AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant (s): BLUESCOPE STEEL LIMITED Invention Title: PANEL CONSTRUCTION The following statement is a full description of this invention, including the best method for performing it known to me/us: P78310AU.1 Pat_Set_Fding Applicatin 20094-15.doc (S) - 2 PANEL CONSTRUCTION Technical Field 5 The present invention relates generally to composite panels, to assemblies for use in composite panels and processes for use in composite panel construction. The invention has been developed especially, but not exclusively, for tilt-up wall panel construction, and is herein described in that context. However, it is to be appreciated that the invention is not limited to that use. 10 Background Known pre-cast concrete tilt-up wall panels are either cast on a building site or off-site and thereafter transported to the site. In either case, on the building site the panels are 15 positioned on an underlying support structure, typically a rebated concrete slab, to form the walls for the building. Thereafter, the roof of the building is constructed to complete the main structure of the building. In International Patent Application W02006/058390, the applicant discloses a tilt-up 20 wall panel that is in the form of a composite structure having a profiled sheet and cementitious material cast on the sheet. In the formation of composite structures as tilt-up wall panels, it is a requirement to control the dimensions and shape of the panel. This is necessary as the resultant panel 25 needs to be made to relatively precise tolerances and the casting of a cementitious material onto the underlying sheets induces hydrostatic forces that need to be contained to maintain dimensional control in the resulting panel. Accordingly, there is an ongoing need to refine methods of construction of composite panels which take into consideration these requirements. 30 Summary of the Invention According to a first aspect, there is provided a base assembly for use in a composite panel, the base assembly comprising a frame and a skin mounted to the frame, wherein 35 a settable material is arranged to be cast onto the skin in formation of the composite panel. N:\Sydney\Cases\Patent\780O0-78999\P7831O.AU.1\SpecisP78310.AU.1Innovaton Specification 15.06.09.doc -3 In the specification, the term "composite" is used in a general sense to specify that the panel is made from separate elements without requiring a particular interrelationship between those elements. 5 In accordance with this aspect a frame is provided which forms part of a resulting composite panel. The existence of the frame can provide additional strength and rigidity to the skin so as to provide better dimensional control in construction of the panel. Further, the frame may have a secondary function, such as being used in lifting of the composite panel during transport and/or as framing in a resulting wall 10 incorporating the composite panel. As such, the frame may remain as an integral part of the composite panel or may ultimately be removed from the panel, for example when the panel is installed in its in-use position. In a particular form, the skin overlays the frame. Such an arrangement is particularly 15 advantageous where the frame is to be used in a subsequent structure formed from the composite panel, such as when the panel is used in tilt-up wall panel construction. The skin of the base assembly may take various forms. In a particular embodiment the skin is formed from one or more sheets. In one form, the one or more sheets are 20 profiled sheets and in a particular embodiment those profiled sheets are made from metal. In a particular embodiment the one or more profiled sheets include formations that are arranged to be at least partially embedded in the settable material. In this way the formations provide shear elements to assist in load transfer and bonding between the settable material and the base assembly. 25 In one form, the skin includes a plurality of profiled sheets which are in side-by-side relation and interconnect along their adjacent sides. In a particular form, the profiled sheets are fixed to the frame by mechanical fasteners. 30 The skin may be formed from other type of sheet. For example the skin may be formed from one or more substantially flat sheets, such as that made from fibrous cement board or from timber products such as ply. In this latter application, where the sheets are substantially flat, separate shear 35 connectors may be provided in the base assembly which are arranged in use to be fixed to and extend from the skin so as to be arranged to be embedded in the settable material cast on the skin. In this way the shear connectors allow transfer of load between the N:\Sydney\Cases\Patent\78000-78999\P7831O.AU.1\Specis\P78310.AU.1Innovation Speofication 15.06.09.doc -4 settable material and the base assembly. In one form, these shear connectors may be in the form of mechanical fasteners such as large nails or screws which typically extend through the skin and are fixed to the underlying frame. These screws or nails are designed to stand proud of the skin so that they can be embedded in the settable 5 material. In one form, the frame is formed from a plurality of interconnected steel and/or timber elements. Typically these elements are assembled generally in plane and as indicated above where the composite panel is used in tilt-up wall construction those frame 10 elements may form part of the framing of the resultant wall. In this way, the framing may act as battens to secure plasterboard or the like to the composite panel or alternatively, may be used to support window framing and the like. In a further aspect, the invention relates to a composite panel comprising a base 15 assembly according to any form described above and a settable material cast on the skin of the base assembly. In one form, a composite panel is a wall panel and in particular a "tilt-up" wall panel. 