Note: Descriptions are shown in the official language in which they were submitted.
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AIR BEAM WITH STIFFENING MEMBERS AND AIR BEAM STRUCTURE
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S. Provisional
Patent
Application No. 61/094,710 filed September 5, 2008, which is incorporated
herein by
reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to air supported structures.
More
particularly, the present invention relates to air supported structures
resistant to high static or
dynamic load or both.
BACKGROUND OF THE INVENTION
[0003] There have historically been a variety of air supported structures.
That is,
structures which are internally pressurized. US 3,159,165 to Cohen et al., for
example,
teaches a shelter or enclosure relying on pressurized air for support. As such
structures
require a constant air pressure to maintain the structure, a constant supply
of pressurized air
and a sealed entry/exit to reduce air loss.
[0004] Another approach is to form an inflatable structural member, which are
combined and covered to form a structure. These are commonly referred to as
"air beams".
This construction does away with the necessity that the structure be
pressurized, but air
beams are inherently susceptible to bending and collapse.
[0005] Conventional inflatable shelters utilize complex shaped inflatable
members that are difficult to manufacture. These shelters are erected only as
small units not
larger than about 20m in width or diameter. They are created very often in
such a way that
once damaged the entire shelter must be replaced. Shelters employing multiple
tubes that
are connected one to each at the apex are difficult to cover by a fly. But the
most important
drawback of these shelters is that they can be built only with relatively
smaller dimensions.
[0006] When a larger shelter is built in this way, it wrinkles, buckles and
collapses
under snow or high wind loads, even if the dimensions of the tubes or pressure
in the tubes
is increased.
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[0007] US 5,735,083 to Brown et al. teaches an air beam made up of a
cylindrical
braid and lined with a gas-retaining bladder. Linear bundles extending
parallel to the axis of
the cylindrical braid are incorporated within the cylindrical braid to improve
resistance of the
air beam to wrinkling or buckling. In a further implementation, the linear
bundles are made up
into external straps and retained by a coating applied to the braided fibres.
[0008] It is, therefore, desirable to provide an improved structural member,
structure,
method of assembly/disassembly, and design.
SUMMARY OF THE INVENTION
[0009] A large inflatable structure includes pneumatic tubular columns
(arches)
covered on both sides by flexible membranes. The column are placed side by
side what
creates a wall and enclosure of the space. The structure includes two side
walls equipped
with large doors providing the entrance to the structure. The design of the
structure is
oriented to the fact that the dimensions of the structure could be very large
of the order of
100m width 200m long and 50 m high and satisfy the safety conditions against
buckling and
burst of the columns. The pneumatic columns are under the internal pressure of
the air and
keep their shape by means of the set of cables reinforcing them in the plane
of the tubes.
The tubes are covered with external and internal membrane-fly attached to the
columns. The
columns can be also supported by an external support member connected to
support
towers on both ends of the structure. The use of the support member and towers
is related to
the dimensions of the structure. Smaller structures require only reinforcing
by side and
internal cables. Larger structures benefit from support member(s) and towers.
[0010] The structure is built in the way that it is easy dismantle and
removable. The
columns are easily deflected and erected or replaceable.
[0011] Due to the fact that the structure consists of a composition of tubular
pneumatic elements, cables and support towers, it requires special
computational tools able
to deal with different types of the elements of the structure. The pneumatic
column is a very
flexible member of the system and it is not possible to predict its buckling
conditions using
method and software that are commercially available on the market.
Particularly, the
application of cables, which provide the support only when they are in tension
produce great
difficulties when attempting to apply the conventional finite element software
and methods.
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The method of the calculations used to define buckling strength and stability
is based on the
theory utilizing the idea of pneumatic hinges to determine buckling loads.
[0012] The method of pneumatic hinges was described in the papers S.A.
