WO2020181323A1

WO2020181323A1 - Method and apparatus for structural support

Info

Publication number: WO2020181323A1
Application number: PCT/AU2020/050214
Authority: WO
Inventors: Darby Hamour
Original assignee: Darby Consulting Services Pty Ltd
Priority date: 2019-03-08
Filing date: 2020-03-06
Publication date: 2020-09-17
Also published as: AU2020236662A1

Abstract

A building construction technique is disclosed for fully offsite prefabrication of permanent hollow panel formwork for building a structural wall portion. Components that define the formwork also reinforce the settable composite that fills it, once cured, and provide a gap between the structural component and the formwork shuttering against which the settable composite sets, the gap being effective for protecting the components against structural failure when the wall portion is exposed to external high temperature caused by fire. Preferably, the structural components are in the form of C- or Z-profiled studs having flanges to which a spacer element attaching to the shuttering is fastened for establishing the gap.

Description

Method and apparatus for Structural Support

Field of invention

[01] The present disclosure relates to a building construction technique for fully offsite prefabrication of formwork for building a structural wall. Formwork having dual functionality is described, in which components that define it also reinforce the settable material that fills it, once the settable material is cured. The invention herein disclosed has been developed for structural walls and structural columns but can be applied to horizontal structural slab reinforcement formwork.

Background Art

[02] Reinforced concrete walls are commonly used in all types of building construction. Reinforced concrete is predominantly the main way to build superstructures for withstanding all expected building loads. One of the ways to build reinforced concrete is to build steel cages of reinforcing bars (rebars), build formwork around the cages and then pour concrete into the formwork. This is known as the“cast in-situ” process, where the formwork is stripped away after the concrete has set. This process is very labour intensive and very dependent on-site conditions, which accordingly makes it the slowest process with which to build walls, columns and slabs.

[03] To overcome the slow cast in-situ process, it is known to use a precast concept, where walls and slabs are cast and cured off-site and are delivered to site for erection. Although this is so far the fastest way to build on site, it still comes with the disadvantages of resultant weak structural connections between precast members. Moreover, there is risk associated with heavy lifting and logistics and weight limitations on precast panels, these being dictated by the maximum truck carrying weight and crane capacity for lifting.

[04] Figure 1 shows, in partially cut-away perspective view, a modular prior art panel, usually 1200mm in length and manufactured to the height of an intended wall. The panels are delivered to site, where they are assembled to form the wall. This construction method is very slow, as it involves labour to assemble the panels, place steel rebars between them, and introduce the settable material into the space separating them. Also, the function of the structural studs is only to offer spacing between the two containment sheets - not to offer any structural strength as a reinforcement to the wall. [05] In other attempts to overcome the slowness of the cast in-situ process and precast logistic limitations, different versions of modular formwork systems have been proposed, one for example having a panel with two opposing containment sheets (metal or other material) separated by flanged spacers or studs, wherein the flanges are fixed at both ends to the containment sheets. While such modular wall panel systems will overcome the weight disadvantage of precast and the slow process of cast in-situ, they still involve a significant amount of on-site labour to erect panels in place, fix steel bar reinforcement and then pour concrete. Although these are quicker than cast in-situ, they are still more time- consuming than precast, which makes them less favoured in a busy construction market and only to be used if site conditions do not allow for precast, for example where site conditions preclude crane use.

[06] The wall system of patent application publication US2005/0016104 shows the use of horizontal and vertical bars that are fixed to studs by saddles, thereby to offer reinforcement to the wall. Again, the illustration clearly does not show stud to have a reinforcement role, as it does not comply with conditions mentioned in the previous paragraph.

[07] A prior art formwork system described in US patent 6,688,066 shows the panel being filled with a light weight, low density filling that is used for non-structural, non loadbearing purposes, hence the absence of rebar reinforcement. This stud system is mainly used to strengthen the flanges of the stud so that it withstands a light-weight mix pressure. The material is lightweight gauge that uses the stud as the actual spacer between shutters, and not for structural reinforcement.

