FIELD OF THE INVENTION

[001], The present invention relates generally to structural members used in building construction. More particularly, the invention is directed to timber structural members having an I-beam configuration being formed from two timber flanges connected together by a web.

BACKGROUND TO THE INVENTION

[002], It is known in the art to provide a composite timber structural member having a general I-beam configuration. Typically, an elongate planar web (fabricated from materials as diverse as plywood, metal, and plastic) is used to join paired parallel timber flanges. Each flange has a slot running along its length, and the web inserts into the slots so as to provide the composite structure. An adhesive may be used at the interfaces of the flange slot and the web to provide for more secure connection between the components.

[003], In use, the web resists shear forces while the flanges resist any bending moment occasioned on the beam. While the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web, the section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion.

[004], It is noted in prior art I-beam composite timber structural members that splitting or cracking can occur in a flange and/or web when exposed to high loads. Furthermore, the planar web may at least partially dislodge from the flange into which it inserts. As will be readily appreciated splitting, cracking and web dislodgement may be addressed by increasing the cross-sectional area of web and/or the flanges. Whilst generally effective, that approach increases the cost of production given the need for large diameter timbers and more material overall. Larger diameter timbers are becoming increasing scarce, and there is a general preference to use more readily available smaller diameter timbers where possible without compromising safety.

[005], Apart from any cost and supply issues, it is desirable to improve the load-carrying performance of an I-beam timber composite structural member without increasing the amount of material used whilst avoiding problems of cracking, splitting or web dislodgement.

[006], It is an aspect of the present invention to provide an improvement to prior art composite timber structural members so as to improve load carrying performance and/or decrease the propensity of splitting, cracking and web dislodgement. It is a further aspect of the present invention to provide a useful alternative to prior art composite timber structural members.

[007], 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 claim of this application.

SUMMARY OF THE INVENTION

[008], In a first aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions being disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together presenting only planar and curved external surfaces to the internal surfaces of its/their respective slots, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

[009], In a second aspect, the present invention comprises a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together being devoid of any outwardly directed sharp comer, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

[010], In one embodiment of the first or second aspect, the long edge region(s) of the web is/are the region(s) that is/are disposed within the slot.

[Oi l], In one embodiment of the first or second aspect, the tongue region(s) has/have a planar terminal face.

[012], In one embodiment of the first or second aspect, the tongue region(s) has/have opposing lateral planar faces.

[013], In one embodiment of the first or second aspect, the tongue region(s) is/are of substantially even thickness.

[014], In one embodiment of the first or second aspect, the tongue region(s) is/are at least about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% the thickness of the shoulder region (s) from it/they which extends. [015], In one embodiment of the first or second aspect, the web, when viewed end-on, has an axis of symmetry.

[016], In one embodiment of the first or second aspect, the web extends to a depth of between about 20% to about 80% of the diameter of the flange into which it is disposed.

[017], In one embodiment of the first or second aspect, the web extends the full length of the flanges, or extends beyond the length of the flanges, or the web is shorter than the length of the flanges.

[018], In one embodiment of the first or second aspect, the web is formed of a relatively high strength planar material.

[019], In one embodiment of the first or second aspect, the web is formed of a material selected from the group consisting of: timber, processed timber; chipboard, oriented strand board, plywood, metal sheet, metal plate, fibre reinforced cement sheet, plastic, and fibre reinforced plastic material.

[020], In one embodiment of the first or second aspect, the first and/or second flange has a substantially circular cross-section.

[021 ]. In one embodiment of the first or second aspect, the first and/or second flange is a timber pole or a timber round.

[022], In one embodiment of the first or second aspect, the first and/or second flange is/are a peeler core.

[023], In one embodiment of the first or second aspect, the first and/or second flange has/have a planar surface distal to the planar web and at about 90 degrees to the flange slot. [024], In one embodiment of the first or second aspect, the first and/or second slot(s) is/are oversized so as to accommodate its respective long edge region with a layer of adhesive.

BRIEF DESCRIPTION OF THE FIGURES

[025], FIG. 1A illustrates in end view a composite structural member of the present invention.