20 In one form, the frame of the composite panel is used as framing in a resulting wall using the composite panel. In a particular form, the frame is disposed on one face of the panel. However, in another form, a second skin or other covering may be applied to the frame which in turn forms one face of the panel thereby causing the frame to be internal to the composite panel. 25 In a particular form, the settable material is cementitious. In a particular form, the frame comprises at least one void that extends through the panel. In this way the void may be used to accommodate other elements such as 30 preformed window elements and the like where the composite panel is used in walling systems. In yet a further aspect, the invention is directed to a method of forming a composite panel comprising the steps of providing a base assembly having a frame and a skin 35 mounted to the frame, and casting a settable material onto the skin of the base assembly. N:\Sydney\Cases\Patent\78000-78999\P78310AU.1\Specis\P7B310.AU.1Innovation Speafication 15.06.09.doc -5 In one form, the method further comprises using the frame to provide support for the skin to maintain the shape of the skin during casting of the settable material. In a particular embodiment, the method further comprises the steps of providing at least 5 one void in the base assembly, and casting the settable material on the skin of the base assembly and around the void so that the void extends through the resulting composite panel. In a particular form of the method the base assembly is in accordance with any form 10 described above. In one form of the methods described above, the settable material is cementitious. In yet a further aspect, the invention is directed to a method of forming a wall comprising the steps of providing a composite panel incorporating a frame, and 15 installing the composite panel in an upright condition and using the frame as framing for the wall. Brief Description of the Drawings 20 It is convenient to hereinafter describe embodiments of the present invention with reference to the accompanying drawings. The particularity of the drawings and the related description is to be understood as not superseding the generality of the preceding broad description. 2S In the drawings: Fig. I is an exploded view of a base assembly for a composite panel according to a first embodiment; Fig. 2 is a side elevation of the base assembly of Fig. 1 with edge formers in place; 30 Fig. 3 is an exploded view of a variation of the base assembly of Fig. I where the frame of the base assembly is modified; Fig. 4 is a partial perspective view of a composite panel formed using the base assembly of Fig. 1; Fig. 5 is a side view of the composite panel of Fig. 4; 35 Fig. 6 is an exploded view of the skin and frame of a base assembly for a composite panel according to a second embodiment; Fig. 7 is a perspective view of the base assembly of Fig. 6; and N:\Sydney\Cases\Patent\78000-78999\P78310.AU.1\Specis\P78310.AU.1Innovation Specification 15.06.09.doc -6 Fig. 8 is a side view of the base assembly of Fig. 7. Detailed Description of the Drawings 5 Turning firstly to Figs. I and 2, a base assembly 10 is disclosed for use in a composite panel 50 (see Fig. 4) and includes two main components being a frame 12 and skin 14. In the illustrated form, the frame is made from frame elements 16 which in the illustrated form are interconnected in plane and which are typically made of timber or steel sections. The skin 14 overlays the frame 12 and is fixed to the frame by any io suitable means such as by mechanical fasteners 18 as shown. The skin 14 as shown in the embodiments of Fig. 1 and 2 is formed from profiled roll formed steel sheet having upstanding formations 20 which are arranged to be embedded in the cementitious (or other settable material) layer 52 (see Fig. 4) which is applied to the skin and which will be described in more detail below. 15 In use, the composite panel 50 finds particular application in tilt-up wall panels for use in the construction of both commercial and residential developments. In such applications, the panel is made either off-site or on-site and is moved from a generally horizontal condition to an installed condition where it is disposed in a generally vertical 20 orientation by suitable lifting equipment such as a crane. In the present embodiment, the composite panel 50 includes the base assembly 10 and the cementitious layer 52 which is cast on the base assembly when it is in a generally horizontal position as best illustrated in Fig. 2. During this casting process the 2S cementitious material 52 is cast directly onto the skin 14 so that the formations 20 of the skin become embedded in that cementitious layer. In this way the cementitious layer is keyed to the base assembly and shear can be accommodated across those components. To provide adequate formwork for the casting of the cementitious layer, edge forms 22, 30 24 may be provided. In one form these edge forms may be traditional timber formwork which is arranged to be stripped after hardening of the cementitious layer or alternatively the edge forms may be steel sections 24 which are designed to remain in place and thereby form part of the composite panel 50. 