[08] Published patent application US 2017/0328060 A1 describes a formwork stud system that includes a plurality of flanged studs, a top channel, a bottom channel and a plurality of horizontal and vertical bars. A corrugated metal sheet is fixed on either side of the plurality of the stud flanges. While this wall system can be advantageous in the building of a wall system including round bar reinforcement on site, it fails to utilise the metal studs within the wall to provide any structural reinforcement to the wall system. This is evident from the system’s reliance on conventional round steel bars for reinforcing the concrete wall, with the pouring of concrete taking place later, once the formwork system has been erected on site. Also, the containment metal sheets are directly fixed to the metal studs, which is not structurally acceptable in cases where the metal studs or spacers are used as reinforcement, because of the likelihood of thermal degradation leading to failure when exposed to high temperatures such as those associated with building fires. Standards and codes pertaining to concrete structures generally specify that there must be allowance for a minimum 20mm to 30mm of concrete cover for all steel reinforcements for fire resistance and structural integrity. For example, according to Australian Standard AS3600, the minimum concrete cover must be 25mm over reinforcement, as per Fire Resistance Period (FRP) table 5.7.2.

[09] International patent publication WO2019/148245 (PCT/AU2019/050074) describes use of a plastic connector that holds conventional steel reinforcement rods (rather than structural studs) to an external vertical metal cladding. Modules 2.4m in length are fabricated at the full wall height, either off-site or on-site. The system is heavily dependent on the quality of welding for fastening together the conventional steel rods. This makes it very labour intensive and requires stringent quality control procedures to ensure that the welding will withstand concrete hydrostatic pressure. Also, the connector, being made of a plastics compound such as polyethylene, will be very likely to fail in the event of fire, leaving the external cladding to delaminate from the face of the concrete.

[010] US patent number 8,978,331 B2 describes a formwork system that utilises the internal metal studs for vertical reinforcement with direct fixing by adhesion of thick containment sheets made of cement directly onto the stud flanges of the internal studs. This system comes closest to addressing the failings of the prior art, but still has a few disadvantages:

1. The patent specification states clearly that there must be holes in the middle of the structural stud to let the concrete flow through. With reference to column 1 1 paragraphs 20 and 25, the minimum total aperture area is 20% of the stud surface area. This will reduce the reinforcement by 20% and clearly weaken the structural stud against tension. That means more steel weight is needed to overcome steel loss resulting from provision of the apertures.

2. The thickness of the wall (excluding containment sheets) is exactly the stud width, which results in the flanges having no concrete cover, as the containment sheets are directly fixed by adhesion to the external face of the flange. This means that a portion of the stud’s overall surface is not available for contact with the cured settable material, which in turn means a lower percentage of composite action between the stud and the settable material. The less the percentage of composite action, the greater the quantity of material that must be used to compensate for the loss of surface keying with concrete to form a full composite action.

3. Direct fixing of the structural board on the so-called structural stud will allow for rapid heat transfer into the studs in the case of fire, reducing structural strength and weakening mechanical properties, unless the structural board or containment sheet is thick enough to protect the structural stud. Thickening the boards to 20mm on each side of the stud will make the overall assembly unacceptably heavy. Also, in the event of fire it is very likely that the structural boards will delaminate and peel from the studs - especially if an epoxy adhesive, which tends to fail under combustion temperatures, has been used for gluing the boards to the studs. Failure will expose the studs directly to the fire, increasing the chance of early structural failure of the wall.

4. To compensate for the above-mentioned losses and inefficiencies, more material will be used, the thickened construction boards adding heavy weight to the formwork system and making it less economical.

[011] A prior art system disclosed in international patent application PCT/AU2004/001835 provides a modular wall system of foldable panels that is assembled on-site. Once erected, to claim structural adequacy, the settable material to be reinforced, for example concrete, is introduced.

[012] The above prior approaches have met with limited success in addressing the challenges facing the construction industry, in particular the challenge of utilising the material that is used to build the formwork in a simultaneous structural reinforcement role, to meet stipulated structural specifications.

[013] Accordingly, it would be advantageous to provide an alternative formwork system that results in more rapid construction than precast methods and yet gives the advantage of stronger structural connections, despite being poured on site compared with being cast in situ.

