The present invention relates to a kit of connectors for assembling a structural beam of polygonal cross section using sheet members, and to such a structural beam suitable for use as an eaves beam and/or ridge beam in a roof structure.

A conventional roof is typically formed from timber framing. Eaves beams run around the perimeter of the roof, on top of the walls defining the structure being roofed, and one or more ridge beams define the top edge(s) of the roof. Sloped rafters may be connected at one of their ends to the eaves beams and at the other end to a ridge beam, supporting it. The arched structure formed by the rafters supports roof insulation and tiling. For increased strength, the rafters are often interconnected by additional beams such as collar ties, wind braces, joists, props and purlins, all of which are well-known in the building construction industry.

In the case of a conventional glazed conservatory roof, again the perimeter of the roof is typically defined by eaves beams and the top edge is defined by one or more ridge beams. Interconnection between the eaves beams and ridge beam(s) is provided by glazing bars, which support sheets of glazing material therebetween. Due to the weight of sheets of glazing material, additional supports, such as tie bars, are often required to ensure that the roof is of sufficient strength.

It is clear that in either of the above examples, substantial skill is required in building a conventional building or conservatory roof structure. For instance, each part of the structure (such as the eaves beams) must be produced within relatively precise tolerances, and the roof must be designed and assembled so that the stress from the weight of the roof is propagated correctly. Building such roofs therefore requires the expertise of professional builders, incurring substantial costs. Further, the use of professional builders brings with it the risk of unexpected delays and/or additional costs. In addition, conventional beams of the required strength have considerable bulk and weight, complicating transport of materials to the site and potentially requiring heavy lifting equipment to install.

In either of the above roof designs, the eaves beam may take the form of a box beam, that is to say a beam of hollow cross section formed by joining together four elongate sheet members into an elongate cuboidal 'box'. When a box beam undergoes a bending moment, it functions in a similar fashion to an I beam, with adjacent surfaces on opposite sides of the neutral axis functioning as the flanges and resisting largely shear forces, with the surfaces connecting these adjacent surfaces functioning as the web and largely resisting bending stresses. Use of a box beam may decrease the weight of the eaves beams, however it adds complexity to the design and assembly processes as the box beam must be manufactured precisely to the specific dimensions required for each roof. Further, attaching other beams or components to box beams can be more difficult due to the beams' hollow section, as traditional joints, such as dovetail joints, are unsuitable.

It is therefore an object of the invention to obviate or mitigate at least one of the aforesaid disadvantages, and/or to provide an improved or alternative structural beam for roof construction, and which may be used especially as an eaves beam in a roof structure.

According to a first aspect of the present invention there is provided a kit of connectors for assembling a structural beam of polygonal cross section using at least three sheet members, the kit comprising:

at least one fixed-angle connector for connecting two sheet members at a fixed relative angle, and

at least two pairs of hingedly cooperative connectors, each pair for connecting two sheet members at a variable relative angle, so as to enable completion of the polygonal cross section.

The range of relative angles that can be accommodated between pairs of hingedly cooperative connectors may allow beams of a wide variety of geometries to be assembled using standardised connectors, simply by altering the sizes of the sheet members. This may allow beams of the geometry required by a specific project to be produced and assembled relatively quickly and inexpensively. For instance, if the beam must span a distance with particularly little sag its vertical height may easily be increased, thereby increasing its first moment of area and therefore its stiffness. Further, the connectors may allows the beams to be manufactured and even assembled before delivery to the site. A sheet member is any component of sheet-like geometry. Each sheet member may or may not be hollow, uniform and/or planar in shape. Reference to the polygonal shape of the beam's cross section should not be construed as including only flat-sided polygons or only regular polygons. One or more surfaces of one or more of the sheet members may be complex in shape and/or arcuate in cross section.

Although it is possible and within the scope of the present invention that the connectors may effectively form "point" or "nodal" connections which are distributed along the overall length of the structural beam, it is particularly preferred that each connector be elongate. Provision of elongate connectors along the vertices of the beam may serve to provide additional structural strength.

