NZ756430B2 - Improved roll-formed structural member - Google Patents

Abstract

improved roll formed structural member is provided that can have its structural properties adapted for a desired purpose, by optionally fitting reinforcing members. The roll-formed structural member comprising a pair of generally C-shaped channel elements nested together, to form a body having a substantially rectangular cross-section profile. The first and second web portions at one or both of the top and/or bottom of the body narrow towards each other to define a recessed region, adapted for optionally receiving forcing members. substantially rectangular cross-section profile. The first and second web portions at one or both of the top and/or bottom of the body narrow towards each other to define a recessed region, adapted for optionally receiving forcing members.

Description

IMPROVED ROLL-FORMED STRUCTURAL MEMBER FIELD OF THE INVENTION The present invention relates to an improved roll-formed structural member.

More particularly, but not exclusively, it relates to an elongate roll-formed structural member which can be reinforced.

BACKGROUND OF THE INVENTION Roll-formed structural members are known to be a versatile building component with many advantageous properties. Roll-formed structural members are usually formed by bending one or more metal sheets into a desired profile using rollers. The resulting hollow structural member is quick and simple to install, light weight, durable in many environments, provides straight beams and can be easily manufactured to the required width, depth and length dimensions.

However, in some building applications, these simple traditional structural members may not be strong enough to perform under larger loads without requiring many different profiles. Consequently, a large number of profiles may be required to meet a wide range of structural demands.

It may therefore be valuable to provide an improved roll-formed structural member/assembly with improved flexibility and/or strength properties as required in different building applications.

In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention.

Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

It is an object of the present invention to provide an improved roll-formed structural member which overcomes or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

BRIEF DESCRIPTION OF THE INVENTION According to a first aspect, the invention broadly comprises an elongate roll- formed structural member comprising: a pair of generally C-shaped channel elements nested together, the pair of generally C-shaped channel elements forming a body having a substantially rectangular cross-section profile, the body comprising: first and second flanges substantially parallel and spaced apart at a top and bottom of the body respectively, and first and second web portions separating the first and second flanges, the first and second web portions being substantially parallel and spaced apart at sides respectively, and wherein the first and second web portions at one or both of the top and/or bottom of the body narrow towards each other and defines a recessed region, and wherein said structural member further comprises one or more external elongate reinforcing elements configured to be coupled onto the recessed region(s) of the elongate roll-formed structural member.

According to another aspect the flange adjacent the recessed region has a flange width less than a width of the space between the first and second web portions.

According to another aspect the flange adjacent the recessed region has a flange width at least less than the widest space between the first and second web portions.

According to another aspect the recessed region is at the uppermost or lowermost ends of the body.

According to another aspect the external reinforcing element(s) coupled onto the recessed region(s) results in a box-section in which the external reinforcing element(s) lie within a general rectangular profile or envelope.

According to another aspect the recessed region comprises a recess width between one and five times a wall thickness of the elongate external reinforcing element.

According to another aspect the recessed region comprises a recess width between one and three times the wall thickness of the elongate external reinforcing element.

According to another aspect the elongate external reinforcing element(s) coupled to the recessed region form a wall thickness between two and six times a wall thickness of the web portions without reinforcement.

According to another aspect the elongate external reinforcing element(s) coupled to the recessed region form a wall thickness between three and five times the wall thickness of the web portions without reinforcement.

According to another aspect the member further comprises fasteners to couple the external elongate reinforcing element onto the body, the fasteners being one or a combination of screws, rivets, bolts, adhesives, welds.

According to another aspect each elongate external reinforcing element comprises a C-shaped cross-section having a flange-corresponding portion and two web- corresponding portions depending from the flange-corresponding portion.

According to another aspect the two web-corresponding portions of an outermost external elongate reinforcing element do not protrude outward past the widest region of the web portions.

According to another aspect the elongate external reinforcing element comprises a cross-sectional profile to fit over a corresponding recessed region of the body.

According to another aspect the elongate external reinforcing element extends along a full length of the elongate roll-formed member.

According to another aspect the elongate external reinforcing element extends a partial length along the elongate roll-formed member.

According to another aspect two elongate external reinforcing elements are coupled to one or both of the first and second flanges.

