AU2022202080B1 - A Structural Beam and Method of Manufacture - Google Patents

Abstract

Described herein is a structural beam comprising timber laminate in combination with a stiffening elements that allows a timber laminate to achieve a greater structural standard. In one embodiment, the wood laminate beam comprises timber lamella adhered together with a generally oblong cross section shape and a longitudinal length, the cross-section shape comprising relatively shorter width sides and longer depth sides. The wood laminate beam shorter width sides have elongated recesses and the stiffening element(s) are located and adhered inside the elongated recesses in the wood laminate beam. The manufacturing method comprises providing a wood laminate beam, forming at least one elongated recess into the wood laminate beam shorter width side or sides, and nesting and adhering at least one stiffening element into the at least one elongated recess. 17

Description

ASTRUCTURALBEAMAND METHODOFMANUFACTURE TECHNICAL FIELD

Described herein is a structural beam and method of manufacture. More specifically, a structural beam

is described comprising timber laminate in combination with a second material of higher stiffness and

strength.

BACKGROUND ART

Further aspects and advantages of the structural beam and methods of manufacture will become

apparent from the ensuing description that is given by way of example only.

Existing art in relation to structural beams used in construction comprise steel beams e.g. I-beams, U

sections, H-sections and so on. Steel beams are very strong but are heavy and costly. Wooden beams

made from a single piece of timber may be used and have the advantage of being of comparatively lower

cost but timber has a far lower structural capacity and is prone to variation in properties along timber

beam length.

An answer to the problems of timber beams has been the preparation and use of wood laminates, being

a series of smaller width timber strips or lamella, and multiple lamella adhered together or laminated to

form a beam. This approach is more expensive than a solid timber beam but the laminate approach

does avoid variations in timber quality issues and greatly improves the structural properties of the beam.

Wood laminates however have a far lower elasticity and bending capacity than steel. Despite this, there

is a growing desire for use of timber in construction due to the rising cost of steel and lower weight of

wood leading to lighter weight buildings that are easier to manufacture and which have useful benefits

in seismic regions.

Wood laminates need to achieve a structural grade (SG) standard to be approved for structural use (SG6

or SG8 standard form NZS3604/3603). In practice this means selecting timber with minimal if any

imperfections to achieve the structural grade for the length which in turn leads to a higher timber

composite cost and a downgrade in considerable 'lower grade' timber stock. It would be useful to be

able to use more lower grade timber stock to reduce material cost, reduce waste, and meet the growing

demand for timber as a structural construction material.

Composite timber or steel beams have been considered in the art such as the Flitchl beam. Typically,

such beams use a 'sandwich' style approach where a laminate is manufactured from wood layers with a

steel layer between the wood layers that are nailed together to form a beam. The steel layer in these art

embodiments is placed between two wood layers through the interior of the beam and the steel layer

extends across the beam width and length dimensions. This approach improves the beam strength and elasticity but uses a considerable amount of steel hence is costly. This steel layer approach also only adds strength about a continuous plane or planes centred along the beam minor axis . A central steel layer is also not optimal in terms of strength enhancement based on the inventor's experience.

An alternative form of beam that addresses at least some of the above problems or at least provides the

public with a choice may be of benefit.

SUMMARY

Described herein is a structural beam comprising timber laminate in combination with a second material

with higher stiffness and strength. The resulting beam has enhanced structural properties and may be

used to enhance the overall beam strength and stiffness or to use lower quality and less expensive

timber laminate yet still meet structural requirements seen from higher cost wood laminates. Methods

of manufacture of the beam are also described.

In a first aspect, there is provide a structural beam comprising:

a wood laminate beam comprising:

timber lamella adhered together with a generally oblong cross-section shape

and a longitudinal length, the cross-section shape comprising relatively shorter width

sides and longer depth sides; and wherein,

both of the wood laminate beam shorter width sides have at least one

elongated recess cut into and opening to a surface of the wood laminate beam, the at

least one elongated recess extending along at least 80% of the wood laminate beam

length and a smooth planar face on the longer depth sides; and

at least one stiffening element located and adhered inside the at least one elongated recess in

the wood laminate beam, wherein the at least one stiffening element substantially fills the at least

one recess in which the at least one stiffening element is located and adhered to.

