Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITE STRUCTURAL MEMBER
FIELD OF THE INVENTION:
The invention relates to a structural member, generally. In
particular, the invention relates to a structural member constructed
of composite materials.
BACKGROUND OF THE INVENTION:
Structural members (e.g., columns or beams) may be constructed of
a variety of building materials, such as concrete, wood or steel,
each of which has particularly advantageous or disadvantageous
structural and load bearing properties. For example, concrete alone
has fairly good compressive strength however its tensile and
bending strength .can be improved greatly with the use of
reinforcing materials such as hoop steel. Without any
reinforcement, however, transverse and axial loads may cause a
concrete support structure to spall and ultimately fail.
Wood is often used in structural applications because it too has
good load bearing properties. Wood may be described as an
orthotropic material. It , has unique and independent mechanical
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properties in the directions of three mutually perpendicular axes
(longitudinal, radial and tangential).
When a wooden beam is subj ected to a load that is perpendicular to
the longitudinal direction of the wood body, the wood fibers
opposite the load are subjected to tension forces and wood fibers
adjacent the load are subjected to compression forces. Under a
heavy load, ~a wood beam rnay fail in. either the compressive or
tensile half of the wood beam.
There are drawbacks to using non-reinforced wood as a building
material. For example, wood deteriorates under certain conditions,
such as a high moisture or wet environment. Wood is primarily
composed of cellulose, lignin, hemicelluloses and minor amounts of .
extraneous materials. Cellulose is a high-molecular-weight linear
polymer consisting of chains of glucose monomers. The cellulose
molecules are arranged in ordered strands, which in turn are
organized into the larger structural elements that make up the cell
wall of wood fibers. Lignin is concentrated toward the outside and
between the cells. It is the cementing agent that binds individual
cells. It is a three-dimensional phenyl-propanol polymer. The
hemicelluloses are associated with cellulose and are branched, low
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molecular weight polymers composed of several different kinds of
pentose and hexose sugar monomers. As the cellulose, lignan,
hemicelluloses structure deteriorates, the wood fiber strength is
compromised and as a result, so are its load bearing capabilities.
Under this weakened condition, the wood is more prone to failure
under load. Also, despite any environmental deterioration, wood,
under a high load may still experience compression or tension
failure if it is not reinforced.
Previous attempts to reinforce concrete, wood or steel support
structures (e.g., Michalcewiz US5,505,030) involve using pre-made
reinforcing layers which are attached or fitted to the element being
reinforced, thereby increasing the reinforced element's
compressive, shear or load bearing capacity. Solutions of this type,
however, are merely prophylactic because they do not address the
underlying problem of using a building material that is susceptible to
load failure: The effective use of casing reinforcing materials, such
as described by Michalcewiz, is further limited by the fact that they
are merely surface treatments. It may not be possible to apply
reinforcing materials to. parts of a structure that are not readily
accessible.
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There remains a need for a composite structural member with
increased resistance to failure under load.
SUMMARY OF THE INVENTION:
The present invention provides a structural panel comprising a
frame having a longitudinal frame axis a plurality of beam elements
mounted in the frame, each of the beam elements has a respective
longitudinal beam axis generally parallel to the frame axis a
reinforcing fibre wrapping that extends around each of the beam
elements, the wrapping has a fibre direction running generally
obliquely to the beam axis a plurality of wire strands that extend
about the wrapping, the wire strands run generally parallel to the
beam axis and the frame axis; an outer layer of reinforcing fibre
mat that surround the frame, the wrapped beams and the wire
strands, the mat has a majority of its fibres running generally
parallel to the frame axis and, a solidified epoxy resin that extends
throughout and encasing the beam elements, beam wrapping, wire
strands, outer layer and frame.
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The reinforcing fibre mat of the beam wrapping may be a woven
mat having about the same quantity of fibres extending in each of
two generally orthogonal directions.
