AU2011205080B2 - Transfer of racking forces through a truss in a wall panel - Google Patents

Abstract

S\NRI- C'M i IXC A truss flor transferring racking loads in the plane of a wall, the truss comprising a pair of spaced apart upright chords and an arrangement of webs which interconnects the chords, 5 wherein, in at least one of upper and lower end sections of the truss, an end web extends between ends of the chords to interconnect them and a respective web in a pair of diagonal webs extends between each chord and the end web to interconnect the chord and end web. whereby corners of space are defined within the end section at opposite lateral sides thereof' by the end web and chords, the corners being accessible such that tie-down 10 connections can be formed at them.

Description

A U S T RALIA Patents Act 1990 2011205080 29 Jul 2011

COMPLETE SPECIFICATION

Name of Applicant: Illinois Tool Works Inc. Actual Inventors: Bernard Joseph KENNELLY Afzal LAP IIIR Address for Service: DAVIES COLL1SON CAVE, Patent Attorneys, 1 Nicholson Street, Melbourne, Victoria 3000. Invention Title: " Transfer of racking forces through a truss in a wall pane” FOR A STANDARD PATENT (ORIGINAL)

Details of Associated Provisional Application No.: 2010904460 filed 5 October. 2010

The following statement is a full description of this invention, including the best method of performing it known to us: Γ \NRI*«MtblM)Cr\KI.I.W/K II‘M | DO(* - ?.W7/1 1 C \NKf\>fibHDCOKI.I.\’7K.{r

I UOC 2011205080 29 Jul 2011 - 1 -

TRANSKKR OF RACKING FORCKS THROUGH Λ TRUSS IN Λ WAIT. PLANK

The present invention relates to improvements in the transfer ol'raeking loads through wall structures. The invention has particular, though not exclusive, application to narrow 5 bracing panels, and especially, though not exclusively, limber trusses.

Commonly, construction of orthogonal, or planar structures like domestic timber framed construction requires a lateral bracing system to ensure stability under the loads to which the structure is likely to be exposed. The forces resisted by the bracing system are caused 10 by a combination of dead, live and wind loads that can be applied in various combinations in various directions. 1'he bracing system is distributed throughout the structure and properly connected to transfer the applied loads through the structure to the foundations. 15

The most cHkient/cost effective bracing systems transfer the loads in shear through the various planar surfaces.

Rach of the planar surfaces forming the bracing system has shear resistance built in by 20 means of either diagonal bracing (commonly metal strap or angle) or some form of sheathing (commonly plywood or hardboard) so that the shear resistance is achieved by diaphragm action. These components are commonly known as bracing units.

The bracing units arc designed for different load capacities, which vary depending on the 25 loads applied to the structure and the number of bracing panels sharing the load.

To form an integral system, all bracing units have to be connected together where required to transfer the loads through to the foundation. These connections have also to be conservatively designed to transfer the loads properly. 30

Common examples of lateral bracing systems are detailed in the Australian Standard for timber framed construction. AS 1684 - 2010. 1' .NKl’nnhl iH'CvKI.i.1' 'Κ«ι·Π Η 2011205080 29 Μ 2011 -2-

For both the bracing panels and the connections, increased capacity is reflected by increased cost. 5 The examples provided in AS 1684-2010 are used in most instances because their details are well understood by the building industry, they make very economical use of materials for their given capacity, they are simple to install on site by commonly used methods, i.e. nails, screws etc., so that comparatively less skill is required on site, they are quick to install, because of their known methods of connection, requiring comparatively less labour 10 on site, and they are easy to inspect for compliance.

