FIELD OF THE INVENTION This invention is concerned with a novel structural member and novel building structures incorporating structural members according to the invention.

BACKGROUND ART Timber, as a structural material, is becoming a progressively more expensive commodity due to dwindling resources and environmental constraints on traditional logging procedures.

Moreover, as living standards rise, the cost of skilled labour and other materials required in the construction of dwellings continues to increase quite dramatically.

The high cost and scarcity of traditional construction materials in combination with the high cost and scarcity of skilled labour has led to the increased usage of alternative building materials and methods in an endeavour to contain costs.

In particular, there has been a marked increase in popularity of "kit" homes designed for erection by owner builders. Generally speaking, these kit homes comprise prefabricated frame members for walls and roof structures and often are constructed from light gauge rolled steel section, the frame members being of a conventional configuration. Again, generally speaking, these kit homes are designed for erection on a pre-cast concrete slab which limits these structures in practice to substantially level building sites.

While the construction of these pre-fabricated kit homes is in many cases, quite straightforward and able to be accomplished with relatively few tools and relatively unskilled labour, many are far too complex

for owner builders to attempt. In any event, the input of the average owner builder is limited to erection of the structural frame with inner and outer wall cladding, roofing, guttering, interior and exterior trim, plumbing and electrical wiring having to be left to skilled tradesmen.

Accordingly, the "conventional" configuration and skilled labour requirements for kit home structures, combined with the requirement for a substantially level building site, offer only limited cost savings in terms of materials and labour.

SUMMARY OF THE INVENTION

It is an aim of the present invention to overcome or ameliorate at least some of the prior art problems associated with construction of dwellings and to provide a more cost effective and flexible structural system.

According to one aspect of the invention there is provided a structural member comprising:- a rigid, substantially planar member; and, a ribbed steel member extending over a major face of said planar member, said ribbed steel member being secured to said planar member by fixing means to act, in use, as a pre-stressing element for said structural member.

The planar member may be comprised of any suitable material such as reconstituted timber, a timber laminate, fibre reinforced cement, laminated materials comprising a low density core material sandwiched between outer skins of high density material and the like.

The ribbed steel member may be fabricated by any suitable process including bending or roll forming. Preferably said ribbed steel member comprises a plurality of spaced parallel lateral flanges connected by respective upright web members.

Suitably said web members are alternatively inclined.

The adjacent flanges may be equally or unequally spaced. The adjacent flanges may be of the same or differing transverse width.

If required adjacent pairs of web members may be inclined at differing angles and/or said adjacent pairs of web members may be of differing transverse widths.

The ribbed steel member may be secured to said planar member by any suitable fastening means.

Preferably said fastening means extend through respective apertures in first flanges adjacent said major face of said planar member.

Suitably said fastening means comprise screw or bolt members.

If required said structural member may include a further substantially planar member secured to said ribbed steel member via second flanges spaced from said first flanges.

Suitably, hollow apertures between said second flanges and adjacent webs contain an insulating material . Alternatively or in addition, insulating material is located between said first flanges and adjacent webs .

According to yet another aspect of the invention there is provided a building structure comprising:- a plurality of spaced portal frame members; floor bearers extending between opposite upright members of said portal frame members; and, a flooring structure comprising a plurality of structural members described above, said structural members extending between adjacent floor bearers to provide a planar pre-stressed floor.

Suitably said upright members are telescopically

associated with spaced foundation members secured, in use, in an earth surface.

Said foundation members may be comprised of tubular right angle or channel section metal elements. Said foundation members may be secured in a ground surface in concrete footings.

Alternatively said foundation members comprise a tubular steel shaft having one or more helical flights thereon to enable, in use, securing in a ground surface by rotation to penetrate said ground surface.

The portal frame members may be constructed as a unitary member or as separate elements bolted together.

If required the building structure may comprise outer wall panels and/or roofing panels in accordance with a first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be fully understood and put into practical effect, reference is now made to various preferred embodiments illustrated in the accompanying drawings in which:-

FIG 1 illustrates a cross sectional view of one embodiment of a floor panel . FIG 2 illustrates a cross sectional view of an alternative embodiment of a floor panel.