The beams may be made up of a plurality of panels having adjacent
faces laminated together and having a grain running along the beam
axis.
The structural panel may be a bridge deck having an upper face
coated with a road surfacing material.
The upper face may be canted with a longitudinally extending
centre section higher than and sloping toward opposite side edges
of the structural panel to promote drainage.
BRIEF DESCRIPTION OF THE DRAWINGS:
Preferred embodiments of the present invention are described
below with reference to the accompanying drawings iri which:
Figure 1 is a schematic view illustrating a composite structural
member according to the present invention
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Figure 2 is a schematic view illustrating a beam according to the
present invention and the beam's grain orientation relative to its
longitudinal axis
Figures 3a - b are schematic views illustrating alternate orientations
of a fibrous material in sheet form and its orientation as it extends
about and between a plurality of beams according to the present
invention
Figures 4a - b are schematic views illustrating the use of a fibrous
material in cord form and its orientation as it extends about and
between a plurality of beams according to the present invention
Figures 5a - b are schematic views illustrating the use of a fibrous
material in both sheet and cord form in a structure according to the
present invention.
Figures 6 is a perspective cross-sectional view of a composite
structural member according to an embodiment of the present
invention
Figure 7 is a cross-sectional view of a bridge and its associated
components assembled using a composite structural member
according to an embodiment of the present invention
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Figure 8 (a) is a schematic plan view of a structural panel according
to an alternate embodiment of the present invention
Figure 8 (b) is a schematic cross-sectional view of the structural
panel of Figure 8 (a)~
Figure 9 is a plan view of a frame element of the structural panel of
Figure 8 (a) according to the present invention
Figure 10 (a) is a longitudinal cross-sectional view of the frame of
Figure 9 according to an embodiment of the present invention
Figure 10(b) is a longitudinal cross-sectional view of the frame of
Figure 9 according to an alternate embodiment of the present
invention;
Figure 10 (c) is a cross-sectional view of the frame of 'Figure 9
according to an embodiment of the present invention
Figure 11 is a. partial plan view of an end portion of a beam element
of the structural panel of Figure 8 according to an embodiment of
the present invention;
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Figure 12 is a perspective view of an end portion of a beam element
of the structural panel of Figure 8 according to an embodiment of
the present invention
Figure 13 is a perspective cross-sectional view of a bridge deck
according to an embodiment of the present invention
Figure 14 is a perspective view of a beam element of the structural
panel of Figure 8 according to an embodiment of the present
invention
Figure 15 is an exploded view of the constituent components of the
structural panel of Figure 8 according to an embodiment of the
present invention and,
Figure 16 is a perspective cross-sectional view of the structural
panel of Figure 8 according to an embodiment of the present
invention.
DETAILED DESCRIPTION:
Figure 1 illustrates a composite structural member (CS1VI) 10 made
in accordance with a preferred embodiment of the invention.
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Referring to Figures 1 - 2 and 6, the CSM 10 has a plurality of
beams 20, each beam having a longitudinal axis 22 and at least one
side 24 generally parallel to and facing at least part of a side 26 of
at least one adjacent beam 20. A fibrous material 30 extends about
and between the beams 20. A potting material 40 permeates the
fibrous material 30 and encases the beams 20. The fibrous material
30 and potting material 40 are selected to yield a resistance to
bending in the CSM 10 that is greater than the combined individual
resistance to bending of the beams 20.
Each beam 20 has a grain direction 28 that is generally aligned with
the longitudinal axis 22. and is preferably a member selected from
the group consisting of wood and wood composites. In an alternate
embodiment, the beams 20 may be constructed of concrete,
fiberglass, and possibly other materials with properties similar to a
wooden beam.