The bracing panels have to be distributed throughout the structure, in terms of both position and orientation, to transfer effectively the loads applied to it. Λ particular length of wall will thus have to transfer a given (or known) amount of racking force. 15

In past years, most domestic and similar structures would have sufficient unbroken wall length for the bracing recommendations within AS 1684 to be applicable adequately in most, if not all, instances in a given building, the racking resistance required per metre of wall thus being relatively low since numerous bracing units would be able to be included 20 within a given wall. However, the continued market trend is to have more openings and larger openings in more walls within the structures, e.g. for doors, windows, larger connected living areas and adjoining alfresco areas. As bracing panels are precluded from running across the openings, the amount of unbroken wall panel where bracing panels can be located is restricted. Coupled with this, there is also a popular acceptance of large open 25 living areas, which, in turn, results in fewer internal walls to share bracing loads, thus increasing the demand on external walls. In the case of two storeyed structures, the demand is even greater as all of the loads at the upper level need to be transferred through the lower level walls into the foundations. 30 These high demands cannot be met by narrow sheet bracing units due to their low capacities, in some instances leaving engineers with no option but to specify steel portal

H:\sbt\Interwoven\NRPortbl\DCOSBT\ 13034588_1 .DOC 2011205080 06 Feb 2017 -3- frames or the steel version of a wall truss brace (PT Brace) in timber framed structures. Most, if not all, builders are reluctant to use steel components in timber frame structures, which, among other things, are expensive, hence the need for improvements in the racking load transfer capacities in timber wall truss brace applications. 5

As bracing panels become narrower, the shear strength of the panel becomes less critical, and the resistance to racking deflection or “sway” (by flexural movement) and deflection caused by minute movement in the connection to the foundation becomes more critical, such deflection being exaggerated in the case of narrow (short-length) panels. 10

Becoming increasingly common are instances of bracing capacity requirements, as a result of the widths of unbroken wall spaces being much less, far exceeding the recommendations of AS 1684. 15 To be effective, individual narrow wall bracing panels need to be rigid within themselves and to have good shear and moment fixity at their bases (i.e. connection to the foundation).

According to a first aspect of the present invention, there is provided A truss for transferring racking loads in the plane of a wall, the truss comprising a pair of spaced apart 20 upright chords and an arrangement of webs which interconnects the chords, wherein, in at least one of upper and lower end sections of the truss, an end web extends between ends of the chords to interconnect them and a respective web in a pair of diagonal webs extends between each chord and the end web to interconnect the chord and end web, whereby comers of space are defined within the end section at opposite lateral sides thereof by the 25 end web and chords, tie-down connections to the truss being formed at said comers, close to laterally outer extremities of the truss, and wherein, in the or each end section within which are defined comers at which tie-down connections are formed, a transverse web extends from a junction of one diagonal web and the chord to which said one diagonal web is connected to a junction of the other diagonal web and the chord to which said other 30 diagonal web is connected, to interconnect the chords.

In one embodiment of the invention, a said end web and a said pair of diagonal webs are

H:\sbt\Interwoven\NRPortbl\DCC\SBT\1298460l _l DOC 2011205080 01 Feb 2017 -4- provided in only one of the end sections of the truss, whereby only two said comers are defined. In that embodiment, the one end section may be the lower end section. In another embodiment of the invention, a said end web and a said pair of said diagonal webs is provided in each of the upper and lower end sections, whereby four said comers are 5 defined. In the latter embodiment the tmss may, with fixity established by said connections at both end sections, provide a portal action.

Preferably, the transverse web and end web in the or each end section are parallel. Preferably, the end web(s) extend horizontally. 10

Preferably, the diagonal webs in the or each pair converge to connect to the end web at a common node. The pair(s) may thus (each) form V-shaped brace. Preferably, the or each common node is located at a central position along the end member between the (respective) connections. Alternatively, it is conceivable, particularly in the case of a 15 relatively wide truss, that each diagonal web in the pair may connect to a respective node, to which a web other than the other web in the pair also connects.

Preferably, in the or each pair of diagonal webs, the webs connect to the chords at the same level. 20

Preferably, in the or each end section in which said corners are defined, the end web is perpendicular to the chords.

Preferably, in the or each end section in which said corners are defined, an axis along 25 which each diagonal web extends forms an included angle with an axis along which the end member extends which is between about 30° and about 60°.

In a preferred embodiment of the invention, a hole is formed through the end web, adjacent each said comer, through which a tie-down rod extends such that an end thereof protrudes 30 into the comer and receives a fastening element for effecting the tie-down connection.