According to another aspect at least one elongate external reinforcing element is coupled to both the first and second flanges.

According to another aspect two elongate external reinforcing elements are coupled to each of the first and second flanges.

According to another aspect the first and second webs have indentations in a mid-region extending longitudinally along the elongate roll-formed structural member to improve structural performance of the member.

According to another aspect the body cross-section including the recessed region extends along at least a significant portion of the length of the elongate roll-formed member.

According to another aspect the invention broadly comprises a method of forming an elongate roll-formed structural member comprising: providing metal sheets, bending the metal sheets with rollers to form a pair of generally C-shaped channel elements, nesting the pair of generally C-shaped channel elements together to form a body having a substantially rectangular cross-section profile, the body comprising: first and second flanges substantially parallel and spaced apart at top and bottom of the body respectively, and first and second web portions separating the first and second flanges, the first and second web portions being substantially parallel and spaced apart at respective sides, and bending the metal sheets to form a recessed region where the first and second web portions at one or both of the top and/or bottom of the body narrow towards each other, and fitting one or more elongate external reinforcing elements with a predetermined length onto one or both of the flanges.

According to another aspect the method further comprises fitting one or more elongate external reinforcing elements with a predetermined length onto one or both of the flanges.

According to another aspect the method further comprises providing fasteners to couple each elongate external reinforcing element onto the flanges.

According to another aspect the predetermined length of the elongate external reinforcing elements is the same as the length of the body of the elongate roll-formed structural member to reinforce the whole member.

According to another aspect the predetermined length of the elongate external reinforcing elements is less than the length of the body of the elongate roll-formed structural member to reinforce part of the member.

According to another aspect the method further comprises forming indentations extending longitudinally in a mid-region along the elongate roll-formed structural member to improve structural performance of the member.

According to another aspect the body cross-section including the recessed region extends along at least a significant portion of the length of the elongate roll-formed member.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

As used herein the term “and/or” means “and” or “or”, or both.

As used herein “(s)” following a noun means the plural and/or singular forms of the noun.

The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example only and with reference to the drawings in which: Figure 1 shows an end view of an elongate roll-formed structural member.

Figure 2 shows a perspective view of the elongate roll-formed structural member.

Figure 3 shows an exploded end view of the elongate roll-formed structural member.

Figure 4 shows an exploded perspective view of the elongate roll-formed structural member.

Figure 5 shows an end view of the elongate roll-formed structural member within a rectangular envelope.

Figure 6 shows a perspective view of two elongate roll-formed structural members coupled together with a connection plate.

Figure 7 shows a close-up perspective view of an elongate roll-formed structural member.

Figure 8 shows an exploded view of two roll formed C-shaped channel elements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS According to various aspects of the present invention as illustrated in figures 1- 8, there is provided an elongate roll-formed structural member 1 and method of forming the member which will now be described. It will be appreciated that these figures illustrate the general principles of the structure and construction, and that the invention is not limited to the precise configurations illustrated.

The general structure of various embodiments of the present invention as shown in the figures will now be described followed by a description of the method of forming the elongate roll-formed structural member 1.

General Application, Characteristics and Structure As shown in figures 1 and 3, the roll-formed structural member 1 has a body having a substantially rectangular cross-section profile. The body 10 has a profile cross-section resembling a rectangular shape (including a square), despite also having some features such as indentations 18 which do not substantially change the main profile. The resulting elongate roll-formed structural member 1 is hollow and lightweight.

A lightweight structural member is simple to work with, may have lighter foundation requirements due to less building weight, and can be transported easily.

The roll-formed structural member 1 can be used as a building component such as in framing, walls, roofing members, or flooring for example. Such beam members provide excellent strength for their weight, making them particularly suitable for certain types of structures being clear span structures, portals, mezzanine floors, alternatives to where laminated wood beams or structural steel are used, for example.

Preferably, the roll-formed structural member 1 is formed from metal such as hot-dipped galvanised cold rolled steel. This is beneficial as the structural member 1 will perform well in many environments and is less likely deteriorate due to rot, burn due to fire or erode in comparison to other material such as timber.

It is anticipated that other metals or materials with similar strength and durability characteristics may be used.