In a preferred embodiment, the surfaces of the wooden beams 20
and the fibrous material 30 should be treated to clean and prepare
the surfaces for bonding. To enhance the bonding between the
wooden beams 20 and the fibrous material 30, the wooden beams
should be dry with their surfaces relatively free from grease,
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excessive dust, etc. Preferably the surfaces should be rough to
enhance adhesion. A water proofing treatment might also be
considered, particularly where the CSM 10 is to be used in a
submersed or partially submersed environment and there is a risk of
the encapsulating material being damaged so as to expose the
wooden beams 20 to water.
Referring to Figures 3 - 5, the fibrous material 30 is constructed, of
engineering materials having a high tensile . strength. In alternate
embodiments, a fibrous material 30 having higher or lower tensile
strength and modulus properties may be used depending on the
particular application of the invention.
Referring to Figure 5a, an embodiment of the fibrous material 30 is
in sheet form 32. In an alternate embodiment depicted in Figure 5b,
the fibrous material is in cord form 36. The fibrous material 30 in
the sheet form 32 may have variety of fiber architectures. In a
preferred embodiment, the fibers 34 are woven. Alternately, the
fibers 34 may be braided or knitted. The majority of the fibers 34
in the sheet form 32 are preferably unidirectional in the longitudinal
direction of the sheet form.
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Referring now to Figure 3a, the fibers 34 of the sheet form 32 are
preferably aligned generally transversely (i.e. non-parallel) relative
to the longitudinal axis 22 of the beams 20. Figure 3b illustrates an
alternate embodiment where the fibers 34 of the sheet form 32 are
aligned generally diagonally relative to the longitudinal axis 22 of
the beams 20.
Figure 4a illustrates a further embodiment. The fibers 34 of the
cord form 36 run generally transversely relative to the longitudinal
axis 22 of the beams 20. Figure 4b illustrates a still further
embodiment where the fibers 34 of the cord form 36 run generally
diagonally relative to the longitudinal axis 22 of the beams 20.
Figure 6 depicts a still further embodiment wherein the fibrous
material 30 extends around an individual beam 20, but does not
extend around any adjacent beams 20.
In a preferred embodiment of the invention, the fibrous material is a
member selected from the group consisting of glass, carbon,
KevlarTM, aramids, nylon, possibly natural fibers (e.g. hemp) and
combinations of the foregoing.
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Referring now to Figure 1, the potting material 40 is 'a curable resin
such as vinyl esters, poly esters, urethanes, BMIs, phenolics,
acrylics, epoxies, cynate esters and thermoplastics. The potting
material is preferably an epoxy that has exceptional adherence to
steel, such as the Jeffco 4101-08 epoxy resin and Jeffco 4101-18
epoxy hardener as manufactured by Jeffco Ltd of San Diego,
California.
The term "resin" refers to any substance, or combination of
substances, of a suitable viscosity, such that they can be used to
impregnate the fibrous materials and surround the plurality of
beams and ultimately undergo a physical state transformation from a
low viscosity fluid to a rigid solid state wherein said transformation
can occur via various means such as chemical reactions, a thermal
cycle, etc. and acts as a binding matrix of the fibrous material and
beams to create a final composite material.
A "Vacuum Assisted Resin . Transfer Method" (VART) may be
utilized to encase the beam/fibrous material structure in resin. This
is a known method of impregnating fibers with resin.
SAMPLE APPLICATIONS:
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Bridge construction is a sample application of the CSM 10 of the
present invention that illustrates its unique and enhanced load
bearing properties over prior generation composite structural
materials.
Referring to Figure 7, a bridge 70 consisting of a substructure and a
superstructure is illustrated. Substructure elements include
abutments 72, piers or pilings. Superstructure elements, which sit
atop the substructure, include stringers and or a deck 74. These
structural elements experience compression and tension forces
from several potential sources. For example, an abutment 72, pier
or piling, would experience compression forces 76 from the weight
of the superstructure, the weight of any body positioned on the
superstructure and the weight of the abutment 72 pier or piling
itself. Superstructure elements, such as the decking 74, may
experience compression forces 77 and tension forces 78 from the
weight of the decking 74 itself as well as any body 79 sitting on the
decking. The combined compression and tension forces may cause
the bridge structural elements to buckle (in the areas experiencing
compression forces) and or snap (in areas experiencing tension).
