AU675801B2 - Yieldable bracket - Google Patents

Description

~---rrrr~ P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT *owe*: :0 Invention Title: YIELDABLE BRACKET The following statement is a full description of this invention, including the best method of performing it known to the Applicant:- This invention relates to brackets used to secure the lower chords of trusses to the top plates of wall frames during the erection of metal or S• timber framed buildings, in particular, relatively small buildings, such as cottages, sheds and others in which the frame may comprise prefabricated wall frames and/or trusses. The invention was devised primarily for use in relation to frames made from structural members that are roll-formed from light gauge sheet metal, and is described primarily with regard to that application hereinafter. However it may also be applied with benefit to buildings in which either or both of the wall frames and trusses is or are of timber.

In such buildings every effort is made to contain costs. Thus, individual structural members are carefully designed, having regard to the loads each will be called upon to carry in the finished building frame, 2 so that each may be made from the least weight of material compatible with its long term duty. So much so that individual frame elements or sub-assemblies may appear quite flimsy until fully incorporated in the finished structure. In particular a free standing internal wall frame is normally vulnerable to failure until its top is secured against lateral movement by its attachment to surrounding parts of the structure.

When erecting buildings of the kind in question it is usual for the skeleton to be finished, that is to say, all of the wall frames to be stood up and the roof trusses to be put in place, before the wall linings, roof *w lo covering, ceilings and similar cladding elements are affixed.

6 see 9 0Those so called cladding elements load up the skeleton, but also contribute appreciably to its eventual rigidity and stability. Therefore as erection proceeds, and before the cladding is applied, there is a e 6 requirement that the top plates of the internal wall frames be secured to o S• 15 the lower chords of the trusses to stabilise the skeleton (for example, to allow workers to climb thereon, without damage or danger) prior to the installation of the cladding. Hitherto, the truss and wall frame have been secured together by a simple, angle shaped sheet metal bracket having .a horizontal flange fastened to the top of the top plate of the wall frame and a vertical flange fastened to the side of the bottom chord of the truss.

The trusses are designed to bear the weight of the roof covering on the basis that loads will be applied to the truss at predetermined design points, being, at least in the case of the supporting reactions, at or near the ends of the lower chord remote from internal walls.

Customarily the lower chord is spaced above the tops of internal walls, but when conventional angl 'Lrackets are used to secure the truss to the internal wall plates as described above, undesirable reaction loads and torsional stresses are imposed on the lower chord and/or the top wall plate at the position of the bracket when the truss sags, as it must, when the weight of the roof covering is imposed on it. To overcome this, angle-shaped sheet metal brackets in which the vertical flange has elongated slots have been devised. These slots extend in the vertical direction, and replace the normal fastener holes. However, for such angle brackets to work the fasteners must not be tightly fixed through the vertical flange to the lower chord so as to allow sliding movement 0 lo between the lower chord and the bracket upon loading of the chord.

This thus relies on the correct application of fasteners i.e. non standard, o0 and thus effectivel" precludes the use of devices such as nail guns.

oo The present invention is based on the appreciation that if the design of prefabricated building frames is to be honed to the optimum, even such apparently minor deficiencies, that have been previously Signored, must be addressed.

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00 0 Therefore an object of the present invention is to provide a bracket which alleviates one or more of those deficiencies.

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The invention consists in a bracket, for connecting the lower chord of a roof truss to the top of an internal wall frame, of the kind comprising a wall affixture portion adapted to be connected to a wall frame and a truss affixture portion adapted to be connected to a truss, claracterised in that a resiliently yieldable connecting portion joins the said affixture portions.

It is preferable for the bracket itself to be inexpensive and as readily applied on site as are conventional brackets. To those ends, IL 1 preferred embodiments of the invention comprise a sheet metal bracket comprising a wall affixture portion adapted to be fastened to the top surface of a wall plate, truss affixture portion adapted to be fastened to a side surface of a lower chord of a roof truss, and a connecting portion extending between the affixture portions, at least a part of said connecting portion being offset 'horizontally with respect to its junction with the truss affixture portion to enable said truss affixture portion to rise and fall relative to the wall affixture portion as a result of resilient S" flexure of the connecting portion.

S

By way of example, two embodiments of the above described invention are described in more detail hereinafter with reference to the accompanying drawings.

Figure 1 is a side elevation of a yieldable bracket according to the V t *invention.

O .15 Figure 2 is a front elevation of the bracket of figure 1 as seen when viewed in the direction of the arrow marked 2 in that figure.

Figure 3 is a plan view of the bracket of figure 1 as seen when viewed in the direction of the arrow marked 3 in that figure.

Figure 4 is a view similar to figure 1 of another embodiment of the invention.

Figure 5 is a plan view of the bracket of figure 4.

Figure 6 is a development of the bracket of figure 4 showing a strip precursor of that bracket.

