disclosure there may be a gap so that there is no contact between laterally-
adjacent air
beams when the air beams are static. FIG. 2A shows the first layer 10A as an
outer
layer and the second layer 10B as being an inner layer, which may also be
referred to as
an interior layer. The second layer 10B may define the dimensions of the
interior space
12.
FIG. 3 shows a cross-sectional, top plan view of a number of different
configurations of air beams 14 that may be useful in making the ribs 15 of the
structure
10. The structure 10 may comprise ribs 15 of the same configuration or the
ribs 15
may be of different configurations. FIG. 3A shows a first configuration with a
single
air beam 14 with a diameter of about 0.8 meters. FIG. 3B shows a second
configuration of air beams with a first layer 10A that includes two air beams
14A and a
second layer 10B with two air beams 148, the air beams 14 in the second
configuration
have a diameter of about 0.4 meters. FIG. 3C shows a third configuration of
air beams
with a first layer 10A with a single air beam 14A and a second layer 10B with
a single
air beam 14B. The air beams 14 in the third configuration have a diameter of
about 0.8
meters. FIG. 3D shows a fourth configuration of air beams that includes a
first layer
10A, a second layer 10B and an intermediate layer 10C, each layer in the
configuration
has a single air beam with a diameter of about 0.8 meters. Within the second,
third and
fourth configurations, the air beams 14A of the first layer 10A are
substantially aligned
centrally with the air beams 10B of the second layer 10B. As used herein, the
expression "aligned centrally" refers to the relative position of an air beam
in one layer
compared to one or more air beams in another layer. The aligned centrally
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the center point of an air beam of one layers is aligned with the center point
of an air
beam in another layer so that if a straight line was drawn that extends from
the center
point of one of the air beams being referred to - where the line extends
substantially
orthogonal to the respective layer of the air beam being referred to - that
line may also
extend through the center point of an air beam in another layer (see line Z1
in FIG. 4B).
FIG. 4 shows a top plan view of a number of different configurations of air
beams 14 that also may be useful in making ribs 15 of the structure 10. FIG.
4A shows
the first configuration of FIG. 3A. FIG. 4B shows the second configuration
with a first
layer 10A and a second layer 10B, wherein the air beams 14A of the first layer
10A are
substantially aligned with the air beams 10B of the second layer 10B.
FIG.4C shows a fifth configuration of air beams 14 with a single air beam 14A
from the first layer 10A for every two air beams 14B of the second layer 10B
with the
air beam 14A aligned offset and in between the two air beams 14B. As used
herein, the
expression "aligned offset" refers to a central point of an air beam in one
layer being
offset relative to the central point in an air beam in an immediately adjacent
layer. If a
straight line was drawn that extends from the center point of one of the air
beams being
referred to - where the line extends substantially orthogonal to the
respective layer of
the air beam being referred to - that line will not extend through the center
point of an
air beam in the immediately adjacent layer (see line Z2 in FIG. 4C). Rather
that line
will extend through a lateral edge region of an air beam in the immediately
adjacent
layer. In some embodiments of the present disclosure, when air beam 14A (in
layer
10A) is of equal diameter to air beams 14B (in layer 10B) (as shown in FIG. 4C
and
4D) a line be drawn to connect the centers of these three air beams and this
line will
define an equilateral triangle.
FIG. 4D shows a sixth configuration with a single air beam 148 from the
second layer 10B for every two air beams 14A of the first layer 10A. The
single air
beam 14B is aligned approximately in between the two air beams 14A of the
first layer
10A.
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FIG. 4E shows a seventh configuration with an intermediate layer 10C that is
made up of a single air beam 14C that is positioned in the middle of and
aligned
approximately in between the two air beams 14A of the first layer 10A and two
air
beams 14B of the second layer 10B.
FIG. 4F shows an eighth configuration with two air beams 14A of the first
layer
10A is aligned approximately in between and three air beams 14B of the second
layer
10B.
FIG. 4G shows a ninth configuration that includes a single air beam 14A of the
first layer 10A, two air beams 14C of the intermediate layer 10C and three air
beams
14B of the second layer 10B. The air beams 14 in this ninth configuration are
all
aligned approximately in between the air beams of an adjacent layer.