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Preferably, the truss is a timber truss, comprising timber chords and webs. Preferably the webs and chord are formed from standard sections of timber, such sections typically being rectangular in cross section. Typical cross sectional dimensions may comprise 35mm x 90mm, 45mm x 90mm and, less commonly, 90 mm x 90 mm. 5

Preferably, the truss comprises webs and chords which are interconnected by nail plates.

Preferably, the truss has a height of between about 2.4 m and about 3.6 m and a width of between about 0.35 m and about 1.2 m. More preferably, the truss has a height of between 10 about 2.7 m and about 3.0 m and a width of between about 0.45 m and about 0.9 m. More preferably, width of the truss does not exceeding about 0.9 m.

Preferably, the width of the truss is between about one seventh and about one third of the height of the truss. 15

According to a second aspect of the present invention, there is provided a bracing panel comprising a truss in accordance with said first aspect.

Also disclosed herein is a truss for transferring racking loads in the plane of a wall, the 20 truss including at least one comer which is formed by interconnected ends of an upright chord of the truss and an end web of the truss, the interconnected ends defining a cavity into which an end of a tie-down rod extending through the end of the end member can be received, the cavity being accessible to permit attachment of a fastening element to the rod end to effect a tie-down connection at the comer. Preferably, an end face of the chord is in 25 abutting engagement with the end web at the comer such that compressive loads in an upright direction are transferrable through the corner. Preferably, the upright chord comprises first and second chord members arranged in side-by-side relation, the end face is defined by the first chord member, and an end of the second chord member is spaced from the end web whereby the cavity is defined between that end and the end web. Preferably, 30 the second chord member is laterally outward of the first chord member. Preferably, the or each end face directly abuts the end web. Preferably, the end face is orthogonal to a

H:\sbt\Interwoven\NRPortbl\DCC\SBT\12984601_l .DOC 2011205080 01 Feb 2017 -6- longitudinal axis of the chord. Preferably, a hole is formed through the end member at the comer to receive the rod. Preferably, the cavity opens laterally outwardly. Preferably, the upright chord and end web are formed from timber. Preferably, the upright chord and web are interconnected by at least one nail plate secured between a front face or rear face of the 5 end web and a front face or rear face, respectively, of the chord. Preferably, the upright chord and web are connected by a pair of nail plates secured between the front faces and the rear faces. Preferably, the nail plates bound the cavity at front and rear positions thereof. Preferably, the truss comprises a plurality of said comers. In one embodiment of the invention, the tmss comprises two said comers, each of which is at a bottom end of the 10 tmss. In another embodiment of the invention, the tmss comprises four said comers, two of which are at a bottom end of the tmss and the other two of which are at a top end of the tmss. Also disclosed herein is a wall structure including said tmss to which the or each tiedown connection has been effected. 15 Preferably, an opening is formed on at least one lateral side of the tmss. An opening is formed on each lateral side of the truss. The opening may be formed through the wall structure or to the/each side thereof.

Also disclosed herein is a bracket for forming a tie-down connection between a tmss for 20 transferring racking loads in the plane of a wall and a structure above or below the wall, the bracket comprising a flat base member which can be secured against a laterally outer face of an upright chord of the tmss adjacent an upper end or lower end, respectively, of the tmss and a rod which extends from the base member such that, when the base member is so secured, the rod projects, in general alignment with the chord, beyond the end for 25 fixing to the structure.

Preferably, the base member is configured in the form of a strip.

Preferably, the base member comprises a plate. 30

Preferably, the base member is configured with holes therethrough for receiving fastening

H:\sbt\Interwoven\NRPortbl\DCC\SBT\12984601_l .DOC 2011205080 01 Feb 2017 -7- elements to secure the base member to the chord.

In a preferred embodiment of the invention, the rod is formed separately from the base and attached thereto. Preferably, the rod is attached to an outer face of the base member. 5

Preferably, the rod is welded to the base member.