L- The bracket illustrated by figures 1 to 3 is formed from a single strip of sheet metal, preferably galvanised steel. It comprises a flat, wail affixture portion 4, a flat, truss affixture portion 5 and a stepped connecting portion 8 extending from one affixture portion to the other.

The wall affixture portion 4 is adapted, by means of fastener clearance holes 6, to be secured flatly against the upper surface of a wall plate, and the truss affixture portion 5 is likewise adapted by means of fastener clearance holes 7 to be secured flatly against a side surface of the lower chord of a truss.

10 The connecting portion 8 lies to one side of the plane of the truss affixture portion 5 and its linear junction 9 therewith, that is to say it is offset horizontally with respect to that junction. Therefore the truss affixture portion 5 may rise and fall as a result of resilient flexure or bending of the connecting portion. In the present instance, the flexure o* 15 may occur, for the most part, at the step line 10 and junction line 9, but in other embodiments the connecting portion may be more uniformly curved, so that bending occurs more or less evenly throughout the portion.

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Furthermore, it is not essential that all of the connecting portion should project in the horizontal direction to one side of its junction with the truss affixture portion, provided that some part of it does so. For example, a generally S shaped or zig-zagged connecting portion may extend downwardly from the truss affixture portion to a junction with the wall affixture portion directly below its junction with the truss affixture portion. The necessary flexure would then be enabled as a result of the "crests" of the connecting portion being horizontally offset from those junctions.

6 The bracket illustrated by figures 4 to 6 is generally similar to the figure 1 embodiment. It comprises a wall affixture portion 14 with fastener clearance holes 16, a truss affixture portion 15 with fastener clearance holes 17, and a stepped connecting portion 18, all functionally similar to the corresponding parts of the first described embodiment.

In this instance the bends at the junction lines are obtuse, as is the bend at the step line, and radiused or curved. This enhances the flexibility of the connecting portion. in this embodiment, that flexibility is s" further increased by slots 21 formed in the connecting portion for that a* 6 purpose.

000 It should be noted that in these embodiments of the invention, parts of the connecting portions are offset from the planes of both of the affixture portions. Thus, in each instance, the truss affixture portion and the wall affixture portion are interchangeable and may not acquire 15 identifiable separate identities until installed in a building structure. This comment may appl.t with more force to other embodiments in which the affixture portions are geometrically identical.

The illustrated embodiments may be made by passing a sheet 9 0 steel strip through a repetitive punching machine, which punches the clearance holes and slots 21 (if present) at appropriate intervals. That pre-punched strip may then pass to a press wherein the several fold lines are formed and the strip is cropped to length to form finished brackets.

it should be noted that in the figure 4 embodiment there are more fastener clearance holes than would be used in any particular installation, and that those holes vary in size. This is to enable appropriate holes to be chosen for each installation, depending, for example, on whether the affixture portion in question is nailed to a timber member or fastene.- by screws or rivets to a metal member.

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Claims (6)

1. A bracket, for connecting the bottom of a roof truss to the top of an internal wall frame, of the kind comprising a wall affixture portion adapted to be connected to a wall frame and a truss affixture portion adapted to be connected to a truss, characterised in that a resiliently yieldable connecting portion joins the said affixture portions.

2. A sheet metal bracket comprising a wall affixture portion adapted to be fastened to the top surface of a wall plate, a truss affixture portion Sadapted to be fastened to a side surface of a lower chord of a roof truss, 9 o. and a connecting portion extending between the affixture portions, at least a part of said connecting portion being horizontally offset with respect to its junction with the truss affixture portion to enable said truss affixture portion to rise and fall relative to the wall affixture portion as a result of resilient flexure of the connecting portion. C

3. A bracket according to claim 2 wherein said connecting portion is a stepped or curved length of sheet metal integral with said affixture portions. 0

4. A bracket according to claim 3 wherein said connecting portion is slotted to increase its flexibility.

A bracket substantially as described herein with reference to figures 1, 2 and 3, or 4, 5 and 6 of the accompanying drawings. -I 9

6. In combination, a wall frame, a roof truss above and extending across said wall frame, and a bracket according to any one of the preceding claims extending from said truss to said frame. Applicant JOHN LYSAGHT (AUSTRALIA) LIMITED Date 21 September 1993 Attorney ROBERT G. SHELSTON F.I.P.A.A. of CARTER SMITH BEADLE e S o** O .5O L-L- L_ ABSTRACT A sheet metal yieldable bracket, for connecting the lower chord of a roof truss to the top of an internal wall frame of a framed building, comprises a flat wall affixture portion (4 or 14) pierced by a plurality of fastener clearance holes a flat truss affixture portion (5 or pierced by further fastener clearance holes and a stepped connector portion (8 or 18) extending from one affixture portion to the other. in use, the affixture portions may be fastened to the wall frame and truss respectively to hold them together but at the same time allow the truss to deform under load without the transmission of substantial loads to or from the frame. Figure 4. *e *6 r r 1