[014] An object of the invention is to provide a system that is significantly lighter than precast in weight during transportation, allowing for the use of lighter cranes and transportation to site of larger volumes per delivery, and helping to reduce the carbon footprint compared with known systems. [015] Also, an alternative system, as herein proposed, will allow optimal use of the formwork materials as steel reinforcement. This is expected to help reduce steel consumption by utilising the formwork elements to be the concrete reinforcement steel. The resultant reduction in materials provides an environmentally greener construction methodology than current alternatives.

[016] In this description, the term “horizontal support” refers to support against deformation of a vertically disposed panel in a direction orthogonal to the plane defined by a major surface of the panel, that is to say in a direction having a horizontal vector.“Vertical support” refers to support provided by vertically disposed elongate elements against deformation in a direction parallel to the plane of the major surface.

[017] The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or elsewhere as at the priority date of the present application.

[018] Further, and unless the context clearly requires otherwise, throughout the description and the claims, the words‘comprise’, ‘comprising’, and the like are to be construed in the inclusive sense of“including, but not being limited to” - as opposed to an exclusive or exhaustive sense meaning“including this and nothing else”.

SUMMARY OF THE INVENTION:

[019] The present disclosure relates to a formwork system that is deliverable to a construction site fully fabricated and ready to be erected for the pouring of settable material into it. An example of the settable material is concrete, as this is typically used in construction. However, other suitable materials are not to be considered excluded. It is of course possible to assemble the formwork system on site, should this be preferable to the user.

[020] According to a first aspect of the invention described in this disclosure, there is provided a hollow panel formwork structure comprising first and second cladding sheets operatively fastened in substantially parallel planes on opposite sides of first and second reinforcement elements, each comprising an elongate stud, thereby to define between them a form into which a settable compound is receivable, the studs providing reinforcement against deformation of the form orthogonal to either of said planes, removing need for alternative or supplementary reinforcement means against said deformation.

[021] The formwork system preferably comprises a at least two structural studs arranged side-by-side in a row and to which containment sheets are fixed in operative orientation as cladding. Preferably, but not exclusively, the studs are fabricated of metal. Other suitable structural materials, for example basalt fibres, may be used as alternatives, as may any other suitable reinforcement material. The studs are vertically disposed and spaced equally along the length of a planned wall.

[022] The studs of the row are placed on a manufacturing jig table during assembly of the formwork panel, spaced at required intervals, after which the containment sheets are fixed to the flanges of the studs. Suitable fixing means include, without limitation, self drilling screws or riveting.

[023] The studs comprise two opposing flanges joined by a middle web.

[024] In an embodiment, the flanges extend orthogonally from the opposed sides of the middle web.

[025] The flanges and the web provide the studs with an elongate cross-sectional area that in use will be equivalent to the cross-sectional area of the steel rebars they replace, as specified in the structural engineering design calculations for the structure concerned.

[026] The spacing between the studs is governed by the spacing instructed in the structural engineering design for the steel reinforcement spacing between rebars.

[027] The cladding sheets, also known and referred to herein as shutters, comprise a plurality of individual shutter strips arranged vertically one upon the other to extend horizontally along the length of the intended vertical wall. The strips have flaps for fixing to and being supported by the flanges of the studs. The flaps are located on the side of the strip that when fixed in operative position, faces the flange. Preferably, at each intersection between adjacent strips contacting the flange surfaces, fixing is by fastening means, for example by several screws or rivets.

[028] The wet concrete hydrostatic pressure on the shutters will dictate the number of fixings needed to give the required support reaction force to the flaps of the shutters. The higher the pressure, the more closely the studs need to be spaced, hence offering more fixings per unit length of the wall. As concrete pressure on shutters is directionally proportional to the wet concrete height inside the formwork before curing, an increased number of fixing points results in less stress per fixing.

[029] A second function of the structural studs is to provide a substrate to which the containment sheets may be secured, by virtue of the internally facing flaps of the shutter strips being fixed to the abutting outward facing major surface of each flange.

[030] The flanges of the studs hence work simultaneously to provide a connecting substrate interface for, and as spacers between, the two opposing faces of the containment sheets, extending substantially from the bottom to the top of the intended wall. The shutters are held in place by fixing them at every contacting interface between the structural stud flanges and the shutter flaps. The two contacting surfaces, namely the metal shutter flap and the structural stud flanges, come into abutment at frequency and distance intervals calculated to withstand the hydrostatic pressure of the settable material.