Each pair of hingedly cooperative connectors may comprise an axle connector, which is mountable along an edge of one sheet member and which defines an axle element, pairable with a socket connector, which is mountable along an edge of another sheet member and which defines a socket element configured for rotation about the axle element. Such an arrangement may provide an advantageously simple, strong and/or reliable hinged connection. The kit may comprise at least two, and preferably three, fixed-angle connectors. For instance, the kit may be for assembling a structural beam of quadrilateral cross section, and comprise two fixed-angle connectors and two pairs of hingedly cooperative connectors. Alternatively the kit may be for assembling a structural beam of pentagonal cross section, and comprise three fixed-angle connectors and two pairs of hingedly cooperative connectors. Beams built from such kits may exhibit advantageous strength and/or adaptability of design. For instance, a beam of pentagonal cross-section may exhibit greater flexibility of geometry, while a beam of quadrilateral cross section may be constructed more quickly and out of fewer parts Where the kit has at least two fixed-angle connectors, each may be substantially identical in cross section, meaning that they are interchangeable, thus adding to the overall simplicity of the kit. All the pairs of hingedly cooperative connectors may be substantially identical in cross section. Again, the resultant interchangeability means that a structural beam can be formed with minimal instruction. The at least one fixed-angle connector may be configured to connect said two sheet members in a substantially mutually orthogonal orientation, i.e. at substantially 90° to one another, in a rigid manner. Where the kit has more than one fixed-angle connector, one, more than one or all of the fixed-angle connectors may be so configured. A finished beam with one or more of said connectors would therefore have two sheet members at right angles to one another, which may be useful in mounting two components to the panel in particular relative configurations. For instance, one elongate component may be mounted end-on against one of the sheet members and another elongate component may be mounted side-on against the other of the sheet members. Those elongate components would run parallel to one another.

Advantageously, one or more of the connectors (being fixed-angle or hingedly cooperative) may comprise a mounting element for attachment of an additional structure or component, such as a hooked, flanged or shelf-like component. The mounting element(s) may provide an advantageously simple attachment mechanism. The mounting elements being on connectors may allow the load applied to the mounting elements to be spread across a larger region of the beam.

For simplicity of manufacture and with a view to keeping costs as low as possible, one or more of the connectors (being fixed-angle or hingedly cooperative) may be sections of extrusion.

Said extrusion may be made of a metal such as aluminium alloy, a polymer, or any other suitable material. Alternatively or in addition, one or more of the connectors may be a bent sheet component, a stamped component, a forged component, a moulded or cast component, or may take any other suitable form.

In some circumstances, two of the connectors may be connected by a common sheet member integrally formed therewith, i.e. the common sheet member may have a connector formed along each of its long edges. The two connectors may be identical or different. Such a common sheet member would replace one of the at least three sheet members used to form a structural beam, and may be formed of a different material to the other sheet members. Indeed, the common sheet member may also be a section of extrusion. The common sheet member may comprise a void therein. Utilisation of a common sheet member may advantageously reduce the number of parts from which a beam must be assembled, decreasing assembly time.

According to a second aspect of the invention there is provided a structural beam of polygonal cross section for use as a roofing eaves beam and/or ridge beam, the beam comprising at least three sheet members interconnected by a kit of connectors according to the first aspect of the invention.

Such a beam may easily be made to have geometry that negates the need for fitting additional mounting brackets. For instance, components to be mounted to the beam by abutment with one of its faces, rather than using brackets, as outlined in more detail below. This may widen the mechanical suitability of the beam, and/or reduce construction time. Further, the beam may be of advantageously light weight, simplifying transport requirements and/or negating the need for heavy lifting equipment.

The beam may be of any suitable length. It may or may not taper, curve and/or change cross sectional shape along its length.

Where each connector is elongate, each may be aligned substantially parallel to the longitudinal axis of the beam. This arrangement may be advantageously strong and/or rigid. In such an arrangement, each connector may run along substantially the whole length of the beam. This arrangement may further increase the strength and/or rigidity of the beam.

Each pair of hingedly cooperative connectors comprised in the structural beam may be secured in a particular relative orientation by an adhered, welded, soldered or brazed portion, or by one or more fasteners, so as to provide additional rigidity to the beam once constructed.

The at least three sheet members interconnected by the kit of connectors may be arranged peripherally to define an elongate cavity of polygonal cross section within the beam. This cavity may advantageously reduce the weight of the beam. As outlined above, reference to polygonal shape should not be construed as requiring said polygon to be regular or straight-sided.

Where the beam has an elongate cavity, at least a portion of the elongate cavity may contain a foam or honeycomb material. Such contents may advantageously increase the strength of the beam. Instead or in addition, at least a portion of the elongate cavity may contain a thermally and/or acoustically insulative material.