35 The purpose of the frame 12 is twofold. Firstly, the use of the frame 12 is to provide rigidity to the skin 14 so that the skin does not unnecessarily deform under the hydrostatic pressure induced on the skin during casting of the settable material. In this N:\Sydney\Cases\Patent\780O0-78999\P78310.AU.1\Specis\P78310.AU.1Innovation Specification 15.06.09.doc -7 way there is control over the shape and dimensions of the resulting composite panel 50 which is important when those panels are used in wall systems and the like. A second function of the frame 12 is that it can be used as part of the framing in the resulting wall structure. In the embodiment illustrated in Figs. 1 and 2, the frame is constructed in a s similar manner to a conventional stud wall. Once the composite panel 50 is positioned into a vertical orientation as best illustrated in Fig. 4, the frame 12 is then ready to receive internal cladding such as plasterboard or the like. Furthermore, whilst not shown, the base assembly, 10 and resulting composite panel 50, may include voids to receive other wall elements such as window framing and the like. Such voids can be 10 easily created in the base assembly merely by cutting out portions of the skin and providing necessary formwork on casting of the cementitious layer so as to maintain the void clear of the cementitious material thereby allowing the void to pass entirely through the panel. 15 A variation of the base assembly 10 is disclosed in Fig. 3. Where base assembly 30 incorporates frame 32 is of a simpler construction as compared to the frame 12 of the base assembly 10 shown in Fig. 1. However the frame 32 is still adequate to provide some rigidity to the skin 34 (which again is in the form of profiled metal sheet) so as to maintain dimensional control of the resulting composite panel on casting of the 20 cementitious layer 52. However the layout of the frame 32 is to merely provide battens for the application of facing panels to the composite panel 50 when installed as part of a wall. Whilst not shown, the composite panel 50 may include additional reinforcement such as 25 mesh and/or bars and/or fibres and/or cables and other suitable reinforcement which is embedded in the cementitious layer. The reinforcement may be connected directly to the profiled decking sheet, for example by being weld or mechanically fastened to the sheet. 30 Furthermore, the composite panel as illustrated is formed with rebated sides 54 that enable adjacent composite panels to be positioned side-by-side in overlapping relationship. An alternative embodiment of the base assembly for use in a composite panel is shown 35 in Figs. 6 to 8. In that embodiment, the base assembly 40 again includes a frame 42 which may be identical to that disclosed in the earlier base assembly embodiments 10, 30 described above. The main variation between the embodiment of base assembly N:\Sydney\Cases\Patent\78000-78999\P7831O.AU.1\ Specis\P7831O.AU.1nnovation Specification 15.06.09.doc -8 shown in Fig. 6 and the earlier embodiment is that the skin 14 is formed from a substantially flat sheet. The skin 44 may be formed from a relatively low tensile strength material such as fibre cement board or timber ply or the like. Further a sarking layer (not shown) may be provided between the board and the frame to inhibit water s penetration through the composite panel. To enable effective shear transfer between the cementitious layer and the base assembly 40, shear connectors 60 may be provided. In the illustrated form, these shear connectors may be provided as mechanical fasteners such as large nails if the framing is 10 made from timber or screws if the frame 42 is made from steel elements. Such mechanical fasteners may also be used to affix the sheet 44 to the frame 42. These mechanical fasteners 46 are arranged to extend into the frame (as best illustrated in Fig. 8) but are also arranged to stand proud from the skin 44 (as best shown in Fig. 7). In this way on casting of a cementitious layer over the skin 44 the fasteners 46 become 15 embedded within that cementitious layer thereby allowing shear transfer between the base assembly 40 and the cementitious layer. Accordingly, a composite panel and base assembly is provided which is able to accommodate the hydrostatic forces applied during casting of the cementitious layer so 20 as to maintain a high degree of dimensional control in the resulting panel. Further the panel incorporates a frame which may be used to strengthen the composite panel so as to enable it to be transported and in particular lifted during an installation process where the panel is used in tilt-up walling systems and which can also provide framing in the resulting wall structure. Further an advantage of the invention is that it is ideally suited 25 to form the composite panels on site wherein the framing can be assembled, laid flat and wherein the skin is secured over the framing and affixed in place. Thereafter the composite panel can be cast directly on the skin. Once the cementitious layer is hardened any additional formwork can be stripped leaving the composite panel ready for installation. 30 In the claims which follow and in the preceding summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", that is the features specified may be associated with further features in various embodiments of the invention. 35 N:\Sydney\Cases\Patent\78000-78999\P7831O.AU.1\Speas\P7B310.AU.1Innovation Specification 15.06.09.doc - 9 Variations and modifications may be made without departing from the spirit or ambit of the invention. 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