As best shown in figure 8, in the most preferred configurations, the body 10 of the elongate roll-formed structural member is formed from a pair of generally C-shaped channel elements 11, 12 nested together (facing towards each other).

Preferably, the nested C-shaped channel elements 11,12 hold each other together, and no welding is necessary. For example, the C-shaped channel elements 11, 12 are coupled together by techniques known to a person skilled in the art such as crimping or clinching. Alternatively, the C-shaped channel elements 11 are welded or spot welded.

Preferably, the pair of C-shaped channel elements 11, 12 are similar or the same shaped.

The elongate roll-formed structural member 1 is formed from a metal sheet with a predetermined length. The resulting roll-formed structural member 1 is an elongate structure with a member length 2 as referenced in figure 2. The manufactured member length 2 can be tailored to the building application.

The body 10 of the elongate roll-formed structural member 1 preferably has first and second flanges 21, 22 substantially parallel and spaced apart at a top and bottom 13, 14 of the body 10 respectively.

The body 10 of the elongate roll-formed structural member 1 preferably has first and second web portions 23, 24 separating the first and second flanges 21, 22.

Preferably, the first and second web portions 23, 24 are substantially parallel and spaced apart at sides respectively.

Preferably, the body 10 having a generally rectangular cross-sectional profile is formed by a pair of C-shaped channel elements 11, 12. Each of the of C-shaped channel elements 11, 12 comprises a web portion, and two depending flange portions. When a pair of C-shaped channel elements 11, 12 are nested together, the resulting body 10 comprises flanges 21, 22 of double thickness which improves the strength of the beam.

Preferably, the body cross-section including the recessed region 30 (introduced later) extends along at least a significant portion of the length 2 of the elongate roll- formed member 1.

A significant portion can be defined as a member 1 which has the described cross-section (including a recessed region 30) along at least a portion of the length 2, such that it has a material effect on the member 1. Preferably, the cross-section including the recessed region 30 is long enough such that when it receives one or more external reinforcing members 40, 40’ (introduced later), it will have a material effect (e.g. strengthening the member 1).

In some configurations, the body cross-section extends over half the length 2 of the member 1.

In some configurations, that the body cross-section extends less than half of the length 2 of the member 1 (but still a significant portion, such that it has a material effect on the member).

In some configurations, the body cross-section extends over the full length It is anticipated, that very localised changes to the cross-section of the member 1 (e.g. ribs, small dents etc.) will not be considered a cross-section along a significant portion of the length 2 of the member 1.

Due to the improved strength of the present invention, it should be appreciated that in some configurations, the elongate roll-formed structural member 1 can have web portions 23, 24 of shorter lengths compared to traditional beams. This can allow for more usable internal floor area in some building situations.

Recessed Portion As best shown in the exploded views of the roll-formed structural member 1 in figures 3 and 4, in the most preferred configurations, the web portions 23, 24 at a top and/or bottom of the of the body 10 narrow towards each other and defines a recessed region 30. In some configurations, the recessed region 30 is formed at one of the top or bottom 13, 14 of the body 10. In other configurations, the recessed region 30 is formed at both the top and bottom 13, 14 of the body 10.

In the preferred configurations, the recessed region 30 is at the uppermost or lowermost ends 13, 14 of the body.

Preferably, the recessed region 30 is not located at a mid-region 15 of the body . Instead in the preferred configurations, each recessed region 30 is located at a segment of the web portions 23, 24 immediately adjacent the flange.

Preferably, the recessed region 30 is narrowed such that the width 3 between the first and second web portions 23, 24 at the recessed region 30 is less than the width 4 at a mid-region 15 of the body (as shown in figure 3).

Preferably, the flange 21, 22 adjacent the recessed region 30 has a flange width less than a width 4 of the space between the first and second web portions.

Most preferably, the flange 21, 22 adjacent the recessed region 30 has a flange width 5 at least less than the width 4 of the widest space between the first and second web portions as referenced in figure 3.

The recessed region 30 is configured to receive an external component onto the body 10 of elongate roll-formed structural member 1.