FIG. 4H shows an tenth configuration that includes three air beams 14A of the
first layer 10A that are each aligned approximately in between three air beams
14B of
the second layer 10B.
While the description of these air beam configurations include specific
dimensions of air beams 14, it is understood that these diameters are examples
only and
the embodiments of the present disclosure are not limited to these specific
dimensions.
Some embodiments of the present disclosure include connection systems for
connecting air beams 14 within a configuration of two or more layers 10 of air
beams
14. Some embodiments of the present disclosure relate to connection systems
that act
as shear control systems for controlling or reducing shear forces between air
beams
14A in one layer and air beams 14B in an adjacent layer.
FIG. 15 shows a shear control system 1 that comprises at least one set of a
strap
100 and a pocket 102. The pocket 102 can be secured to the outer surface of
one air
beam 14A in the first layer 10A and the strap 100 can be wrapped around both
air
beams 14A and 14B and through the pocket 102. The pockets 102 can be secured
by
the use of suitable adhesives and/or attachment techniques such as sonic
welding,
thermal polymer-welding and the like. In some embodiments of the present
disclosure
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the strap 100 can be a webbing ratchet strap and the pocket 102 can be made of
a vinyl
fabric. There can be multiple sets of straps 100 and pockets 102 along the
length of the
air beams 14A, 14B. As will be appreciated by one skilled in the art, the
layer 10A,
10B in which the pocket 102 is secured can be the same or different between
different
sets of straps 100 and pockets 102 that are distributed along the length of
the air beams
14A, 14B. Furthermore, each set of the shear control system 1 may include more
than
one strap 100 and more than one pocket 102. For example, there may be a pocket
102
secured to an air beam 14 in each layer 10, or not. While FIG. 15 shows two
layers, it
is understood that the shear control system 1 may be used in configurations
that have
more than two layers.
FIG. 16 shows a shear control system 2 that comprises one or more sets of a
first hug strap 104, a second hug strap 106 and a length of webbing 108. The
first hug
strap 104 is secured about the outer surface of one air beam 14A and the
second hug
strap 106 is secure about the outer surface of an air beam 14B in an adjacent
layer 10.
Each hug strap 104, 106 may have a loop extension (not shown) that is
positioned in
the contact area between the two air beams 14A and 14B. The hug straps 104,
106 can
be positioned in an offset manner (as shown in FIG. 16) so that the loop
extensions are
positioned proximal each other so that the hug straps 104, 106 arc configured
for
receiving a portion of the length of webbing 108 therethrough for connecting
the air
beam 14A to air beam 14B. As will be appreciated by one skilled in the art, in
configurations that have more than two layers 10, the hug straps 104, 106 may
each
have more than one extension loop positioned at each contacting surface
between the
layers 10 of the configuration.
FIG. 17 shows a shear control system 4 that comprises one or more sets of a
pair of fixed point connectors 109 and bracing straps 110. In this shear
control system,
each of the fixed point connections 109 can be loop or circular members, such
as 0
rings or D rings, and one of the pair of fixed point connections is secured to
the outer
surface of air beam 14A and the other fix point connection of the pair is
secure to the
outer surface of air beam 1411. The bracing straps 110 are connected at
opposite ends
to the fixed point connection 109 that make up a pair. The bracing straps 110
can have
an adjustable length so that when they are shortened a tension load acts on
the fixed
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point connections 109 to restrict or prevent movement of air beam 14A relative
to air
beam 14B. As shown in the non-limiting example of FIG. 18, the fixed point
connection 109 can be positioned so that the bracing straps 110 are oriented
in a pattern
of alternating direction. As will be appreciated by one skilled in the art,
the number of
fixed point connection 109 and bracing straps 110 utilized in this example of
the shear
control system can be variable based upon the length of the air beams 14 used
and the
number of layers 10 in a given configuration.
FIG. 18 shows a shear control system 5 that is similar to the system shown in
FIG. 17. The primary difference in the system of FIG. 18 is that there are
only two sets
of fixed point connections 109 and bracing straps 110 and each set is
positioned near an
end of the air beams 14A and 14B.
