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 present invention is directed to the field of construction, and in
particular building
construction. Included within the present invention are structural timber
members capable of
bearing loads required in applications such as bearers, floor joists, roof
rafters, beams,
columns and the like.
BACKGROUND TO THE INVENTION
Timber is a renewable natural resource useful in the construction of buildings
and other
structures. When trees are harvested there is significant wastage of woody
material.
Typically this material is used in relatively low value applications such as
fuel for heat
generation, wood chips, landscaping products, the production of bio fuels and
the like.
While these are effective uses of waste products they do not add value to the
product, and
.. merely minimise economic loss on the cost of timber production.
Timber products act to sequester carbon dioxide for decades, thereby assisting
in limiting
climate change. This is a practical advantage and a point of difference in
marketing the
sustainable forestry industry, and the products produced from timber. However,
these
advantages are diminished or lost where woody waste material is combusted or
otherwise
transformed to release carbon dioxide. Many current uses for wood waste
release
significant amounts of carbon dioxide into the atmosphere, thereby
exacerbating climate
change and undermining the carbon sequestration advantages of timber products.
As one example, so-called "peeler cores" (which are typically 60 to 80 mm
diameter) result
from logging for plywood products. Peeler cores are often used to fuel forest
kilns, or
chipped for use in landscape applications. Wood of diameter less than 80 mm
diameter is
often left on the forest floor.
A further problem in the art is the significant time taken for a tree to be
ready for harvest.
The main trunk and branches of the tree must be of sufficient diameter to
allow for the
economical production of products such as sawn timber. A shorter production
cycle would
allow for increases in production capacity for a given area of land as a
function of time.
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The present Applicant has previously proposed load bearing timber members in
international
patent application PCT/AU2009/001453 (published as W0/2010/057243). While
effective in
structural applications, these prior art beams are formed from timbers that
are implicated in
some of the problems referred to supra in so far as the component timbers are
necessarily
harvested in a wasteful manner Furthermore, these prior art beams are formed
from
relatively expensive timbers and for some applications are excessive in weight
or moisture
content.
It is an aspect of the present invention to provide timber structural beams
than can be
fabricated with less wastage of woody material and/or from timbers that are
faster to harvest
and/or more economically and/or at a lighter weight. It is a further aspect to
provide an
alternative to prior art timber beams.
The discussion of documents, acts, materials, devices, articles and the like
is included in this
specification solely for the purpose of providing a context for the present
invention. It is not
suggested or represented that any or all of these matters formed part of the
prior art base or
were common general knowledge in the field relevant to the present invention
as it existed
before the priority date of each provisional claim of this application.
SUMMARY OF THE INVENTION
In a first aspect the present invention provides a structural member
comprising: a first timber
round having a first cooperating surface extending longitudinally along the
length thereof, a
second timber round having a second and a third cooperating surfaces extending
longitudinally along the length thereof, and a third timber round having a
fourth cooperating
surface extending longitudinally along the length thereof wherein, the first
cooperating
surface is shaped to cooperate with the second cooperating surface, and the
third
cooperating surface is shaped to cooperate with the fourth cooperating
surface, the first,
second and third timber rounds are secured together to form a structurally
integral unit in
which the first cooperating surface is in contact with the second cooperating
surface, and the
third cooperating surface is in contact with the fourth cooperating surface,
and the first,
second and third timber rounds are substantially parallel to each other, and
wherein the first,
second and third timber rounds are secured to each other by a plurality of
fasteners spaced
along the length of the member, the plurality of fasteners comprising
fasteners provided at
both acute and obtuse angles from a longitudinal axis of the structural
member, the
fasteners extending through the first, second and third timber rounds,
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The present invention further provides a structural member comprising: a first
timber round
having a first cooperating surface extending longitudinally along the length
thereof, a second
timber round having a second and a third cooperating surfaces extending
longitudinally
along the length thereof, and a third timber round having fourth and fifth
cooperating
surfaces extending longitudinally along the length thereof, and fourth timber
round having a
sixth cooperating surface extending longitudinally along the length thereof
wherein, the first
cooperating surface is shaped to cooperate with the second cooperating
surface, and the
third cooperating surface is shaped to cooperate with the fourth cooperating
surface, and the
fifth cooperating surface is shaped to cooperate with the sixth cooperating
surface, the first,
second, third and fourth timber rounds are secured together to form a
structurally integral
unit in which the first cooperating surface is in contact with the second
cooperating surface,
and the third cooperating surface is in contact with the fourth cooperating
surface, and the
fifth cooperating surface is in contact with the sixth cooperating surface,
and the first,
second, third and fourth timber rounds are substantially parallel to each
other, and wherein
the first, second, third and fourth timber rounds are secured to each other by
a plurality of
fasteners spaced along the length of the member, the plurality of fasteners
comprising
fasteners provided at both acute and obtuse angles from a longitudinal axis of
the structural
member, the fasteners extending through the first, second, third and fourth
timber rounds,
The present invention further provides a structural member comprising. a first
timber round
having a first cooperating surface extending longitudinally along the length
thereof, a second
timber round having a second and a third cooperating surfaces extending
longitudinally
along the length thereof, and a third timber round having fourth and fifth
cooperating
surfaces extending longitudinally along the length thereof, and a fourth
timber round having
sixth and seventh cooperating surfaces extending longitudinally along the
length thereof,
and a fifth timber round having an eighth cooperating surface extending
longitudinally along
the length thereof wherein, the first cooperating surface is shaped to
cooperate with the
second cooperating surface, and the third cooperating surface is shaped to
cooperate with
the fourth cooperating surface, and the fifth cooperating surface is shaped to
cooperate with
the sixth cooperating surface, and the seventh cooperating surface is shaped
to cooperate
with the eighth cooperating surface, the first, second, third, fourth and
fifth timber rounds are
secured together to form a structurally integral unit in which the first
cooperating surface is in
contact with the second cooperating surface, and the third cooperating surface
is in contact
with the fourth cooperating surface, and the fifth cooperating surface is in
contact with the
sixth cooperating surface, and the seventh cooperating surface is in contact
with the eight
cooperating surface, and the first, second third, fourth and fifth timber
rounds are
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substantially parallel to each other, and wherein the first, second, third,
fourth and fifth timber
rounds are secured to each other by a plurality of fasteners spaced along the
length of the
member, the plurality of fasteners comprising fasteners provided at both acute
and obtuse
angles from a longitudinal as of the structural member, the fasteners
extending through the
first, second, third, fourth and fifth timber rounds.
The present invention further provides a structural member comprising: a first
timber round
having a first cooperating surface extending longitudinally along the length
thereof, a second
timber round having a second and a third cooperating surfaces extending
longitudinally
along the length thereof, and a third timber round having fourth and fifth
cooperating
surfaces extending longitudinally along the length thereof, and a fourth
timber round having
sixth and seventh cooperating surfaces extending longitudinally along the
length thereof,
and a fifth timber round having eighth and ninth cooperating surfaces
extending
longitudinally along the length thereof, and a sixth timber round having a
tenth cooperating
surface extending longitudinally along the length thereof wherein, the first
cooperating
surface is shaped to cooperate with the second cooperating surface, and the
third
cooperating surface is shaped to cooperate with the fourth cooperating
surface, and the fifth
cooperating surface is shaped to cooperate with the sixth cooperating surface,
and the
seventh cooperating surface is shaped to cooperate with the eighth cooperating
surface, and
the ninth cooperating surface is shaped to cooperate with the tenth
cooperating surface, the
first, second, third, fourth, fifth and sixth timber rounds are secured
together to form a
structurally integral unit in which the first cooperating surface is in
contact with the second
cooperating surface, and the third cooperating surface is in contact with the
fourth
cooperating surface, and the fifth cooperating surface is in contact with the
sixth cooperating
surface, and the seventh cooperating surface is in contact with the eighth
cooperating
surface, and the ninth cooperating surface is in contact with the tenth
cooperating surface,
and the first, second third, fourth, fifth and sixth timber rounds are
substantially parallel to
each other, and wherein the first, second, third, fourth, fifth and sixth
timber rounds are
secured to each other by a plurality of fasteners spaced along the length of
the member, the
plurality of fasteners comprising fasteners provided at both acute and obtuse
angles from a
longitudinal axis of the structural member, the fasteners extending through
the first, second,
third, fourth, fifth and sixth timber rounds.