In the most preferred configurations, the recessed region 30 is configured to receive an external elongate reinforcing element 40. The resulting structure is a box- section in which the reinforcing element(s) lie within a general rectangular profile or envelope 50 as shown in figure 5.

Preferably, the external elongate reinforcing element 40 and fasteners 9 are located inside the rectangular envelope 50 so that external components of a structure (such as external plates, purlins and girts etc.) can be mounted close to the member 1 without interference from the external reinforcing element and fasteners.

In some configurations, the recessed region 30 reduces flexural moment (bending) by about 9% in comparison to an elongate roll-formed structural member without the recessed region.

Flexural moment in the preferred configurations reduces as the body cross- section including the recessed region 30 extends along at least a significant portion of the length 2 of the elongate roll-formed member 1.

Reinforcing Member In the preferred configurations, one or more external elongate reinforcing elements 40, 40’ are configured to be coupled onto the recessed region(s) 30 of the elongate roll-formed structural member 1.

It is anticipated in some independent configurations, the elongate roll-formed structural member 1 does not include an external elongate reinforcing element 40. This type of configuration can be seen in figure 3, if the reinforcing elements 40, 40’ are taken away.

In these configurations, the improvement of the roll-formed structural member 1 lies with the recessed region 30 which provides an option to receive an external component without unduly compromising the strength of the structural member.

However, in the most preferred configurations, external elongate reinforcing elements 40, 40’ are present, and are coupled onto the recessed region(s) 30 of the elongate roll-formed structural member 1. The reinforcing elements 40, 40’ are advantageous as they can help strengthen the roll-formed structural member 1, by offering better resistance against structural failure such as by buckling, separating, or at least become structures which creak which is undesirable.

In some configurations including the external elongate reinforcing elements 40, 40’, the strength of the roll-formed structural member 1 can increase by approximately 250%.

It is anticipated that the number, length and thickness of the reinforcing elements 40, 40’ should be tailored to the specific loading requirement.

Preferably, each elongate external reinforcing element 40, 40’ comprises a C- shaped cross-section having a flange-corresponding portion 41 and two web- corresponding portions 42 depending from the flange-corresponding portion (referenced in figure 3). The flange-corresponding portion 41 is located directly or indirectly over the first or second flanges 21, 22 of the body 10. The two web-corresponding portions 42 is located directly or indirectly over the first and second web portions 23, 24 of the body Preferably, the elongate external reinforcing element 40, 40’ comprises a cross- sectional profile to fit over a corresponding recessed region 30 of the body 10, as best shown in figures 1 and 3.

Preferably, the recessed region 30 comprises a recess width 31 between one and five times a wall thickness 43 of the elongate external reinforcing element 40.

Most preferably, the recessed region 30 comprises a recess width 31 between one and three times the wall thickness 43 of the elongate external reinforcing element In the preferred configurations, improved strength characteristics of the roll- formed structural member 1 is due to an increase in wall thickness 6 at important regions of the structural member.

In some configurations, the increased wall thickness 6 may be due to overlapping ends 16, 16’ of the C-shaped channel elements 11, 12 which form the flanges 21, 22.

In some configurations, the external reinforcing element(s) 40, 40’ form the increased wall thickness 6 in addition to the overlapping ends 16, 16’ of the C-shaped channel elements 11, 12 as referenced in figure 1.

Preferably, the elongate external reinforcing element(s) 40, 40’ coupled to the recessed region 30 form a wall thickness 6 between two and six times a wall thickness of the web portions 7 without reinforcement.

In the preferred configurations, the elongate external reinforcing element(s) 40, 40’ coupled to the recessed region 30 form a wall thickness 6 between 2 and 5 times a wall thickness of the web portions 7 without reinforcement.

In some configurations the wall thickness of the web portions 7 is two to five mm thick.

The external elongate reinforcing elements 40, 40’ and the recessed region 30 features work in synergy to provide an elongate roll-formed structural member 1 with improved structural properties while providing a substantially planar outer profile particularly with attached reinforcement element(s).

Preferably, the two web-corresponding portions 42 of an outermost external elongate reinforcing element 40’ do not protrude outward past the widest region 25 of the web portions 23, 24.