Not shown in the drawings is a shear control system (Ctrl) that comprises
paired
strips of hook and loop portions of a hook and loop fastener that are secured
to the
outer surface of two air beams 14 and each potion extends along the entire
axial length
of each air beam and each portion is positioned within the contacting area so
that when
the two air beams 14 are brought close enough together the hook and loop
portions
connect to form the hook and loop fastener.
FIG. 20 shows a shear control system 3 that is similar to the system (Oil) but
the paired strips of a hook portion 120A and a loop portion 120B are not
continuous
along the entire axial length of air beams. Rather the portions 120A and 120B
are
smaller lengths that do not extend the entire axial length of the air beams
14. Each air
beam 14 may have multiple pairs of laterally displaced hook portions 120A or
loop
portions 12013 that arc positioned along the length of the air beam 14.
FIG. 19 shows examples of experimental data obtained from four-point bending
experiments where air beams with 65 cm diameters were connected into a two
layer
configuration using each of the shear control systems 1 through 5. The bending
experiments were conducted with the air beams inflated to a low pressure (1
psi) and a
high pressure (2 psi). As shown in FIG. 19 the system (Ctrl) and system 3 had
the
highest breakpoint results (with minimal differences between the two hook and
loop
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fastener based systems), which is an indication of the ability of these
systems to restrict
movement of the air beams of one layer relative to another layer.
FIG. 20 also shows an example of a connection system that includes the shear
control system 3 and a lateral connection system that comprises straps 122 and
126 that
each extend laterally from an air beam 14A in layer 10A. Strap 122 can include
a first
portion 124A of a fastener 124, such as a hook portion 124A of a hook and loop
fastener 124 and strap 126 can include a second portion 124B of the fastener,
such as
an associated loop portion 124B of the hook and loop fastener 124. The person
skilled
in the art will appreciate that there is no requirement that the fastener 124
is a hook and
loop fastener 124, rather the first portion 124A merely needs to be mateable
with the
second portion 124B to form a completed (fastened) fastener 124. Further
examples of
the fastener 124 include buckles, press fit fasteners and the like. Air beam
14A also
includes non-continuous hook portion 120A that are positioned axially along
the length
of air beam 14A. Air beam 14B has loop portions12013 that are positioned
axially
along the length of the air beam 14B and positioned to mate with the hook
portions
120A of air beam 14A. FIG. 21 also shows the components of the connection
system
on each of air beam 14A and air beam 14B. The person skilled in the art will
appreciate that FIG. 21 is not limiting and the hook portions 120A, 124A and
the straps
122 and 126 can be part of air beam 1413 and the loop portions 120B, 124B can
be part
of the air beam 14B.
FIG. 22 shows how the hook portion 120A can be positioned proximal to the
loop portion 120B to mate and form a complete (fastened) hook and loop
fastener 120
(as shown within the hash lined circle of FIG. 22). FIG. 22 also shows one
example
arrangement whereby the strap 122 of one air beam 14A can be positioned around
an
outer portion of air beam 1413 and the strap 126 can also be positioned around
the outer
portion of air bean 1413 so that hook portion 124A can mate with loop portion
124B to
make a complete (fastened) hook and loop fastener 124 (as shown within the
hash lined
circle in FIG. 22). As one skilled in the art will appreciate, the drawings
show the
straps 122 and 126 as extending from air beams 14A and the air beam 1413 as
including
the fasteners 120B but this is but one example that may provide easier access
to the
straps 122 and 126 for mating the fasteners to make the completed hook and
loop
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fasteners 124. In some embodiments of the present disclosure, the straps 122
and 126
may extend laterally from the air beam 14B and the air beam 14A may include
fastener
portion 120B.
FIG. 23 shows one example of the connection system used to interconnect
multiple air beams 14A of one layer with air beams 14B of another layer by
using the
portions of the hook and loop fasteners 120, 124 described herein above to
restrict or
reduce shear between layers of air beams and to provide a configuration with
any gap
between laterally adjacent air beams of one layer.