[026], FIG. 1 B illustrates a magnified view of the upper flange of the composite structural member of FIG. 1 showing more clearly the curved shoulder and tongue regions.

[027], FIG. 2 illustrates in lateral view the composite structural member of FIG. 1. The arrow shows the view direction with reference to the end-on view of FIG. 1.

[028], FIG. 3 illustrates in plan view the composite structural member of FIG. 1. The position of the web is shown. In reality the web would not be visible in plan view. The arrow shows the view direction with reference to the end-on view of FIG. 1.

[029], Unless otherwise indicated herein, features of the drawings labelled with the same numeral are taken to be the same features, or at least functionally similar features, when used across different drawings.

[030], The drawings are not prepared to any particular scale or dimension and are not presented as being a completely accurate presentation of the various embodiments.

[031],

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

[032], 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, or indeed any embodiment covered by the claims.

[033 ]. 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.

[034], 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 various places throughout this specification are not necessarily all referring to the same embodiment, but may.

[035], As used herein, positional terms such as “lateral”, “across”, “above”, “below”, “higher”, “lower”, “upward”, “downward”, “plan view” and the like are to be considered with reference to a composite timber structural member oriented as shown in FIG. 1. It will be appreciated that upon installation, a structural member of the present invention may be orientated in any way such that, for example, the upper edge of the web may face downwardly toward the ground, or laterally.

[036], In a first aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions being disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together presenting only planar and curved external surfaces to the internal surfaces of its/their respective slots, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

[037], In a second aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together being devoid of any outwardly directed sharp corner, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

[038], The present invention is predicated at least in part on the inventors’ discovery that an improved or alternative composite timber structural member having an I-beam configuration is provided where the web long edge regions are devoid of sharp external comers. Such comers are found in external comers of 90 degrees, and also less than 90 degrees where a comer is bevelled, for example.

[039], More particularly, the long edge region of the web may be formed into a shoulder region (the shoulders being curved or rounded, and not formed into sharp comers) and a tongue region (the distal end of the tongue also having curved or rounded comers rather than sharp comers). [040], Without wishing to be limited by theory in any way, it is proposed that prior art webs concentrate load forces at the sharp comers thereof, leading to cracking and splitting of the flange around the slots and/or the web itself, sometimes leading to dislodgement of the web from its position in the flange slot. Failure in prior art structural member disposed horizontally was often seen to occur from the bottom of the lower chord straight upwards (i.e. 90 degrees to the horizontal) and about one-third the way along the member. The use of rounded comers is proposed to distribute forces more evenly through the flange, thereby limiting the magnitude of a force along any vector.

[041], A further advantage of rounding the web comers is that a greater surface area for the contact of adhesive is provided, thereby increasing level of bonding between the web and the flange.

[042], Moreover, the formation of a shoulder portion at the edge region of a web, with a tongue portion extending therefrom is proposed to provide further advantage as load forces are distributed into two regions of the flange: into the region surrounding the shoulders and also deeper into the flange in the region surrounding the tongue terminus. Rounding the comers of the shoulder region has the same advantages as for the tongue, as discussed supra.

[043 ]. Furthermore, the formation of a relatively thin tongue portion requires less wood to be removed from the flange in order to form the flange slot. The tongue is thinner than the remainder of the web, and therefore the slot terminus deep in the flange can also be thinner. Leaving more wood in flange increases the ability of the flange (and therefore the structural member as a whole) to better resist load forces.

[044], The invention will now be more fully described by reference to the non-limiting embodiments of the drawings.

[045], Turning firstly to FIG. 1 a composite structural member (10) is show in end-on view revealing the I-beam-like configuration. The composite stmctural member (10) comprises a first timber flange (15), a second timber flange (20) and a web (25). Each of the flanges (15, 20) has a flattened region (30, 35) to allow mounting of the member (10) on other planar building structures, or to allow other such structures to be mounted on the member (10).