[031] The structural studs have a series of small apertures in the form of flared holes punched through the middle web. The reduction in stud cross sectional area is kept to be less than 7% of the cross-sectional area of the stud. The reduced cross-sectional area is the difference between the total cross-sectional area of the stud and the hole diameter cut through the stud web. The equivalent area of each hole is its diameter multiplied by the thickness of the stud web. The holes are flared or suitably embossed to promote mechanical keying with the settable material. The holes are not required for use as passages through which the settable material may flow; instead they are intended to allow horizontal reinforcement bars specified in a structural engineering design for the intended wall to penetrate through the series of the structural studs along the entire length of the wall to be supported by the rims of the holes in the hollow panel formwork.

[032] The flared punched holes are not aligned in any given line taken the shortest distance between the flanges of a stud. Such a line will intersect at most one hole. This allows for the maximum cross-sectional area of the structural stud to be utilized for reinforcement. The holes are preferably formed in a staggered array distributed either sides of the axial centreline of the middle web of the structural studs.

[033] Another feature of the structural stud design is to have small wavy profiled ribs during rolling forming production along its whole surface to provide keying that will promote mechanical locking with the settable material once it is cured. This will enhance the percentage of composite actioning between stud surface, preferably steel, and the settable material, preferably concrete. [034] The structural studs are preferably of predetermined shape profile. Preferred profiles include a C-, Z-, H- and U-shapes having a web connecting a pair of opposed flanges. The studs may further include lips extending inwardly from the remote long edges of the flanges.

[035] The flanges define opposed faces adapted for fixing to containment sheets or shutter strips by suitable fixing means.

[036] In a preferred form of the invention, the containment sheets are manufactured from rolled formed wide metal strips that are adapted to be located and stacked on top of each other with a major elongate edge from one abutting an opposing major elongate edge of the next, to be fixed to one face of the plurality of the structural studs. It will be appreciated by those who are skilled in the art that the containment sheet material is not limited to metal, but may be any other material such as fibreglass polymer concrete sheets or any other material that can perform without deformation under the hydrostatic pressure exerted by the settable material poured into the hollow panel formwork.

[037] Thus, each rolled formed strip has a major edge, defining a bottom edge when operatively located, along which edge a lip extends. Each strip has an opposite top major edge along which an elongate channel runs lengthwise. The channel is configured to receive the bottom lip of a strip stacked upon it in use for forming a containment sheet assembly.

[038] Between the top and bottom edges of the sheet the strip is recessed for providing an elongate concavity between it and the flange face to which it will be fixed. This concavity allows for a gap to be maintained around the structural studs and the shutter strip surface, permitting flow of the settable material to surround each of the plurality of structural studs. The gap thus created avoids having to cut through the web of the stud to form extra-large holes for allowing concrete to flow through the stud to fill the next space between neighbouring studs in the row; instead the gap allows flow to take place around the stud, which saves the structural stud cross section from being weakened by cutting, punching or otherwise removing material from it.

[039] A second function of the strip concavity feature is to accommodate enough fillable space around each of the structural studs for establishing at least the regulated minimum degree of cover stipulated in building codes over structural reinforcement elements, being the studs in this case. This arrangement enables full coverage of the structural stud surface, including the web, flanges and their lips, so that they are completely submerged inside the settable material and results in increased structural composite action. It will be appreciated that the prior art does not address this aspect, but instead proposes directly fixing the sheet to the stud flange, thus weakening the structural composite action. Without concrete cover entirely enveloping the studs, or other similar internal vertical structural elements, direct conductive heat transfer from directly fixed containment sheets into the stud flanges will diminish the fire rating of the structural wall.

[040] Another function of the concavity in the strip surface is to conceal internal fixings to the structural studs from exterior view. This improves the aesthetics of the formwork panel.

[041] The upper edge of the recessed strip is configured with a ridge and channel formation that will allow for sliding location of the lip of the strip to be placed above it to seat inside the channel of the sheet strip below for ease of assembly.

