Improved web connection to wood flanges

Abstract

A wood structural member having an I-beam configuration having a first slotted wood flange and a second slotted wood flange, and a web having opposing tongues. Each of the opposing tongues is disposed in a respective slot to connect the first flange and the second flange.

Description

Technical Field

[0001] The present invention relates generally to structural members for use in building construction. More particularly, the present invention is directed to a timber structural member having an I-beam construction formed from two timber flanges connected together by a web. Background Art

[0002] It is known in the art to provide composite timber structural members having a generally I-beam configuration. Typically, an elongated planar web (made from a variety of materials such as plywood, metal and plastic) is used to join pairs of parallel timber flanges. Each flange has a slot extending along its length, and the web is inserted into the slot to provide a composite structure. Adhesives may be used at the interface of the flange slot and the web to provide a more secure connection between the components.

[0003] In use, the web resists shear forces while the flanges resist any bending moments occurring on the beam.While the I-section is a very efficient form for carrying both bending and shear loads in the plane of the web, the section has reduced capacity in the transverse direction and is also inefficient in carrying torsion.

[0004] It has been noted in prior art I-beam composite timber structural members that splitting or cracking may occur in the flanges and / or webs when exposed to high loads. In addition, the planar web may be at least partially displaced from the flanges into which the webs are inserted. As will be readily appreciated, splitting, cracking and web displacement may be addressed by increasing the cross-sectional area of ​​the webs and / or flanges. While generally effective, this approach increases production costs given the need for larger diameter timber and more material overall. Larger diameter timber is becoming increasingly scarce and there is a general preference to use more readily available smaller diameter timber whenever possible without compromising safety.

[0005] Apart from any cost and supply issues, it would be desirable to improve the load carrying performance of I-beam composite timber structural members without increasing the amount of material used, while avoiding problems with cracking, splitting or web displacement.

[0006] One aspect of the present invention is to provide improvements to prior art composite timber structural members so as to improve load bearing properties and / or reduce the tendency to split, crack and web displacement. Another aspect of the present invention is to provide a useful alternative to prior art composite timber structural members.

[0007] The discussion of documents, acts, materials, devices, articles and the like included in this specification is 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

[0008] In a first, but not necessarily the broadest, aspect, the invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein; and a web having a first long edge region and an opposing second long edge region, the first long edge region and the second long edge region being disposed in the first and second longitudinal grooves, respectively, wherein the first long edge region(s) and / or the second long edge region(s) comprise a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together presenting only a planar and curved outer surface to the inner surface of their respective grooves, and each groove being shaped and dimensioned so as to receive a long edge region disposed therein.

[0009] In a second aspect, the present invention comprises a composite timber structural member comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein; and a web having a first long edge region and an opposing second long edge region, the first long edge region and the second long edge region being disposed in the first longitudinal groove and the second longitudinal groove, respectively, wherein the first long edge region(s) and / or the second long edge region(s) comprise a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together being free of any outwardly directed sharp corners, and each groove being shaped and sized to receive a long edge region disposed therein.

[0010] In one embodiment of the first or second aspect, the long edge region(s) of the web are the region(s) arranged within the groove.

[0011] In one embodiment of the first or second aspect, the tongue region(s) have a planar end face.

[0012] In one embodiment of the first or second aspect, the tongue region(s) have opposing lateral planar faces.

[0013] In one embodiment of the first or second aspect, the tongue region(s) have a substantially uniform thickness.

[0014] In one embodiment of the first or second aspect, the tongue region(s) are at least about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% of the thickness of the shoulder region(s) from which it or they extend.

[0015] In one embodiment of the first or second aspect, the web has an axis of symmetry when viewed from the end.

[0016] In one embodiment of the first or second aspect, the web extends to a depth of between about 20% and about 80% of a diameter of the flange in which the web is disposed.

[0017] In one embodiment of the first or second aspect, the web extends the full length of the flange or extends beyond the length of the flange, or the web is shorter than the length of the flange.

[0018] In one embodiment of the first or second aspect, the web is formed from a relatively high strength planar material.

[0019] In one embodiment of the first or second aspect, the web is formed from a material selected from the group consisting of: wood, processed wood; wood chip plywood, oriented strand board, plywood, metal sheet, metal plate, fiber reinforced cement sheet, plastic and fiber reinforced plastic material.

[0020] In one embodiment of the first or second aspect, the first flange and / or the second flange has a substantially circular cross-section.

[0021] In one embodiment of the first or second aspect, the first flange and / or the second flange is a timber pole or timber round.

[0022] In one embodiment of the first or second aspect, the first flange and / or the second flange is a log core.

[0023] In one embodiment of the first or second aspect, the first flange and / or the second flange has a planar surface away from the planar web and at about 90 degrees to the flange groove.