Preferably, the two web-corresponding portions 42 of the outermost external elongate reinforcing element 40’ is on the same plane or recessed inward from the widest region 25 of the web portions as shown on figure 1.

An elongate roll-formed structural member 1 with a substantially planar outer profile where the reinforcing elements 40, 40’ do not protrude outwardly from the main body 10 is beneficial. A structural member 1 with a substantially planar outer profile will sit against other building components such as other framing, other structural members, or connection elements etc. better. For example, as shown in figures 6 and 7, the roll- formed structural member 1 abuts against a connection plate 8 evenly. The points of contact between the structural member 1 and the connection plate 8 do not decrease with the presence of the reinforcement elements 40, 40’. The resulting interaction between the components is stable.

Configurations where the reinforcement elements 40, 40’ are received in a recessed portion 30 also provides a structural member which is safer to handle. If the reinforcement element 40, 40’ does not protrude outwardly, it will not catch on items such as workers’ clothing or other items, or scratch or cut workers working with the structural members 1.

Furthermore, the recessed region 30 acts as a locator on the structural member 1, such that it becomes easier for the external elongate reinforcing element 40 to align and position the reinforcing element over the body 10 of the member.

In the preferred configurations, the elongate roll-formed structural member 1 further comprises fasteners 9 to couple the external elongate reinforcing element 40 onto the body 10.

Preferably, the fasteners 9 are one or a combination of screws, rivets, bolts, adhesives, welds, spot welds etc.

It is anticipated that any other suitable fasteners known to a person skilled in the art may be used.

In some configurations, the elongate external reinforcing element 40 extends along a full length 2 of the elongate roll-formed structural member 1 as shown in figure 2. A structural member 1 with reinforcement along its full length 2 may be advantageous as the full member is reinforced to improve the structural properties of the member.

In other configurations, the elongate external reinforcing element 40 extends a partial length along the elongate roll-formed member 1’ as shown in figure 6.

Preferably, in these configurations, the elongate external reinforcing element 40 provides localised reinforcement, and a region 17 of the member will remain unreinforced.

Preferably, the elongate external reinforcing element 40 extends along at least a significant portion of the length 2 of the elongate roll-formed member 1, such that it will have a material effect on the member.

A partially reinforced member 1’ is advantageous as it is cost-effective and less resources are required to reinforce the member. Furthermore, the resulting reinforced member 1’ is more lightweight which has further benefits such as the potential for lighter foundations due to the lighter structure.

Preferably, the recessed region 30 does not affect the structural performance of the member 1. Meanwhile, the recessed region 30 provides a space to receive external reinforcing elements 40 when and where it is required.

Whether or not the reinforcement element 40 is required may for example depend on the load the member 1 is supporting and/or the length 2 of the member.

Preferably, the reinforcement element 40 will be located where the reinforcement is necessary, such as a region where failure is likely to occur along the member.

Typically, the greatest loadings are towards the ends of a beam, therefore it may be necessary to only improve strength these points by adding the reinforcement element The length of reinforcement element 40 needed may be determined by load factors. For example, a very long span with heavy loading may require full reinforcement (i.e. the length of the reinforcement element is the same as the length of the full structural member itself). Preferably, the length of reinforcement element 40 is significant such that it has a material effect on the member 1.

In figure 6, two elongate roll-formed structural members 1, 1’ connected by a connection plate 8 is shown. The external elongate reinforcing element 40 extends along the entire length of structural member 1, while only extending a partial length along structural member 1’. The reinforcing element 40 is located towards one end of structural member 1’.

In the preferred configurations, the elongate reinforcing elements 40 are external components, configured to be coupled onto an outer surface of the body 10 of the roll-formed structural member 1. An external reinforcing element 40 is beneficial as it acts as a visual indicator. The presence and location of the external reinforcement element 40 can be seen which is useful.

An external reinforcing element 40 will help workers determine which orientation the structural member 10 is in and help determine if the member has been reinforced. As workers can visually see the external reinforcing element 40 on the outer surface of the structural member, this can be beneficial in some situations, such as allowing for building inspection from the ground.

In contrast, if the structural member 1 was internally reinforced, it would be difficult to determine whether the structural member has any reinforcement, and the location of such reinforcement.

