AU2004100112A4 - A stiffening plate for a roof clamp - Google Patents

Description

A STIFFENING PLATE FOR A ROOF CLAMP This invention relates to a stiffening or reinforcement plate for a roof clamp.

In particular, the invention is directed to a stiffening plate adapted to be used in conjunction with an existing roof clamp to increase the rating of the roof clamp, i.e. to increase the resistance of the roof clamp to uplift forces.

BACKGROUND

ART

Wind generates an uplift force on the roof of a building, and the roof components are normally secured by tie-down rods or roof bolts. Such tie-down rods or bolts have their bottom ends securely fastened, typically to the floor or the walls of the building.

Roof clamps are used on the upper ends of the tie-down rods or bolts to restrain the roof components against uplift forces.

Australian patent application no. 41799/85 describes various types of roof clamps. For ease of reference, Figs. 1-4 herein reproduce some of the drawings of patent application 41799/85 showing a prior art roof clamp assembly.

As shown in Figs 1-4, a prior art roof clamp assembly includes a metal bracket A having an aperture G adapted to receive a tie-down rod or bolt B therethrough. In use, the bracket A is placed over the tie-down rod or bolt B, and onto a roof member F which rests upon a building frame H. The building frame H may be a timber frame, masonry wall or other wall structure of a building. The roof member F is typically the top plate of a building frame, an upper or lower chord of a roof truss, or a rafter. A washer C is placed over the tie rod B on top of the bracket A, and a nut D is threaded onto the tie rod B to tension the tie rod and hold the roof member F firmly onto the building frame H. A coach screw E may also be used for positioning the bracket A on the roof member F.

The prior art roof clamp assembly shown in Fig. 4 serves to restrain the roof members against uplift forces. Typically, a metal bracket A formed of 6mm steel plate provides around 9kN of resistance to uplift. Although this is sufficient for residential buildings in most urban areas, buildings in areas subject to high wind loads, such as coastal locations, cyclone-prone regions and open plains, require higher-rated roof clamp assemblies for withstanding higher uplift forces. Thicker or stronger roof clamps brackets must therefore be manufactured to meet such higher wind load ratings.

The requirement for roof clamp brackets of different thicknesses and/or strengths adds to manufacturing and inventory costs, thereby raising the prices of such 2 products to builders and other consumers. Moreover, since relatively few higher rated roof clamps are required, the increased cost of manufacture may not be justified economically by the low demand.

It is an aim of this invention to overcome or ameliorate one or more of the above described disadvantages by providing a stiffening plate for a roof clamp which enables a higher rating to be achieved in a simple and economical manner.

SUMMARY OF THE INVENTION In one broad form, the present invention provides a roof clamp assembly for restraining a roof member against uplift forces, the clamp assembly comprising a metal bracket placed on the roof member, the bracket having an aperture therein, a stiffening plate juxtaposed with the metal bracket and having an aperture therein aligned with the aperture in the metal bracket, an elongate member passing through the aligned apertures in the bracket and stiffening plate, and fastening means on the elongate member for securing the stiffening plate and bracket on the roof member to thereby resist uplift forces on the roof member.

Typically, the elongate member is a threaded bolt, and the fastening means is a nut adapted to be threaded on the bolt.

In another form, the invention provides a method of strengthening a roof clamp assembly of the type comprising a metal bracket held against a roof member by a tiedown rod or bolt to thereby restrain the roof member against uplift forces, the method comprising the step of juxtaposing a stiffening plate with the metal bracket to thereby increase the resistance of the roof clamp to uplift forces.

In yet another form, the invention provides a stiffening plate for use with a roof clamp of the type comprising a metal bracket adapted to be held against a roof member by a tie-down rod or bolt to thereby restrain the roof member against uplift forces, the stiffening plate being adapted to be held by the tie-down rod or bolt in juxtaposition with the bracket to thereby increase the resistance of the roof clamp to uplift forces.

In a preferred embodiment, the stiffening plate is an angled member formed of metal sheet.

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevation of a prior art bracket for a roof clamp.

Fig. 2 is a plan view of the bracket of Fig. 1.

Fig. 3 is a sectional end elevation of the bracket of Fig. 1.

Fig. 4 is an elevation of a prior art roof clamp assembly using the bracket of Fig. 1.

Fig. 5 is a perspective view of a stiffening plate suitable for use with the roof clamp assembly of Fig. 4.