[042] The present invention allows for full assembly of the above components into formwork for either a wall, slab or column module as a prefabricated system that can be manufactured off-site for delivery to site, where erection and pouring of the settable material only remain to be performed.

[043] The size of a module of the formwork system in the present disclosure is not limited by factors such as weight, because the containment panels are hollow and lightweight for transport, since the formwork is not filled with concrete until erected on site. The panel dimensions are limited logisti cally by the biggest panel size able to be delivered and lifted on site.

[044] The formwork system in the present disclosure has no standard specific dimensions. Each construction project will have its own shop drawings, allowing for all door and window openings and any other provisions to accommodate logistical challenges.

[045] In implementing the invention, architects and structural engineers will be required to determine the formwork system thicknesses and heights, as would be done in using any other conventional formwork or precast system.

[046] Further features will be described and become clear in the course of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS [047] The embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a perspective cross-sectional view of a prior art modular wall of standard dimensions, comprising fibre cement sheets glued to thin gauge metal or plastic studs, which have large, wide openings to let the settable material flow through to occupy the spaces between studs.

Figure 2 is an enlarged axial cross-section of an embodiment of a C-profile stud that is suitable for use in the invention of the present disclosure.

Figure 3 is an example of a Z-profile stud that is also suitable for use in the present

invention, shown in (a) front, (b) perspective and (c) profile views.

Figure 4 shows two versions of C-profile studs (a) and (b) in (i) front, (ii) perspective and (iii) profile views.

Figure 5 shows an embodiment of a metal shutter strip that forms part of the external containment sheets in the formwork of Figure 6. A perspective view is found in (a) and an end or profile view in (b).

Figure 6 provides in (a) perspective and in (b) end views of a portion of a partially assembled form in a preferred embodiment of the invention, with the near side shutters removed to show the internal components. Figures 6(c) and (d) are callouts showing detail from the views in (a) and (b) respectively.

Figure 7 provides in (a) perspective and in (b) end views of a portion of a partially assembled form in an alternative embodiment to the preferred embodiment of Figure 6. Figures 7(c) and (d) are callouts showing detail from the views in (a) and (b) respectively.

Figure 8 provides in (a) perspective and in (b) end views of a portion of a partially assembled form in an alternative embodiment to the preferred embodiment of Figure 6. Figures 8(c) and (d) are callouts showing detail from the views in (a) and (b) respectively.

Figure 9 is a perspective view of an assembled wall formwork system using the components of this disclosure. FigurelO is the perspective view of a structure having several wall formwork modules of Figure 6, after on-site erection of the formwork system panels.

Figurel 1 is the perspective view of four walls using panel systems of Figure 6 erected for creating a lift shaft on-site.

Figurel 2 is a plan view of a corner connection of two walls of the system of Figure 6, using

L shaped bar reinforcement.

Figure 13 is a plan view of a corner connection of two walls of the system of Figure 6, using hook shaped bar reinforcement.

Figure 14 is a cross section side view showing typical connection detail between the wall formwork system of Figure 6 and a structural slab (when the wall system is used as a fagade/end wall situation).

Figure 15 is a cross section side view showing typical connection detail between the wall formwork system of Figure 6 and a structural slab using ferrules.

Figure 16 is a cross section side view showing typical connection detail options between two walls protruded by a structural slab.

Figure 17 is a plan view of T-connection of two wall formwork systems in which one is perpendicular to the other.

Figure 18 is a side view of T-connection of two wall formwork systems where one is perpendicular to the other.

Figure 19 shows in plan view a further embodiment of the wall formwork system in a column application.

DETAILED DESCRIPTION

[048] For the structural stud in any claimed structural stud wall system to offer structural reinforcement, two main conditions must be considered in reinforcement calculations relating to the whole cross section area of the structural stud:

1. The internal metal structural studs must be completely enveloped by the settable material. In the case of concrete, the stud must be covered by at least 25mm, to conform to applicable structural concrete standards as mentioned earlier. 2. Hole area within the structural studs must be kept to a minimum to avoid weakening. If their effective cross-sectional area is reduced significantly by having excessive hole area, they are rendered practically insignificant for structural considerations.

