AU785340B2

AU785340B2 - Improved metal section

Info

Publication number: AU785340B2
Application number: AU27617/02A
Authority: AU
Inventors: Yuri Arguedas; Christopher Lee Healy
Original assignee: Stramit Corp Pty Ltd
Current assignee: Stramit Corp Pty Ltd
Priority date: 2001-08-07
Filing date: 2002-03-25
Publication date: 2007-01-25
Anticipated expiration: 2022-03-25
Also published as: AU2006252112A1; AUPR686701A0; AU2761702A

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Stramit Corporation Limited Actual Inventors: Christopher Lee Healy Yuri Arguedas Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: IMPROVED METAL SECTION Our Ref: POF Code: IRN 665391 The following statement is a full description of this invention, including the best method of performing it known to applicant: 1 orm soatorm~cptloms.doc IMPROVED METAL SECTION The present invention relates to a load bearing section formed from metal sheet and has been designed especially but not exclusively as a light gauge purlin or girt and is herein described in that context. However, it is to be appreciated that the invention has broader application and may be used in other load bearing applications such as for floor joists and the like.

Purlins and girts are predominantly used to support roof or wall sheeting in industrial, rural and commercial buildings. While commonly attached to fabricated steel frames, the members are on occasion also used in small and medium sized buildings for the structural frame.

Typically the purlins and girts are installed in continuous runs over the supporting frame where the individual members are aligned and fastened together with their adjacent ends overlapping. The lap length is typically in the order of 5% to 15% of the span length of the members between adjacent S 15 supports but may be more or less depending on the design loading. In many cases, one or more rows of bridging is required to give lateral restraint to the purlins and girts to resist flexual torsional or lateral buckling. When installed the *interconnected purlins or girts function as a load bearing beam and are designed not only to support static loading applied to the cladding but also

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dynamic wind loading.

Traditionally purlins and girts have either a C or Z cross-section and range in size from 100mm to 350mm in web size. Another cross-section is a "top hat" which includes a main part which is shaped as an inverted channel i having opposing side walls or webs which are interconnected by a flange that forms a bridge between the webs. The section also includes lateral flanges extending outwardly from the lower margin of each web to provide locations to fasten the section to its support structure.

An aim of the present invention is to provide improvements to such load bearing metal sections. A particular aim is to provide a cross-section which is economic to manufacture and exhibits improved performance.

Accordingly, the present invention provides an elongate load bearing section formed from sheet metal, the section having a substantially constant top hat profile in cross-sections along its longitudinal extent; W. SandWOD.2 RNC No DclaO6\27617.O2 Wooi 19 Da 0640o wherein, relative to an upright orientation for that profile, the section includes opposing webs which are interconnected by a common, laterally extending first flange at an upper end thereof, and a respective second flange extending laterally outwardly from each web at a lower end thereof; and wherein each of the webs includes a first web part which forms the major part thereof and a second part disposed between the first part and the first flange, and each second web part is disposed between the first web part and the first flange and is inclined relative to the first web part towards the first flange so that the second web part extends at an oblique angle to both the first flange and the first web part.

Accordingly, the present invention provides an arrangement wherein the web between the flanges in a load bearing metal section is not linear. Rather, the web includes the second part which is adjacent the first flange and which is inclined so as to extend obliquely to both the first flange and the first web part.

1 5 In this way, the second web part forms a chamfer at the junction between the main part of the web and the first flange.

This arrangement has substantial practical benefit. Firstly, the *introduction of the inclined second web part improves the stiffness of the overall web as it reduces the effective length of the web for the purposes of calculating its resistance to lateral, distortional and local buckling under loading applied to the flanges. Secondly, the introduction of the second part improves the ability of certain cross-sections to nest within a like section as required at a lap.

Specifically, in the top hat cross-section, one section is able to be moved i transversely relative to the other section to interfit the elements together in their nested configuration. The introduction of the second web part in these sections 0:provides a contact surface for that section which is spaced from its adjacent flange. This arrangement induces a bending moment in that section which assists in deforming the sections adequately to enable them to interfit in their nested configuration.