Said foam and/or thermally or acoustically insulative material may be polymeric foam, such as polyurethane foam, or a natural product, such as sheep's wool. Where at least a portion of the elongate cavity contains a foam or honeycomb material, and at least a portion contains thermally or acoustically insulative material, said portions of the cavity may or may not be the same. For instance, a portion of the cavity may comprise an aluminium honeycomb structure the cells of which are filled with glass fibre insulation, or a portion may be filled with a foam which also has thermally and/or acoustically insulative properties.

Where the beam has an elongate cavity, the beam may comprise one or more intermediate support structures positioned within the cavity. The support structures, which may increase the strength or the rigidity of the beam, may be webs, struts, ties, combinations thereof, or may take any other suitable form. Alternatively, or in addition, said foam and/or thermally or acoustically insulative material may provide a support function from within the beam. The support structures may be substantially evenly distributed along the length of the cavity, or may be concentrated about points where the beam undergoes increased loading (for example in regions where other components are mounted to the beam).

Beneficially, at least one of the sheet members comprised in the structural beam may be made from composite material, preferably a lightweight material (having a density of less than 700kg/m ³ ).

Accordingly, the composite material may be carbon fibre, glass fibre, oriented strand board or any other suitable material. To enable provision of structural beams of a plurality of different cross sections, at least one of the sheet members may be of different geometry to at least one of the other sheet members, though all sheet members are preferably of the same length. According to a third aspect of the invention there is provided the use of a structural beam of polygonal cross section according to the second aspect of the invention in a roof structure.

Use of such a beam in a roof may simplify the assembly of the roof, allowing workers of a lower skill level to assemble it (thus reducing the cost of assembly and limiting the possibility of unexpected expenses or delays). For instance, it is believed that in many situations, a roof according to the third aspect of the invention may be delivered and assembled by two handymen with a van. Further, use of the beam may reduce the weight of the roof, reducing the stress exerted on the supporting walls and limiting or negating the need for further support structures.

For a better understanding, the present invention will now be more particularly described, by way of non-limiting example only, with reference to and as shown in the accompanying drawings (not to scale) in which:

Figure 1 is a perspective view of the structure of a conventional roof;

Figure 2 is a perspective view of the structure of a conventional glazed roof;

Figure 3 is a cross-sectional end view of a structural beam of polygonal cross-section according to a first embodiment of the invention;

Figure 4 is a cross-sectional end view of a fixed-angle connector of the structural beam of Figure 3;

Figure 5 is a cross-sectional end view of a pair of hingedly cooperative connectors of the structural beam of Figure 3;

Figure 6 is a cross-sectional end view of the structural beam of Figure 3 in position as a roofing eaves beam;

Figure 7 is a cross-sectional end view of a structural beam of polygonal cross section according to a second embodiment of the invention; and

Figure 8 is plan view of three exemplary structural beams connected by mitre joints.

Figure 1 shows the skeleton of an exemplary generic roof 1A of the type described above, in position atop a structure shown in dotted outline. An eaves beam 2 runs along the top of each wall 4 of the structure, defining the perimeter of the roof 1A. In this case a single ridge beam 6 defines the top edge of the roof. The ridge beam is supported by a number of rafters 8, which also support a roof covering (not shown) such as tiles, insulation and breather membrane that can be fitted above. The rafters 8 are arranged in pairs along the length of the ridge beam 6, usually at a predetermined spacing, and alternate pairs of rafters 8 are provided with additional structural support in the form of a collar tie 10. One or more walls 4 beneath the roof may not be of uniform construction, and may incorporate features such as windows and/or doors. A skeleton of an exemplary glazed conservatory roof 1 B as described previously is shown in Figure 2 in position atop a conservatory structure shown in dotted outline. As with the generic roof shown in Figure 1 , the glazed roof 1 B has eaves beams 2 running along the top of the conservatory walls 4' to define its perimeter, and a ridge beam 6 defining its top edge. In this case the ridge beam 6 is supported by glazing bars of three different types:

- a glazing bar referred to herein as a "transom glazing bar" 12, which extends at a substantially 90° angle to both the ridge beam 6 and the eaves beam 2 to which it is attached;

a glazing bar referred to herein as a "hip glazing bar" 14, which extends along a diagonal edge of the roof, from an end of the ridge beam 6 to a corner at which two eaves beams 6 meet; and

a glazing bar referred to herein as a "splay glazing bar" 16, which extends at a non-90 ° angle to both the ridge beam 6 and the eaves beam 4 to which it is attached.

Between the glazing bars 12, 14, 16, panes of glazing material (not shown) are supported. Again, one or more conservatory walls 4' beneath the roof may not be of uniform construction, and will usually incorporate features such as windows and/or doors.

