AU2020200529A1

AU2020200529A1 - Improved girder design

Info

Publication number: AU2020200529A1
Application number: AU2020200529A
Authority: AU
Inventors: Owen David Brewerton
Original assignee: Alpine Buildings Nz Ltd
Current assignee: Alpine Buildings Nz Ltd
Priority date: 2019-02-22
Filing date: 2020-01-24
Publication date: 2020-09-10

Abstract

A girder formed from a single folded metal sheet, said sheet being folded such that the girder is formed using only a single thickness of metal sheet on any part of the girder; 5 the girder providing two adjacent rectangular cross-section cavities separated by a reinforcing wall. 7 CL) CLu CL3 Cu 00-- CFL CD

Description

CL)

CLu

CL3 Cu

-- CFL CD IMPROVED GIRDER DESIGN

Technical Field The present invention relates to a new design for a metal girder, and to a method for making this girder. In this specification, the term "girder" is used throughout to refer to a heavy duty support member for use in construction, which can be used as a girder or as a beam or as a joist or a purlin, or as any component where load-bearing support is required.

Background Art It is known to form metal girders from folded sheet, but in general, designs made in this way tend to be relatively light weight. Further, a majority of the folded sheet designs require multiple complex folds or need multiple sections to form a closed-in girder, and thus are comparatively expensive to produce.

A further problem is that several of the known girder designs require at least one wall to be made of a double thickness of sheet, and this causes problems if the girder is to be hot dipped galvanised after forming.

Where two thicknesses of sheet overlie each other, moisture and/or air is trapped between the sheets, and this expands "explosively" when the girder is placed in the galvanising bath, often causing dangerous splashing of the bath.

Disclosure of Invention It is an object of the present invention to provide a design for a metal girder suitable for production by folding sheet metal, but which requires a minimal number of folds to form a girder capable of bearing heavy loads.

The present invention provides a girder formed from a single folded metal sheet, the girder providing two adjacent rectangular cross-section cavities separated by a reinforcing wall, using only a single thickness of metal sheet.

Preferably, each free end of the sheet is welded to the adjacent sides of the formed girder.

The present invention further provides a method of forming a girder as described above, including the steps of: • selecting a length of sheet metal having a length greater than, or equal to, the desired length of the finished girder; • bending one end of said sheet through 90 degrees and then forming a second 90 degree bend spaced from the first 90 degree bend by a distance equal to the desired width of the top of the girder; • bending the other end of said sheet through 90 degrees and then forming a second 90 degree bend spaced from the first 90 degree bend by a distance equal to the desired width of the bottom of the girder; • forming a third 90 degree bend in said other end of said sheet such that said end of said sheet forms a reinforcing wall which extends across the width of the girder at the midpoint of the height of the girder; • securing said one end and said other end of said sheet to the corresponding adjacent side of the formed girder, intermittently or continuously along the length of the girder; • wherein the distance between the first 90 degree bend on said one end of said sheet and the first 90 degree bend on the other end of said sheet is equal to the height of the girder.

As used herein, the term "rectangular" is used in the usual geometrical sense and includes square cross-section.

Preferably, the girder is formed by roll-forming, but other folding methods may be used.

Brief Description of Drawings By way of example only, two preferred embodiments of the present invention are described in detail, with reference to the accompanying drawings, in which:

Figure 1 shows an isometric view of a first embodiment of the present invention; and

Figure 2 shows an isometric view of a second embodiment of the present invention.

Best Mode for Carrying Out the Invention Referring to Figure 1 of the drawings, a girder 10 is formed by folding a 3 mm thick steel sheet to form two adjacent rectangular cavities 11, 12 separated by a reinforcing wall

13. Each of the cavities 11, 12 has a width W of 100 mm; the overall height H of the girder is approximately 350 mm. The cavity 11 has a height C1 of 174 mm; the cavity 12 has a height C2 of 173 mm. It will be appreciated that the size and proportions of the girder can be varied as required for different applications. The sheet thickness also can be varied as required.

For example, a girder 10 may be made of a 2 mm thick steel sheet with the same structure as shown in Figure 1. Typically, such a girder would have an overall height H of approximately 200 mm and a width W of approximately 50 mm.