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A composite structural member of the type described in the present
invention dissipates the compression and tension forces over the
whole of the structural member, unlike individual structural
members, such as wooden beams or glue-laminated timber (glulam).
This load dissipating property of the CSM 10 permits the
construction of bridges of .greater scale and enhanced load-bearing
properties. This is because the load-bearing versus weight ratio of
the composite structural member of the present invention is several
times that of concrete or steel.
Bridge construction using the CSM 10 creates an integrated
structure where the decking is self-supporting, rather than simply
used as cladding. The structural strength of the CSM 10 stems from
the fact that the combined strength of the CSM 10 components
exceeds that of the beams and the potted encasement elements on
their own, in the configuration in which they are present.
ALTERNATE EMBODIMENT:
Referring to Figure 8 (a) - (b), 15 and 16, a composite structural
member according to a preferred embodiment of the present
invention is illustrated. The composite structural member or
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structural panel 100 ~ is comprised of a frame 101 having a
longitudinal frame axis 103. A plurality of beam elements 105 are
mounted in the frame 101, each of the beam elements 105 has a
respective longitudinal beam axis 107 that is generally parallel to
the frame axis 103. The beam elements 105 are wrapped in a beam
wrapping 109 of reinforcing fibre mat that extends around each of
the beam elements 105, the beam wrapping 109 has a fibre direction
running generally on a bias with (or obliquely to) the beam axis 107.
The structural panel 100 further includes a plurality of wire strands
111 that extend about the wrapping 109. The wire strands 111 run
generally parallel to the beam axis 107 and the frame axis 103.
There may also be transverse wire strands 151. The frame 101,
wrapping 109, beams 105 and wire strands 111 are further wrapped
and surrounded by an outer layer of reinforcing fibre mat 113 that
has a majority of its fibres 115 extending longitudinally generally
parallel to the frame axis 103. A solidified epoxy resin 117 extends
throughout and encases the beam elements 105, beam wrapping
109, wire strands 111, outer layer 113 and frame 101.
Referring to Figure 9, the frame 101 defines and determines the
approximate size and shape of the structural panel 100. In a
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preferred embodiment, the frame 101 is comprised of two side
members 119 positioned opposite each other and running generally
parallel to the longitudinal frame axis 103. The side members 119
are connected to each other via two end members 121, which are
positioned opposite each other and generally orthogonal to the side
members 119. In an alternate embodiment, the frame 101 is a
unitary structure. Any other frame configuration known to those
skilled in the art that defines and determines the approximate size
and shape of the structural panel 100 may be employed.
The frame 101 may be comprised of steel. In a preferred
embodiment, the frame 101 is comprised of a mild steel, such as a
44W High Strength Low Alloy steel, although any standard grade
steel that can be flame cut, formed, drilled, welded and/or machined
by any normal means may be employed.
Referring to Figure 10(a), cross-sectional view of the frame 101
along the frame axis 103 according to a preferred embodiment of
the present invention is illustrated. The frame 101 of structural
panel 100 is configured to receive at least opposite ends of the
beams 105. The end members 121 are recessed or cut out along
their respective lengths in order to provide a beam receiving
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surface 123 for receiving opposite ends of - the beam 105. The
recess 125 may be of any shape known to those skilled in the art
(e.g. flat, bevelled or curved) that defines a beam receiving surfaee
123. An alternate embodiment of the end members 121 is
illustrated in Figure 10(b). In this embodiment, the end members
121 are not cut out, but,rather, the end members 121 have at least
one hole or passage 127 passing through the end members 121. A
fastener 129 passes through the respective end members and
secures the beams 105 to the frame 101.