FIG 3 illustrates an alternative embodiment of the floor panel of FIG 2.

FIG 4 illustrates a floor panel joint. FIG 5 illustrates a cross sectional view of a portal frame building structure in accordance with a further aspect of the invention.

FIG 6 shows an enlarged partial cross-sectional view of the portal frame structure in the region shown generally at "A" in FIG 5.

FIG 7 shows a partial isometric view from above of the structure shown in FIG 5.

DETAILED DESCRIPTION In FIG 1 , a floor panel 1 comprises a rectangular sheet 2 of fibre reinforced cement, reconstituted timber particle board or the like. Secured to an under surface of sheet 2 is a roll formed or folded steel sheet structural element 3 comprising spaced upper flanges 4 and spaced lower flanges 5, the upper and lower flanges 4, 5 respectively being connected by inclined webs 6. The upper flanges 4 are secured to sheet 2 by screws or bolts (not shown) to form a rigid structural beam member capable of supporting both live and dead loads over substantial span distances.

In a typical application as shown, the floor panel is say 900 mm wide and 3600 mm long. The sheet 2 is 19 mm thick timber particle board and includes tongues or grooves (not shown) on its edges to engage with corresponding grooves or tongues in an adjacent panel. Typically, the steel structural element 3 is comprised of a 1.0 - 1.2 mm galvanised steel sheet with a flange width of about 30 mm and a vertical spacing between upper and lower flanges 4 and 5 of about 120 - 140 mm. As shown the floor panels 1 are secured to floor bearer 7, preferably by self tapping screws (not shown). The floor bearer 7 is a steel or timber I beam or similar member which is bolted to brackets 8 attached to tubular steel uprights 9 of prefabricated portal frames (not shown).

A wall girt 10 in the form of a steel C section is secured between adjacent portal frame uprights 9 by means of self tapping screws (not shown) engaging with brackets (not shown) attached to uprights 9. A bottom wall plate 11 in the form of a roll formed light gauge steel channel 12 is secured to and supported by wall girt 10 and the edge of floor panel 1.

The floor panels 1 as shown replace the traditional bearer/joist/flooring combination hitherto employed in dwelling constructions which do not employ a concrete slab floor. Panels 1 offer substantial savings over traditional flooring structures in reduced mass, easier handling and transportation, reduced materials consumption, reduced labour costs in handling and installation and less skilled labour than previously required. Flooring panels of the type described may be used in conventional building structures, but as will be described in more detail later, these panels permit a simple and innovative kit home construction employing portal frames. Depending upon the load bearing requirements, the floor panels may be constructed with structural elements of differing configurations of steel sheet guage, flange width and flange spacing, both laterally and vertically. Because the structural elements act as pre-stressing members, floor panels may be engineered to suit varying span distances and load bearing capacities.

It will be noted that the "open" channels between adjacent lower flanges 5 provide a convenient region for location of utility services such as power, water drainage etc. The "closed" channels between adjacent upper flanges 4 not only provide a region for placement of utility service conduits but also serve to act as a thermal insulation barrier for the floor surface.

FIG 2 illustrates an alternative embodiment of the floor panel of FIG 1.

In this embodiment the edge flanges 4a are half the width of the inner flanges 4 to enable the sheet 2 to be fully supported to its outer longitudinal edges. FIG 3 illustrates yet another embodiment of the invention.

In this embodiment a lower sheet 2a is secured to lower flanges 5 to provide even greater rigidity to the panel.

If required the channels between upper flanges 4 or lower flanges 5 or all channels may be filled with an insulating material such as polystyrene or polyurethane foam or other such insulating material or a fire resistant insulating medium.

In modifications of the panel of FIG 3, the panels may be used as load bearing walls without the need for spaced girts to support the wall panels against wind loading. The panels, suitably configured, may also be used for non load bearing walls or even as roofing sheets without the need for rafters and battens. A variety of conventional edge joining and weatherproofing techniques may be employed to interlock adjacent edges of the panels.