In the top hat section, each of the opposing webs includes a first major web part, and a second web part inclined to the first web part and disposed adjacent the first flange which forms a bridge. In the arrangement, both webs WASr.\26\RNC No Deloc 06Q7617-2 poi 19 Da 064o include a said second web part, and preferably the web parts extend inwardly towards one another.

Preferably each second web part is designed to extend a sufficient length to provide a significant reduction in the effective length of its respective web, but not be so great as to have a tendency to buckle when loading is applied to the section flanges. In a preferred form, the ratio of the length of the second web part to the thickness of the metal in the section is in the range of 10:1 to 50:1.

In a further preferred form of the invention, each web includes a third web part disposed adjacent the second flange, and which is inclined relative to the first major part of the web, towards the second flange so that said third web part extends at an oblique angle to both said second flange and said first web part. The third web part may be inclined in the same direction as the first web part, or in the opposite direction.

It is convenient to hereinafter describe embodiments of the present 1 5 invention with reference to the accompanying drawings. It is to be appreciated that the particularity of the drawings and the related description is to be understood as not superseding the generality of the preceding broad description of the invention.

In the drawings: Figure 1 is a cross-section of a top hat metal section; Figure 1B is a variation in the top flange of the section of Figure 1; and Figure 2 illustrates the top hat section of Figure 1 in engagement with a like section.

*i :Figure 1 illustrates, in cross-section, a top hat metal section 10 which is 999999 designed as a light gauge purlin or girt. The section 10 is made from metal sheet having a thickness in the order of 0.6 to 1.6 mm and is typically made by

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W: XSaaO\06\RNC No DdrmO6\27617-02 spi 19 Dw 06doc a roll forming process, although other processes, such as folding or pressing operations, known to those skilled in the art may be used to form the section.

The top hat section 10 is formed generally as an inverted channel having opposing webs 11, 12 which taper inwardly towards each other. The section includes in the orientation shown in Figure 1, a top flange 13 which interconnects the webs 11, 12 and a pair of bottom flanges 14, 15 which are formed at the lower margin of the respective webs 11, 12 and which extend outwardly therefrom. The bottom flanges 14 and 15 are designed to receive fixing elements, such as tek screws or the like, to secure the section 10 to an underlying structure. In the illustrated embodiment, each of the bottom flanges includes a pair of minor ribs 16 which form a channel 17 therebetween which S. provides a fixing location for those flanges 14 and 15. Further, each of the bottom flanges 14 and 15 includes a turned up edge 18 which extends to the terminal edge 19 of the metal sheet.

In use, the top hat section 10 is used predominantly to support roof or wall sheeting which is fastened directly to the first flange 13. However, the section 10 may have other load bearing applications such as floor joists which are similarly supported on the first flange 13. Typically the sections are installed in continuous runs over the supporting frame where the individual members are S 20 aligned and fastened together with their adjacent ends overlapping. The lap length is typically in the order of 5% to 15% of the span length of the members between adjacent supports but may be more or less depending on the design loading.

The webs 11, 12 are each formed from three web parts 20, 21 and 22.

Referring to web 11, the first web part 20, which forms the major part of the web 11, is located intermediate the section flanges 13 and 14. The first web part in the illustrated form is linear, although it is to be appreciated it may include additional ribbing or re-entrant portions as required. A second web part 21 is disposed intermediate the first web part 20 and the top flange 13.

The second web part 21, which is significantly shorter than the first web part extends at an oblique angle to the first web part so as to be inclined towards the top flange 13. The third web part 22 which interconnects the second flange 14 to first web part 20 also extends at an oblique angle to the first web part 11 so N \N45J47compls idoc 6 as to provide an inclined surface which extends towards the respective second flange 14. The other web 12 has a similar structure and like features have been given like reference numerals.