[0024] In one embodiment of the first or second aspect, the first groove(s) and / or the second groove(s) are oversized to accommodate their respective long edge regions with the adhesive layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A An end view of a composite structural member of the present invention is shown.

[0026] Figure 1B An enlarged view of the upper flange of the composite structural member of FIG. 1 is shown, more clearly showing the curved shoulder and tongue regions.

[0027] Figure 2 The composite structural member of Figure 1 is shown in side view. The arrows indicate the viewing direction with reference to the end view of Figure 1 .

[0028] Figure 3 The composite structural member of Figure 1 is illustrated in plan view. The location of the web is shown. In practice, the web would not be visible in the plan view. The arrows show the viewing direction with reference to the end view of Figure 1.

[0029] Unless otherwise indicated herein, features of the drawings labeled with the same reference numerals when used across different drawings are considered to be the same features, or at least functionally similar features.

[0030] The drawings are not drawn to any particular scale or size and are not presented as a completely accurate representation of the various embodiments. DETAILED DESCRIPTION

[0031] After considering this description, it will be apparent to those skilled in the art how to implement the present invention 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, not limitation. Therefore, this description of various alternative embodiments should not be construed as limiting the scope or breadth of the present invention. In addition, statements of advantages or other aspects apply to specific exemplary embodiments, and are not necessarily applicable to all embodiments, or indeed any embodiment covered by the claims.

[0032] Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "include" and "comprising", are not intended to exclude other additives, components, integers or steps.

[0033] References throughout this specification to "one embodiment" or "an embodiment" mean 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, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification are not necessarily all referring to the same embodiment, but may.

[0034] As used herein, positional terms such as "laterally", "across", "above", "below", "higher", "lower", "upward", "downward", "plan view" and the like will be considered with reference to the composite timber structural member oriented as shown in Figure 1. It will be appreciated that when installed, the structural member of the present invention may be oriented in any manner, such that, for example, the upper edge of the web may face downwardly towards the ground or laterally.

[0035] In a first, but not necessarily the broadest, aspect, the invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein; and a web having a first long edge region and an opposing second long edge region, the first long edge region and the second long edge region being disposed in the first and second longitudinal grooves, respectively, wherein the first long edge region(s) and / or the second long edge region(s) comprise a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together presenting only planar and curved outer surfaces to the inner surfaces of their respective grooves, and each groove being shaped and dimensioned so as to receive a long edge region disposed therein.

[0036] In a second, but not necessarily the broadest, aspect, the invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein; and a web having a first long edge region and an opposing second long edge region, the first long edge region and the second long edge region being disposed in the first and second longitudinal grooves, respectively, wherein the first long edge region(s) and / or the second long edge region(s) comprise a shoulder portion from which a tongue portion extends, the tongue portion having a thickness that is less than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together being free of any outwardly directed sharp corners, and each groove being shaped and sized to receive a long edge region disposed therein.

[0037] The present invention is based at least in part on the inventors' discovery that an improved or alternative composite timber structural member having an I-beam construction is provided wherein the long edge regions of the web are free of sharp external corners. Such corners exist in 90 degree external corners and also in the case where the corner is, for example, beveled, less than 90 degrees.

[0038] More specifically, the long edge region of the web may be formed as a shoulder region (the shoulder is curved or rounded and not formed as a sharp corner) and a tongue region (the distal end of the tongue also has a curved or rounded corner instead of a sharp corner).

[0039] Without wishing to be bound in any way by theory, it is proposed that the web of the prior art concentrates load forces at its sharp corners, resulting in cracking and splitting of the flange around the slot and / or the web itself, sometimes resulting in displacement of the web from its position in the flange slot. Failure is often seen in horizontally disposed prior art structural members straight up (i.e., 90 degrees from horizontal) from the bottom of the lower chord and about one-third of the way along the member. The use of rounded corners is proposed to more evenly distribute the forces through the flange, thereby limiting the magnitude of the forces along any vector.

[0040] An additional advantage of rounding the web corners is that it provides a larger surface area for the adhesive to contact, thereby increasing the bond level between the web and flange.

[0041] Furthermore, it is proposed to form a shoulder portion at the edge region of the web, with the tongue portion extending from this shoulder portion, to provide further advantages, since the load forces are distributed into two regions of the flange: into the region around the shoulder, and also deeper into the flange in the region around the end of the tongue. Rounding the corners of the shoulder region has the same advantages as discussed above for the tongue.

[0042] Furthermore, forming 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 rest of the web, and therefore the end of the slot deep in the flange can also be thinner. Leaving more wood in the flange increases the ability of the flange (and therefore the structural member as a whole) to better resist load forces.

[0043] The present invention will now be described more fully by way of non-limiting examples with reference to the accompanying drawings.