FIG 4 shows yet another alternative embodiment of the panel wherein the edge flanges 4a extend beyond the edges of sheet 2. The edge flanges are not secured to the sheet 2 during manufacture such that when adjacent sheets 2 are abutted flanges 4a may overlap as shown.

In this embodiment there is shown a tongue 7 and groove 8 joint in the adjacent sheets 2.

FIG 5 shows a cross sectional view of a building structure in accordance with a further aspect of the inventio .

The structure 10 comprises a plurality of spaced portal frames 11 , each comprising outer upright members 12, transverse roof beams 13 and a central upright member 14. The upright outer members 12 and central upright member 14 are secured to adjustable or telescopic foundation members 15 secured in the earth. Extending between the outer and inner uprights are floor bearers 16, supported on which are a plurality of load bearing floor panels 17 generally

according to FIGS 1-4.

A roof sheeting material 18 is secured to purlin

19 attached to and extending between adjacent portal frame roof beams 13. In one form of ceiling structure, a ceiling sheet

20 is attached to ceiling battens 21 supported on strongbacks 22 suspended from roof purlin 19. Alternatively, the ceiling sheet 20 may be secured to battens 23 secured to the underside of purlins 19. Preferably the portal frames 11 are fabricated from 75 mm square rolled steel joist "RSJ" uprights and 150 x 14 universal beam "UB" roof bearers adapted to be bolted together on site.

After the foundations 15 comprising either square section tubular steel members, right angle members or channel shaped members are secured in concrete footings 15a, upright members 12 and 14 are positioned in or in association with the foundation members 15. Roof beams 13 are then bolted to uprights 12 and 14 and then the entire portal frame structure is elevated to a desired height, levelled and clamped to the foundation members 15. Bolt holes are then drilled into the upright members 12, 14 through pre-prepared bolt holes in foundation members 15 and the structure is bolted together.

Typically, for a structure having a floor area of 7.2 metres x 10.8 metres, four portal frames are spaced at 3.6 metre intervals.

After the portal frames are erected, floor bearers 16 are bolted to brackets on uprights 12, 14 and prefabricated floor panels 17 are then positioned on and secured to the floor bearers 16.

Purlins 19 are then screwed to the upper flanges of roof beams 13 and the roofing is secured to the purlins 19 in a conventional manner.

An outer wall cladding may then be attached in a conventional manner together with conventional

internal wall structures. Alternatively the outer and/or inner walls may comprise prefabricated panels.

The portal frame structure described provides a structural integrity which avoids the need for load bearing external or internal walls.

FIG 8 shows a detailed view of an adjustable foundation structure in accordance with yet another aspect of the invention.

As shown the foundation 15 comprises a length of right angle section steel 20 embedded in a concrete footing 15a. An anchor member 22 is welded to the base of angle member 20.

A portal frame tubular upright 23 is bolted to the angle member 20 by spaced bolts 24 at 90° to each other. The region encircled in FIG 6 is a cross sectional view through A-A.

In FIG 6 an enlarged, view of region A in FIG 5 is shown for greater clarity.

After foundation posts 15 are secured and levelled, a perimeter plate 30 is secured about the upper portions of posts 15. Uprights 12 are then mounted on foundation posts 15 and subsequently the roof beams 13 are bolted to the upper ends of outer uprights 12 and inner uprights 14 (shown in FIG 5). Floor bearers 16 are then attached to the uprights 12 by bolts (not shown) via brackets (not shown) on uprights 12.

Prefabricated floor panels 17 are then positioned on floor bearers 16 by means of self tapping screws 31 between the upper flanges 32 of bearers 16 and the lower flanges 33 of reinforcing element 34.

FIG 7 shows a schematic isometric view from above of the frame structure of the arrangement shown generally in FIG 5. In this arrangement however the inner uprights 14 have been dispensed with and the adjacent ends of the roof beams 13 are joined by bolted brackets 35.

It will be readily apparent to a skilled addressee that many modifications and variations may be made to the invention without departing from the spirit and scope thereof.