It is anticipated that the number and location of external reinforcement elements 40 may vary as required for the application.

In some configurations, at least one elongate external reinforcing element 40 is coupled to both the first and second flanges 21, 22.

In some configurations, two elongate external reinforcing elements 40. 40’ are coupled to each of the first and second flanges 21, 22.

In other configurations, only one of the first or second flanges 21,22 have reinforcing elements 40.

In some configurations, only one elongate external reinforcing element 40 is coupled to one or both of the flanges 21, 22.

In other confirmations, two elongate external reinforcing elements 40, 41’ are coupled to one or both of the first and second flanges 21, 22. Preferably, two elongate external reinforcing elements 40, 41’ are coupled to: a) The first flange 21, b) The second flange 22, or c) Both the first and second flanges 21, 22 as shown in figure 2.

It is anticipated more elongate external reinforcing elements 40 may be coupled to the flanges 21,22 as required.

Optionally, the first and second webs 23, 24 have indentations 18 in a mid- region 15 extending longitudinally along the elongate roll-formed structural member to improve the structural performance of the member (referenced in figures 2 and 3).

Method of Forming Structural Member Following the description of the structure of the present invention described above, a general description of the method of forming the elongate roll-formed structural member 1 will now be described.

To form the elongate roll-formed structural member 1 as described above, firstly metal sheets are provided.

Preferably, the metal sheets are progressively formed with rollers to form a pair of generally C-shaped channel elements. The process of roll-forming to form elongate components is known to a person skilled to the art and will not be described further in detail.

The pair of generally C-shaped channel elements 11, 12 are then nested together (as shown in figure 8) to form a body 10 having a substantially rectangular cross-section profile.

Preferably, the body 10 is formed with flanges 21, 22 and web portions 23, 24 as described above.

In the preferred configurations, the metal sheets are bent to form the recessed region 30 where the first and second web portions 23, 24 at one or both of the top and/or bottom of the body 10 narrow towards each other.

After the body 10 of the elongate roll-formed structural member 1 has been formed, in the preferred configurations, one or more elongate external reinforcing elements 40, 40’ with a predetermined length is fitted onto one or both of the flanges 21, In some configurations, the predetermined length of the elongate external reinforcing elements 40, 40’ is the same as the length 2 of the body 10 of the elongate roll-formed structural member 1, so that the whole member is reinforced.

In other configurations, the predetermined length of the elongate external reinforcing elements 40, 40’ is less than the length of the body 10 of the elongate roll- formed structural member to reinforce only a part of the member 1.

Preferably, fasteners 9 as described above are used to couple each elongate external reinforcing element 40, 41 onto the flanges 21, 22.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Claims (26)

1. An elongate roll-formed structural member comprising: a pair of generally C-shaped channel elements nested together, the pair of generally C-shaped channel elements forming a body having a substantially rectangular cross-section profile, the body comprising: first and second flanges substantially parallel and spaced apart at a top and bottom of the body respectively, and first and second web portions separating the first and second flanges, the first and second web portions being substantially parallel and spaced apart at sides respectively, and wherein the first and second web portions at one or both of the top and/or bottom of the body narrow towards each other and defines a recessed region, wherein said structural member further comprises one or more external elongate reinforcing elements configured to be coupled onto the recessed region(s) of the elongate roll-formed structural member.

2. The elongate roll-formed structural member as claimed claim 1, wherein the flange adjacent the recessed region has a flange width less than a width of the space between the first and second web portions.

3. The elongate roll-formed structural member as claimed in claim 2, wherein the flange adjacent the recessed region has a flange width at least less than the widest space between the first and second web portions.

4. The elongate roll-formed structural member as claimed in any one of claims 1 to 3, wherein the recessed region is at the uppermost or lowermost ends of the body.

5. The elongate roll-formed structural member as claimed in claim 4, wherein the external reinforcing element(s) coupled onto the recessed region(s) results in a box- section in which the external reinforcing element(s) lie within a general rectangular profile or envelope.

6. The elongate roll-formed structural member as claimed in claims 5, wherein the recessed region comprises a recess width between one and five times a wall thickness of the elongate external reinforcing element.