The webs 11 and 12, with their respective inclined web parts 21 and 22 are significantly stiffer as compared to a linear web, which thereby improves their resistance to lateral buckling under the application of loading applied along the flanges 13, 14 and 15. In particular, the introduction of the oblique surfaces in the form of the second and third web parts 21 and 22, reduces the effective length of each web which is used to calculate the resistance of the section to 10 lateral buckling to being the length of the respective first web part oooo To ensure that the introduction of the second and third web parts does not in fact reduce the strength of the section 10, the length of those web parts is restricted so that the ratio of the length of these web parts to the thickness of the section is in the range of 10:1 to 50:1. By keeping within this range, the full section of these web parts has the effect of resisting compressive buckling at a stress level at or approaching the yield or proof stress of the section material.

A further advantage of the configuration of the webs 11 and 12 of the i' section 10 is that it assists in nesting of the section with a like section as required at a lap. Figure 2 illustrates the section 10 being inserted within the 20 channel of a like section 101. In Figure 2, the sections 10, 101 are in an intermediate position wherein they are first in contact and therefore the sections must deform to be able to move further to their fully nested configuration (not shown). Specifically in this intermediate position, it is apparent that by virtue of the oblique second web parts 21, the leading point of engagement of the section 10 with the inner surface of the section 101 is at the bottom margin 23 of the second web parts 21. This contact point is displaced from the top flange 13, and in view of this displacement, a bending moment is generated in the respective webs 11 and 12 which biases those webs to pivot about the upper margin 24 of the respective second web parts 21. This bending moment assists in deformation of the inner section 10 so as to enable the sections 10, 101 to move more easily into their fully nested configuration.

Figure 1A illustrates a variation on the section 10 wherein the top flange, rather than being planar, is formed as a very shallow channel which extends N:ARN1,+5147v mpzj-ipdoc along the longitudinal direction of the section 10. This variation in the shape of the top flange 13 is designed primarily to further assist the section to deform when being moved into a nested configuration.

Accordingly, the present invention provides metal sections, with novel web configurations which are economic to manufacture, and which exhibit enhanced performance both in its resistance to lateral buckling and, in many cases, to its ability to nest with a like section.

It is to be appreciated that variations and/or modifications may be made to the parts previously described without departing from the spirit or ambit of the invention.

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Claims

1. An elongate load bearing section formed from sheet metal, the section having a substantially constant top hat profile in cross-sections along its longitudinal extent; wherein, relative to an upright orientation for that profile, the section includes opposing webs which are interconnected by a common, laterally extending first flange at an upper end thereof, and a respective second flange extending laterally outwardly from each web at a lower end thereof; and wherein each of the webs includes a first web part which forms the major part thereof and a second part disposed between the first part and the first flange, and each second web part is disposed between the first web part and the first flange and is inclined relative to the first web part towards the first flange so that the second web part extends at an oblique angle to both the first flange and the first web part. S 15

2. A section according to claim 1, wherein the respective second web parts extend inwardly towards one another.

A section according to either claim 1 or 2, wherein the first part of the two opposing said webs extend inwardly towards each other towards said upper oo end thereof.

4. A section according to any one of claims 1 to 3, wherein each said second flange is configured to receive fasteners to secure said section to an °O*o underlying structure.

A section according to any one of claims 1 to 4, wherein said first flange is formed as a shallow channel. o 25

6. A section according to any of claims 1 to 5, wherein the ratio of the length of the second web part to the thickness of the metal in the section is in the range of 10:1 to 50:1.

7. A section according to any one of claims 1 to 6, wherein each web further includes a third web part disposed adjacent the respective one of the second flanges, said third web part being inclined relative to the first part of the web towards the second flange so that said third web part extends at an oblique angle to both said second flange and said first web part. W \,andr2OU6\PNC No DOlM6\27617.O2 spoi 19 D c 64oc 9

8. A section according to claim 7, wherein the ratio of the length of the third web part to the thickness of the metal in the section is in the range of 10:1 to 50:1.

9. A load bearing section according to claim 1, substantially as herein described with reference to the accompanying drawings. S. op 000 0 000S00 0 00 @0 0 0 0 0000 ego 0 00 0 0@ *0 0 00 0 0 0000 0000 0 0000 @0 0 0@ .0 0 000.00 0 OS 0 SO 00 0O 0 00 S Og W \Smdi&2006\JL\C No DcldeO6\27617-02 spooi 19 Dao 06dmo