The present invention further provides a structural member comprising: a first
timber round
having a first cooperating surface extending longitudinally along the length
thereof, a second
timber round having a second and a third cooperating surfaces extending
longitudinally
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along the length thereof, and a third timber round having fourth and fifth
cooperating
surfaces extending longitudinally along the length thereof, and a fourth
timber round having
sixth and seventh cooperating surfaces extending longitudinally along the
length thereof,
and a fifth timber round having eighth and ninth cooperating surfaces
extending
longitudinally along the length thereof, and a sixth timber round having tenth
and eleventh
cooperating surfaces extending longitudinally along the length thereof, and a
seventh timber
round having a twelfth cooperating surface extending longitudinally along the
length thereof
wherein, the first cooperating surface is shaped to cooperate with the second
cooperating
surface, and the third cooperating surface is shaped to cooperate with the
fourth cooperating
surface, and the fifth cooperating surface is shaped to cooperate with the
sixth cooperating
surface, and the seventh cooperating surface is shaped to cooperate with the
eighth
cooperating surface, and the ninth cooperating surface is shaped to cooperate
with the tenth
cooperating surface, and the eleventh cooperating surface shaped to cooperate
with the
twelfth cooperating surface, the first, second, third, fourth, fifth, sixth
and seventh timber
rounds are secured together to form a structurally integral unit in which the
first cooperating
surface is in contact with the second cooperating surface, and the third
cooperating surface
is in contact with the fourth cooperating surface, and the fifth cooperating
surface is in
contact with the sixth cooperating surface, and the seventh cooperating
surface is in contact
with the eighth cooperating surface, and the ninth cooperating surface is in
contact with the
tenth cooperating surface, and the eleventh cooperating surface is in contact
with the twelfth
cooperating surface, and the first, second third, fourth, fifth, sixth and
seventh timber rounds
are substantially parallel to each other, and wherein the first, second,
third, fourth, fifth, sixth
and seventh timber rounds are secured to each other by a plurality of
fasteners spaced
along the length of the member, the plurality of fasteners comprising
fasteners provided at
both acute and obtuse angles from a longitudinal axis of the structural
member, the
fasteners extending through the first, second, third, fourth, fifth, sixth and
seventh timber
rounds.
In one embodiment, one or more of the timber rounds, or all of the timber
rounds, has/have a
diameter of less than about 125 mm, or about 100 mm, or about 75 mm, or about
70 mm, or
about 65 mm, or about 60 mm, or about 55 mm, or about 50 mm, or about 45 mm,
or about
mm. In another embodiment, one or more of the timber rounds, or all of the
timber
rounds, hasihave a diameter of less than about 60 mm. In another embodiment,
one or
more of the timber rounds, or all of the timber rounds, is/are a peeler core.
In one embodiment, the plurality of fasteners includes adjacent fasteners
provided at
35 alternating acute and obtuse angles to the longitudinal axis of the
structural member. In
another embodiment, the fasteners are applied at an acute angle of between
about 10 to
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about 70 to the longitudinal axis of the structural member, and at an obtuse
angle of
between about 1100 to 170 to the longitudinal axis of the structural member.
In another
embodiment, the fasteners are applied at an acute angle of between about 250
and about
45 to the longitudinal axis of the structural member, and at an obtuse angle
of between
about 1350 and about 1550 to the longitudinal axis of the structural member.
In one embodiment, the timber structural member comprises one or more holes
interposed
between adjacent acute and obtuse angled holes. In another embodiment, the
hole(s)
interposed between adjacent acute and obtuse angled holes are at an angle
which bisects
the angle made by the adjacent acute and obtuse holes. In another embodiment
the hole(s)
interposed between adjacent acute and obtuse angled holes are at an angle
substantially
orthogonal to a flat cooperating surface of the timber structural member.
In one embodiment, the acute and obtuse angled holes and/or the interposed
holes are
disposed along the plane running along the central longitudinal axis of the
timber structural
member.
In one embodiment, the first cooperating surface is a substantially flat
surface provided by
removing a minor segment along the length of the first timber round, the
second cooperating
surface is a substantially flat surface provided by removing a minor segment
along the length
of the second timber round, the third cooperating surface is a substantially
flat surface
provided by removing a minor segment along the length of the second timber
round, the
fourth cooperating surface is a substantially flat surface provided by
removing a minor
segment along the length of the third timber round, the fifth cooperating
surface (where
present) is a substantially flat surface provided by removing a minor segment
along the
length of the third timber round, the sixth cooperating surface (where
present) is a
substantially flat surface provided by removing a minor segment along the
length of the
fourth timber round, the seventh cooperating surface (where present) is a
substantially flat
surface provided by removing a minor segment along the length of the fourth
timber round,
the eighth cooperating surface (where present) is a substantially flat surface
provided by
removing a minor segment along the length of the fifth timber round, the ninth
cooperating
surface (where present) is a substantially flat surface provided by removing a
minor segment
along the length of the fifth timber round, the tenth cooperating surface
(where present) is a
substantially flat surface provided by removing a minor segment along the
length of the sixth
timber round, the eleventh cooperating surface (where present) is a
substantially flat surface
provided by removing a minor segment along the length of the sixth timber
round, and the
twelfth cooperating surface (where present) is a substantially flat surface
provided by
removing a minor segment along the length of the seventh timber round,
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In one embodiment, the first, second, third, fourth, fifth (where present),
sixth (where
present), seventh (where present), eighth (where present), ninth (where
present), tenth
(where present), eleventh (where present), or twelfth (where present)
substantially flat
cooperating surface is parallel to any other substantially flat cooperating
surface of the
timber structural member.
In one embodiment, the first, second, third, fourth. fifth (where present),
sixth (where
present), seventh (where present), eighth (where present), ninth (where
present), tenth
(where present), eleventh (where present), and twelfth (where present)
substantially flat
cooperating surfaces are parallel to each other.
In one embodiment, the structural member is provided with a plurality of holes
passing
through the first, second, third, fourth (where present), fifth (where
present), sixth (where
present), and seventh (where present) rounds, each hole being shaped to
receive one of the
plurality of fasteners. In another embodiment, the plurality of holes includes
holes formed at
an acute angle to the longitudinal axis of the structural member and holes
formed at an
obtuse angle to the longitudinal axis of the structural member. In another
embodiment, the
fasteners are secured in the holes by an adhesive. In one embodiment, the
holes are sized
to allow sufficient clearance between their edges and the fasteners to allow
each fastener to
be encapsulated by the adhesive within the relevant hole. In another
embodiment, the
encapsulation of the fasteners by the adhesive prevents the fasteners from
contacting the
sides of the holes in which they are located. In another embodiment, the ends
of the
fasteners are provided with caps, the caps preventing exposure of the ends of
the fasteners
to the environment.
In one embodiment, wherein the fasteners are reinforcement bars.
In one embodiment, an end of the first timber round is provided with a first
radial cut, and an
end of the second timber round is provided with a second radial cut, and an
end of the third
timber round is provided with a third radial cut, and an end of the fourth
timber round (where
present) is provided with a fourth radial cut, and an end of the fifth timber
round (where
present) is provided with a 'fifth radial cut, and an end of the sixth timber
round (where
present) is provided with a sixth radial cut, and an end of the seventh timber
round (where
present) is provided with a seventh radial cut, the ends of the first, second
third, fourth
(where present), fifth (where present), sixth (where present), and seventh
(where present)
timber rounds being adjacent one another in the timber structural member, and
the radial
cuts shaped and positioned to allow the timber structural member to engage
with a further
member, the further member having a rounded cross-section.