Preferably, the rod is configured with exterior formations to be able to be fixedly set into a foundation. 10

Preferably, the rod is formed with a thread so as to be able to receive a threaded fastening element to fix it to the structure. Preferably, the thread defines said formations.

Also disclosed herein is a wall structure including: 15 a truss for transferring racking loads in the plane of the wall structure; and at least one bracket as defined above wherein the base member is secured against an upright face of an upright chord of the truss adjacent an upper or lower end thereof and the rod projects beyond the end and is fixed to a structure above or below, respectively, the truss to form a tie-down connection. 20

Preferably, an opening is formed on at least one lateral side of the truss including the bracket(s). An opening may be formed on each lateral side of that truss. The opening may be formed through the wall structure or to the/each side thereof. 25 Preferably, the face is a laterally outer face.

Preferably, the wall structure including the bracket(s) includes a plurality of said brackets. Preferably, the wall structure includes said brackets secured adjacent lower ends of laterally spaced apart upright chords of the truss to form said connections to a structure

H:\sbt\lnterwoven\NRPortbl\DCC\SBT\12984601_l .DOC 2011205080 01 Feb 2017 -8- below the truss at opposite lateral sides of the truss. The structure may comprise, for example, a foundation on which the truss is supported. Alternatively or additionally, the wall structure may include said brackets secured adjacent upper ends of the upright chords of the truss to form said connections to a structure above the truss at opposite lateral sides 5 of the truss. The structure above the truss may comprise a roof structure. In the case where the wall structure comprises said brackets adjacent both lower and upper ends of the truss, the truss can have portal action in the wall structure.

The present invention will now be described, by way of non-limiting example only, with 10 reference to the accompanying drawings, in which:

Figures 1A to 1C are schematic front elevation views showing trusses of varying width in accordance with a preferred embodiment of the invention;

Figure 2 shows detail A in Figure 1A; 15 Figure 3 A is a schematic front elevation view showing part of an alternative truss;

Figure 3B is a view of Section X-X in Figure 3A;

Figures 4A and 4B are schematic front and side elevation views of a bracket which ties down a “wall truss” or bracing truss; and

Figure 5 is an elevation view of a trussed portal frame incorporating such brackets. 20

The disclosure herein applies to trusses for transferring racking loads in the plane of a wall, and involves arrangement of tie-down connections close to laterally outer extremities of trusses, at upper and/or lower ends thereof, whereby the lateral spacing between each of those connections and the lateral side of the truss at the same end and opposite to that at 25 which the connection is located is increased, whereby so too is racking load transfer capacity.

Three variants of a truss 1 according to a preferred embodiment of the present invention 30 are illustrated in Figures 1A to 1C and are of similar construction, the trusses 1 having widths W of 750 mm, 600 mm and 450 mm respectively. 2011205080 01 Feb 2017

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Each truss 1 comprises a peripheral frame 11 defined by first 3 and second 5 upright chords and top 7 and bottom 9 web members which extend between upper ends and lower ends respectively of the chords 3,5. Each truss further comprises an interior web structure 5 13 arranged within and fixed to the peripheral frame 11.

In the present embodiment, the chords 3,5 are each formed from two lengths 3A,3B, 5A,5B of timber each having a rectangular cross-section of 90 x 35mm, which are laminated in a plane parallel to the direction in which their longer cross sectional 10 dimension extends, to form a "double laminate", though in other embodiments either or each chord may, for example, comprise only a single length of timber or more than two laminated lengths of timber. The bottom horizontal web 9, in this embodiment, comprises a pair of side-by-side rectangular cross section 90 x 45 mm lengths of timber arranged on edge (i.e. so that their longer cross sectional dimensions extend parallel to a vertical plane), 15 forming a double laminate. The top horizontal web 7, in this embodiment, comprises a single rectangular cross section 35 x 90mm arranged on flat (i.e. so that its longer cross - 10- 2011205080 29 Μ 2011 sectional dimension extends perpendicular to the vertical plane). The orientation of the plane oflamination of each laminate member in the truss 1 is not limited to that shown in the illustrations. It may be different for each member and is usually determined by strength, standard material size constraints and wall thickness requirements. 5