Fig. 6 is a plan view of the stiffening plate of Fig. Fig. 7 is an elevation of the stiffening plate of Fig. Fig. 8 is an elevation of a roof clamp assembly using the stiffening plate of Fig. DESCRIPTION OF PREFERRED EMBODIMENT As described above, Fig. 4 illustrates a prior art roof clamp assembly using the known roof bracket illustrated in Figs. 1-3. Typically, the bracket A is made of 6mm thick steel plate, and the clamp provides about 9kN resistance to uplift.

Figs. 5-7 illustrate a stiffening plate 10 for a roof clamp, according to a preferred embodiment of the invention. The stiffening plate 10 is designed for use with a metal bracket A of a conventional roof clamp, and increases the rating of the roof clamp assembly.

The stiffening plate 10 comprises an L-shaped metal plate adapted to be placed on the conventional roof clamp bracket A. The stiffening plate 10 has an aperture 11 which aligns with a corresponding aperture in bracket A, and the tie-down rod B locates in the aligned apertures as shown in Fig. 8.

The stiffening plate 10 also has a second aperture 12 which aligns with a corresponding aperture in the bracket A to accommodate the coach screw E.

In use, stiffening plate 10 is simply placed on top of the metal bracket A in "piggyback" fashion to form a composite bracket for a roof clamp assembly, as shown in Fig.

8. The angle section 10A abuts against an associated angle section of the bracket A, to automatically align the apertures in the stiffening plate 10 with the corresponding apertures in the bracket A. The tie-down rod or bolt B passes through the aligned bolt holes, and the composite bracket is placed on top of a roof member F (which is typically the bottom or upper chord of a roof truss, a rafter or upper wall plate). The coach screw E is used to locate and secure the composite bracket onto the roof member F, while the nut D threaded on the tie-down rod or bolt B is used to tension the composite bracket against the roof member F.

The stiffening plate 10 increases the overall rating of the composite roof clamp assembly. For example, a stiffening plate made from 6mm steel plate used in conjunction with a 6mm thick clamp bracket typically increases the uplift resistance to 27kN. A stiffening plate made from 3mm steel plate typically increases the uplift resistance to 17kN.

The abovedescribed stiffener plate has several advantages, including: The stiffening plate may be made easily and economically from readily available steel plate; The stiffening plate need only be used as and where required; The stiffening plate increases the rating of the composite roof clamp assembly.

The foregoing describes only one embodiment of the invention, and modifications which are obvious to those skilled in the art may be made thereto without departing from the scope of the invention. For example, the stiffening plate may also be used with roof clamps of types and as shown in patent application 41799/85. The hole 11 in the stiffener plate 10 is sufficiently wider than the diameter of the bolt B to accommodate the stiffener plate 10 being at an oblique angle to the bolt B.

Claims (8)

1. A roof clamp assembly for restraining a roof member against uplift forces, the clamp assembly comprising a metal bracket placed on the roof member, the bracket having an aperture therein, a stiffening plate juxtaposed with the metal bracket and having an aperture therein aligned with the aperture in the metal bracket, an elongate member passing through the aligned apertures in the bracket and stiffening plate, and fastening means on the elongate member for securing the stiffening plate and bracket on the roof member to thereby resist uplift forces on the roof member.

2. A roof clamp assembly as claimed in claim 1, wherein the stiffening plate is an angled member made of metal plate, placed on top of the bracket.

3. A roof clamp assembly as claimed in claim 1 or 2, further comprising threaded fastening means passing through aligned second apertures in the stiffening plate and the bracket, and being threaded into the roof member.

4. A roof clamp assembly as claimed in any one of claims 1 to 3, wherein the elongate member is a threaded bolt, and the fastening means is a nut adapted to be threaded on the bolt.

A method of strengthening a roof clamp assembly of the type comprising a metal bracket held against a roof member by a tie-down rod or bolt to thereby restrain the roof member against uplift forces, the method comprising the step of juxtaposing a stiffening plate with the metal bracket to thereby increase the resistance of the roof clamp to uplift forces.

6. A method as claimed in claim 5, wherein the stiffening plate is an angled member formed from metal plate, the stiffening plate being placed on top of the bracket.

7. A stiffening plate for use with a roof clamp of the type comprising a metal bracket adapted to be held against a roof member by a tie-down rod or bolt to thereby restrain the roof member against uplift forces, the stiffening plate being adapted to be held by the tie- down rod or bolt in juxtaposition with the bracket to thereby increase the resistance of the roof clamp to uplift forces.

8. A stiffening plate as claimed in claim 7, wherein the stiffening plate is an angled member formed of metal plate.