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In one embodiment, the axes of the first, second, third, fourth (where
present), fifth (where
present), sixth (where present) and seventh (where present) radial cuts are
aligned. In
another embodiment, the axes of the first, second, third, fourth (where
present), fifth (where
present), sixth (where present), and seventh (where present) radial cuts are
parallel. In
another embodiment, the axes of the first and/or second and/or third and/or
fourth (where
present), and or fifth (where present) and/or seventh (where present) radial
cuts are angled
to allow the timber structural member to form an angled connection with the
further timber
round.
In one embodiment, an end of the first timber round is provided with a first
axial bore sized to
receive a first connecting dowel, and an end of the second timber round is
provided with a
second axial bore sized to receive a second connecting dowel, and an end of
the third timber
round is provided with a third axial bore sized to receive a third connecting
dowel, and an
end of the fourth timber round (where present) is provided with a fourth axial
bore sized to
receive a fourth connecting dowel, and an end of the fifth timber round (where
present) is
provided with a fifth axial bore sized to receive a fifth connecting dowel,
and an end of the
sixth timber round (where present) is provided with a sixth axial bore sized
to receive a sixth
connecting dowel, and an end of the seventh timber round (where present) is
provided with a
seventh axial bore sized to receive a seventh connecting dowel the ends of the
first, second,
third, fourth (where present), fifth (where present), sixth (where present),
and seventh (where
present) timber rounds being adjacent one another in the timber structural
member.
In one embodiment, the first connecting dowel is centrally positioned within
the first bore to
be coaxial with the first timber round, and the second connecting dowel is
centrally
positioned within the second bore to be coaxial with the second timber round,
and the third
connecting dowel is centrally positioned within the third bore to be coaxial
with the third
.. timber round, and the fourth connecting dowel (where present) is centrally
positioned within
the fourth bore to be coaxial with the fourth timber round, and the fifth
connecting dowel
(where present) is centrally positioned within the fifth bore to be coaxial
with the fifth timber
round, and the sixth connecting dowel (where present) is centrally positioned
within the sixth
bore to be coaxial with the sixth timber round, and the seventh connecting
dowel (where
.. present) is centrally positioned within the seventh bore to be coaxial with
the seventh timber
round.
In one embodiment, the first, second, third, fourth (where present), fifth
(where present),
sixth (where present), and seventh (where present) connecting dowels are
centred
respectively in the first, second, third, fourth (where present), fifth (where
present), sixth
(where present), and seventh (where present) bores by centring rings,
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In one embodiment, the timber structural member has a length being a standard
length used
in building construction. In another embodiment, the timber structural member
has a length
of about 1200 mm, or about 2400 mm, or about 3600 mm.
In one embodiment, the connecting dowels are selected from a group comprising
a mild
steel rod and a high strength steel rod In another embodiment, the connecting
dowels are
secured in the respective bores by an adhesive.
In one embodiment, the bores are sized to allow sufficient clearance between
their edges
and the relevant connecting dowel to allow the connecting dowel to be
encapsulated by the
adhesive within the relevant bore.
In one embodiment, the first timber round is secured to the second timber
round, and the
second timber round is connected to the third timber round, and the third
timber round is
connected to the fourth timber round (where present), and the fourth timber
round is
connected to the fifth timber round (where present), and the fifth timber
round is connected
to the sixth timber round (where present), and the sixth timber round is
connected to the
seventh timber round (where present), by use of an adhesive applied to the
first and/or
second and/or third and/or fourth and/or fifth (where present) and/or sixth
(where present)
and/or seventh (where present) and/or eighth (where present) and/or ninth
(where present)
and/or tenth (where present) and/or eleventh (where present) and/or twelfth
(where present)
.. cooperating surfaces.
In a further aspect, the present invention provides an extended span timber
structural
member comprising two or more timber structural members as described herein,
the timber
structural members being connected to each other by the end faces. In one
embodiment,
the timber structural member has a length of greater than 3 about metres.
In a further aspect of the present invention there is provided a method for
fabricating a
timber structural member, the method comprising the steps of: providing a
first timber round
having a first cooperating surface extending longitudinally along the length
thereof, providing
a second timber round having a second and a third cooperating surfaces
extending
longitudinally along the length thereof, providing a third timber round having
a fourth
cooperating surface, and optionally a fifth cooperating surface extending
longitudinally along
the length thereof, optionally providing a fourth timber round having a sixth
cooperating
surface, and optionally a seventh cooperating surface extending longitudinally
along the
length thereof, optionally providing a fifth timber round having an eighth
cooperating surface,
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and optionally a ninth cooperating surface extending longitudinally along the
length thereof,
optionally providing a tenth timber round having a sixth cooperating surface,
and optionally a
eleventh cooperating surface extending longitudinally along the length
thereof, and
optionally providing a seventh timber round having a twelfth cooperating
surface, and
extending longitudinally along the length thereof, wherein, the first
cooperating surface is
shaped to cooperate with the second cooperating surface, and the third
cooperating surface
is shaped to cooperate with the fourth cooperating surface, securing the
first, second, third,
fourth (where present), fifth (where present), sixth (where present), and
seventh (where
present) timber rounds together to form a structurally integral unit in which
the first
cooperating surface is in contact with the second cooperating surface, and the
third
cooperating surface is in contact with the fourth cooperating surface, and the
fifth
cooperating surface (where present) is in contact with the sixth cooperating
surface (where
present), and the seventh cooperating surface (where present) is in contact
with the eight
cooperating surface (where present), and the ninth cooperating surface (where
present) is in
contact with the tenth cooperating surface (where present), and the eleventh
cooperating
surface (where present) is in contact with the twelfth cooperating surface
(where present),
and the first, second, third, fourth (where present), fifth (where present),
sixth (where
present), and seventh (where present) timber rounds are substantially parallel
to each other,
and wherein the step of securing comprises the step of applying a plurality of
fasteners
spaced along the length of the member at both acute and obtuse angles from a
longitudinal
axis of the structural member such that the fasteners extend through the
first, second, third,
fourth (where present), fifth (where present), sixth (where present), and
seventh (where
present) timber rounds.
In one embodiment, the method comprises the step of applying one or more
fasteners
interposed between adjacent acute and obtuse angled fasteners.
In one embodiment of the method, one or more of the timber rounds, or all of
the timber
rounds, has/have a diameter of less than about 125 mm, or about 100 mm, or
about 75 mm,
or about 70 mm, or about 65 mm, or about 60 mm, or about 55 mm, or about 50
mm, or
about 45 mm, or about 40 mm. In another embodiment, one or more of the timber
rounds,
or all of the timber rounds, has/have a diameter of less than about 60 mm, In
another
embodiment, one or more of the timber rounds, or all of the timber rounds,
is/are a peeler
core.
In one embodiment of the method, the plurality of fasteners comprise adjacent
fasteners
provided at alternating acute and obtuse angles to the longitudinal axis of
the structural
member.
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In one embodiment of the method, the fasteners are applied at an acute angle
of between
about 10 to about 70 to the longitudinal axis of the structural member, and
at an obtuse
angle of between about 1100 to 170 to the longitudinal axis of the structural
member. In
another embodiment the fasteners are applied at an acute angle of between
about 25 and
about 450 to the longitudinal axis of the structural member, and at an obtuse
of about 135 to
about 1550 to the longitudinal axis of the structural member.
In a further aspect, the present invention provides a timber structural member
produced by
the method as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a perspective view of a structural member in accordance with an
embodiment
of the present invention.
Fig. 2 shows a diagrammatic view (not to scale) of a structural member in
accordance with
an embodiment of the present invention. The member is composed of three sub-
members
which are joined by alternating obtuse and acute fasteners.
Fig.3 shows a diagrammatic view (not to scale) of a structural member in
accordance with an
embodiment of the present invention. The member is composed of three sub-
members
which are joined by alternating obtuse and acute fasteners, and also
interposed fasteners.
Fig. 4 shows a diagrammatic end-on view of a structural member in accordance
with an
embodiment of the present invention. The member is composed of four sub-
members, the
sub-members derived from peeler cores.