Lukasiewicz and L. Balas, "Collapse Loads of a Cylindrical and Toroidal Free
Standing
Membrane": International Journal of Mechanics of Structures and Machines,
18,(4) 1990
pp 499-513 and S.A. Lukasiewicz and L. Balas. "Collapse Modes of Inflatable
Membranes"
International Journal of Mechanics of Structures and Machines, 18,(4) 1990 pp
483-497.
[0013] It is known that if the internal forces and moments in a pneumatic
column reach a certain critical value the column collapses. Therefore, to
determine load
carrying capabilities of the structure it is necessary first to find the
forces and moments in the
column, and second, to determine if these forces are in a safe range. A method
of analysis
"Space Frame Cable System Analyzer" (SFCSA), preferably embodied in software
using
finite element modeling has been developed and used to predict the values of
the normal
forces and bending moments in the pneumatic columns of the present invention.
The method
has been developed on the assumption that the problem is static. Then the idea
of
pneumatic hinges was utilized to determine the buckling loads. SFCSA is a
space frame
finite element analysis program which integrates curved pneumatic columns and
cables-
tension only link elements. The tension only feature of the cables is
implemented by
iterations. In each iteration step, if a cable is in tension, its stiffness is
added to system
general stiffness matrix. If the cable is in compression its stiffness is
removed from system
general stiffness matrix, and the calculations are repeated. This procedure is
followed until
stiffness of all cables in tension is added to system general stiffness
matrix, and stiffness of
all cables not in tension is removed from the system general stiffness matrix.
In addition, the
effect of large finite displacements of the columns may also be included in
each iteration.
[0014] The calculations of the stability of the structure and loads causing
the collapse
of the structure have been performed for two types of load: for snow and wind
loads. The
dead load due to the weight of the structure was included in both cases.
[0015] The positions of the attachment of the cables to the pneumatic columns
may
be obtained by analysis through the method of the FSCSA software. Using the
FSCSA
method it is possible to optimize the position of the cables.
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[0016] It is an object of the present invention to obviate or mitigate at
least one
disadvantage of previous apparatus and method for designing and providing air
supported
structures.
[0017] In one aspect the present invention provides a structural member having
an
elongate pneumatic tubular column, a plurality of stiffening members, and
means for
connecting the tubular column and the stiffening members.
[0018] In one embodiment, the structural member is adapted to form an arch
having
an inner side and an outer side, the plurality of stiffening members connected
with the tubular
column on the inner side.
[0019] In one embodiment, the stiffening members include a cable extending
between two connectors, the connectors fixed to the tubular column.
[0020] In a further aspect the present invention provides an air beam
structure having
a plurality of structural members having a plurality of elongate pneumatic
tubular columns,
separated one from another by a gap, a plurality of stiffening members
connected with the
elongate pneumatic tubular columns, and a flexible membrane covering the
plurality of
structural members and the gap.
[0021] In one embodiment, the air beam structure includes a support structure,
above
the air beam structure, the support structure adapted to support at least a
portion of the air
beam structure.
[0022] In one embodiment, the support structure includes at least two support
towers,
a support member extending between the at least two support towers.
[0023] In one embodiment, a plurality of support cables extend between the
support
member and the structural members.
[0024] In one embodiment, the support member is a suspended cable. In one
embodiment, the support member is a suspended structural beam.
[0025] In a further aspect, the present invention provides a method of
constructing an
air beam structure including providing an elevated support structure, adapted
to support at
least a portion of the air beam structure, providing a plurality of structural
members having a
plurality of elongate pneumatic tubular columns, separated one from another by
a gap, and a
plurality of stiffening members connected with the elongate pneumatic tubular
columns,
supporting each of the plurality of structural members from the support
structure prior to
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connecting the stiffening members, and covering the outer side of the
structural members
with a flexible membrane covering the plurality of structural members and the
gap.
[0026] In a further aspect, the present invention provides a method of
determining the
size and placement of a plurality of stiffening members for a pneumatic
tubular column,
including selecting a selected stiffening member from the plurality of
stiffening members, the
selected stiffening member having a stiffness, adding the stiffness to a
system general
stiffness matrix if the selected stiffening member is in tension, subtracting
the stiffness from
the system general stiffness matrix if the selected stiffening member is in
compression, and
repeating the steps for remainder of the plurality of stiffening members in
order to determine
the system general system matrix.