The web structure 13 includes a plurality of diagonal 15 and horizontal 17 web members, each of which extends between and is fixed to the chords 3. 5. l'iach web member 15/17. in this embodiment, comprises a single length of 90 x 35mm section timber arranged on Hal. The truss 1 includes nail plates 30 which secure the webs 7, 9 to the chords 3. 5. the webs 10 in the web structure 13 both to other webs in that structure and to the peripheral frame 11. and the individual timber lengths to each other in each chord. Hach truss 1 further comprises nail plates 30 on its rear side (not shown). Those nail plates have the same configuration and layout as the nail plates 30 on the front side of the respective truss 1. 15 Hach truss 1 is dimensioned to extend between a bottom plate 40 and top plate 42 in a wall frame structure. In some instances, either or each end horizontal web may form the respective wall frame top/bottom plate.

In the arrangement shown in each of Figures 1A to 1C, to each side of the truss 1 is an 20 opening through the wall (of which the truss 1 forms a part) defining a space 44. where racking loads within the wall cannot be transferred between the roof structure and foundation. Part of either space may nevertheless be occupied by a structural component, for example a lintel. By way of exemplification, in the arrangement shown in Figure I A. the laterally outer member 5Λ in the chord 5 is shorter than the laterally inner member in 25 that chord, such that a rebate is defined at the upper end of the chord 5 to receive the end of a lintel 46, whereby a prop stud is defined which supports that end. Also by way of exemplification, the laterally outer member 3A and 3B in each of chords 3 and 5 in the arrangement depicted in Figure IB is configured as a prop stud supporting a respective lintel 46, whereas the chords 3, 5 in the arrangement shown in Figure 1C arc configured as 30 full length studs, in which each member 3A,3B, 5A,5B extends to the top plate 42, with no lintel being supported by either chord. .KKl’miMUirrwCU.vnxlIl·»; I IXir 2011205080 29 Jul2011 -11-

Lach truss 1 is secured against the bottom plate 40 by tie-down rods which are set into the foundation and extend through the bottom plate 40 and web 9. A nut .37 is screwed onto a threaded upper end of each rod 35 and bears down against a respective 50 x 50 mm washer 5 plate 39 received against upper face of web 9.

In each of the arrangements depicted in Figures 1A to 1C, the web structure 13 includes a downwardly convergent or V-shaped pair of first and second diagonal webs 23 and 25. Diagonal web 23 extends from the junction between first chord 23 and a first end of 10 lowermost horizontal chord 17 to a central position along web 9. Likewise, diagonal web 25 extends from the junction between second chord 5 and a second end oflowermost horizontal web 17 to the central position. Hach of webs 23.25 comprises a single length of 90 x 35 timber on flat, though in other embodiments may, depending on requirements, comprise two or more laminated components. A nail plate 30 secures lower ends of the 15 diagonal webs 23,25 to web 9. Another nail plate 30 secures the upper end of web 23 to the first end oflowermost horizontal web 17, and both these ends to the first chord 3. A further nail plate 30 secures the upper end of web 25 to the second end of lowermost horizontal web 17, and both these ends to the second chord 5, and additionally secures the lower end of the diagonal web immediately above lowermost horizontal web 17 to the 20 second end of that web and to the second chord 5.

Advantageously, owing to the provision of the downwardly convergent pair of webs 23,25. there is no obstruction at cither of the lower corners of the space contained within the peripheral frame 11. so that each washer plate 39 can touch the laterally inner face of the 25 respective chord 3/5, whereby there is established, at the lower end of the truss/bracing panel, a relatively large lateral spacing between each tie-down rod and the laterally outer extremity of the truss/bracing panel abutting the bottom plate 40 at the lateral side opposite to that at which the rod is located, that spacing defining the moment arm of the racking load in a respective one of the two, i.e. left-to-right/clockwisc and 30 right-to-lcft/anticlockwise, directions. Accordingly, the racking load capacity of the connections is relatively high in both directions, unlike in the case of a conventional truss.