DETAILED DESCRIPTION OF THE INVENTION
After considering this description it will be apparent to one skilled in the
art how the invention
is implemented in various alternative embodiments and alternative
applications. However,
although various embodiments of the present invention will be described
herein, it is
understood that these embodiments are presented by way of example only, and
not
limitation. As such, this description of various alternative embodiments
should not be
construed to limit the scope or breadth of the present invention. Furthermore,
statements of
advantages or other aspects apply to specific exemplary embodiments, and not
necessarily
to all embodiments covered by the claims.
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Throughout the description and the claims of this specification the word
"comprise' and
variations of the word, such as "comprising" and "comprises' is not intended
to exclude other
additives, components, integers or steps.
Reference throughout this specification to "one embodiment" or "an embodiment"
means that
a particular feature, structure or characteristic described in connection with
the embodiment
is included in at least one embodiment of the present invention. Thus,
appearances of the
phrases "in one embodiment" or in an embodiment" in venous places throughout
this
specification are not necessarily all referring to the same embodiment, but
may.
In a first aspect, the present invention provides a structural member
comprising:
a first timber round having a first cooperating surface extending
longitudinally along the
length thereof,
a second timber round having a second and a third cooperating surfaces
extending
longitudinally along the length thereof, and
a third timber round having a fourth cooperating surface extending
longitudinally along the
length thereof wherein,
the first cooperating surface is shaped to cooperate with the second
cooperating surface,
and the third cooperating surface is shaped to cooperate with the fourth
cooperating surface,
the first, second and third timber rounds are secured together to form a
structurally integral
unit in which the first cooperating surface is in contact with the second
cooperating surface,
and the third cooperating surface is in contact with the fourth cooperating
surface, and the
first, second and third timber rounds are substantially parallel to each
other, and wherein the
first, second and third timber rounds are secured to each other by a plurality
of fasteners
spaced along the length of the member, the plurality of fasteners comprising
fasteners
provided at both acute and obtuse angles from a longitudinal axis of the
structural member,
the fasteners extending through the first, second and third timber rounds.
Applicant proposes that beams having significant load bearing capacity may be
formed by
the use of three of more timber rounds fastened together, each timber round
being of
relatively small diameter. The use of small diameter rounds for producing a
load bearing
member is a significant departure from the prior art. At the filing date of
this application.
timber rounds of small diameter were thought to be of no use (or at least
limited use) in
building construction given the lack of load bearing capability of members
having a limited
cross sectional area. In some embodiments, 4, 5, 6, or 7 timber rounds are
used.
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The present Applicant has discovered that beams having three or more timber
rounds, with
the rounds fastened together in a specified manner, provide a beam having an
unexpected
load bearing capacity which is greater than the additive capacity of the
individual rounds.
Another advantage of some embodiments includes a lower weight per unit length
of
member. The avoidance of members having a large cross-sectional area may, in
some
embodiments, provide for a lighter product. This assists in lowering freight
costs and easing
handling.
Weight advantages are also gained by the ease of drying smaller rounds, as
discussed
further infra,
A further advantage of some embodiments is a lower cost per unit length. As
discussed in
the Background section, many parts of a tree are wasted in the felling and
milling processes.
The present members may be formed from such waste, and indeed in some
instances from
branches that are ordinarily left on the forest floor to decompose.
Another advantage for some embodiments is that the relatively small rounds dry
faster
and/or to a greater extent and/or completely, Smaller rounds have a greater
surface area to
volume ratio, and so moisture is more quickly and/or more completely extracted
from the
wood. Kiln drying can be an important step in the lumber production process,
ensuring that
gross dimensional changes through shrinkage are confined to the drying
process. Ideally,
wood is dried to that equilibrium moisture content as will later (in service)
be attained by the
wood. Thus, further dimensional change will be kept to a minimum.
Dried timber is lighter, and stronger than green timber in most strength
properties, and may
be easier to impregnate. Dry wood also generally works, machines, finishes and
glues
better than green timber. Paints and finishes also last longer
Larger rounds may never be sufficiently dried before use, or may take an
impractical or
uneconomical period of time to dry.
A further advantage of using 4, 5, 6, or 7 small diameter (40 mm to 60 mm)
rounds to form
composite structural members is that such small rounds may be used in
manufacture even
with relatively high moisture content. Without wishing to be limited by
theory, it is proposed
that the shrinking stresses in smaller rounds is far less than large rounds,
and so composite
members formed from smaller rounds may be dried after manufacture. This
provides a time
advantage in manufacture, given that is possible to manufacture the members
without pre-
drying the rounds. Alternatively, the manufacturer is not forced to keep a
stock of pre-dried
rounds,
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Yet a further advantage of the use of multiple rounds (including 4, 5, 6, or 7
rounds) is that
any imperfection in a region of a round (that may cause a structural weakness)
is at least
partially compensated for by the wood in rounds directly above and/or below
the
imperfection. While each round in a composite member may have an area of
weakness, the
likelihood of two rounds having a weakness at the same point is very unlikely.
The timber rounds used in the context of the present invention have diameters
of less than
those disclosed in Applicant's prior international patent application
PCT/AU2009/001453, In
an embodiment of the structural beam one, two or three round(s) has/have a
diameter of
less than about 125 mm. In another embodiment one, two or three round(s)
has/have a
diameter of less than or less than about 100 mm In yet a further embodiment
one, two or
three round(s) has/have a diameter of less than or about 75 mm.
It has been surprisingly found that even smaller diameter rounds (of between
about 40 mm
to about 50 mm, such as peeler cores) may be used to fabricate useful timber
structural
members. Where rounds of such small diameter are used, it is typical that 4.
5, 6, or 7
rounds are required to achieve a composite member of useful strength. The
resultant
composite structural members may be used as very low cost joists. Such
structural
members may have widths as low as 40mm.
Applicant has further found that such joists can be further strengthened
(where necessary)
by placing a two or more members side-by-side (such that each similar element
abuts
lengthWse) and cross laminating with dowel and adhesive and/or gusset plates
and the like
to provide a stronger multi-joist with two or more members.
Typically, the diameters of the rounds are substantially equal.
The timbers used for the first and/or second and/or third timber rounds may be
so-called
"true round sections", 'true rounds". Timber rounds are described in Section 6
of Australian
Standard 1720, and are typically produced from softwood trees grown
commercially as
renewable forest plantation timber. These timbers are typically fast growing,
easily
harvested, and have a low natural defect rate.
Various species of timber are suitable to form the true rounds, particularly
those types of
species that tend to have a relatively constant diameter for a considerable
portion of their
length to minimise waste during the trimming and circularising processes.
Plantation pine
materials, such as slashpine or Carribaea hybrids, tend to form suitable true
rounds. Other
materials that might be considered include Douglas fir, and various eucalypt
species,
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True rounds are particularly strong since the natural strength of the timber
fibres is not
disrupted by sawing or other treatment. The integnty of the round is
maintained, and the
trimming process required to circularise the round does not greatly affect the
overall strength
of the round. The natural characteristics of timber are that the central core
or pith of the
round is relatively soft and has low structural strength. The periphery of the
timber, on the
other hand, is much harder and the timber fibres are able to carry a high
tensile load, Also,
this hard outer layer is more resistant to water absorption and attack by
insects, and thus by
keeping the outer circumference of the timber largely intact in the process of
preparing a true
round, the structural integrity of the timber is maintained
The rounds in some forms of the invention do not strictly conform to
Australian Standard
1720, and may be of a smaller diameter such that the Standard is not satisted.
However, by
the fastening of at least three rounds together a required load bearing
capacity may be
nevertheless attained.
In some embodiments, the rounds are "peeler cores". As is understood by the
skilled
person, a peeler core is a round pressure treated post. A peeler core has been
turned in a
milling machine to the point that substantially all the soft wood has been
removed (for
plywood manufacturing), leaving the hardwood core which is typically dense and
inflexible.
The milling process peels off the bark, cambium layer, sapwood, and even some
of the
heartwood to make veneer panels. This leaves no sapwood on the post.
The hardwood core of a peeler core does not absorb the pressure treatment and
preservatives as well as the softwood resulting in an inferior post that will
typically not last as
long as a post with treated softwood on the exterior.