Figure 3 shows a structural beam of polygonal cross section 18 according to a first embodiment of the invention. The beam 18 is constructed from five sheet members 20a-20e, interconnected by connectors to form an elongate beam (its longitudinal axis being normal to the page from the perspective of Figure 3) of polygonal cross section. The beam of the first embodiment has three elongate fixed-angle connectors 22, one connecting sheet members 20a and 20e, one connecting sheet members 20b and 20c and one connecting sheet members 20c and 20d. The beam also has two pairs 24 of elongate, hingedly cooperative connectors, one pair connecting sheet members 20a and 20b and one pair connecting sheet members 20d and 20e. Being formed from five sheet members 20a-20e, the beam has a non-uniform pentagonal cross sectional shape. The sheet members 20a-20e are arranged co-operatively to enclose a cavity 26 in the centre of the beam. The cavity 26, being enclosed by the inner faces of the pentagonally-arranged sheet members, is also of pentagonal cross section. Some of the connectors 22, 24 have one or more fins 25 which may be used as positioning guides, for instance to space a sheet of internal or external cladding (not visible) from the beam 18 by an appropriate distance and/or to hold it at the appropriate angle relative to the beam. Further, in this embodiment each of the connectors 22, 24 is a section of an extrusion. Some of the connectors 22, 24 have one or more hollows 27 positioned to keep the wall thickness of the extrusion as uniform as possible, thereby improving the strength and finish of the extrusion and reducing its cost.

Figure 4 shows in more detail the fixed-angle connector 22 that joins sheet members 20a and 20e. The fixed-angle connector 22 is elongate, its longitudinal axis being normal to the page from the perspective of Figure 4. It therefore runs parallel to the longitudinal axis of the beam. The connector 22 has two slots 28, each of which is adapted to receive a lateral end 30a, 30e of one of the sheet members 20a, 20e. The shape and relative orientation of the two slots 28 determines the relative position of the two sheet members 20a, 20e. In this embodiment the slots are at substantially 90° to each other and the base 32 of one slot 28 is adjacent to the inner side 34 of the other joint. The sheet members 20a, 20e are therefore positioned substantially orthogonally relative to one another, and their lateral ends 30a, 30e are positioned in a relationship akin to a butt joint. In this embodiment the connectors 22, 24 are bonded in place using an adhesive such as epoxy resin, but in other embodiments they may be held in place by friction fit, via serrations or using fasteners, or in any other suitable fashion

In the first embodiment as illustrated in Figure 3, each of the fixed-angle connectors 22 are substantially identical in cross-section and are all aligned with their longitudinal axes parallel to that of the beam 18. This substantially identical cross section allows them all to be made using substantially the same tooling and techniques, which can simplify production and assembly processes due to greater parts interchangeability. Further, as the fixed-angle connectors 22 are sections of extrusion, their identical nature therefore allows them all to be produced using the same extrusion die, and indeed allows them to be cut from the same extrusion.

Figure 5 shows in more detail the pair 24 of hingedly cooperative connectors which connect sheet members 20a and 20b. The pair 24 comprises an axle connector 36 and a socket connector 38, each of which is elongate with its longitudinal axis being normal to the page from the perspective of Figure 5. Each therefore also runs parallel to the longitudinal axis of the beam. The axle connector 36 has a slot 28', which is adapted to receive a lateral end 30b of a sheet member 20b, and an axle element 40 with a convex bearing surface 42. The socket connector 38 also has a slot 28" adapted to receive a lateral end 30a of a sheet member 20a. Further, socket connector 38 has a socket element 44 with a concave bearing surface 46. The axle element 40 of the axle connector 36 and the socket element 44 of the socket connector 38 are complimentarily shaped to form a hingedly rotatable coupling. In other words, the socket connector 38 is rotatable relative to the axle connector 36, about a rotational axis defined by the axle element (the rotational axis being parallel to the longitudinal axis of the axle connector 36, and therefore parallel to the beam 18). The sheet members 20a, 20b connected by the pair 24 of hingedly cooperative connectors are therefore rotatable relative to one another, allowing the angle between them (shown as angle a in Figure 3) to be varied.

The socket connector 38 mounted on sheet member 20a has a mounting element 48. The mounting element 48 of this embodiment takes the form of a short shelf used for mounting a roofing SIP, as outlined below, and has a centring groove 47. The centring groove 47 is configured to receive the tip of a fastener such as a self-drilling screw (not visible) and restrain the tip as the fastener is driven to prevent it skidding along the surface of the mounting element 48.