[0027] In one embodiment, the stiffening member is a tension member. In one
embodiment, the tension member is a cable.
[0028] Other aspects and features of the present invention will become
apparent to
those ordinarily skilled in the art upon review of the following description
of specific
embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Embodiments of the present invention will now be described, by way of
example only, with reference to the attached Figures, wherein:
[0030] Fig. 1 is a perspective view of a structure of the present invention in
an
embodiment having air columns reinforced by external stiffening members;
[0031] Fig. 2 is a cross-section view of the structure of Fig. 1;
[0032] Fig. 3 is a perspective view of a structure of the present invention in
an
embodiment having a longitudinal support member above and connected with the
structure;
[0033] Fig. 4 is a cross-section view of the structure of Fig. 3;
[0034] Fig. 5 is a perspective view of a structure of the present invention in
an
embodiment having a plurality of longitudinal support members above and
connected with
the structure;
[0035] Fig. 6 is a cross-section view of the structure of Fig. 5;
[0036] Fig. 7 is a cross-section view of a structure of the present invention
in an
embodiment having a plurality of longitudinal support members above and
connected with
the structure and guy members;
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[0037] Fig. 8 is a cross-section view of a structure of the present invention
in an
embodiment having a plurality of longitudinal support members above and
connected with
the structure and internal stiffening members;
[0038] Fig. 9 is a perspective partial cross-section view of a wall section of
the
structure of Figs. 1, 3, or 5 showing spacing between adjacent columns;
[0039] Fig. 10 is a detail cross-section view of a column or structural member
of the
present invention, showing the cable and column connection;
[0040] Fig. 11 is a detail view showing a rigid opening associated with a
structure of
the present invention;
[0041] Fig. 12 is a structure of the present invention having a support tower
protruding through the structure;
[0042] Fig. 13 is a structure of the present invention having a shape selected
to
include/exclude non-uniform areas/spaces;
[0043] Fig. 14 is a detail of a portion of the support structure of the
structure of Fig.
12;
[0044] Fig. 15 is a detail view of an end portion of the structure of Fig. 5;
[0045] Fig. 16 is a further view of the structure of Fig. 5;
[0046] Fig. 17 is an embodiment of a connector for use with a structure of the
present
invention;
[0047] Fig. 18 is an embodiment of a connector for use with a structure of the
present
invention;
[0048] Fig. 19 is a perspective detail view of a portion of the structure of
Fig. 5;
[0049] Fig. 20 is a side view the structure of Fig. 12; and
[0050] Fig. 21 is an end view of the structure of Fig. 5.
DETAILED DESCRIPTION
[0051] Generally, the present invention provides a method and apparatus for
designing and providing an air beam structure.
[0052] Referring to Figs. 1 and 2, a structure 10 of the present invention is
assembled from a plurality of structural members 20 covered by a flexible
membrane 30. The
structural member 20 includes an elongate pneumatic tubular column 40 formed
into an arch
shaped air beam. A plurality of stiffening members in the form of cables 50
are connected
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with the tubular column 40 by connectors 60. As shown, the cables 50 generally
traverse the
inside of the tubular column 40 to increase its resistance to bending,
buckling, collapse or a
combination of bending, buckling, or collapse from exterior loads such as
wind, snow, sand,
ice etc.
[0053] The structure 10 may include one or more end wall doors 25 and/or side
wall
doors 27.
[0054] The positions of the connectors 60 on the columns 40 are defined by
means
of the FSCSA method for each case. A preferred design of the attachment
provides that the
forces act on the columns perpendicularly to the pneumatic columns only.
[0055] The large structure column is not able to carry a snow load. The snow
provides a large vertical load which may cause the wrinkling or buckling of
the column.