In a second aspect, there is provided a method of manufacturing a structural beam comprising:

providing a wood laminate beam manufactured from timber lamella adhered together

with a generally oblong cross-section shape and a longitudinal length the cross-section shape

comprising relatively shorter width sides and longer depth sides;

forming on both of the wood laminate beam shorter width sides, at least one

elongated recess into and opening to a surface of the wood laminate beam, the at least one

elongated recess extending along at least 80% of the wood laminate beam length, the wood

laminate beam having a smooth planar face on the longer depth sides; and

nesting and adhering at least one stiffening element into the at least one elongated

recess.

Advantages of the above include the ability to produce structural beams of SG8 or far higher standard in

terms of strength and elasticity. Alternatively, it is possible to achieve SG8 or higher standard using a

wood laminate beam that, without stiffening element(s), would have a structural grade of less than SG8

or less than SG7, or less than SG6, or less than SG5. In other words, a less expensive and currently waste

or low grade timber could be used in higher value structural applications. A further advantage is that the

structural beam described may have greater uniformity in strength and elasticity along its length than a

comparable wood laminate beam. Wood inherently has varying properties being a natural material. The

combination of stiffening element(s) and wood laminate means that the final product is very uniform

along its length in terms of strength and elasticity or at least more uniform than a usual range of

averages for batch of wood laminate beams.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the structural beam and methods of manufacture will become apparent from the

following description that is given by way of example only and with reference to the accompanying

drawings in which:

Figure 1 illustrates a beam axes and force directions experienced by a beam;

Figure 2 illustrates a perspective and end view of a steel bar embodiment where a single bar is located

and adhered into a single recess located on either side of a wood laminate beam to form the structural

beam herein;

Figure 3 illustrates a perspective and end view of a similar steel bar arrangement but with two recesses

and two bars on either side of the wood laminate beam;

Figure 4 illustrates a perspective and end view of a further similar steel bar arrangement but with three

recesses and three bars on either side of the wood laminate beam;

Figure 5 illustrates a perspective and end view of a rebar embodiment using three rebar located and

adhered into three recesses on either side of a wood laminate beam;

Figure 6 illustrates a perspective and end view of a further rebar embodiment using nine rebar located

and adhered into three recesses, three rebar in each recess on either side of the beam;

Figure 7 shows how a standard coupling plate may be fastened to the wood laminate beam using

standard wood screws and with no requirement for special drilling and fastening equipment;

Figure 8 illustrates a front view of a test configuration used to measure the structural beam strength

hand elasticity;

Figure 9 illustrates a beam positioned in the testing machine prior to testing;

Figure 10 illustrates the only observed failure of the steel / timber bond line, compression edge of beam

number 287620;

Figure 11illustrates the rebar reinforced beam when loaded in the test configuration prior to testing;

and

Figure 12 illustrates the load deflection plots for the beams using the two different types of steel

reinforcement.

DETAILED DESCRIPTION

As noted above, described herein is a structural beam comprising timber laminate in combination with a

stiff material. The resulting beam has enhanced structural properties and may be used to enhance the

beam strength or to use lower quality and less expensive timber laminate yet still meet structural

requirements seen from higher cost wood laminates. Methods of manufacture of the beam are also

described.

For the purposes of this specification, the term 'about' or 'approximately' and grammatical variations

thereof mean a quantity, level, degree, value, number, frequency, percentage, dimension, size, amount,

weight or length that varies by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% to a reference

quantity, level, degree, value, number, frequency, percentage, dimension, size, amount, weight or

length.

The term 'substantially' or grammatical variations thereof refers to at least about 50%, for example 75%,

85%,95% or 98%.