While FIG. 23 shows a configuration where the layers are aligned offset, the
person skilled in the art will appreciate that the positioning of the hook
portions 120A,
124A and the loop portions 120B, 124B can be adjusted so that the air beams of
the
two (or more) layers are aligned centrally. Without being bound by any
particular
theory, when air beams in two or more adjacent layers are aligned centrally,
there can
be increases in the structural strength of the structure, which means that
larger spans
can be contemplated. In contrast, when air beams in two or more adjacent
layers are
aligned offset and the air beams within each layer are laterally abutting,
there may be
improved blast-related properties (e.g. a further attenuation of any
transmitted pressure
through the layers of air beams) and this may be because the respective air
beams are in
a somewhat nested position relative to each other.
Examples
Example 1: Material-Property Analysis
The inventors performed an initial analysis that illustrates the benefit of a
multilayer configuration of air beams 14. This analysis was based on comparing
the
first configuration (FIG. 3A) and the second configuration (FIG. 3B). This is
a useful
comparison, because it allows a comparison of stiffness and load-bearing
properties on
the basis of the same width, depth, and area of wall section (as shown by the
dotted
squares shown in FIG. 3A and FIG. 3B).
A complication arises, however, in the case of inflated fabric structures such
as
air beams. For conventional engineering materials, the material properties are
not
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dependent on the arrangement; for fabric structures, the effective material
properties are
highly dependent on prestress loading (among other parameters), and there is a
tight
relationship between prestress loading, inflation pressure, and tube diameter.
In order
to compare the first and second configurations on an equitable basis, the air
beams of
the second configuration must be inflated at precisely twice the pressure as
the air beam
in the first configuration. This is referred to as the "constant prestress"
(versus
"constant pressure") condition.
Table 1 provides theoretical stiffness properties and predicted span length of
the
first, second, third and fourth configurations of air beams.
Table 1. Theoretical stiffness and span values for four configurations of air
beams.
Configuration Type
8
First Second Third Fourth
Configuration Configuration Configuration Configuration
75%
(constant
Stiffness pressure)
100% 300% 633%
relative to First Configuration 150%
(constant
prestress)
Low estimate 100% n/a 173% 252%
High estimate 100% n/a 200% 300%
Testing focused on four-point flexural tests to determine the overall
structural
response of an air beam within each of the first, second, third and fourth
configurations
to a bending load, and to determine an appropriate value for the modulus of
elasticity, E
(also known as Young's Modulus).
Briefly, the four-point flexural tests were performed as follows:
Load was applied continuously using a winch system with the load measured by
a load cell and the displacement was measured by a draw-wire sensor attached
to the
bottom of the air-beam configuration being tested. The load and displacement
data
were recorded using a computer data-acquisition system.
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Load was applied to the air-beam configuration being tested through two 30 cm
(12") wide load straps that were draped over the air-beam configuration and
attached to
an aluminum frame hanging below the configuration. The straps were located at
about
1/3 of the span of the air-beam configuration for the majority of the tests.
For this
series of tests the span between the supports was about 4.65 m (load strap
spacing 1.55
m for 1/3 span loading). A number of tests were also performed with the straps
near
the center of the configuration (strap spacing 66 cm (26")).
The air-beam configurations were supported by yokes that matched the
curvature of the air beams within the configurations to minimize any
deformation of the
air beams at the supports. The yokes were hinged and set on casters to allow
for
rotation and horizontal displacement as the configuration bent under the
influence of
the load.
= Table 2 summarizes experimental results from four-point bending tests
on single layers of air beams and on double layers of air beams to assess
structural properties of the air beam layers.
Table 2. A summary of experimental results from four-point bending tests
performed
on single layers of air beams with diameters of 50 cm, 65 cm and 80 cm and on
double
layers of air beams with each layer having air beams with diameters of 50 cm
or 65 cm.
Data Source kFe
Configuration
(Study No.) (N/mm) (N)
50cm 0 2 6.47 624.06
Single-Layer 65 cm 0 3 11.78 1439.97
80 cm 0 1, 2 17.30 2742.93
100 cm S.D.
4A, 48 16.87 2274.29
(2x 50 cm 0)
Dual-Layer
130 cm S.D.
48 29.39 4060.07
(2x 65 cm 0)
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In Table 2, Fc represents the mean collapse load of each configuration of air
beams. The dual-layer configurations tested both show substantially higher Fe
values
as compared to the single-layers made up of air beams with the single layers.