Eventually the column may collapse causing the collapse of the whole
structure. To improve
the buckling strength of the pneumatic tubular column 40 the internal cables
50 are installed
along the pneumatic tubular column 40. The cables 50 may increase the bending
stability of
the pneumatic tubular column 40 by up to 30% or more.
[0056] Referring to Figs. 3 and 4, the structure 10 of the present invention
may be
assembled from a plurality of structural members 20 covered by the flexible
membrane 30. A
support structure 70 is fixed above the structure 10 to support at least a
portion of the
structure 10. The support structure 70 includes a support member 80 extending
between
support towers 90. The support member 80 may comprise a suspended cable 100
supported
by a plurality of suspension support cables 107 from a suspension cable 105
from the
support towers 90 (somewhat like a suspension bridge). A plurality of support
cables 110
extend between the suspended cable 100 and one or more of the structural
members 20.
Alternatively, the support member 80 may be a structural member, such as a
beam or series
of beams.
[0057] Referring to Figs. 5, 6, 11, 16, and 21 the structure 10 of the present
invention
is assembled from a plurality of structural members 20 covered by a flexible
membrane 30
(for example a fly 35). The support structure 70 is fixed above the structure
10 to support at
least a portion of the structure 10. The support structure 70 includes the
support members 80
extending between the support towers 90. The support member 80 may comprise a
suspended cable 100 supported by a plurality of suspension support cables 107
from a
suspension cable 105 from the support towers 90 (somewhat like a suspension
bridge). A
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plurality of support cables 110 extend between the suspended cable 100 and one
or more of
the structural members 20. Alternatively, the support member 80 may be a
structural
member, such as a beam or series of beams.
[0058] Referring to Fig. 7, a plurality of guy members in the form of guy
wires 120
extend between the structural members 20 and an anchor 130 fixed into the
ground 140 or
otherwise fixed (such as an anchored or weighted body). The guy wires 120 may
connect
directly or indirectly to any or all of the structural member 20, the towers
60, the support
member 80, or a combination of these components.
[0059] Referring to Fig. 8, a plurality of internal guy members in the form of
internal
wires 150 extend between the structural members 20 and an anchor 130 fixed
into the
ground 140 or otherwise fixed (such as an anchored or weighted body). The
internal guy
wires 150 may connect directly or indirectly to the structural member 20
and/or the
towers 60, or a combination of these components.
[0060] Referring to Fig. 9, the structural members 20 of the structure 10 may
be
separated by a gap 160. The gap 160 may be as small as substantially zero,
that is adjacent
structural members 20 may abut each other. Typically, the gap 160 would be
substantially
uniform along the length of the structure 10, but that is not required. One or
more of the gaps
160 may be used to provide side access to the structure 10, for example via
the side wall
door 27 (see Fig. 1)
[0061] Referring to Fig. 10, stiffening members in the form of cables 50
extend
between connectors 60. The connectors 60 are fixed to the structural member
20.
[0062] Referring to Fig. 11, a rigid structure (in this case, as an example
the side wall
door 27 in the form of a rigid frame door system) may be incorporated into the
structure 10.
In this Fig. 11, the flexible membrane 30 (for example the fly 35) is shown as
semi-
transparent to better illustrate the structural members 20.
[0063] Referring to Figs. 12, 14, and 20 a portion of the support structure 70
may be
internal to the structure 10 and another portion of the support structure 70
may be external to
the structure 10. As show, the support towers 90 extend through the wall or
roof or both of
the structure 10 to support the support member 80 substantially external to
the structure 10.
Also shown in Fig. 12, other items may extend through the wall or roof or both
of the
structure 10, for example a flare stack 180 or other process equipment or
structures such as
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pressure vessels, towers, columns, flare stacks, piping, walkways, pressure
relief valves,
flare piping, pipe racks etc.
[0064] Referring to Fig. 13, the structure 10, may include a non-uniform
shape. For
example, as shown, the structure 10 may be shaped to encompass a selected
area/space
within the structure 10 and/or to avoid a selected area/space outside the
structure 10. A step
190 is one example of such adaptation.