In this first embodiment, the concave bearing surface 46 of the socket connector 38 extends though just over 180°. This allows the axle connector 36 and socket connector 38 to be clipped together by inserting the axle element 40 into the socket element 44. Inserting the axle element 40 forces the socket element 44 to flex slightly to allow the axle element to enter, after which it springs back to its original shape and rotatably retains the axle element. In this embodiment the axle element 40 also has a flat portion 49. The flat portion 49 provides the axle element 40 with a region of reduced diameter, allowing it to be inserted into the socket element 44 more easily (since the socket element must flex less when the region of reduced diameter is inserted).

Though each pair 24 of hingedly cooperative connectors are configured to be rotatable relative to one another, the range of motion of one or more pairs 24 may be limited. In some situations, hinged cooperation between one or more pairs 24 may be substantially prevented, securing the pair (and therefore the sheet members mounted thereto) at a particular angle. For instance, in situations where the beam 18 is to undergo substantial load, it may be preferable for all pairs 24 of hingedly cooperative connectors to be secured at a predetermined relative angle. Fixing the relative angle of a pair 24 of hingedly cooperative connectors essentially transforms the pair into a single fixed-angle connector.

The above limitation or prevention of relative movement of a pair 24 of hingedly cooperative connectors can be brought about in any suitable fashion, for instance by gluing, soldering, brazing or welding the pair 24 of connectors together. Alternatively, the pair 24 of connectors may be limited or fixed in their relative rotation by one or more fasteners such as screws. The socket connector 38 comprises two centring grooves 47' to assist insertion of such fasteners as outlined above.

Figure 6 shows the structural beam 18 of the first embodiment positioned on top of a wall (generally denoted 52) and functioning as an eaves beam, with a load-bearing structural insulating panel ("SIP") 50 mounted to it. The SIP takes the place of a more traditional rafter or glazing bar. Sheet member 20a (along with the connectors 22, 24 attached thereto) defines an abutment surface 54 against which the SIP 50 is positioned. In this embodiment, the SIP 50 is clamped against the abutment surface 54 by a clamping mechanism (not shown), and rests on the mounting element 48 described previously. In this embodiment the SIP 50 has an elongate mounting strip 56 which rests on the mounting element 48 of the beam 18. For additional structural rigidity a plurality of screws (not shown) are driven through the mounting element 48 of the beam 18 and into the mounting strip 56 of the panel 50 to secure it in position. In this embodiment, the mounting element 48 functioning as a shelf also enables the panel 50 to be rested in place before being clamped and secured as indicated above, simplifying the assembly process of the roof.

With SIPs 50 mounted as roofing panels as described above, it is clear that the angle of the roof determines the required angle of the panel, which in turn determines the angle at which sheet member 20a must be held. Given that the angle of roofs can vary considerably, the flexibility in beam geometry which can be provided by the present invention may be particularly advantageous when the beam is to be used in such an application. Due to the range angles which can be accommodated by the pairs 24 of hingedly cooperative connectors, the angle of sheet member 20a can be varied simply by altering the dimensions of one or more of sheet members 20b-20e. For example, if a beam in which sheet member 20a was nearer to vertical was required, this could be achieved (for instance) by increasing the vertical height of sheet member 20d and reducing the horizontal width of sheet member 20c. The internal angle (shown as angle β in Figure 3) between sheet members 20d and 20e would therefore be decreased, and the internal angle a between sheet members 20a and 20b would be increased (these changes being accommodated within the range of motion of the pairs 24 of hingedly cooperative connectors), therefore sheet member 20a would be nearer vertical.