Applying the empirical result factor of 93% to actual span data, and assuming
a
maximum practical span of a structure that is constructed with ribs 15 of the
first
configuration is about 33.5 meters (about 110 feet), this provides low and
high
estimates for the maximum predicted span of dual-layer and triple-layer
structures, as
shown in Table 3 below.
Table 3. A summary of calculated span lengths for the first, third and fourth
configuration of air beams.
Configuration Type 8
First Third Fourth
Configuration Configuration Configuration
Maximum predicted Low 33.5 m (110') 56.0 m (184')
81.4 m (267')
span High 67.1 m (220') 100.6 m (330')
Example 2: Blast-Tube Testing
A blast tube 200 is a type of shock tube, an example of which is shown in FIG.
5A. Briefly, the blast tube 200 comprises a driver section 202 in which an
explosive
event 204 is triggered. The pressure wave, which may also be referred to as a
blast
wave, shock wave or a blast pulse, generated by the explosive event 204
travels through
a transition section 206 and into a driven section 208. The driven section 208
includes
an upstream wall-mounted pressure sensor 210 and a front pressure-sensor 212.
Adjacent the front pressure-sensor 212 is positioned a test sample 216 that
may include
a fly 218. Behind the test sample is a rear pressure-sensor 214. The pressure
sensors
212, 214 were disc-type pressure sensors. During these experiments, the front
pressure-sensor 212 was positioned about 0.5 meters (about 20 inches) away
from the
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fly 218 and the rear pressure-sensor was positioned about 2.13 meters (about
seven
feet) from the front pressure-sensor 212. The pressure information captured by
the
pressure sensors was transmitted to a computer run software program for
analysis and
display.
FIG. 5B shows the configurations of air beams 14 that were tested in the blast
tube 200 as test samples 216. All of the air beams 14 tested in the blast tube
200 had a
diameter of about 0.6 meters. Test sample 21613 includes two individual air
beams 14
with a fly 218, a fly 218 and a gap 213 between the two air beams, this is a
further
example of the first configuration. The fly 218 may be made of polyvinyl
chloride,
polyester or a combination thereof. Test sample 216131 is the same as test
sample 216B
except the fly 218 is made from an auxetic material, this is another example
of the first
configuration. In certain configurations where there is no gap 213 between
laterally
adjacent air beams 14, those laterally adjacent air beams 14 are configured to
be in an
abutting relationship or position. Test sample 216C includes three individual
air beams
14 with a fly 218 and no gap 213 between the air beams 14. Test sample 216C is
another example of the first configuration. Test sample 216D includes three
air beams
14A that arc positioned adjacent the fly 218 to form the first layer 10A and
three air
beams 14B that form the second layer 10B. The three air beams 14B arc adjacent
to
and aligned centrally with the air beams 14A of the first layer 10A. Test
sample 216E
includes the first layer 10A of three air beams 14A, the second layer 10B of
three air
beams 14B and the intermediate layer 10C of three air beams 14C. All of the
air
beams 14 in test sample 216E are aligned centrally with adjacent air beams 14.
FIG. 6 through FIG. 13 show examples of overpressure data that was captured
in the blast tube 200. FIG. 6 shows three lines of captured data from: the
upstream
pressure sensor 210, shown as line 210A; the front pressure sensor 212, shown
as line
212A and the rear pressure sensor 214, shown as line 214A when there is no
target
sample present, which may be referred to herein as a reference shot. The
reference shot
allowed an examination of the characteristics of the blast pulse, and how the
blast-pulse
profile changes as the blast wave transits the length of the blast tube 200.
Without a
specimen in the test section, the incident pulse is undisturbed by target
reflections.
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Table 4 shows the characteristics of the reference shot.
Table 4. A summary of the reference shot characteristics.