The term 'comprise'and grammatical variations thereof shall have an inclusive meaning - i.e. that it will

be taken to mean an inclusion of not only the listed components it directly references, but also other

non-specified components or elements.

Structural Beam

In a first aspect, there is provide a structural beam comprising:

a wood laminate beam comprising:

timber lamella adhered together with a generally oblong cross-section shape

and a longitudinal length, the cross-section shape comprising relatively shorter width

sides and longer depth sides; and wherein,

both of the wood laminate beam shorter width sides have at least one

elongated recess cut into and opening to a surface of the wood laminate beam, the at

least one elongated recess extending along at least 80% of the wood laminate beam

length and a smooth planar face on the longer depth sides; and

at least one stiffening element located and adhered inside the at least one elongated recess in the wood laminate beam, wherein the at least one stiffening element substantially fills the at least one recess in which the at least one stiffening element is located and adhered to.

Method of Manufacture

In a second aspect, there is provided a method of manufacturing a structural beam comprising:

providing a wood laminate beam manufactured from timber lamella adhered together

with a generally oblong cross-section shape and a longitudinal length the cross-section shape

comprising relatively shorter width sides and longer depth sides;

forming on both of the wood laminate beam shorter width sides, at least one

elongated recess into and opening to a surface of the wood laminate beam, the at least one

elongated recess extending along at least 80% of the wood laminate beam length, the wood

laminate beam having a smooth planar face on the longer depth sides; and

nesting and adhering at least one stiffening element into the at least one elongated

recess.

Structural

Structural means the structural beam achieves SG8 standard in terms of strength and elasticity. In one

embodiment, the structural beam achieves at least SG9, or SG10, or SG11, or SG12, or SG13, or SG14, or

SG15, or SG16, or SG17, or SG18 standard. In the inventor's experience, it would be possible to achieve

structural standards well in excess of SG18. For example SG50 could be achieved if desired.

In an alternative embodiment, the structural beam achieves SG8 or higher standard and uses a wood

laminate beam that, without stiffening element(s), would have a structural grade of less than SG8 or less

than SG7,or less than SG6,or less than SG5.

A further aspect of the above described structural beam is that the overall structural beam has greater

uniformity in strength and stiffness than a comparable wood laminate beam. Wood inherently has

varying properties being a natural material. The combination of stiffening element(s) and wood laminate

means that the final product is very uniform along its length in terms of strength and elasticity or at least

more uniform than a usual range of averages for a batch of wood laminate beams.

Further, the term structural also refers to modulus of elasticity about bending in a major or minor axis.

As may be appreciated, bending of a structural beam may occur about one or both of a major (X-X) or

minor (Y-Y) axis from a force as demonstrated in Figure 1. The extent of bending may be measured as a

deflection.

The structural beam described herein increases the strength and stiffness in bending about both major

X-X and minor Y-Y axes. The structural beam described herein increases strength and stiffness more efficiently than prior art sandwich style beams with a steel plate. This is understood to be because the stiffening element described further herein is located away from a neutral axis in both bending modes than a central steel plate or layer thus experiences a greater amount of tension or compression in bending and hence reacts proportionately more to the tension or compression force. The beam design described however may mainly target bending about the major X-X axis.

Modulus of elasticity may be a useful comparison measure. The inventor has found that a structural

beam manufactured from pure timber lamella that would normally achieve SG6 standard (hence have a

modulus of elasticity of 6GPa) can be increased to a modulus of elasticity of 20GPa or higher about a

major X-X axis by use of the design described herein and a modulus of elasticity about the minor Y-Y axis

increased to around 8~10GPa. This is understood to be a higher gain than that seen for prior art wood

and steel sandwich style beams and the current approach uses far less steel than prior art designs.

Beam

The term 'beam' is used herein to refer to an elongated length of material used in construction to

support a load thereon e.g. from roofing. The beam may support a structural lateral or orthogonal

loading or end on loading.

Wood Type

Wood that may be used to manufacture the wood laminate beam may be the same as those already

used in the art such as those from the Pinus genus, Pseudotsuga genus, Picea genus and many others.