[046], Considering now FIG. IB, greater detail of the web (25) insertion into the upper flange (15) is shown. A slot (40) is formed in the first flange (15), and having a first relatively wide portion (40a) which communicates with the outside, and a more narrow portion (40b) at the blind end. In terms of fabrication, a tool could be used to rout a narrow slot for the full depth, and then a different tool used to rout the wider portion at more shallow depth to form the bipartite slot shown in FIG. IB.

[047], The end region of the web (25) has a shape and dimensions that generally follow those of the slot (40) is so far as a relatively thick shoulder portion (45) is provided and a relatively thin tongue portion (50). The shoulder portion (45) comprises paired opposed rounded shoulders (one marked 55). The tongue portion (50) comprises paired opposed rounded shoulders (one marked 60), and a planar terminal face (65).

[048], The slot (40) conforms very closely to the shape of the web portions (45, 50) however is slightly oversized to allow for adhesive to retained in the slot (40) after insertion of the web portions (45, 50). In embodiments where only frictional engagement is relied upon, there would be no need for oversizing the slot (40).

[049], As discussed supra, the use of rounded comers (55, 60) better distribute load forces throughout the flanges (15, 20) so as to avoid problems such as splitting, cracking and web dislodgement.

[050], Reference is now made to FIG. 2 and FIG. 3 showing respectively lateral and plan views of the composite structural member (10). The structural member (10) will generally be very elongate so as to be useful in spanning supports in building construction. [051], The diameter of the flanges (15) and (20) and the dimensions of the web (25) are selected so that the structural strength of the composite member will meet predetermined design and load bearing requirements.

[052], The flanges (15) and (20) are comprised of timber poles. In one embodiment, one or more of the round flanges 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, the flange(s) has/have a diameter of less than about 60 mm.

[053], In some embodiments, a flange is a “peeler core”. As is understood by the skilled person, a peeler core is a by-product of process of removing the outer layers of wood for plywood manufacturing (often by a milling process) to the point that substantially all the soft wood has been removed, leaving the heartwood 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.

[054], The heartwood 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.

[055], Applicant has discovered an economically and technically viable use for peeler cores in that the cores may be used in a structural member 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.

[056], Peeler cores are essentially a waste product of forestry, having little value in the market. In one embodiment, the present invention is directed to structural members whereby all round flanges are peeler cores. [057], The round flanges may be so-called "true round sections", or "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.

[058], 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.

[059], True rounds are particularly strong since the natural strength of the timber fibres is not disrupted by sawing or other treatment. The integrity 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

[060], 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 satisfied.

[061], Where first and second flanges are used, the flanges may have different cross- sectional areas, or the cross-sectional areas may be similar or identical.

[062], In a preferred form of the invention, the web (25) is formed of a plywood or plywood like material which is well known in the art, and a bonding material selected will such that a high strength timber to timber bond is achieved between the web (25) and the timber from which the flanges (15) and (20) are made. If necessary, the composite member may be treated after assembly, such as by heat treatment, to ensure that the web to flange bond is of high strength.

[063 ]. Typically a resin based waterproof structural adhesive will be used to bond the web

(25) to flanges (15, 20).

[064], As mentioned previously, the web material can be formed of any suitable material and the strength and thickness of the web will depend on the overall strength requirements of the joist, the diameters of the log, and like considerations. Clearly, if a high strength web is required, a thicker plywood material, for example, may be used. Other web materials might comprise steel or other metal plate or sheet, fibrous cement or like material, or other high strength planar materials such as chipboard, particle board, oriented strand board, and plastics type materials.

[065], The present structural members can be used in many structural contexts, and may be used as a floor bearer, a floor joist, a lintel, a heavy duty stud, a roof framing member, a roof rafter, a roof hanging/strutting beam, a portal frame member, a column, a bottom chord, a beam/column, or a pier.

[066], For some applications it may be necessary to end-join the present structural members, and in which case a dowel connection may be used. In addition or alternatively, the ends of the flanges may be scalloped and the web appropriately terminated so as to facilitate end joining.

[067], Those skilled in the art will appreciate that the invention described herein is susceptible to further variations and modifications other than those specifically described. It is understood that the invention comprises all such variations and modifications which fall within the spirit and scope of the present invention. [068], Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.