AU6252200A - Girder bracket & method of fastening thereof - Google Patents

Description

GIRDER BRACKET AND METHOD OF FASTENING THEREOF Technical Field The present invention relates to a girder bracket for connecting timber structural members and a method of fastening the same.

Background .9 *9 *o S•Girder brackets are utilised in the construction industry to connect and transfer loads between timber structural members. Typically such girder brackets are used to transfer loads from standard trusses and secondary girder trusses to a primary girder truss. The girder Sbrackets can also be fixed to a beam to enable standard trusses or secondary girder trusses to be supported by the beam.

i •Smaller, lower load carrying girder brackets known as '"joist hangers" are typically used to transfer loads from secondary timber members to primary timber members. The timber members may be solid timber, laminated timber or timber trusses.

The girder brackets are typically fabricated from steel sections by a forming operation such as stamping or punching.

Truss to truss connections are conventionally achieved by either of two types of girder bracket. The first type is a "bolt-on" girder bracket incorporating a number of holes for receiving nails and/or bolts. The second type is a "press-on" girder bracket incorporating a nail plate and a formed boot section to carry the secondary truss.

The "bolt-on" girder bracket is traditionally fastened to the girder truss timber members using bolts, nuts and washers in which bolt holes are drilled in the timber members S•to exactly match the pre-drilled bolt holes in the brackets. The drilling is achieved by either a single or a double drill. This is a slow, tedious process and sometimes dangerous, particularly if the hole being drilled also has to pass through steel nail plates embedded in the timber. The S 10 disadvantage with such a bracket is that the method of fastening ie. the positioning of bolts, •washers and nuts and the tightening process which follows, takes much time, effort and skill to achieve. As secondary trusses can only be connected to girder trusses on site, the drilling S. process in many instances necessitates the use of a scaffolding system for a carpenter/workman to safely work. As the construction industry has various structural needs, 15 "bolt-on brackets" have been made in various bolt-hole sizes such as 12mm, 16mm or thereby requiring carpenters to maintain a regular supply of each size bolt and drills depending on the bolt size called for.

Another disadvantage of these "bolt-on" brackets is that in many instances the wing members which are fastened to the primary truss each only have one bolt hole, making them prone to rotation, whilst the boot only has two bolt holes.

A further disadvantage is that the drilling of bolt holes into a timber bottom chord of the truss necessitates, in many instances, the need to increase the original designed size of the bottom chord by one size, which increases the usage and cost of timber.

A further disadvantage of these "bolt-on" brackets is that the normal failure point of a horizontal tearing of the timber is in line with the bolt holes in the girder truss bottom chordhence, a nail plate is used on each side of the girder bracket to provide additional strength to S: the connection.

0. 0.: S: The "press-on" girder bracket is traditionally fastened to the girder truss timber *o member using a hydraulic press to embed its nail plate component into the timber. This method of fastening is fast, once the bracket has been accurately placed and hammered in 0..0 position to avoid movement during pressing. The disadvantage of this bracket and its method 00000is that its use is restricted. It cannot be used where embedded nail plates are already located on •the truss timber member.

•.oJoist hangers, the smaller girder brackets, are conventionally fastened with hand-held hammered in nails and an occasional bolt as the design requires. The disadvantage of this bracket and its method of fastening, is the number of nails of the correct size, diameter and length required in the correct location.

The present invention seeks to ameliorate the problems of prior art girder brackets and their fastening method.

In one broad form the present invention comprise a girder bracket for connecting timber structural members, said bracket comprising a trough having a bottom wall and two spaced apart sidewalls on either side thereof, two wing members each of which project from one of the respective sidewalls at one end of said trough in directions substantially orthogonal to the longitudinal axis of said trough, wherein each wing has at least three spaced apart holes therein for receiving fasteners, and each sidewall has at least two spaced apart holes therein for receiving a fastener.

In another form the present invention comprises a girder bracket for connecting timber structural members, said bracket comprising a trough having a bottom wall and two spaced apart sidewalls on either side thereof, two strap members each of which project from one of "the respective sidewalls at one end of said trough in a direction substantially parallel to the *o longitudinal axis of said trough, two wing members each of which project from one of the 0 respective sidewalls at the opposite end of said trough in directions substantially orthogonal to ooooe the longitudinal axis of said trough, wherein each wing has at least three spaced apart holes S 15 therein for receiving fasteners, and each sidewall has at least one hole therein for receiving a fastener, and each said strap has at least two spaced apart holes therein for receiving fasteners.

Preferably each sidewall has at least a first stiffening rib formed therein.

Preferably each wing member has at least a second stiffening rib formed therein.

Preferably the second stiffening rib of each wing member is a continuation of the first stiffening rib of its respective sidewall.

Preferably the at least three spaced apart holes in each wing are spaced apart in a triangular relationship.