Applicant has discovered an economically and technically viable use for peeler
cores in that
the cores may be used in a composite timber product such as that disclosed
herein. The
use of multiple peeler cores (and even those with a diameter down to about 70,
60, 50 or 40
mm) can produce a member which is useful in construction and yet is highly
cost-effective.
As discussed in the Background section, peeler cores are essentially a waste
product of
forestry, having little value in the market. In one embodiment, the present
invention is
directed to timber structural members that are comprised of peeler cores only.
Given the low diameters of peeler cores, it will be appreciated that a greater
number of
rounds may be required to achieve any desired structural property. For
example, while a
structural member composed only of larger diameter rounds may only require 2
or 3 rounds,
the use of peeler cores may require 4, 5, 6,7 or 8 rounds to achieve a useful
result.
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Accordingly, in a further aspect the present invention provides a structural
member
comprising: a first timber round having a first cooperating surface extending
longitudinally
along the length thereof, a second timber round having a second and a third
cooperating
surfaces extending longitudinally along the length thereof, and a third timber
round having
fourth and fifth cooperating surfaces, and fourth timber round having a sixth
cooperating
surface extending longitudinally along the length thereof wherein, the first
cooperating
surface is shaped to cooperate with the second cooperating surface, and the
third
cooperating surface is shaped to cooperate with the fourth cooperating
surface, the first,
second and third timber rounds are secured together to form a structurally
integral unit in
which the first cooperating surface is in contact with the second cooperating
surface, and the
third cooperating surface is in contact with the fourth cooperating surface,
and the first,
second and third timber rounds are substantially parallel to each other, and
wherein the first,
second and third timber rounds are secured to each other by a plurality of
fasteners spaced
along the length of the member, the plurality of fasteners comprising
fasteners provided at
both acute and obtuse angles from a longitudinal axis of the structural
member, the
fasteners extending through the first, second and third timber rounds.
In one embodiment, the first, second, third and fourth timber rounds are all
peeler cores, and
optionally peeler cores having a diameter of between about 40 mm and about 60
mm
Without wishing to be limited by theory in any way, it is proposed that the
use a higher
number of rounds results in a structural member of a strength greater than
simply the
additive values of each individual round. Such members may be stiffer and less
liable to
deform or deflect than would be otherwise expected. It is thought the each
added round
provides a further shear face, with each added shear face provided an
incremental
advantage.
In one embodiment, the plurality of fasteners includes adjacent fasteners. The
use of
smaller diameter rounds requires special consideration of the acute and obtuse
angles at
which the fasteners are provided in order to, in some circumstances, provide a
required load
bearing capacity. Advantage is found where the acute angle is equal to or
greater than
about 20 , 25 , 30 , 350, 40 , 450, 50 , 55 , 600, or 65 . The acute angle may
be less than
about 700, 65 , 600, 550, 500, 450, 40 , 350, 30 , or 250. In one embodiment
the acute angle
is about 450. The skilled person understands that the angles specified herein
are not
required to be precisely those cited numerically. Indeed, there is typically
no requirement for
great accuracy in the art with variations of 5% in these angles generally
being tolerated.
However, where required by engineering specifications to provide for a
predetermined load
bearing capacity, a lower tolerance may be provided for.
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Typically the obtuse angle is calculated by the addition of 90 to the acute
angle. In some
embodiments, the obtuse angle is equal to or greater than about 110 , 115 ,
120 , 125 ,
130 , 135 , 140 , 145 , 150 , or 155 . The obtuse angle may be less than about
160 , 155 ,
150 , 145 , 140', 135', 130 , 125 , 120 , or 115'. In one embodiment, the
obtuse angle is
about 135 .
In some embodiments (and including embodiments where the rounds are peeler
cores, and
where 4, 5, 6, 7, or 8 peeler cores are used in a structural member) acute
fastener angles of
between 25 degrees and 35 degrees, and particularly about 30 degrees are used.
An
optimum angle of 30 degrees (irrespective of member height, width or pin size
etc) is
proposed. Maximum advantage may be found in embodiments where the maximum
adhesive coverage of the longest fastener possible for that member (at maximum
length,
that being the hypotenuse length) which all occurs at about 30 degrees.
The cooperating surfaces of the timber rounds may be of any configuration
deemed suitable
by the skilled artisan, however the surfaces are typically substantially flat.
Given the use of
three rounds in the present structural members, the second (central) round may
have two
cooperating surfaces: a first cooperating surface configured to abut the first
round and a
second cooperating surface to abut the third round.
The rounds may be machined or otherwise treated to remove a minor segment
along the
length of the round in order to provide a flattened cooperating surface. The
proportion of the
flattened cooperating surface to the diameter of the round is selected to
provide the
structural member being manufactured with a suitably sized cross section. A
suitable minor
segment size for removal may be a segment with a depth of approximately 0.2
times the
diameter of the round - i.e. for a 75 mm round a minor segment with a depth of
approximately 15mm is removed. The proportions may be altered depending on the
particular structural application that may be required.
Applicant has found that reducing cooperating surface area width leads to an
increase in the
crushing effect referred to supra if below a critical surface area.
Furthermore, the advantage
of the shear face effect discussed supra diminishes.
In light of the above, it will be appreciated that advantage may be gained
where the number
of rounds is increased to sacrifice bearing surface.
In some embodiments, the structural member has a lower width for the shear
faces for the
internal rounds (for example, rounds 2, 3, 4, and 5, of a 6 round member),
this allowing a
greater height. As one example, for a 50mm diameter member, a shear zone 20 mm
width
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provides a height of 44 mm. In another example, a shear zone of 40 mm provides
a height
of 3Ornm.
For some applications, account may be taken of the height to width ratio of
the composite
structural member. It is preferred for some applications that the height to
width ratio does
not exceed about 5:1. By way of example, a 40 mm wide member made from 40rnm
diameter rounds should not exceed 200 mm in height.
Prior to joining the machined rounds to create the structural member, the
rounds may be
treated with a preservative to provide service life protection. Varying
degrees of protection
can be imparted dependent upon the intended application of the structural
member. A
suitable preservative may be provided by employing the process known as
Ammortiacal
Copper Quaternary (ACQ) which is Chromium and Arsenic free.
Once provided with cooperating bearing surfaces (as described above) the
rounds are
secured together. The rounds are firstly brought together using a jig, and the
structural
member is laminated along the cooperating interfaces.
The first second and third rounds may abut in any configuration deemed
suitable by the
skilled artisan, including in a stacked configuration i.e. the first directly
over the second, and
the second directly over the third). In that configuration, the first and
third rounds have a
single cooperating surface each, and the second round has two cooperating
surfaces, as
described supra.
Alternatively, the rounds may be configured such that each round abuts two
other rounds,
such that each round has two cooperating surfaces.
Where the cooperating surfaces are substantially fiat, at least two or three
of the surfaces
are substantially parallel. Typically all substantially flat cooperating
surfaces are parallel.
The present timber beams comprises fasteners, which may be inserted into holes
drilled
through the structural member, for example by drilling through the three
rounds. Fasteners
are then inserted into the holes and are fixed in place, optionally using an
adhesive bonding
material.
The skilled person will be capable of selecting an appropriate fastener type,
and may choose
from pins, dowels, rods, or bolts. In one embodiment, the fasteners are
deformed
reinforcement bars of the type typically used in the concrete construction
industry.
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The fasteners may be inserted by any method deemed appropriate by the skilled
artisan,
and may be manually rotated into the final position, or in rotated with the
assistance of an
electric drill or similar device.
Alternative fasteners include, for example, hot dipped galvanised deformed or
Y-bar dowels,
or any other dowel/rod/fastener with suitable strength properties for the
requirements of the
structural member and environmental conditions to which the structural member
will be
exposed. For example, and depending upon the proposed application of the
structural
member, fasteners of varying corrosion protection can be deployed.
The positions and angles of the holes may be selected to ensure that once
fasteners have
been secured in place sufficient bonding occurs to ensure true composite
action of the
structural member.