In other embodiments where the beam 18 is used as an eaves beam, roofing structures may be mounted differently. For instance, the external surface of sheet member 20e (and the connectors 22, 24 attached thereto) may function as an abutment surface against which roofing components (e.g. panels, rafters or glazing bars) are fitted. Alternatively or in addition, components may be fitted solely to one or more of the connectors 22, 24, with none of the sheet members 20a-20e providing an abutment surface. In some situations, the above mounting mechanisms (or any other) may be used in combination. For instance, the beam 18 may function as an eaves beam in a partially glazed roof, with SIPs 50 for the non-glazed portion mounted against sheet member 20a and glazing bars (not shown) for the glazed portion mounted with their undersides against sheet member 20e. In this arrangement, sheet members 20a and 20e being held substantially orthogonally by the fixed-angle connector 22 therebetween is beneficial as it ensures that the glazing beams (not shown) and panels 50 are aligned parallel to one another. In situations where the weight of the beam 18 is of most concern, the connectors 22, 24 may be of minimal length and the cavity 26 may be empty. In the first embodiment however, each of the connectors 22, 24 runs substantially the entire length of the beam. Further, the cavity 26 is filled with polyurethane foam (not shown) and has a plurality of intermediate support structures (not shown) spaced along its length. The polyurethane foam provides structural support to the sheet members 20a-20e, improving the load-bearing capabilities of the beam 18. The foam also acts as thermal insulation and sound-proofing. The support structures (not shown) take the form of substantially planar webs aligned normal to the longitudinal axis of the beam. Each is of complementary polygonal shape to that of the cavity 26 such that it fits inside with minimal clearance. The web therefore acts to hold the sheet members 20a-20e apart, preventing the beam from buckling. In addition, each web is bonded to the inner surfaces of the sheet members 20a, 20e such that it acts to prevent the sheet members being pulled apart from each other.

Figure 7 shows a beam 82 according to a second embodiment of the invention. The beam 82 of the second embodiment is similar to the beam 18 of the first embodiment, therefore only the similarities will be discussed. While the beam 18 of the first embodiment was formed from five sheet members (20a-20e in Figure 3), the beam 82 of the second embodiment is formed from four sheet members 20a-20d, giving it a quadrilateral cross sectional shape enclosing a quadrilateral cavity 26. Further, it has two fixed-angle connectors 22 rather than three. In addition, the two pairs 24 of hingedly cooperative connectors take a different form. Each axle connector 36 has a second convex bearing surface 54 in addition to the convex bearing surface 42 on its axle element 40, and also a concave bearing surface 56. Similarly, each socket connector 38 has a second concave bearing surface 58 in addition to the concave bearing surface 46 on its socket element 44, and also a convex bearing surface 60. Furthermore, one of the sheet members 20c' takes the form of a common sheet member, with the connectors 22, 38 on each of its lateral ends being formed integrally therewith. The common sheet member 20c' and its connectors 22, 38 are all formed from a section of a single aluminium extrusion. In this embodiment the common sheet member 20c' defines a void 61 , which may contain insulation and/or intermediate support structures such as those discussed in relation to the cavity 26 of the beam of the first embodiment, but which is primarily to reduce the overall weight of the component. The positioning of mounting elements 48 is also different in the second embodiment, with mounting elements present on the fixed-angle connector 22 joining sheet members 20a and 20b, the axle connector 36 attached to sheet member 20d, the socket member 38 which is part of the common sheet member 20c', and on the sheet member 20c' itself. The mounting elements 48 on the common sheet member 20c' serve as attachment points for external guttering when the beam 82 serves as an eaves beam in a roofing structure.

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined by the appended claims. For instance, though the mounting elements discussed herein are each part of a connector or common sheet member, in other embodiments the mounting elements may take any other suitable form. For instance, they may take the form of mouldings or bent sheet brackets bonded to a sheet member or attached thereto via fasteners.

Furthermore, though each pair of hingedly cooperative connectors described above comprise an axle connector and a socket connector, they may take any other suitable form. For instance, each connector of a pair may be rotatable relative to the other via a flexure bearing or a knife-edge bearing. Further, one or more localised areas of one or more of the sheet members of may be thickened by bonding an additional layer to its internal and/or surface. These thickened areas may be coincident with support structures in the beam, where present, and/or in locations where additional components may be attached (for instance by driving fasteners through the additional component and into the thickened section).

For the avoidance of doubt, where reference is made to connectors extending substantially the entire length of the beam, this refers to connectors that extend substantially the entire length of the edge of the beam to which they are attached. For example, as shown in Figure 8, where two beams 62 intersect at a mitre joint 63, a connector 64 on the inside edge of a beam may be significantly shorter than a connector 66 one on the outside edge of the same beam. Nonetheless, both such connectors extend substantially the entire length of the beam as defined herein. The above also holds where connectors may be of different lengths due to the beam being curved. Further, connectors which exhibit one or more breaks along their length may still be considered to extend along substantially the entire length of a beam. For instance, each connector may comprise two or more pieces aligned in series (for instance a 4m long beam may have a single connector made out of two 2m long sections), and/or a connector may be slightly shorter than the beam, for instance to provide clearance at a joint 63 (as is shown in Figure 8).

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the invention as defined in the claims are desired to be protected. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention, where appropriate.