Preferably the at least two spaced apart holes in each sidewall are four spaced apart holes. Preferably the four spaced apart holes are spaced apart in a rectangular relationship.

Preferably the second stiffening rib of each wing member is disposed between two of the at least three spaced apart holes therein.

Preferably the girder bracket is fastened to the timber member utilising screws.

Preferably the screws are driven in place by a hand held powered screw gun Brief Description of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of a girder bracket in accordance with the present invention; Figure 2 is a perspective view of the girder bracket of Fig. 1 affixed to timber trusses; Figure 3 is an exploded perspective view of another embodiment of a girder bracket in accordance with the present invention and timber trusses; Figure 4 is a plan view of the girder bracket shown in Figure 3; Figure 5 is an end view of the girder bracket shown in Figure 3; and Figure 6 is an elevation view of the girder bracket shown in Figure 3.

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10 S 15 Mode of Carrying Out Invention Figures 1 to 2 depict an embodiment of a steel girder bracket 1 for connecting timber truss structural members 2 and 3. The bracket 1 comprises a trough 4 having a bottom wall and two spaced apart sidewalls 6,7 either side thereof. The trough 4 functions as a "girder boot" adapted to receive truss member 3. Two substantially coplanar wing members 10,11 project orthogonally from ends of respective sidewalls 6,7.

Each wing member 10, 11 has four holes 12 therein, spaced apart in a staggered relationship. Each sidewall 6,7 has four holes 13, spaced apart in two rows in a staggered relationship. This staggered relationship ensures that no two bolts pass through the same grain of the timber Each sidewall 6,7 and its respective wing member 10,11 has three raised stiffening ribs 15 formed therein. Each stiffening rib 15 has a first portion 15a on the sidewall and a second portion 15b on the wing member. The stiffening ribs 15 provide structural integrity to the bracket 1, even though it has a large number of holes therein.

In use, bracket 1 may preferably be secured to timber members 2 and 3 utilising screws 16 through the various holes 12 and 13. Preferably, screws 16 are driven in place utilising a powered screw gun. One type of screws suitable for such fastening are "Metal Teks" roofing screws, marketed under the trade mark Buildex.

S. With the present embodiment a carpenter (or workman) armed with a supply of screws :16 carried in a waist bag or the like, may utilise a small hand held power tool and attachment 9 to fix the screws 16 in place, with relevant ease. The use of such power driven screws 16 eliminates the pre-drilling of the timber trusses 2 and 3 before fastening and the tightening process, as would be required with the prior art "bolt-on' brackets. As the use of power driven screws do not require the same accuracy of drilling as that required with "bolt-on brackets, the °expensive scaffold system for supporting the carpenter can be replaced with a step ladder.

The positioning of the four holes 12 in each wing member 10,11 allow for screws 16 to be inserted into truss member 2 in a moment connection, thereby preventing the "girder boot" from rotating and making the connection stronger, more stable and stiffer than with the prior art fastening method.

The positioning of the four spaced apart holes 13 in each sidewall 6,7, allow for screws 16 to be inserted into truss member 3 in a moment connection, thereby preventing it from 8 rotating within the "girder boot". The positioning of eight screws 16, four screws 16 through holes 13 on each of sidewalls 6,7 not only resist the torsional effect of the structural member being necessary.

Figures 3 to 7 depict a further embodiment of a girder bracket 1 for connecting timber truss structural members 2 and 3. The bracket 1 comprises a trough 4 having a bottom wall and two spaced apart sidewalls 6,7 either side thereof. Each sidewall 6,7 has a respective strap members 8,9 projecting therefrom in a direction parallel to the longitudinal axis L of trough 4.

S.The trough 4 and strap members 8,9 form a "girder boot" adapted to receive truss member 3.

Two wing members 10,11 project from the opposite ends of respective sidewalls 6,7. The 10 wing members 10,11 are substantially orthogonal to longitudinal axis L.

4S Each wing member 10, 11 has four holes 12 therein, spaced apart in two rows.

Each sidewall 6,7 has three holes 13 therein diagonally disposed therein. Each strap member o.o° 8,9 has two spaced apart holes 14 near its free end.

Each sidewall 6,7 and its respective wing member 8,9 have three raised stiffening ribs ooooo formed therein. Each stiffening rib 15 has a first portion 15a on the sidewall and a second portion 15b on the wing member. The stiffening ribs 15 provide structural integrity to the bracket 1, even though it has a large number of holes therein.

In use, bracket 1 may preferably be secured to timber members 2 and 3 utilising screws 16 through the various holes 12,13 and 14. Preferably, screws 16 are driven in place utilising a powered screw gun. One type of screws suitable for such fastening are "Metal Teks" roofing screws, marketed under the trade mark Buildex.