7. The elongate roll-formed structural member as claimed in claim 6, wherein the recessed region comprises a recess width between one and three times the wall thickness of the elongate external reinforcing element.

8. The elongate roll-formed structural member as claimed in anyone of claims 5 to 7, wherein the elongate external reinforcing element(s) coupled to the recessed region form a wall thickness between two and six times a wall thickness of the web portions without reinforcement.

9. The elongate roll-formed structural member as claimed in claim 8, wherein the elongate external reinforcing element(s) coupled to the recessed region form a wall thickness between three and five times the wall thickness of the web portions without reinforcement.

10. The elongate roll-formed structural member as claimed in any one of claims 5 to 9, comprising fasteners to couple the external elongate reinforcing element onto the body, the fasteners being one or a combination of screws, rivets, bolts, adhesives, welds.

11. The elongate roll-formed structural member as claimed in any one of claims 5 to 10 wherein each elongate external reinforcing element comprises a C-shaped cross- section having a flange-corresponding portion and two web-corresponding portions depending from the flange-corresponding portion.

12. The elongate roll-formed structural member as claimed in claim 11, wherein the two web-corresponding portions of an outermost external elongate reinforcing element do not protrude outward past the widest region of the web portions.

13. The elongate roll-formed structural member as claimed in claims 5 to 12, wherein the elongate external reinforcing element comprises a cross-sectional profile to fit over a corresponding recessed region of the body.

14. The elongate roll-formed structural member as claimed in any one of claims 5 to 13, wherein the elongate external reinforcing element extends along a full length of the elongate roll-formed member.

15. The elongate roll-formed structural member as claimed in any one of claims 5 to 13, wherein the elongate external reinforcing element extends a partial length along the elongate roll-formed member.

16. The elongate roll-formed structural member as claimed in any one of claims 5 to 15, wherein two elongate external reinforcing elements are coupled to one or both of the first and second flanges.

17. The elongate roll-formed structural member as claimed in any one of claims 5 to 16, wherein at least one elongate external reinforcing element is coupled to both the first and second flanges.

18. The elongate roll-formed structural member as claimed in claim 17, wherein two elongate external reinforcing elements are coupled to each of the first and second flanges.

19. The elongate roll-formed structural member as claimed in any one of claims 1 to 18, wherein the first and second webs have indentations in a mid-region extending longitudinally along the elongate roll-formed structural member to improve structural performance of the member.

20. The elongate roll-formed structural member as claimed in any one of claims 1 to 19, wherein the body cross-section including the recessed region extends along at least a significant portion of the length of the elongate roll-formed member.

21. A method of forming an elongate roll-formed structural member comprising: providing metal sheets, bending the metal sheets with rollers to form a pair of generally C-shaped channel elements, nesting the pair of generally C-shaped channel elements together to form a body having a substantially rectangular cross-section profile, the body comprising: first and second flanges substantially parallel and spaced apart at top and bottom of the body respectively, and first and second web portions separating the first and second flanges, the first and second web portions being substantially parallel and spaced apart at respective sides, and bending the metal sheets to form a recessed region where the first and second web portions at one or both of the top and/or bottom of the body narrow towards each other, and fitting one or more elongate external reinforcing elements with a predetermined length onto one or both of the flanges.

22. The method of forming an elongate roll-formed structural member as claimed in claim 21, further comprising providing fasteners to couple each elongate external reinforcing element onto the flanges.

23. The method of forming an elongate roll-formed structural member as claimed in claim 21 or 22, wherein the predetermined length of the elongate external reinforcing elements is the same as the length of the body of the elongate roll-formed structural member to reinforce the whole member.

24. The method of forming an elongate roll-formed structural member as claimed in claim 21 or 22, wherein the predetermined length of the elongate external reinforcing elements is less than the length of the body of the elongate roll-formed structural member to reinforce part of the member.

25. The method of forming an elongate roll-formed structural member as claimed in claims 21 to 24, further comprising forming indentations extending longitudinally in a mid-region along the elongate roll-formed structural member to improve structural performance of the member.

26. The method of forming an elongate roll-formed structural member as claimed in any one of claims 21 to 25 wherein the body cross-section including the recessed region extends along at least a significant portion of the length of the elongate roll-formed member.