Specific examples include Pinus radiata, Douglas fir, spruce, larch, gum and so on. The plant species

from which the wood may be produced is not understood to be critical to the structural beam described

herein although, as may be appreciated, some woods are preferred for structural applications over other

woods.

The wood may be treated for longevity and for use above or in ground.

Laminate beams such as those produced already by the applicant may be used to form the wood

laminate beam albeit, that they are modified in accordance with the above description.

Wood Laminate Beam Shape

The wood laminate beam shape provided above, referring to a 'generally oblong cross-section shape', is

provided for ease of reading. It should be appreciated that the structural beam may have varying cross

section shapes and may even be square, circular or semi-circular, three-sided or with five or more sides.

These additional shapes are intended to be covered herein and the gist of the structural beam described

comprising a cross-section shape with recesses and stiffening element(s) does not change due a change in wood laminate beam cross-sectional shape.

Lamella Adherent

The timber lamella may be adhered together using adhesives. The adhesives may be epoxy glue,

resorcinol glue, or other glues or glue combinations providing similar properties.

Recess and Stress Positioning

The recesses described may be located at points experiencing greatest stress across the structural beam

in the event of a bend loading in a major and/or minor axis being place on the structural beam. This may

be so that the stiffening element(s) in the elongated recess(es) provides the greatest degree of stiffening

to the structural beam.

For example, at the exterior of the structural beam widest sides, a stiffening element(s) in a recess

closest to a point lateral loading would undergo the greatest level of compression experienced across

the structural beam length. On the opposing side, the stiffening element(s) would experience the great

tension loading experienced across the structural beam length. By having the stiffening element(s)

located at both the highest compression and tension points, the extent of structural beam deflection is

minimised and the optimum amount of stiffening element(s) can be utilised. By comparison, a steel

layer located in the centre of the wood laminate beam would need to be comparatively thicker to

achieve the same level of stiffness as having steel at the outer edges described. A steel layer also would

have considerable extra material relative to the stiffening element(s) described herein and it is possible

that at least some of the steel layer may well provide little if any benefit at all to the structural beam in a

bend loading scenario. Discrete recessed stiffening element(s)s may therefore be tailored to where the

strength is needed most to optimise strength and stiffness.

It was found that locating the elongated recesses and stiffening elements therein on the shorter width

sides, i.e. minor Y-Y axis sides, was sufficient to provide the stiffening strength desired. No elongated

recesses and stiffening elements were required on the major axis sides to achieve a desired increase in

strength and stiffness. This reduces manufacturing and material costs of the structural beam yet still

achieves the desired designed for strength.

Recess Location and Size

The at least one elongated recess in the wood laminate beam shorter side may be centred across the

shorter side width and comprises approximately 10-80% of a total width of the shorter width side.

By contrast, where multiple recesses are located in the shorter width side, the multiple recesses may

also be centred, each of the multiple recesses located equidistant from each other across a total width of the structural beam shorter width side optionally, with one recess located on a central axis of the structural beam shorter width side.

For example, if a side comprises two elongated recesses, each recess may be located on either side of

the central axis of the structural beam, with an equal distance between the structural beam edges and

central axis. If the structural beam has three recesses, one recess may be located along the structural

beam centre and the other two recesses located equidistant on either side of the central recess.

Recess Quantity

Each structural beam may comprise 1-6, or 2-6, or 2-3 elongated recesses and each elongated recess

may comprise 1-4, or 1-3, or 1-2, or single stiffening element. The number of elongated recesses used

on one shorter width side of the structural beam may be matched on the opposing structural beam

shorter width side by a complementary number and placement of elongated recesses. The number of

elongated recesses used may be a function of structural beam width and design loadings required.

Recesses Distant to Long Sides

All elongated recesses may remain distant to an outer edge of the structural beam and may not open to

the wood laminate beam longer depth side or sides.