The diameters of the holes and the dimensions of the fasteners may be selected
in
accordance with the intended application of the structural member. The holes
may be sized
to allow the fasteners to fit with sufficient clearance as dictated by the
performance
properties of the adhesive bonding material being used. The diameter of the
holes may be
from about 03 mm to about 4 mm larger than the greatest diameter of the
fastener to be
Inserted therein.
The skilled person understands that measurements used in the nomenclature of
deformed
bars may not properly reflect the true dimensions of the bar, and that
independent
measurements should be made before deciding a diameter for the receiving hole.
For
example, what is commonly termed a "16 mm" bar is typically 17.5 mm at the
widest
diameter, and so where a 1 mm gap is required between the fastener and the
hole wall, a
hole of 19.5 mill diameter is used.
In one embodiment the holes and fasteners are of a relatively small diameter.
Fasteners
equal to or less than about 12 mm or about 10 mm in diameter may be used. For
example,
an N10 deformed bar (Mesh and Bar Pty Ltd, Australia) may be used. Relatively
small
diameter holes require lesser amounts of glue (where used), thereby increasing
the cost-
effectiveness of the present beams.
When securing the fasteners in the holes a preformed annular centring ring may
be used to
ensure the fastener may be centrally located in the hole. The centring ring
(described below)
allows the adhesive to flow through the ring into the hole to ensure full
encapsulation of the
fastener by the adhesive. The adhesive is injected around the fastener from
one end of the
hole, the other end of the hole allowing air to escape during the injection
process_ This
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ensures uniform distribution of the adhesive around the dowel within the hole.
The adhesive
may be injected using, for example, a trigger cartridge gun or pneumatic
cartridge gun. A
washer (described below) may also be disposed inside the hole across the
interface
between two rounds to prevent glue from escaping at the interface.
Once the members have been located in a jig the fasteners are inserted into
holes and glue
injection takes place. The rounds and are held in place whilst the adhesive
achieves initial
curing. This typically occurs within 4 hours but is dependent upon a number of
variables
including temperature, moisture content of the timber and glue formulation. If
a cambered
structural member is required this can be achieved by applying the camber to
the rounds
and in the forming jig. Applying an initial set to the rounds while the
adhesive cures will
ensure that the pre-camber is maintained in the structural member.
The adhesive bonding material may, for example, comprise a two component epoxy
material
or in some applications a single phase epoxy may be used. Ideally the epoxy
completely
encases the fastener, thereby providing a barrier to corrosion of the fastener
along its entire
length. Specifically, a suitable adhesive is a structural epoxy resin such as
waterproof
thixotropic solvent free epoxy resin. The adhesive bonding material provides
the additional
benefit of providing corrosion protection to the embedded fasteners.
The fasteners may laced through the structural member to provide for a
structural member
which exhibits restraint to longitudinal cracking which is typical of high
load failure. The
precise number, type and angle of insertion of the fasteners will depend on
the intended
application of the structural member.
The fasteners may be inserted in a repeating V-pattern to provide a trussing
effect (see Fig.
2, for example), being the ability of the fasteners (in their diagonal
configuration) to transfer
imposed loads from the bearing surfaces to the outer connection nodes thus
reducing the
amount of stress borne by the wood fibres alone.
In some embodiments, the timber structural member comprises more than one
series of
fasteners. For example, where a first series of fasteners are aligned along
the central axis of
the member, a second series may be provided to the right, and a third series
provided to the
left (when considered in plan view). The second and third series of fasteners
may be
inserted in a repeating V-pattern (and at angles described elsewhere herein
for the central
series of fasteners). In one embodiment, the arrangement of fasteners in the
second and
third series are similar, or substantially identical, with respect to spacing
between fasteners,
and/or the angle at which they are inserted, and/or their absolute positions
within the timber
structural member. These parameters for the second and third series of
fasteners may be
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different to those for the first, central series of fasteners. In some
embodiments, at least two
of the series of three are staggered with respect to each other.
The first, second and third series of fasteners are typically disposed along
parallel lines. The
offset between the first series and the second series, and the first series
and third series of
fasteners is typically substantially equal. The offset size may be affected by
the size of the
holes (larger holes generally dictating a larger offset), and also the width
of the timber
structural member (wider members allowing for greater spacing between the
series of
fasteners). The offset may be greater than about 12 mm, 15 mm, 18 mm, 21 mm,
24 mm,
27 mm 01 30 mm.
The use of multiple series of fasteners disposed longitudinally along the
timber structural
member is typically provided for with timber structural members of width of
greater than
about 40 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm or 200 mm. Broader
members may be suited to applications where it is necessary to spread load
across a larger
bearing surface, for example where the timber structural member is used as a
bearing face
for flooring (such as plywood). In such situations, a bearing surface of the
beam may be
substantially flat to allow close cooperation with a floor board or other
subfloor structure.
Fasteners provided at 900 (i.e. perpendicular to the longitudinal axis of the
structural
member) would not provide any trussing effect and would result in very short
glue bond
lengths per fastener (approximately 2 diameters per pin).
The distance between the ends of adjacent fasteners on the same edge of the
structural
member may be about 1/3 of the cross section of the structural member.
Depending on the intended application of the structural member, either one or
both ends of
the rounds of the structural member may be provided with axial bores and/or
radial cuts to
facilitate connection of the structural member to another member or structure.
The axial bores allow for dowel type end grain connections to be made at each
end of the
structural member. The axial bores are machined into the end (or ends) of the
rounds to a
predetermined depth. Each bore is dimensioned to receive a steel dowel (or
similar) as
shown.
As per insertion of the fasteners as described above, the axial bore will
generally be of
slightly larger diameter than the dowel to allow an adhesive bonding material
to be injected
and fully surround the dowel, thereby ensuring a high strength bonded
connection between
the dowel and the rounds. The adhesive may be injected using, for example, a
trigger
cartridge gun or pneumatic cartridge gun.
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To ensure that the dowel is centred within the bore, an annular preformed
centring ring may
be used. The centring ring (typically an "0" ring) may include a central
aperture having a
diameter substantially the same (or slightly larger) than the dowel to be
used. The
circumference of the centring ring is provided with a number of lugs which are
sized/positioned to engage with the edges of the bore. In use, the centring
rings are placed
and affixed along the dowel with at least one centring ring for each member
that the dowel
will need to pass through.
The dowel is then inserted into the bore through the central aperture of the
centring ring. The
centring ring ensures the dowel is centrally located within the bore and
allows adhesive to be
.. injected into the bore between the edges of the bore and the lugs. The
centring ring may be
made from plastic, metal, ore composee of materials.
A washer may be used across the interface(s) between the structural member 100
and any
other members it is attached to, thereby limiting leakage of glue into the
joints between
members. The washer may comprise an annulus that has a central aperture, the
inner
diameter of the annulus being substantially the same as the dowel, and the
outer diameter of
the annulus being substantially the same as a rebate that is bored axially
aligned with the
bore. The length of the washer can be between 2 and 10 mm, and the length of
the rebate
therefore needs to be at least sufficient to accommodate the washer, with the
washer
crossing from one member, across the interface between them, into another
member. The
inner surface of the annulus has a number of lugs which are sized and
positioned to hold
and centre the inserted dowel in the bore (or hole).
When connecting the structural member to another member or round (or when
connecting
the three rounds of the structural member together), the process generally
entails drilling the
required holes in the relevant members or rounds, inserting the dowel/fastener
(either with or
without using a centring ring), inserting the washers across the joints, and
then injecting the
glue from an exposed end of a hole through the members or rounds.
Alternatively, a dowel/fastener-washer combination can be inserted
simultaneously. If
required, the glue may be injected with the use of a bleeder hole. Once the
glue has been
injected, the dowel/fastener will be encapsulated by glue. The ends of the
doweisifasteners
can be protected from coming into contact with the timber by using an end cap
or dipping the
ends of the dowel in a compound such as liquid rubber so as to create a cap
with a diameter
substantially that of the bore or slightly less.