H:\sbt\Interwoven\NRPortbl\DCC\SBT\12984601_l .DOC 2011205080 01 Feb 2017 - 12- in which a diagonal web member would ordinarily obstruct one of the comers.

Advantageously, the V-shaped profile defined by webs 23,25 helps conceal tie-down connectors within the wall brace, addressing a problem which has been known in the art. 5

At each of the lower comers of the tmss 1, the nail plates have a width which is substantially the same as that of the respective chord 3/5 and is positioned such that its laterally outermost upright edge is adjacent the laterally outermost face of the respective chord, whereby the laterally inner upright edge of each of those nail plates 30 is spaced 10 sufficiently far from the rod 35 so as not to hinder fitting of the washer plates 39 and nuts 37. A lower corner of an alternative tmss 1' is shown in Figures 3A to 3B. In the description of this tmss, the same reference numerals will, where possible/appropriate, be used, as 15 have been used in respect of the tmss 1, to refer to corresponding features.

The tmss Γ may be substantially identical to tmss 1 depicted in any of Figures 1A to 1C, except that each of the lower ends of the chords 3, 5 (only one of which is shown) is formed with a rebate 6 which opens laterally outwardly, and also frontwards and 20 rearwards, the rebate 6 being formed as the result of the laterally outer timber member 3A,5A in each of the chords 3 and 5 stopping short of the top face of the bottom web 9. The rebate 6 is thus a region of space bounded at upper and lower ends by the face of the lower end of the laterally outermost chord member 3A,5A and the upper face of the web 9 (defined by the upper faces of individual members 9A,9B) respectively, and at a laterally 25 inner side by the laterally outer face of the laterally inner timber member 3B,5B.

The upper end of tie rod 35 and nut 37 are received into the respective rebate 6, instead of being received into the space defined within the peripheral frame 11. Each of chords 3,5 is slightly offset such that its laterally outer face is spaced slightly (approximately 6mm) 30 laterally inward of the respective end face of web 9, such that the distance between the end

H:\sbt\lnterwoven\NRPortbl\DCC\SBT\1298460l _l DOC 2011205080 01 Feb 2017 - 13- face and the laterally outer face of the inner member 3B is the same as the width of the washer plate 39, whereby the washer plate 39 does not overhang the end of web 9. It will be appreciated that, whilst each end of member 9 thus protrudes slightly beyond the plane in which the laterally outer face of the respective chord 3/5 lies, the width of the bracing 5 unit is maximised within the available space (which is determined or set by architectural requirements). The framework around windows and doors that are fitted into the resultant openings between the bracing panels usually include a 10-20mm gap between their extremities and the envelope of the opening, so as to accommodate building tolerances, i.e. straight, plumb and square. The small protrusion of the bottom horizontal web is not likely 10 to reduce significantly the fitting adjustment process (e.g. of a window or door frame) on site compared to the more conventional fixing method of fixing by use of an angle bracket.

Owing to the provision of rebates 6, each connection to the foundation 50, via a respective rod 35, can be moved significantly closer to a respective end of web 9, and therefore 15 further from the opposite end of web 9, increasing the moment arm length at the base of the truss Γ and thus the capacity of the connections to transfer racking loads into the foundation 50, whilst continuity between the web 9 and chords 3,5 (via abutment between the lower end of each inner chord member and web member 9) is, advantageously, preserved. 20

The web structure 13 inside the peripheral frame 11 may vary. In particular, because the upper end of rod 35, nut 37 and washer plate 39 are, at each lower corner of the truss Γ, laterally outward of the lower comers of the space within the peripheral frame 11, it would not matter if the lowermost part of the web structure 13 were to comprise, instead of the V-25 shaped pair of webs 23, 25, a single diagonal web, similar to any of webs 15, extending from one chord to the other, a lower end of which would occupy one of the lower corners of the space, consistent with the web structure of a conventional truss.