Recess Depth

The elongated recesses have a relatively small depth being approximately 2-10% of the longer depth side

depth. The elongated recesses are designed to not impact or at least minimise impact on the structural

strength of the wood laminate beam. The depth of an elongated recess may be complimentary to the

depth of the stiffening element therein so that the stiffening element sits flush within the elongated

recess once adhered into the elongated recess.

The elongated recess depth is envisaged to be less than one, only one, or no more than two lamella deep

into the wood laminate beam of the structural beam.

The elongated recess width may be the same or greater than the elongated recess depth.

Recess Width

The elongated recesses have a width that is complimentary to the stiffening element width/diameter. As

noted above, this width may be the same or greater than the elongated recess depth corresponding to a

stiffening element with a width the same or greater than the elongated recess depth. For example, if the

stiffening element has a width or diameter of approximately 12mm, the recess may be approximately

12mm wide and 12mm deep. In another embodiment, if the stiffening element has a width of 30mm

and a depth of 12mm, the recess may have a width of approximately 30mm and a depth of 12mm as

well.

The stiffening element may be nested into or fits snugly into the elongated recess.

The stiffening element may not however be sized to significantly interfere with the elongated recess

width hence the two widths may be evenly matched and plastic deformation of the elongated recess

does not occur when the stiffening element is fitted to an elongated recess.

Recess Length

The elongated recesses in the wood laminate beam may extend along a full length of the structural

beam. If an elongated recess does not extend across the full length, the elongated recess may terminate

about either one or both ends of the structural beam. The recess extends in a continuous manner about

the structural beam centre or mid-point and radiates outwards from the centre

Stiffening Element(s) and Properties

The at least one stiffening element(s) may be selected from: steel, aluminium, metals, metal alloys,

fibreglass or other composite materials.

The at least one stiffening element(s) may have a modulus of elasticity (Youngs Modulus) of at least 60,

or 70, or 80, or 90, or 100 GPa. The modulus of elasticity may be over 180 GPa.

Stiffening Element(s) Terminal Ends

In one embodiment, an end or ends of the at least one stiffening element may terminate prior to an end

or ends of the structural beam. For example, the stiffening element may terminate prior to the

structural beam end by around 10% or less of the overall structural beam length. This may be the case at

both ends of the structural beam. For example, if the beam is 5000mm long, then the stiffening element

terminates approximately 250mm or less from both ends of the structural beam (being 500mm or 10%

of the overall structural beam length). Greater or lower overall structural beam lengths and greater or

lower stiffening element termination points may be used and these dimensions are provided by way of

example only.

Stiffening Element(s) Adherent

The stiffening element(s) may be adhered into the at least one elongated recess via at least one chemical

or mechanical adherent. The chemical adherent may be a glue. For example, the glue may be selected from epoxy or resorcinol glues. The mechanical adherent may be in the form of plates, fasteners or other coupling shapes and devices to adhere the stiffening element(s) into a recess. Combinations of both chemical and mechanical adherents may also be used.

Stiffening Element Shape

The at least one stiffening element may be shaped to conform and nest into the at least one elongated

recess.

Each elongated recess may have an oblong cross-section shape and the stiffening element(s) may have a

complementary oblong shape. For example, a stiffening element may be an oblong bar shaped steel

extrusion with a cross-section shape complementary to the elongated recess oblong bar cross-section

shape.

Alternatively, the stiffening element(s) may have a complementary width and varying cross-section

shapes e.g. a circular or ovoid shape, the diameter corresponding to the elongated recess width. In this

embodiment, the stiffening elements may be reinforcing bar (rebar) steel such as that used in concrete

reinforcing and the rebar may have a width complementary to the elongated recess width. The

elongated recess may be sized so that, once rebar in the above embodiment is adhered into an

elongated recess, the rebar outer diameter lies flush with the outer surface of the structural beam.

The elongated recess depth may be sized so that, once a stiffening element is adhered into an elongated

recess, the stiffening element(s) lie flush with the outer surface of the structural beam.