3. Any steel reinforcement member, whether a stud or a rebar, has to have enough concrete cover to protect the steel against excessive temperatures in the event of fire, as elevated temperatures will weaken the mechanical properties of steel significantly, resulting in its contribution to structural adequacy having to be excluded from consideration.

[049] The structural stud 10, shown in Figure 4 and used in a preferred embodiment of the formwork of the present disclosure, generally comprises a web 12, joining spaced opposed flanges 14, which have lips 16 extending from their major edges remote from the web. The opposed flanges 14 generally extend orthogonally from web 12.

[050] The flanges in Figure 4 are directly opposed to each other, extending from the same face of stud web 12 in the general shape of the letter‘C’, in the manner of a C-beam. Lips 16 extend inwardly towards each other from the flanges 14 and generally orthogonally thereto. The lips help to stiffen the stud, as well as increasing its axial cross-sectional area and total surface area for keying to the concrete filler. However, in less preferred embodiments, the lips may be omitted, if desired.

[051] The flanges in Figure 3, in which like numbering denotes like components, extend from opposite major surfaces of stud web 12 in the manner of a Z-beam configuration. Lips 16 extend inwardly orthogonally to the flange from which they emanate in a direction generally parallel to the web.

[052] The structural studs shown in Figure 3 and Figure 4 are for dual use in the stay- in-place formwork of the present disclosure. They will be discussed in the context of a formwork for formation of a concrete wall panel. However, the present disclosure is not to be construed as being limited to concrete as the settable material, as it may be employed in forming panels of other settable substances used in the construction industry. The studs should also not be limited to being of metal alloys such as steel, but may be made of other structural substances accepted for use in construction, metallic and non-metallic. However, in describing the preferred embodiment, steel studs will be referred to for convenience. [053] The studs function firstly by offering vertical reinforcement once the settable material, namely concrete in this embodiment, is cured within the stay-in-place formwork. In contrast to most prior art structural stud systems, fully utilising the metal structural studs as vertical reinforcement offers huge cost savings by eliminating vertical rebar reinforcement entirely.

[054] The structural studs serve secondly to hold the containment sheets in place under the hydrostatic pressure exerted by the wet concrete while curing. The structural studs are distributed along the entire wall length, so that the wet concrete pressure is distributed evenly over the two sides of the containment sheets, also referred to as shutters.

[055] As mentioned, the stud 10 shown in Figure 4 and Figure 3 may be of rolled formed C-, Z- or other axial sectional profile as known in the industry. It will be appreciated by those skilled in the art that the structural stud, irrespective of shape, requires a profile thickness sufficient to render it strong enough to be considered as a replacement for rebar reinforcement and to withstand the wet concrete hydrostatic pressure, once the metal shutters or containment sheets have been fixed to the structural stud flanges 14 to make the stay- in- pi ace, permanent formwork system.

[056] The studs have rows of staggered, flared punched holes 18 along the web 12 that connects and spaces the flanges. Flared holes offer better locking and keying than unflared holes, once the concrete is cured inside the stay-in-place formwork. This will create a composite action between the structural stud profile and the surrounding concrete.

[057] Staggering holes 18, so that no two given holes are on the same line extending orthogonally from flange to flange, keeps the stud cross-sectional area on any such line to its maximum, thereby not compromising the structural integrity of the stud. Consequently, it can be considered as means of structural reinforcement.

[058] The metal shutter strip-building unit 28 shown in Figure 5 is the unitary component used in building up the external shutters or containment sheets of the permanent wall formwork system of this disclosure. Figure 5(b) shows the end-on sectional profile of the metal strip 28. Strip 28 is manufactured by a known roller forming process to form the required profile out of metals sheets. The profile is designed so that the metal strips can be assembled to lie one atop another along their abutting major elongate edges. An assembly of metal strips 28 edge to edge above each other forms a complete containment sheet to the wall height of the formwork system. [059] Each of the individual strips 28 is profiled as shown in Figure 5 to have a generally planar web portion 36 at one elongate major edge of which is a channel 46 extending horizontally lengthwise for the length of the strip. At the opposite major elongate edge is an elongate offset formation 42, configured to fit into channel 46 of the strip immediately below it, and on to which it is laid for building up a containment sheet unit.