In a preferred embodiment, the frame 101 has longitudinally
extending edge flanges 131 that are generally parallel to the frame
axis 103.
Referring to Figure 16, a perspective cross-sectional view of the
structural panel 100 . is illustrated. The frame 101 preferably has a
plurality of spars 133 extending across the frame between the edge
flanges 131 and the spars 133 have sockets 135 formed therein for
receiving the opposite ends of the beam elements 105.
Referring to Figure 11, an end section 137 of the beam 105
according to a preferred embodiment of the present invention is
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illustrated. The beam 105 is wrapped in a beam wrapping 109
comprised of reinforcing glassy fibres 139. In a preferred
embodiment the glassy fibre is standard fibreglass as sold by Dow
Corning of Corning, New York. In an alternate embodiment, the
glassy fibre is basalt based.
In a preferred embodiment, the beam wrapping 109 is a woven mat
having about the same quantity of fibres 139 extending in each of
two generally orthogonal directions (i.e.., approximately 50% of the
fibres 139 running in each direction). This is achieved by wrapping
the beam wrapping 109 on a bias relative to the beam axis 107.
The beam 105 is further wrapped with wire strands 111. In a
preferred embodiment, the wire strands 111 are incorporated in the
beam wrapping 109. Alternately, the wire strands 111 may be an
element of an additional wire strand wrap 141, which is applied over
top the beam wrapping 109. In either case, the wire strands 111
run generally parallel to the beam axis 107 (Figure 14).
The wire strands 111 are comprised of steel. In a preferred
embodiment, the wires 111 are comprised of high tensile strength
steel.
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Referring to Figures 8(b) and 12, a beam end portion 137 is
illustrated according to a preferred embodiment of the present
invention. The beams 105 are comprised of wood, with each of the
beams being made up of a plurality of laminae 143 having adjacent
faces 145 laminated together and having a grain 147 running along
the beam axis 107. In a preferred embodiment, the laminae 143 are
aligned with the adjacent faces 145 generally parallel to the upper
face 149 of the panel 100.
In a preferred embodiment, the wood laminate beam 105 is
comprised of kiln dried spruce, which provides a high tensile
strength per unit weight. The wood laminae 143 are dried to
approximately 16% moisture or less and fixed to each other using
an adhesive. In a preferred embodiment, the adhesive is
manufactured by Borden Chemical Ltd. of Montreal, Canada,
although any adhesive known to those skilled in the art that is as
strong as or stronger than the wood may be employed.
In an alternate embodiment, the panel 100 may be used in low
stress or low load bearing applications, such.as a wall panel. The
load bearing capabilities and weight of a panel 100 that incorporates
wood laminate beams may be neither required, nor desired. The
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beams 105 may be comprised of a low density material, such as a
foam material, which is both light weight , and able to bear a load.
Any low density material that can bear a load, which is known to
those skilled in the art, may be employed.
Referring ~to Figures 8(a) and (b), the frame 101, beam wrapping
109, beams 105 and wire strands 111 . are further wrapped and
surrounded by an outer layer of reinforcing fibres 113 comprised of
mat reinforcing fibres 115, thereby creating a wrapped structure. In
a preferred embodiment, the reinforcing fibre 115 is a glassy fibre,
such as a standard fibre glass as sold by Dow Corning of Corning,
New York. Ln an alternate embodiment, the glassy fibre is basalt
based.
In a preferred embodiment, the outer fibre wrap 113 has about 90%
of its fibres extending longitudinally and generally parallel to the
frame axis 103. The relative ratio of the fibres 115 as well as the
relative directions in which the fibres 115 extend may vary with the
particular use to which the structural member 100 is put and the
direction and magnitude of the resultant forces exerted on the
structural panel 100. For example, if the structural panel 100 is
used as a roof panel, the fibres 115 may extend equally in all
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directions. If the panel 100 is employed as a bridge deck, then
approximately 80% of the fibres 115 extend longitudinally
(generally parallel with the frame axis 103) and approximately 20%
of the fibres 115 run generally orthogonal to the longitudinally
extending fibres 115.