External Plates and Couplings

External plates or other couplings may be fitted to the structural beam to allow fixing or placement to

other items as is already done in wood laminate beam construction. The fasteners or couplings used

may be typical for use in wood and the fasteners or couplings may fit around the stiffening elements and

may not interfere with the stiffening elements.

Relative Amounts

The structural beam described herein may be predominantly still manufactured from wood hence

retains all of the inherent useful properties of wood but has a greater degree of strength and stiffness.

In one embodiment, less than 1.0, or 0.9, or 0.8, or 0.7, or 0.6, or 0.5, or 0.4, or 0.3% by cross-section

area of the structural beam may comprise the at least one stiffening element(s). That is, 99% or greater

of the cross-section area of the structural beam may be manufactured from wood therefore minimising

expense due to the stiffening element(s) such as steel, rebar or fibreglass.

Optional Covers

In the above embodiments, a cover plate or other aesthetic part may be placed over the shorter width

side or sides to hide the stiffening element(s). This may be desired in some applications where the

shorter width side is visible post construction and where, for aesthetic reasons, it would be useful to

hide the stiffening element(s).

Advantages of the above include the ability to produce structural beams of SG8 or far higher standard in

terms of strength and elasticity. Alternatively, it is possible to achieve SG8 or higher standard using a

wood laminate beam that, without a stiffening element(s), would have a structural grade of less than

SG8 or less than SG7, or less than SG6, or less than SG5. In other words, a less expensive and currently

waste or low grade timber could be used in higher value structural applications. A further advantage is

that the structural beam described may have greater uniformity in strength and elasticity along its length

than a comparable wood laminate beam. Wood inherently has varying properties being a natural

material. The combination of a stiffening element and wood laminate means that the final product is

very uniform along its length in terms of strength and elasticity or, at least more uniform than a usual

range of averages for batch of wood laminate beams.

The embodiments described above may also be said broadly to consist in the parts, elements and

features referred to or indicated in the specification of the application, individually or collectively, and

any or all combinations of any two or more said parts, elements or features.

Further, where specific integers are mentioned herein which have known equivalents in the art to which

the embodiments relate, such known equivalents are deemed to be incorporated herein as if individually

set forth.

WORKING EXAMPLES

The above described structural beam and methods of manufacture are now described by reference to

specific examples.

EXAMPLE 1

In this example, varying forms of examples structural beams are described and shown with reference to

Figures 2 to 7.

Figure 2 shows a steel bar embodiment where a single bar is located and adhered into a single recess

located on either side of a wood laminate beam to form the structural beam herein.

Figure 3 shows a similar steel bar arrangement but with two recesses and two bars on either side of the

wood laminate beam and Figure 4 shows an arrangement with three recesses and three bars located on either side of the wood laminate beam, in this case, with the bars rotated 90 degrees to recess end on into the wood recess.

Figure 5 shows a rebar embodiment using three rebar located and adhered into three recesses on either

side of a wood laminate beam and Figure 6 shows a rebar embodiment using a total of nine rebar

located and adhered into three recesses on either side of a wood laminate beam, three rebar per recess.

In the above embodiments, the structural beam 1 comprises a wood laminate beam 2 made up of

multiple timber lamella 3 adhered together. The wood laminate beam 2 has a generally oblong cross

section shape arrow 4 and a longitudinal length 5, the cross-section comprising a relatively shorter width

sides 6 and relatively longer depth sides 7. Both of the wood laminate beam 2 shorter width sides 6 have

recesses 8 formed and opening into the wood laminate beam 2 width surface 9. The recess 8 or recesses

8 extend along the longitudinal length 5 of the structural beam 1. Smooth planar faces 10 remain on the

longer depth sides 7. The recesses 8 do not penetrate the longer depth sides 7.

Stiffening elements in this example shown in the form of steel bars 20 or rebars 30 are located and

adhered inside the recesses 8.

Not shown is a cover plate or other aesthetic part that may be placed over the shorter widths to hide the

stiffening element(s).