[060] Strips 28, assembled edge to edge to be stacked on top of each other, are fixed to either side of the spaced structural studs 10, via stud flanges 14. The shutter strip has a rigid flap 30, also referred to as a bracket, which is securely fastened to the flange using conventional means such as rivets or screws and the like, as is known in the art. The bracket 30 extends horizontally along the formwork for the length of the intended wall and is immovably fixed to the vertical structural studs 10, so that the spacing between neighbouring studs cannot be changed. The studs are orientated to be substantially vertical, to provide the required degree of vertical reinforcement when the formwork is later filled with concrete.

[061] Figure 6 illustrates a row comprising equally spaced C-profile studs 10 erected to stand perpendicular to concrete base slab 26 with their flanges aligned in two parallel planes. The studs have their holes 18 identically located so that they align. The studs alone are sufficient to replace conventional vertical round reinforcement bars known in conventional formwork systems, where independent horizontal and vertical reinforcement members are used.

[062] Holes 18, when aligned, allow for horizonal reinforcement bars 20 (if needed) to pass through the plurality of the studs in the row, and to extend along the entire wall length. Such horizontal bars are shown in Figure 6, and are added if specified by the structural engineer responsible. Horizontal bars are not shown, in Figure 7 for simplicity but will be added and connected to vertical bars as per engineering specification. The extra holes that are not utilised for passaging horizontal bars allow passage of uncured concrete from one space separated by a web to the next. When the concrete sets, the hole is filled, increasing the integrity of the structure by way of the connection established between adjacent spaces.

[063] Referring further to Figure 6, another way of increasing the mechanical connection or bond between structural studs 10 and the enveloping concrete is to provide the web 12 , flanges 14 and lips 16 with one or more surface discontinuities such as ribs or corrugations 22 during manufacture, to create a roughened surface over preferably the whole stud surface. The roughening enhances the structural properties of the composite section of the overall structure, comprising the studs and the enveloping concrete. The surface roughening need not be restricted to regular, patterned formations, but may be irregularly shaped discontinuities formed on the otherwise visually planar surface. The discontinuities, whatever their form, assist interlocking between the surface and the settable concrete, resulting in a composite end product structure. As shown in Figure 3, the holes in preferred embodiments have flared or embossed circumferential surrounds 24, which stand proud of the surrounding surface and these assists further in the keying and interlocking.

[064] Hole sizes and configurations may vary from wall system to wall system, depending on wall dimensions, structural stud sizes and the amount of reinforcement stipulated in the applicable structural engineering specifications.

[065] In operative configuration, and with reference to Figure 6, a plurality of the structural studs 10 are generally set in a row with their webs 12 parallel to each other, orthogonal to the line defined by the row, with equal spacing along the intended wall length. The line of the wall to be constructed using the formwork is denoted by directional arrow L.

[066] With further reference to Figure 6, the studs in a preferred embodiment are mounted by insertion of one end into a base 26. The base may be a concrete floor or foundation, only a portion of which is represented in the figure. Shutters, formed of individual elongate metallic strips 28, are fixed to the flanges 14 of the studs through spacing flaps 30. These minimise the thermal interface between the actual studs and the shutters and define a void that is fillable with pourable concrete or other settable filler that is of significantly lower thermally conductivity than the material of the stud. Advantageously, this restricts and minimises the passage of heat from the sheets to the stud, preserving the structural integrity of the wall under fire conditions. However, it is not an essential feature that the thermal conductivity be significantly lower, as in an alternative embodiment, the shutters may be made of fibre cement sheeting that than a metal.

[067] An alternative embodiment of the formwork of the invention is illustrated in Figure 7. Here pairs of vertically arranged vertical rebars 32 replace structural studs 10 depicted in Figures 3 and 4. A cladding holder 34 in the form of a flat bar with upturned opposite ends 36, so that it generally resembles an upturned, square-cornered C- or U-shape, serves as a rebar spacer for the vertical rebars in each pair. The central portion 38 of each holder has formations, in this case holes 40, for receiving the vertical bars of each pair. Instead of holes, the vertical bars may be received into concavities formed in the major edges of central portion 38. [068] The cladding holder 34 serves too as a cradle for supporting horizontal rebars (if specified by the structural engineer responsible). Each upturned end portion 36 provides a seating interface at which a shutter strip 28 can be fixed. Fixing may be by mechanical attachment such as a screw or rivet, or by suitable high temperature-resistant adhesive, as is known for application in the art.