[0044] Turning first to FIG. 1 , a composite structural member (10) is shown in an end view revealing an I-beam-like configuration. The composite structural member (10) includes a first timber flange (15), a second timber flange (20), and a web (25). Each of the flanges (15, 20) has a flattened area (30, 35) to allow the member (10) to be mounted on other planar building structures, or to allow other such structures to be mounted on the member (10).

[0045] Now consider Figure 1B, showing more details of the web (25) inserted into the upper flange (15). A slot (40) is formed in the first flange (15) and has a first relatively wide portion (40a) communicating with the exterior and a narrower portion (40b) at the blind end. In terms of manufacturing, a tool may be used to dig a narrow slot at full depth, and then a different tool may be used to dig a wider portion at a shallower depth to form Figure 1B The two-part tank shown in FIG.

[0046] The end region of the web (25) has a shape and size that generally follows the shape and size of the groove (40), provided that a relatively thick shoulder portion (45) and a relatively thin tongue portion (50) are provided. The shoulder portion (45) includes a pair of opposing rounded shoulders (one labeled 55). The tongue portion (50) includes a pair of opposing rounded shoulders (one labeled 60) and a planar end face (65).

[0047] The groove (40) conforms very closely to the shape of the web portions (45, 50), but is slightly oversized to allow adhesive to remain in the groove (40) after the web portions (45, 50) are inserted. In embodiments where only friction engagement is relied upon, it would not be necessary to oversize the groove (40).

[0048] As discussed above, the use of rounded corners (55, 60) better distributes the load forces throughout the flanges (15, 20), thereby avoiding problems such as splitting, cracking, and web shifting.

[0049] Reference now Figure 2 and Figure 3 , which show a side view and a plan view, respectively, of a composite structural member (10). The structural member (10) will generally be very slender so as to be useful for spanning supports in building construction.

[0050] The diameters 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 carrying requirements.

[0051] The flanges (15) and (20) are made of timber rods. In one embodiment, one or more of the round log flanges have a diameter 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) have a diameter less than about 60 mm.

[0052] In some embodiments, the flange is a "log core". As will be appreciated by the skilled artisan, log core is a byproduct of the process of removing the outer layers of wood used for plywood manufacturing (usually through a milling process) to the point where substantially all of the softwood has been removed, leaving behind a core of heartwood that is typically dense and inflexible. The milling process strips away the bark, cambium, sapwood, and even some heartwood to make a veneer panel. This leaves no sapwood on the column.

[0053] The heartwood core of a log core does not absorb pressure treatment and preservatives as well as cork, resulting in inferior columns typically being less durable than columns with treated cork on the exterior.

[0054] Applicants have discovered an economically and technically viable use of log cores, as the cores can be used in structural members such as disclosed herein. Using multiple log cores (even log cores having a diameter of at least about 70, 60, 50 or 40 mm) can produce members that are useful and cost-effective in construction.

[0055] Log cores are essentially a waste product of the forestry industry and have little value in the marketplace. In one embodiment, the present invention is directed to a structural member wherein all of the log flanges are log cores.

[0056] The log flanges may be so-called "true log sections" or "true logs". Logs are described in Chapter 6 of Australian Standard 1720 and are typically produced from softwood trees grown commercially as renewable plantation timber. These timbers are typically fast growing, easy to harvest and have a low rate of natural defects.

[0057] Wood of various species is suitable for forming true logs, particularly those types of species that tend to have a relatively constant diameter over a significant portion of their length to minimize waste during the trimming and rounding process. Plantation pine materials such as slash pine or Caribbean pine hybrids tend to form suitable true logs. Other materials that may be considered include Douglas fir and various eucalyptus species.

[0058] True logs are particularly strong because the natural strength of the wood fibers is not destroyed by sawing or other treatments. The integrity of the log is maintained, and the trimming process required to round the log does not have a great impact on the overall strength of the log. The natural characteristics of wood are that the central core or heartwood of the log is relatively soft and has low structural strength. On the other hand, the periphery of the wood is much harder and the wood fibers are able to withstand high tensile loads. In addition, this hard outer layer is more resistant to water absorption and insect attack, and therefore by keeping the outer circumference of the wood largely intact during the process of preparing true logs, the structural integrity of the wood is maintained.

[0059] Logs in some forms of the invention do not strictly comply with Australian Standard 1720 and may be of a smaller diameter so as not to meet that standard.

[0060] Where a first flange and a second flange are used, the flanges may have different cross-sectional areas, or the cross-sectional areas may be similar or the same.

[0061] In a preferred form of the invention, the web (25) is formed from plywood or plywood-like material as is known in the art, and the bonding material is selected to provide a high strength wood-to-wood bond between the web (25) and the wood from which the flanges (15) and (20) are made. If desired, the composite member may be treated after assembly (such as by heat treatment) to ensure a high strength web-to-flange bond.