Figure 7 shows how a standard coupling plate 40 may be fastened using standard threaded wood

fasteners 50 to the wood laminate beam 2 about the recesses 8 and stiffening elements 20, 30 hence

allowing use of traditional coupling plates 40 despite the amended structural beam 1 design. The ability

to use existing couplings makes the structural beam 1 design herein more versatile since art couplings

need not be changed or amended to suit the new beam design.

EXAMPLE 2

In this example, strength and elasticity tests are described to measure the capability of various designs of

structural beam described herein.

Method

Eight lamella structural beams were produced for testing, seven beams using varying width steel bars

adhered on the outer narrow width sides of each wood laminate beam into complementary recesses.

An eighth sample was tested with three recesses on each width side of the beam and three adhered

rebar per side configuration. The steel bars and rebar were adhered into the recesses using epoxy

adhesive and the lamella adhered together using a resorcinol based adhesive.

Each of the beams had a cross-section depth of 290mm and a shorter width of 90mm.

The beams were tested for bending stiffness and strength in a Grade 1 Baldwin Universal testing machine by a third party test laboratory. The test configuration used is shown in Figure 8 and the test span was 5220mm and load head span of 1740mm with a load head loading speed of 20mm/min.

Each beam was placed into the testing machine for testing. Load was applied to the sample, recording

load and displacement data until failure occurred. The numbering used in Figures 9-11 mirror those

used in Figures 2-7 above.

The apparent modulus of rupture and modulus of elasticity was calculated using the dimensions of the

sample noting that the steel used is recessed and does not contribute to the exterior dimensions of the

beam. Structural grade was assigned to each sample. The grade being the lowest grade based on either

the bending stiffness or the obtained bending stress at the instant of failure. An estimate of the load at

yield (the point at which the steel started to yield), identified by a sudden change to the slope of the load

displacement curve) ,was estimated during the testing of each sample beam.

Figure 9 shows a beam positioned in the testing machine prior to testing. Figure 10 illustrates the rebar

reinforced beam when loaded in the test configuration prior to testing. Figure 11 shows the only

observed failure of the steel/timber bond line, compression edge of beam number 287620 referred to in

Table 2 below.

Results

Table 1 below shows the test data collected for the test beam using three 12mm diameter rebar rods on

the short width sides of the structural beam.

Table 1- Rebar Reinforcing Test Results

Max (Apparent) (Apparent) Load Grade Grade Assigned Lab No: Width Depth Slope load MoEj MoRJ at yield based on based on Structural (mm) (mm) (N/mm) (N) (GPa) (MPa) (N) Stiffness Strength Grade 288073 89.02 288.99 1378.24 69949 19.43 49.11 50000 G-18 G-18 GL18

Table 2 below shows the test data collected for comparative data collected form tests done on structural

beams using 40mmxl0mm flat steel bar stiffening elements.

Table 2 - Steel Bar Reinforcing Test Results

Max (Apparent) (Apparent) Load Grade Grade Assigned Lab No: Width Depth Slope load MoEj MoRj at yield based on based on Structural (mm) (mn) (N/mm) (N) (GPa) (MPa) (N) Stiffness Strength Grade 287615 8913 292.18 1582.74 72394 21.56 49.66 66000 GL18 GLIB GL18 287616 89.03 292.15 1601.99 72807 21.86 50.01 62000 GLIB GL18 GLIB 287617 89.01 293.02 1624.19 71214 21.97 48.64 67000 GL18 GLIB GL18 287618 89.10 292.28 1617.24 70041 22.02 48.03 63000 GLIB GLIB GLIB 287619 88.96 292.73 1592.96 73948 21.62 50.64 65000 GLIB GLIB GLIB 287620 89.11 292.64 1616.66 73384 21.93 50.20 62500 GL18 GLIB GLIB 287621 89.09 292.38 1602.02 71846 21.79 49.24 65000 GLIB GL18 GLIB 287622 89.02 292.47 1584.19 75437 21.55 51.71 65000 GLIB GLIB GLIB 287623 89.09 292.55 1631.25 72102 22.15 49.36 63000 GLIB GL18 GLIB 287624 89.26 292.34 1562.90 74687 21.23 51.11 65000 GLIB GL18 GLIB Average 89.08 292.47 1601.61 72786 21.77 49.86 64350 Minimum 88.96 292.15 1562.90 70041 21.23 48.03 62000 Maximum 89.26 293.02 1631.25 75437 22.15 51.71 67000 Range 0.30 0.87 68.35 5396 0.92 3.68 5000 STDev 0.08 0.27 21.32 1628.3 0.28 1.12 1634 CoV% 0.09% 0.09% 1.33% 2.24% 1.27% 2.24% 2.54% Count 10 10 10 10 10 10 10