The whole girder 10 is formed by folding a single sheet:- one long side 14 is formed by an unbroken length of sheet with a right angled fold 16, 17 at each end to form the short sides 18, 19 of the girder. Two further right angle folds 20, 21 are made at the ends of each of the short sides. One end of the sheet is folded through a further right angle bend 22 at the midpoint of the girder, and extends across the midpoint of the girder to form the reinforcing wall 13, so that the free end 23 of the sheet abuts the interior of the long side 14. The free end 23 of the sheet is secured to the interior of the long side 14 by a weld 24 shown in broken lines.

The other free end 25 of the sheet terminates at the bend 22 i.e. at the midpoint of the second side 26 of the girder. The end 25 is secured to the adjacent side of the girder by a weld 27 shown in broken lines.

The welds 24, 27 may be made by any of a range of suitable known welding techniques.

Referring to figure 2, the girder 30 is similar to the girder 10 of Figure 1, except that the cavities of the girder are closer to a square cross-section:- the width W of each cavity is 100 mm; the overall height H is approximately 150 mm; the cavity 31 has a height of 74 mm; the cavity 32 has a height of 73 mm, and the sheet thickness is 3 mm.

As described with reference to Figure 1, the girder 30 provides two adjacent cavities 31, 32 and an internal reinforcing wall 33. The girder is formed in the same manner as described with reference to Figure 1. The free ends 34, 35 of the sheet are secured by welds 36, 37 indicated in broken lines.

The welding may be e.g. spot or seam welding or any other suitable weld design.

Alternatively, the free ends 23, 25, 34, 35 may be crimped in place.

Another possible construction is to form each free end 23, 25, 34, 35, with an angled tab which extends continuously or intermittently along the corresponding end 23, 25, 34, 35 and which can be welded or riveted or otherwise secured to the adjacent side of the girder.

A further possibility would be to secure a joining bracket or plate over the junction between each free end 23, 25, 34, 35 and the adjacent side of the girder.

The girders have been described as being made of folded sheet steel, but may in fact be made of any of a wide range of suitable metal sheet.

The above described designs provide an excellent strength/weight ratio, and the reinforcing wall protects against lozenging or distortion of the girder. A girder made in accordance with the present invention may be hot dipped galvanised without problems, because it does not require any overlapping sheets.

Claims

1. A girder formed from a single folded metal sheet, said sheet being folded such that the girder is formed using only a single thickness of metal sheet on any part of the girder; the girder providing two adjacent rectangular cross-section cavities separated by a reinforcing wall.

2. The girder as claimed in claim 1, wherein each free end of the sheet is welded to the adjacent side of the formed girder.

3. The girder as claimed in claim 1, wherein each free end of the sheet is crimped to the adjacent side of the formed girder.

4. The girder as claimed in claim 1, wherein each free end of the sheet is formed with a continuous or intermittent angled tab which is secured to the adjacent side of the formed girder.

5. The girder as claimed in claim 1, wherein each free end of the sheet is secured to the adjacent side of the formed girder by means of one or more joining plates or brackets secured over the junctions between each free end of the sheet under the adjacent side of the formed girder.

6. The girder as claimed in claim 1, wherein one side of the girder consists of a continuous unbroken length of sheet metal, each end of which is bent through 90 degrees to form the top and bottom of the girder respectively and then through 90 degrees to form the other side of the girder; one of the ends is then bent through 90 degrees to form a reinforcing wall substantially parallel to the top and bottom of the girder, across the midpoint of the girder; the other end terminates at the midpoint of the girder and is secured to the adjacent side of the formed girder.

7. A method of forming a girder as claimed in claim 6, including the steps of: • selecting a length of sheet metal having a length greater than, or equal to, the desired length of the finished girder; • bending one end of said sheet through 90 degrees and then forming a second 90 degree bend spaced from the first 90 degree bend by a distance equal to the desired width of the top of the girder;

• bending the other end of said sheet through 90 degrees and then forming a second 90 degree bend spaced from the first 90 degree bend by a distance equal to the desired width of the bottom of the girder; • forming a third 90 degree bend in said other end of said sheet such that said end of said sheet forms a reinforcing wall which extends across the width of the girder at the midpoint of the height of the girder; • securing said one end and said other end of said sheet to the corresponding adjacent side of the formed girder, intermittently or continuously along the length of the girder; • wherein the distance between the first 90 degree bend on said one end of said sheet and the first 90 degree bend on the other end of said sheet is equal to the height of the girder.

8. The method as claimed in claim 7 wherein said one end and said other end of said sheet are secured to the corresponding adjacent side of the formed girder by a method selected from the group consisting of: • welding; • crimping; • securing joining plates or brackets over the junction.

Fig.1

Fig.2