[0062] Typically, a resin-based waterproof structural adhesive will be used to bond the web (25) to the flanges (15, 20).

[0063] As previously mentioned, the web material may be formed of any suitable material, and the strength and thickness of the web will depend on the overall strength requirements of the joists, the diameter of the logs, and similar considerations. Obviously, if a high strength web is desired, a thicker plywood material, for example, may be used. Other web materials may include steel or other metal plates or sheets, fiber cement or similar materials, or other high strength planar materials such as wood chip plywood, particle board, oriented strand board, and plastic type materials.

[0064] The structural members of the present invention may be used in many structural environments and may be used as floor supports, floor joists, lintels, heavy columns, roof framing members, roof rafters, roof suspension / support beams, portal framing members, columns, bottom chords, beams / columns, or bridge piers.

[0065] For some applications, it may be necessary to terminate the structural member of the present invention, and in this case, a dovetail connection may be used. Additionally or alternatively, the ends of the flanges may be scalloped and the webs may be terminated appropriately to facilitate end joining.

[0066] Those skilled in the art will appreciate that the invention described herein is susceptible to further variations and modifications besides those specifically described. It is understood that the invention includes all such variations and modifications that fall within the spirit and scope of the invention.

[0067] Thus, the spirit and scope of the present invention should not be limited by the foregoing examples, but is to be construed in the broadest sense permitted by law.

Claims

1. A composite wood structural member, comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein, and a web having a first long edge region and an opposite second long edge region, the first long edge region and the second long edge region being disposed in the first longitudinal groove and the second longitudinal groove, respectively, wherein the first long edge region and / or the second long edge region comprises a shoulder portion, a tongue portion extends from the shoulder portion, the tongue portion having a thickness less than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together presenting only planar and curved outer surfaces to the inner surfaces of their corresponding grooves, and each groove is shaped and sized to accommodate the long edge region disposed therein.

2. A composite wood structural member, comprising: a first timber flange having a first longitudinal groove formed therein; a second timber flange substantially parallel to the first timber flange and having a second longitudinal groove formed therein, and a web having a first long edge region and an opposite second long edge region, the first long edge region and the second long edge region being disposed in the first longitudinal groove and the second longitudinal groove, respectively, Wherein, the first long edge region and / or the second long edge region includes a shoulder portion, a tongue portion extends from the shoulder portion, the tongue portion has a thickness that is smaller than the thickness of the shoulder portion from which the tongue portion extends, the shoulder portion and the tongue portion together do not have any sharp corners pointing outward, and each groove is shaped and sized to accommodate the long edge region arranged therein.

3. The composite structural member according to claim 1 or claim 2, wherein: The long edge region of the web is the region disposed within the groove.

4. The composite structural member according to any one of claims 1 to 3, wherein: The tongue region has a planar end face.

5. The composite structural member according to any one of claims 1 to 4, wherein: The tongue region has opposing lateral planar faces.

6. The composite structural member according to any one of claims 1 to 5, wherein: The tongue region has a substantially uniform thickness.

7. The composite structural member according to any one of claims 1 to 6, wherein: The tongue region is at least about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% of the thickness of the shoulder region from which it or they extend.

8. The composite structural member according to any one of claims 1 to 7, wherein: When viewed end-on, the web has an axis of symmetry.

9. The composite structural member according to any one of claims 1 to 8, wherein: The web extends to a depth of between about 20% and about 80% of the diameter of the flange in which the web is disposed.

10. The composite structural member according to any one of claims 1 to 9, wherein: The web extends the full length of the flange or extends beyond the length of the flange, or the web is shorter than the length of the flange.

11. The composite structural member according to any one of claims 1 to 10, wherein: The web is formed from a relatively high strength planar material.

12. The composite structural member according to any one of claims 1 to 11, wherein: The web is formed from a material selected from the group consisting of: wood, processed wood; wood chip laminate, plywood, oriented strand board, metal sheet, metal plate, fiber reinforced cement sheet, plastic and fiber reinforced plastic material.

13. The composite structural member according to any one of claims 1 to 12, wherein: The first flange and / or the second flange may have a substantially circular cross-section.

14. The composite structural member according to any one of claims 1 to 13, wherein: The first flange and / or the second flange is a timber bar or log.

15. The composite structural member according to any one of claims 1 to 14, wherein: The first flange and / or the second flange is a log core.

16. The composite timber structural member according to any one of claims 1 to 15, wherein: The first flange and / or the second flange has a planar surface facing away from the planar web and at about 90 degrees to the flange groove.

17. The composite timber structural member according to any one of claims 1 to 16, wherein: The first groove and / or the second groove are oversized in order to accommodate their respective long edge regions by the adhesive layer.

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