With the present embodiment a carpenter (or workman) armed with a supply of screws 16 carried in a waist bag or the like, may utilise a small hand held power tool and attachment to fix the screws 16 in place, with relevant ease. The use of such power driven screws 16 eliminates the pre-drilling of the timber trusses 2 and 3 before fastening and the tightening process, as would be required with the prior art "bolt-on' brackets. As the use of power driven screws do not require the same accuracy of drilling as that required with "bolt-on brackets, the S• expensive scaffold system for supporting the carpenter can be replaced with a step ladder.

The positioning of the four holes 12 in each wing member 10,11 allow for screws 16 to be inserted into truss member 2 in a moment connection, thereby preventing the "girder boot" from rotating and thus making the connection stronger, more stable and stiffer than with the prior art fastening method. Preferably these holes 12 are arranged as corners of a trapezium.

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15 Multiple holes 13 diagonally disposed in the sidewalls 6,7, ie. in a row at an oblique angle to the edges 18,19 of each sidewall 6,7, allow for selection of appropriate holes to avoid steel penetration of an embedded plate 17 which may be positioned on truss member 3. All holes 13 on one sidewall may not need to be used for fastening and are provided to allow for selecting an appropriate hole and connection design.

The positioning of the two spaced apart holes 14 in each strap member 8,9, allow for screws 16 to be inserted into truss member 3 in a moment connection, thereby preventing it from rotating within the "girder boot".

The present invention not only eliminates the need for pre-drilling, but also eliminates the need to construct brackets with different size holes. One size of girder bracket of the present embodiment can now be produced with multiple fixing holes 12,13 and 14. One type of fastener (screw 16) can be used on various connection designs, with the only variable being the number of fasteners called for in each design and the length of fastener for single, double or triple bottom chords (structural members). The carpenter need only carry one size fastener Sand needs only to apply the number of fasteners as dictated by the connection design.

S°It should be noted that the present invention allows for originally designed sized bottom chords to be utilised, rather than increasing the design size of such chords by one size to accommodate the drilling of bolt holes, which is sometimes necessary with the prior art brackets.

It should be understood that whilst the abovementioned embodiment has four holes 12, in each wing member 10,11, the bracket 1 is still prevented from rotation if three holes 12 spaced apart in triangular fashion are provided, rather than four. The number of holes is not limited to three or four and may in other embodiments be of a greater number.

11 It should also be understood that the number of holes 13 in the sidewalls 6,7 need not be limited to three and may in another not shown embodiment involve a greater number of spaced apart holes not necessarily disposed diagonally therealong. Furthermore whilst in the present invention the holes 13 in sidewall 6 appear to substantially align with those of sidewall 7, it should be understood that in other not shown embodiments, such alignment is not necessary.

It should be obvious to those skilled in the art that numerous variations can be made to the abovementioned embodiment of the girder bracket without departing from the scope and spirit of the invention.

Claims (8)

1. A girder bracket for connecting timber structural members, said bracket comprising a trough having a bottom wall and two spaced apart sidewalls on either side thereof, two wing members each of which project from one of the respective sidewalls at one end of said trough in directions substantially orthogonal to the longitudinal axis of said trough, wherein each wing has at least three spaced apart holes therein for receiving fasteners, and *m i :each sidewall has at least two spaced apart holes therein for receiving a fastener.

2. A girder bracket for connecting timber structural members, said bracket comprising a trough having a bottom wall and two spaced apart sidewalls on either side o thereof, two strap members each of which project from one of the respective sidewalls at one end of said trough in a direction substantially parallel to the longitudinal axis of said trough, two wing members each of which project from one of the respective sidewalls at the opposite end of said trough in directions substantially orthogonal to the longitudinal axis of said trough, wherein each wing has at least three spaced apart holes therein for receiving fasteners, and each sidewall has at least one hole therein for receiving a fastener, and each said strap has at least two spaced apart holes therein for receiving fasteners.

3. A girder according to claims 1 or 2, wherein each sidewall has at least a first stiffening rib formed therein.

4. A bracket according to claim 3, wherein each wing member has at least a second stiffening rib formed therein.

A bracket according to claim 4, wherein the second stiffening rib of each wing member is a continuation of the first stiffening rib of its respective sidewall.

6. A bracket according to claim 1 and any one of claims 1 to 5 when appended to claim 1, wherein the at least three spaced apart holes in each wing are spaced apart in a triangular relationship.

A bracket according to any one of the preceding claims wherein the at least two spaced apart holes in each sidewall are four spaced apart holes. •oo*

8. A bracket according to claim 7 wherein the four spaced apart holes are spaced •i apart in a rectangular relationship. A bracket according to any one of the preceding claims, wherein the second stiffening rib of each wing member is disposed between two of the spaced apart holes therein. 1't A bracket substantially as hereinbefore described with reference to the accompanying drawings Dated the 5 th October 2000 Multinail Australia Pty Ltd By their Patent attorneys Paul R. Taylor Associates o. oooQ oeoo oooo o oe