Figure 12 shows the load deflection plots for the beams using the two different types of steel

reinforcement.

The results show that the proposed design is highly effective in dramatically increasing the wood

laminate beam strength and elasticity. In the trials, an SG6 standard wood laminate beam was

converted through use of recess positioned stiffening elements to a structural beam of SG18 quality

strength and elasticity being a highly significant and large improvement in structural quality.

The results clearly demonstrate the structural beam design described can markedly increase structural

capacity. Alternatively, it is clearly possible to use a lower grade wood laminate beam and, via the

design and method described, produce a structural beam that would exceed at least SG8 standard.

Aspects of the structural beam and methods of manufacture have been described by way of example

only and it should be appreciated that modifications and additions may be made thereto without

departing from the scope of the claims herein.

Claims (7)

WHAT IS CLAIMED IS:

1. A structural beam comprising a wood laminate beam reinforced with steel flat bars wherein:

the wood laminate beam comprises:

timber lamella adhered together with a generally oblong cross-section shape and a

longitudinal length, the cross-section shape comprising relatively shorter width

sides and longer depth sides; and,

both of the wood laminate beam shorter width sides have at least one elongated

recess cut into and opening to a surface of the wood laminate beam, wherein:

the elongated recess or recesses are centred across a width of the wood

laminate beam shorter width side;

a shape, number and location of elongated recesses used on one shorter

width side of the wood laminate beam is matched on an opposing wood

laminate beam shorter width side by a complementary shape, number and

location of elongated recesses;

each elongated recess has a depth approximately 2-10% of the longer

depth side depth and wherein the depth is no more than two lamella deep

into the wood laminate beam, and each elongated recess has a width

greater than the elongated recess depth;

the elongated recesses extend along a longitudinal length of the wood

laminate beam terminating prior to an end of the wood laminate beam;

the wood laminate beam has a smooth planar face on the longer depth

sides; and

the steel flat bars are located and adhered with adhesive inside each of the elongated

recesses in the wood laminate beam, wherein:

the steel flat bars substantially fill the depth and width of each elongated recess in

which each steel flat bar is located and adhered to,

an outer side of each steel flat bar sits flush with an exterior of the elongated recess

it is received in once adhered into the elongated recess; and

wherein an end or ends of each steel flat bar terminate with the recess end or ends

prior to an end or ends of the wood laminate beam; and

wherein each steel flat bar has an oblong cross-section.

2. The structural beam as claimed in claim 1 wherein the at least one elongated recess in the wood

laminate beam shorter width side comprises 50-80% of a total width of the shorter width side.

3. The structural beam as claimed in claim 1 wherein each wood laminate beam comprises 1-6

elongated recesses on a shorter width side and each elongated recess comprises a single steel

flat bar.

4. The structural beam as claimed in claim 1 wherein all elongated recesses in the wood laminate

beam remain distant to an outer edge of the structural beam and do not open to the wood

laminate beam longer depth side or sides.

5. The structural beam as claimed in claim 1 wherein the steel flat bars have a modulus of elasticity

of at least 60GPa.

6. The structural beam as claimed in claim 1 wherein the steel flat bars are shaped to conform and

nest into the elongated recesses.

7. The structural beam as claimed in claim 1 wherein less than 1.0% by an end cross-section area of

the wood laminate beam comprises the steel flat bars.