Shown in Figures 4A and 4B is a bracket 60 for tying down a truss T for transferring 30 racking forces in a wall. The truss T may be any of the trusses 1 shown in Figures 1A to 1C, or may be simply a conventional truss, in which the lowermost part of the internal

H:\sbt\Interwoven\NRPortbl\DCC\SBT\12984601_l .DOC 2011205080 01 Feb 2017 - 14- web structure 13 comprises a diagonal web member 15. The bracket 60 comprises a flat steel plate, which in this example has a thickness of 3mm, the plate defining a cleat 62, which is formed with a plurality of holes 64 therethrough, which receive fasteners, typically screws 66, for securing the cleat 62 against the laterally outer face F of truss 5 chord C. The bracket 60 further comprises a tie-down rod 68, which in this example comprises M12 (Grade 5.8 carbon steel) tie-down anchor, an upper portion of which is received against an outer face of a lower portion of the plate 62 and welded thereto via continuous fillet welds 69 to both sides of the line of contact between the rod upper portion and cleat lower portion, the welds 69 each extending substantially the entire length of the 10 rod upper portion.

Advantageously, the bracket substantially removes load eccentricities common to typical tie-down configurations, and is configured such that anchorage is effected as close as possible to the laterally outside face of the wall brace. 15

The bracket 60 effects connection between at least one, and preferably each, lower corner of the truss T and the foundation, which lies laterally outward of the peripheral frame P, thus, advantageously, increasing the moment arm and therefore the racking force transfer capacity, though lies only slightly proud of the face F so as to have negligible or no impact 20 on the space 44 adjacent the truss T, bearing in mind that the bracket 60 and screw heads can be concealed by the framing of the opening, typically a window or door frame.

The rod 68 is set into the foundation 50 by conventional means, such as by way of epoxy cement, grout or glue. 25

Within the scope of the invention, fixity can be established between not only the truss base and the foundation but also, alternatively or additionally, the top of the truss and a structure supported upon it. Where such fixity is established at both the bottom and top ends of the truss, the truss functions as a portal frame, rather than in a cantilever fashion as is the case 30 in the arrangements shown in Figures 1A to 1C, as described as follows.

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An example is shown in Figure 5, which depicts an arrangement in which brackets, exemplarily, are exploited to establish fixity at both the top and bottom of each of two trusses T which support a beam B above space 44. In the structure shown, a respective bracket 60 fixes the laterally inner side of each truss T to the foundation 50 at the truss 5 lower end. Moreover, a respective bracket 60 fixes the laterally inner side of each truss T to the beam B at an upper end of the truss T. In the illustrated arrangement, configurational constraints preclude brackets 60 from being utilised at the truss laterally outer corners, though in other arrangements, such use may be possible, whereby racking load transfer capacity is, for each truss, increased in not one but both, rotational directions. 10 In a further example, any of the trusses illustrated in Figures 1A to 1C could be modified such that the web structure 13 incorporates at its upper end a V-shaped web configuration which is substantially the same as that at its lower end and inverted, whereby upper comers of the space within the peripheral frame 11 are "freed up", in the same way as the lower comers of that space, to permit top web 7 to be fixed to the structure it supports, in exactly 15 the same manner as the bottom web 9 is fixed to the underlying bottom plate 40 and foundation 50. In yet a further example, the top comers of the truss 1' may be configured in exactly the same manner as the bottom comers (i.e. with rebates 6) whereby the top web 7 can be fixed to the structure it supports, in exactly the same manner as the bottom web 9 is fixed to the underlying foundation 50. 20

The arrangements disclosed herein offer a number of advantages, including a comparatively high racking load transfer capacity, which is provided by way of prefabricated components. The preferred embodiments are simple in construction and in the manner in which they form tie-down connections, and thus can reduce fabrication and 25 installation expense.