With regard to the fasteners, the end cap may also serve to centre the
fastener in the bore,
in which case the centring devices as discussed above may not be required. The
end caps
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also prevent the ends of the fasteners from being exposed to the environment
and serve to
smooth out/cushion the ends of the fasteners, thereby dealing with a potential
breaking
point.
In some embodiments, the fasteners may be disposed to ensure that no portion
of a fastener
extends outside the member. Many building standards have provisions for fire
proofing
timber components, including a requirement that metal fasteners (as good
thermal
conductors) are appropriately insulated from the environment. Thus, the
fasteners may be
disposed such that at least a certain minimum depth of wood (for example at
least 20 mm)
exists between the end of a fastener and the nearest edge of the member.
Alternatively,
plugs or end caps may achieve the same level of insulation.
In addition to allowing the securing the dowels, the axial bores may also
remove the central
(and usually weakest) part of the rounds. This, in turn, provides enhanced
strength/structural
integrity to the structural member as a whole.
Once the dowels are secured in the structural member their free ends can be
used to
connect the structural member to an additional member/structure. Load forces
experienced
by such a combined structure are then transmitted axially through the rounds
of the
structural member. This serves to add to the strength of the combined
structure.
Further, by housing the connecting dowels within the rounds the dowels are
largely
protected and insulated from 'fire. Other known joining systems make use of
connectors (e.g.
dowels, pins, nails, bolts, plates etc) which are externally fitted. In the
event of a fire, such
externally fitted connectors have been found to transfer heat into the timber
of the joist
resulting in an undesirable increase in the destabilisation of joints. It is
theorised this
increase in destabilisation is caused by the connector becoming so hot that
the timber in the
hole is charred and shrinks away, thereby creating dynamic stresses in now
moving
members.
By providing internal dowel connectors this problem is avoided, and the fire
rating of the
structural member is dependent on the rounds. It is further noted that the
rounds and used in
the present invention are, in their own right, less combustible than sawn
timber.
In use, it is envisaged that the free ends of the dowels will be inserted into
a bore in the
member/structure which is being secured to the structural member. A similar
bonding
arrangement to that described above is used to ensure that both ends of the
dowel are
properly anchored in their respective bores.
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By providing for connection to/with the structural member by a pair of axial
dowels twisting of
the structural member as load is applied is prevented. If required, both ends
of the structural
member can be secured in this fashion, in which case four high strength axial
dowel
connections are used to secure the member in position.
Where the structural member is to be connected to a circular pole or the like
(such as a
further true round), the ends of the rounds may further be provided with
radial cuts. Although
the term ''radial" is used it will be appreciated that the cut need not be
precisely circular and
could have a more general scalloped or concave shape. The radius of curvature,
or the
shape, of the cut is selected to mirror the diameter of a circular pole or
generally concave
shape of another member to which the structural member may be connected. This
provides
for a neat and structurally sound connection with the circular pole or other
member.
The radial cuts may be machined into the rounds using, for example, a
customised large
bore hole saw machine. Further, the angle of the axes of the radial cuts may
be selected to
allow for connection with another member at any orientation.
In a further aspect the present invention provides methods for producing the
timber structural
members described herein
The timber structural members described may be used in any application for
which they are
deemed suitable by the skilled artisan. One particular application is as a
composite joist
formed from the structural member of this invention exhibit numerous benefits
over
traditional single member sections. For example, the structural member may
provide the
appropriate depth to width ratio required for use as a beam: the ratio is
approximately 2 to 1,
making it well suited as a bending member. The members are economically
manufactured
by taking advantage of low cost raw materials, waste material from felling and
milling and
also less expensive softwood species.
In some embodiment, the timber structural member may have a construction such
that for
maximum load bearing capacity the member must be disposed with one face
directed
toward a load vector, while the opposite face points away from the load
vector. As an
example, where the fasteners are arranged in a V-pattern, the timber
structural member
should be installed such that the "V" is upright. The centre of a beam is its
weakest point,
and where a V is disposed toward the centre of a beam the asymmetry becomes
particularly evident. At this point, strength is not compromised where the 'V
is orientated
upright, however if the beam is turned through 180 degrees (such that the "V"
is inverted)
there is a significant distance between the exit points of fasteners pins at
the lower face of
the beam (where the strain/deflection/tension is greatest) leading to a
vulnerability in the
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beam. Accordingly, some embodiments of the invention comprise indicia
indicating the
preferred or required orientation of the timber structural member.
The applications for the structural member of the present invention are the
same as that of
any other beam or beam/column material, including typical domestic
construction. The
structural member is dimensionally suited to higher load applications and can
effectively
replace larger sawn sections in domestic construction and laminated veneer
sections in
commercial constructions.
The applications for the structural member include, by way of non-limiting
example only, floor
members such as bearers or joists, wall framing members such as lintels and
heavy duty
studs, roof framing members such as rafters or hanging/strutting beams, portal
frame
members such as columns, rafters or bottom chords, and beam/column members
including
piers and acoustic barrier posts.
Some embodiments of the present invention are well suited to shorter span
applications,
such as spans of around 3 metres or less. However, where longer spans are
required, there
exists the option of joining multiple members (in a lengthwise manner) to
provide the
required length The multiple members may be joined in any manner deemed
suitable by
the skilled artisan, and may be mitred, dovetailed, finger-jointed, butt-ended
or dowel pinned.
A preferred form of dowel pinning is described in PCT/AL12009/001453.
The present structural members may also be useful as studs, which are
generally of shorter
length than a joist and of decreased thickness. Studs (and indeed structural
members for
any other applications) may be formed by rounds of mixed sizes, for example
70/60/70 mm
or 80f70/80 mm.
As briefly discussed supra, the present structural members may be useful as
joists. Such
joists may be formed into modules of 2.4m by 2.4m to create a very strong
modular flooring
system where the outside or perimeter joists of a module co-operate with the
adjacent and
abutting edge of a joist in a similar module by cross pinning and laminating
and through
pinning and laminating. In this case, modules of 2.4m by 2.4m can abut all the
way around to
another module in an additive manner except for the outside of the shape which
can also
benefit by laminating a further joist to it. Effectively, this new cross
pinned and laminated
double member joist is capable of acting as a bearer when supported at every
2.4m and by
adding an extra joist this system is reduced by that 2.4m length of more
expensive (but
stronger) bearer. A further advantage is that modules can be prefabricated and
delivered to
site with considerable cost and time savings
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Optimum beam depth to span ratios generally stay true for increasing element
numbers in a
beam and when that beam is used as a joist it can still produce the lowest
beam mass per
meter per unit of load carried. Such Joists may comprise 5 x 50 mm rounds to
provide a joist
of 215 mm H, or 6 x 50mm rounds to provide a joist or 210mm H, or even a 7 x
40 mm
rounds to provide a joist of 180mm H.
The skilled person understands that by performing a similar analysis on a
range of
conformations it will be possible to effectively optimise joists based upon
resource availability
and beam function
In some embodiments, the multiple members are not physically joined, and
simply abut each
other in situ.
Embodiments comprising multiple members provide further economic and/or
environmental
advantages given that wood that may have ordinarily been discarded due to
insufficient
diameter and insufficient length may be utilised to produce a high value beam.
The various elements can also be joined to form a range of connections such as
truss nodes
(knee and ridge connections).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Referring to Fig. 1 there is shown (in perspective view) a timber structural
member 100
formed from three rounds 102, 104 and 106. The rounds 102, 104 and 106 are
stacked,
with round 102 having a first cooperating surface (not shown) , round 104
having a second
cooperating surface (not shown) and a third cooperating surface (not shown),
round 106
having a fourth cooperating surface (not shown). The interface between the
cooperating
surfaces of the rounds 102 and 104 is shown at 152. The interface between the
cooperating
surfaces of the rounds 104 and 106 is shown at 154.
The rounds 102, 104 and 106 are drilled with alternating holes at an acute
angle 108, and
holes at an obtuse angle 110.
Inserted into each of the acute 108 and obtuse holes 110 are fasteners 112
which are
dowels.