[0065] Referring to Figs. 15 and 19, a suspended deck 170 may be provided to
improve access to the top area of the structure 10 during the assembly or
disassembly. The
suspended deck 170 may include a platform for persons to walk or work on or
from during
assembly/disassembly or inspection or maintenance of the structure 10. The
suspended
deck 170 may also support one or more trolleys, pulleys, or cranes to lift the
columns 40 or
flexible membrane 30 etc. during the assembly/dismantle process or
maintenance. The
suspended deck 170 could be also equipped with one ore more movable blower(s)
to
facilitate snow removal from the upper portion of the structure 10.
[0066] Referring to Figs. 17 and 18, one embodiment of a connector 60 is
depicted.
The connector 60 provides for attachment of the cable 50 and the structural
member 20. One
skilled in the art will recognize that a variety of apparatus and methods may
be used to affix
or join the cables 50 and the structural member 20 (e.g. elongate pneumatic
tubular column
40) of the structure 10 of the present invention. In one embodiment (not
shown) the
connector 60 of the type disclosed in the co-pending application US 61/094,727
may be
used.
[0067] In erecting or constructing the structure 10 (referring, for example,
to Figs. 3
and 4) the support member 80 in the form of suspended cable 100 is extended
between the
support towers 90. A plurality of structural members 20 are provided along the
length of the
suspended cable 100. The structural members may be separated by the gap 160,
which may
be as little as substantially zero metres. The structural members 20 may be
supported from
the suspended cable 100 during inflation. A plurality of stiffening members in
the form of
cables 50 are connected with the structural members 20 by connectors 60. The
exterior of
the structure 10 is covered with a flexible membrane 30 (for example a fly
35). The interior of
the structure may similarly be covered with a flexible membrane (not shown).
[0068] A space formed between the structural members 20 and the flexible
membrane 30 may be utilized for the purpose of heating and ventilation of the
structure, for
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example by forming a channel which can serve as a conduit for conditioned air
(e.g. heated
or cooled).
[0069] In deconstructing, demolishing, or repairing the structure 10
(referring, for
example, to Figs. 3 and 4) at least a portion of the structure is supported by
the support
member 80 in the form of suspended cable 100. At least one structural member
20 is
unsupported (for example by removing any support cables 110) to form an
unsupported
structural member 20. The unsupported structural member 20 may then be
removed,
repaired or replaced. In a deconstruction or demolition process, the removal
sequence could
be repeated, and once complete, the support member 80 and support towers 90
removed.
[0070] Thermal and pressure expansion of the elongate pneumatic tubular
columns
40 may be compensated by means of selected sequence of the assembly and
erection of the
structure 10.
[0071] The present invention is applicable to a wide variety of structures
including,
but not limited to, construction shelters and storage/maintenance shelters for
vehicles and
aircraft (including deployable variants), command centers, disaster relief,
housing, or medical
facilities. Such structures may be temporary or permanent.
[0072] As used herein, cable, wire etc. mean and include a structural tension
element, which may include wire rope, fabric webbing, metal rods, metal
tubulars, fibre
reinforced composite materials such as fibre reinforced plastic,
carbon/graphite, etc.
[0073] Without limiting the scope of the present invention, generally
speaking, the
structures 10 having a width up to about 30m do not require support towers 90,
structures 10
having a width between about 30m and about 60m benefit from a support
structure 70 having
two support towers 90, and that structures 10 having a width larger than 60m
benefit from a
support structure 70 having four support towers 90.
[0074] In the preceding description, for purposes of explanation, numerous
details
are set forth in order to provide a thorough understanding of the embodiments
of the
invention. However, it will be apparent to one skilled in the art that these
specific details are
not required in order to practice the invention.
[0075] The above-described embodiments of the invention are intended to be
examples only. Alterations, modifications and variations can be effected to
the particular
embodiments by those of skill in the art without departing from the scope of
the invention,
which is defined solely by the claims appended hereto.
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