The arrangements disclosed herein serve to increase the moment arm of racking load transfer within a truss, whereby the inherent strength of a given tie-down connection need not be as great. The arrangements also provide for reduction in magnitude of movement of 30 a given tie-down connection, and in eccentricity between a chord and tie-down connection adjacent the chord. 2011205080 01 Feb 2017

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Moreover, the arrangements are particularly suitable for timber wall frames/trusses, for which there is commonly a preference, particularly among carpenters, over steel wall frames/trusses. 5

The arrangements can also be readily incorporated into a wall structure in which not all of an opening does not occupy the full height of the wall frame, whereby the wall space that remains over the opening can be occupied by a structural component, such as a lintel. Specifically, a narrow bracing panel to which tie-down connections have been effected in 10 accordance with the examples disclosed herein, on either or each of the sides of the opening, can resist racking forces by portal action. Given good shear and moment fixity at the connections, these configurations are more efficient and cost effective than individual narrow bracing units. 15 Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will 20 be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or 25 admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims (20)

1. The claims defining the invention are as follows:

   1. A truss for transferring racking loads in the plane of a wall, the truss comprising a pair of spaced apart upright chords and an arrangement of webs which interconnects the chords, wherein, in at least one of upper and lower end sections of the truss, an end web extends between ends of the chords to interconnect them and a respective web in a pair of diagonal webs extends between each chord and the end web to interconnect the chord and end web, whereby corners of space are defined within the end section at opposite lateral sides thereof by the end web and chords, tie-down connections to the truss being formed at said corners, close to laterally outer extremities of the truss, and wherein, in the or each end section within which are defined comers at which tie-down connections are formed, a transverse web extends from a junction of one diagonal web and the chord to which said one diagonal web is connected to a junction of the other diagonal web and the chord to which said other diagonal web is connected, to interconnect the chords.
2. 2. A truss according to claim 1, wherein it is the upper end section within which are defined corners at which said tie-down connections are formed.
3. 3. A truss according to claim 1, wherein it is the lower end section within which are defined corners at which said tie-down connections are formed.
4. 4. A truss according to claim 1, wherein it is both the upper end section and lower end section within which are defined comers at which said tie-down connections are formed.
5. 5. A tmss according to claim 3 or 4, wherein a hole is formed through the end web of the lower end section, adjacent each corner of space within that end section, through which a respective tie-down rod extends such that an end thereof protrudes into the comer and receives a fastening element effecting the tie-down connection.
6. 6. A tmss according to any one of the preceding claims, wherein the chords and webs are timber.
7. 7. A truss according to any one of the preceding claims, wherein said corners of space were, when the tie-down connections were effected, accessible such that the tie-down connections could be formed.
8. 8. A truss according to any one of the preceding claims, whereinthe transverse web and end web in the or each end section are parallel.
9. 9. A truss according to any one of the preceding claims, wherein the end web(s) extend horizontally.
10. 10. A truss according to any one of the preceding claims, wherein the diagonal webs in the or each pair converge to connect to the end web at a common node.
11. 11. A truss according to claim 10, wherein, the or each pair forms a V-shaped brace.
12. 12. A truss according to claim 10 or 11, wherein the or each common node is located at a central position along the end member between the (respective) connections.
13. 13. A truss according to any one of the preceding claims, wherein, in the or each pair of diagonal webs, the webs connect to the chords at the same level.
14. 14. A truss according to any one of the preceding claims, wherein, in the or each end section in which said corners are defined, the end web is perpendicular to the chords.
15. 15. A truss according to any one of the preceding claims, wherein, in the or each end section in which said comers are defined, an axis along which each diagonal web extends forms an included angle with an axis along which the end member extends which is between about 30° and about 60°.
16. 16. A truss according to any one of the preceding claims, comprising webs and chords which are interconnected by nail plates.
17. 17. A truss according to any one of the preceding claims, having a height of between about 2.4 m and about 3.6 m and a width of between about 0.35 m and about 1.2 m.
18. 18. A truss according to any one of claims 1 to 16, having height of between about 2.7 m and about 3.0 m and a width of between about 0.45 m and about 0.9 m.
19. 19. A truss according to any one of the preceding claims, the width of which is between about one seventh and about one third of the height thereof.
20. 20. A bracing panel comprising a truss according to any one of the preceding claims.