The rounds 102, 104 and 106 of the structural member 100 are provided with
axial bores
160 and radial cuts 162 to facilitate connection of the structural member 100
to another
member or structure.
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The axial bores 160 allow for dowel type end grain connections to be made at
each end of
the structural member 100. The axial bores 160 are machined into the ends of
the rounds
102, 104 and 106 to a predetermined depth. Each bore 160 is dimensioned to
receive a
steel dowel 166 as shown, which in this embodiment is a deformed reinforcement
bar,
similar to the dowel 112 used for cross-doweling between the rounds 102, 104
and 106.
Referring to Fig. 2 there is shown in diagrammatic form (lateral view with
features numbered
in general accordance with Fig. 1), a timber structural member 100 formed from
three rounds
102, 104 and 106. Panel A shows an end view, while Panel B is a lateral view.
The rounds
102, 104 and 106 are stacked, with round 102 having a first cooperating
surface 102A,
round 104 having a second cooperating surface 104A and a third cooperating
surface 104B,
round 106 having a fourth cooperating surface 106A. All cooperating surfaces
102A, 104A,
104B, and 106A are flat and formed by the removal of a longitudinal portion of
each round,
this being more clearly shown in the end view of Panel A.
The rounds 102, 104 and 106 are drilled with alternating holes at an acute
angle 108, and
holes at an obtuse angle 110. The acute angle in this embodiment is 450, and
the obtuse
angle is 1350, as measured by reference to the longitudinal ads of the member
100. It will
be noted that the acute 108 and obtuse 110 drilled holes form a mirror image,
sucti that the
obtuse holes 110 can be seen to form an angle of 450 132 with the lower
surface of round
106, as does the acute drilled holes 110. The holes are disposed along the
vertical plane
running along the central longitudinal axis of the structural member.
Inserted into each of the acute 108 and obtuse holes 110 are fasteners 112
which are
dowels.
The diagram of Fig. 2 is not drawn to scale, with the embodiment shown having
the following
exemplary measurements:
114 40 mm
116 208 mm
118 69 mm
120 225 mm
122 565 mm
124 150 mm
126 432 mm
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128 150 mm
130 2400 mm
The diagram of Fig, 3 is not drawn to scale, with the components being
generally as
indicated in Fig. 2. Different to Fig. 2, the embodiment of Fig, 3 includes
interposed holes
200 disposed as shown. The holes 200 are aligned with the acutely and obtusely
angled
holes, being disposed along the vertical plane running along the central
longitudinal axis of
the structural member, and are angled orthogonally with respect to the flat
cooperating
surfaces. The interposed holes 200 have fasteners inserted therein (not
shown). The
embodiment of Fig. 3 has the following exemplary measurements:
210 1200 mm
212 200 mm
214 1050 mm
216 1350 mm
218 2250 mm
220 2520 mm
222 3450 mm
224 200 mm
226 168 mm
228 35 degrees
230 3600 mm
232 40 mm
234 69 mm
236 80 mm
238 208 mm
The use of interposed holes (with fasteners) provides a substantial advantage
by reinforcing
against deflection at points along the structural beam.
The interposed holes and fasteners may be disposed at regular, semi-regular or
irregular
points along the beam, Generally the interposed holes and fasteners are
inserted at an
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angle bisecting that made by adjacent obtuse and acute holes, Typically the
interposed
holes and fasteners are inserted at an angle orthogonal to flat cooperating
surfaces of the
beam.
Having the benefit of this disclosure, the skilled person is able through
routine
experimentation or trial and error to identify points along a beam where an
advantage is
gained by drilling of an interposed hole and the insertion of a fastener
therein.
EXAMPLES
EXAMPLE 1: Assessment of three member beam, and comparison with two member
beam.
A beam produced generally in accordance with the preferred embodiment above,
by using
three 80 mm members. This beam was compared with a beam produced generally
according to PCT/AU2009/001453, by using two members of 100 mm. In both beams,
fasteners were inserted alternately acutely and obtusely in a repeating V-
shaped manner.
Both beams passed on strength criteria as a joist at 600 ctrs at 3.6 metre
span.
Under service conditions the three member beam shows an acceptable 50% stress
(F11 is
35 Mpa, and F34 is 100 Mpa),
This example demonstrates the usefulness of smaller timber rounds fabricated
from wood
which has previously been discarded or converted into low value products such
as wood
chips. Forming the smaller rounds into a three member beam using the fastening
methods
specified herein provides a higher value product having acceptable structural
characteristics.
EXAMPLE 2: Cost benefit of three member beams.
Applicant proposes that when using the same diameter logs with stiffness
defined by
reference to the moment of inertia (1= bd3/12), and assuming that stiffness is
related to
strength, and deflection is the limiting factor:
It will be noted in the above equation that b is a constant (being the width
of beam), and so it
is possible to compare &for 1, 2, 3, 4 or more members.
For example, when considering a 10 cm diameter member. (80 cm between flats):
when
going from a beam having 2 members (prior art) to 3 members (a beam according
to the
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present invention) the I values will be 16 cm' compared to 24cm3, giving a
ratio of
4096:13824. This lean advantage of almost 3.3 to 1.
In light of the above it is proposed that around 50% increase in costs
provides 3.3 times the
strength of the prior art two member beam
EXAMPLE 3: Beam composed of four members.
Four peeler cores (each of only 46 mm diameter) where cut to remove a slab
from opposing
surfaces, The slabbed cores had a first dimension of 40 mm (taken from the
first planar face
formed from slabbing to the second diametrically opposite planar face), and a
second
dimension of 184 mm. The planar faces formed cooperating surfaces where two
rounds
contacted. An end-on view of the assembled composite member is shown in Fig 4.
The
length of the composite member was 2200 mm.
Analysis yielded the following parameters:
Area: 6306.2195 so in
Perimeter: 432.8113 in
Bounding box X: -23.0769 -- 23.0769 in
Y. -79.9408 -- 79.9408 in
Centroid X: 0.0000 in
Y. 0.0000 in
Moments of inertia X: 13310559.5729 so in so in
Y: 880519.8341 so in so in
Product of inertia XY: -6:6665¨sq in sq in-------------------
-----------------------
Radii of gyration X: 45,9424 in
Principal moments (sq in so in) 1. 880519.8341 along [0,0000 -1,0000]
and X-Y directions about
centroid
The preceding description details embodiments of the invention using three
rounds to form
the timber structural member. It will be appreciated that the teachings herein
may be applied
by the skilled person in the fabrication of timber structural members having
four, five, six,
seven, eight or more rounds.
The above description of the disclosed embodiments is provided to enable any
person
skilled in the art to make or use the invention. Various modifications to
these embodiments
will be readily apparent to those skilled in the art, and the generic
principles described herein
can be applied to other embodiments without departing from the spirit or scope
of the
invention. Thus, it is to be understood that the description and drawings
presented herein
represent a presently preferred embodiment of the invention and are therefore
representative of the subject matter which is broadly contemplated by the
present invention.
It is further understood that the scope of the present invention fully
encompasses other
embodiments that may become obvious to those skilled in the art.
It will be appreciated that in the detailed description and the description of
preferred
embodiments of the invention, various features of the invention are sometimes
grouped
together in a single embodiment, figure, or description thereof for the
purpose of streamlining
the disclosure and aiding in the understanding of one or more of the various
inventive
aspects. This method of disclosure, however, is not to be interpreted as
reflecting an
intention that the claimed invention requires more features than are expressly
recited in each
claim. Rather, as the following claims reflect, inventive aspects lie in less
than all features of
a single foregoing disclosed embodiment
Furthermore, while some embodiments described herein include some but not
other features
included in other embodiments, combinations of features of different
embodiments are
meant to be within the scope of the invention, and from different embodiments,
as would be
understood by those in the art. For example, in the claims appended to this
description, any
of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth.
However, it is
understood that embodiments of the invention may be practiced without these
specific
details. In other instances, well-known methods, structures and techniques
have not been
shown in detail in order not to obscure an understanding of this description.
31
Date recue / Date received 2021-11-26