After the outer fibre mat 113 is applied, the wrapped structure is
permeated with and encased in an epoxy resin that extends
throughout the frame 101, beam wrapping 109, beams 105, wire
strands 111 and outer wrap 113. The epoxy resin impregnates the
fibrous material and surrounds the frame 101 and plurality of beams
105, ultimately undergoing a physical state transformation from a
low viscosity fluid to a rigid solid state and thereby acting as a
binding matrix of the fibrous ematerial (109, 113), frame 101 and
plurality of beams 105 to create a final composite material. In a
preferred embodiment, the epoxy has exceptional adherence
(without the use of special primers) to steel, such as the Jeffco
4101-08 epoxy resin and Jeffco 4101-18 epoxy hardener as
manufactured by Jeffco Ltd. of San Diego, California.
A vacuum assisted resin transfer method (V.A.R.T.) may be used to
encase the wrapped structure in epoxy resin, although any other
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method of impregnating and encasing a wrapped structure that is
known to those skilled in the art may be used.
The wire strands 111 act as a flow medium for the epoxy resin,
thereby ensuring that the resin sufficiently permeates and
surrounds the wrapped structure. The wire strands' 111 function as
a flow medium for the epoxy resin also obviates the need to cut
flow channels into the wrapped structure or any of its components.
The components of the panel 100 (i.e., the frame 101, beams .105,
wraps 109 and 113, and epoxy 117) are selected to have physical
properties that do not vary to such a degree that separation of the
components of the composite panel occurs when the panel 100 is in
use i.e., tensile and compressive forces exerted on the panel 100.
are distributed over the whole of the panel and no one component of
the panel 100 bears a disproportionate degree of load bearing
stress, which would result in separation of the panel 100
components.
Sample Applications:
The structural panel 100 may be used in many different
applications, such as building panels, piles, floor panels, wall panels,
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roof panels, box culverts and retaining walls. Referring to Figure
13, a preferred application of the structural panel 100 as a bridge
deck 500 is illustrated.
The bridge deck 500 has an upper face 501 that is coated in a road
surfacing material 503. In a preferred embodiment, the coating 503
is a ~ latex asphalt, such as manufactured by TJ Pounder Inc. of
Brampton, Ontario, Canada. Latex asphalt is preferred because it
can be applied cold, thereby obviating the need to apply a hot
asphalt mixture, which may potentially compromise the structural
integrity of the structural panel 100. A primer is applied first to the
upper surface and then an approximately one-half inch
(approximately 1.25 cm) layer of latex asphalt is applied. The
opposite face or underside 505 of the deck 500 is painted with UV
stabilised polyurethane.
The upper face 501 of the deck 500 is preferably canted with a
longitudinally extending centre section 507 higher than and sloping
toward opposite side edges 509 of the deck 500 to promote
drainage.
r
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In a preferred embodiment, the deck 500 is thicker at the opposite
side edges 509 than at the centre section 507 thereby providing a
curb 511 at the side edges 509. Having a deck 500 with curbs 511
at the opposite side edges 509 results in overall enhanced stiffness
of the deck 500, thereby allowing it to be thinner at the centre
section 507 than would be required of a panel having the same load
bearing capacity but of generally constant thickness.
The present invention is .defined by the claims appended hereto,
with the foregoing description being illustrative of the preferred
embodiments of. the invention. Those of ordinary skill may envisage
certain additions, deletions and/or modifications to the described
embodiments, which, although not explicitly suggested herein, do
not depart from the scope of the invention, as defined by the
appended claims. For example, the beams may be of non
rectangular cross-sectional configuration (such as circular,
elliptical, triangular etc.) and the beams need not have their
respective longitudinal axes coplanar. Furthermore in some
applications curved rather than straight beams may be desirable.
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