Measurement Location _ P., (Peak), psig
Upstream pressure sensor 6.81
Front pressure sensor 6.59
Rear pressure sensor 5.91
FIG. 7 shows the overpressure-data captured when the target sample 216B (first
configuration with the gap 213) was present. Line 212B shows the pressure data
captured from the front pressure sensor 212 and line 214B shows the pressure
data
captured from the rear pressure sensor 214. The line 214B shows and incident-
peak
pressure that represents the maximum value of blast overpressure (psig)
associated with
the initial shock wave caused by the explosive event 204. Subsequent pressure
peaks
are shown in line 214B that have higher values, but these are associated with
reflections
that occur when the blast wave encounters the target sample 216 (shown as
reflection
peaks in FIG. 7). While these pressure values arc real and do act on the test
sample, a
more accurate assessment of the reduction of transmitted blast overpressure
requires
that the pressure wave transmitted through the structure be compared to the
peak that
would exist if the structure were not present. Therefore, in the present
analysis the
transmitted peak shown in line 214B was compared to the incident-peak pressure
shown in line 212B, and not the reflected peaks. In FIG. 7, the transmitted
pressure
shown in line 214B was about 30.7% lower than the incident-peak pressure shown
in
line 212B. The transmitted pulse retained a shock front.
FIG. 8 shows the overpressure data captured when the target sample 216131
(first configuration with the gap and an auxetie fly) was present in the blast
tube 200.
The transmitted pressure shown in line 214131 was about 35.3% lower than the
incident-
peak pressure shown in line 212B1. The transmitted pressure retained a shock
front.
FIG. 9 shows the overpressure data captured when the target sample 216C (first
configuration with no gap) was present in the blast tube 200. The transmitted
pressure
shown in line 214C1 was about 67.2% lower than the incident-peak pressure
shown in
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line 2120. The incident pressure in this run was higher than for others (8.10
psig vs.
approximately 6.0 psig). The transmitted pulse appears to have a short, finite
rise time,
but still retained a shock-like characteristic.
FIG. 10 shows the overpressure data captured from a second explosive event
(shot) when the target sample 216C (first configuration with no gap) was
present in the
blast tube 200. The transmitted pressure shown in line 214C2 was about 46.8%
lower
than the incident-peak pressure shown in line 212C2. The transmitted pulse
retained a
shock front.
FIG. 11 shows the overpressure data captured when the target sample 216D
(second configuration) was present in the blast tube 200. The transmitted
pressure
shown in line 214D1 was about 78.5% lower than the incident-peak pressure
shown in
line 212D1. The transmitted pulse did not have an associated shock front; the
shock is
completely absent in the transmitted pulse. The maximum transmitted pressure
also did
not occur in the first peak of the transmitted wave.
FIG. 12 shows the overpressure data captured when a second explosive event
204 occurred (second shot) and the target sample 216D (second configuration)
was
present in the blast tube 200. The transmitted pressure shown in line 214D was
about
76.9% lower than the incident-peak pressure shown in line 212D. The
transmitted
pulse did not have an associated shock front. It was determined that the
pressure spikes
shown in line 212D at about t = 11.0 milliseconds (indicated with * in FIG.
12) are
anomalies and can be disregarded.
FIG. 13 shows the overpressure data captured when the target sample 216E was
present in the blast tube 200. The transmitted pressure shown in line 214E was
about
79.9% lower than the incident-peak pressure shown in line 212E. The
transmitted
pulse did not have an associated shock front.
FIG. 14 shows a comparison of the peak-incident pressure data and transmitted
overpressure data captured when the various target samples 216 were present
within the
blast tube 200.
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The first configuration 216B with the gap 213 between laterally adjacent air
beams 14 reduces the overpressure transmitted through the target sample 216 by
about
30-35%. This finding is highly representative of blast resistance at full
structural scale.
Approximately the same degree of overpressure reduction was detected in all of
the
applicant's previous free-field blast studies on single-layer inflated
structures with a
gap between laterally adjacent inflated air beams.
Without being bound by any particular theory, if the inflation pressure and
tube
diameter are kept constant, when the structure 10 has no gap between adjacent
air
beams, the structure 10 is stiffer and capable of carrying a greater load than
a structure
10 with a gap. When the structure 10 has at least two layers 10A, 10B of air
beams 14
with an equivalent tube-diameter and inflation pressure, the structure 10 will
be stiffer
and stronger than a structure 10 with only one layer of air beams 14.
Furthermore, the
configurations of air beams 14 that had at least two layers 10A, 10B fully
defeated the
transmission of a shock wave.
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