[069] Cladding holder 34 will hold at each end one of the two opposing shutter strips 28 from the opposing flaps 30 of the two sides. A series of holders 34 is vertically positioned in spaced relationship with their holes 40 aligned to maintain the vertical orientation and to support the vertical bars in place through the whole height of the formwork for the wall under construction. Once vertical bars 32 are integrated with the holder 34 and cladding strips 28, the horizontal bars (not shown here for simplicity) are secured to the vertical bars by means of cable ties, wire or other known fixing devices already known in the industry. The above process is repeated with further sets of cladding strips 28 being fixed to the series of holders 34 until assembly of the formwork for the wall is complete to the required height. The cladding holder 34 in this embodiment is a replacement for structural stud 10 in Figure 6, and central portion 38 is a replacement for stud web 12 having dimensions to meet the overall required thickness for the wall to be cast.

[070] An alternative embodiment of the formwork of the invention is illustrated in Figure 8. In cases where a sheet board 120 is used as the cladding shutters to replace the cladding design of Figure 6, it will be used in conjunction with an internal top hat section 110 that connects the external cladding board 120 to the wall system. The concept of using a top hat section imitates the cladding design of Figure 5: Here two spacers 1 12 of top hat section 1 10 create space 60 between the flat cladding and adjacent studs 10, allowing for the settable material to flow and fully envelop the studs and thereby to protect the studs against fire as mentioned previously in this disclosure. The external board 120 may be made of any material that can withstand the wet settable material hydrostatic pressure without noticeable deflection or bulging. One of the very favourable materials to be considered is a thin layer of fibre glass concrete or fibre cement sheet. A layer of fibre glass concrete will be more aesthetically pleasing and the finish it presents is popular with many architects. The top hat has two outward flanges 114 that are fastened to the plurality of outward-facing stud flanges 14 with screw or rivets. The board is connected likewise to the top hat flat surface 116 with screw or, in case of fibre glass concrete board, the top hat 1 10 may be cast in during the manufacturing of the thin layer board while it is still wet so that it becomes integrated into one piece. The thin layer board when ready for use will then have a plurality of top hats 110 integrated into its structure.

[071] Assembly of the formwork takes place preferably according to the following steps, with reference to Figure 5 and Figure 6(b):

1. The upwardly directed flap portion 30 of strip 28is fixed to flange 14 of each structural stud 10 by means of self-drilling screws, rivets, welding or any other suitable fastening means. A plurality of horizontal shutter strips 28, when fixed to each of the plurality of studs 10 form an elongate wall surface in strip form.

2. Referring to Figure 6 (b) & Figure 6 (d), once the first shutter strip 28A is fixed in place, preferably at the bottom edge of the intended wall structure, then it is ready to receive the next shutter strip 28B. The next strip will be stacked above it by virtue of complemental nesting formations on the upper and lower elongate surfaces of the respective sheets.

3. The lower metal strip 28A is fixed to present the open end of channel 46 to be upwardly facing, so that it may receive into it offset lower lip 42 of shutter strip 28B on its being placed above it. Lip 42 of shutter strip 28B slides into place to nest in lower strip channel 46.

4. Next, flap 30 of the upper shutter strip 28B is likewise fixed to structural stud 10.

Now two metal shutter strips 28 are fixed to the plurality of structural studs 10 to form the wall formwork system 50.

5. As shown in Figure 5(b) lower lip 42 has a recessed shelf 48, which is configured to rest in operative configuration on the spacer 54 and channel 46 of the lower strip 28A during and after assembly of the strip wall.

6. By repeating the steps above, every shutter strip 28 that is required for making up the formwork containment panel to required wall height is secured in place: That is, bottom lip 42 of upper strip 28B is fitted into channel 46 of lower metal strip 28A and its upper flap 30 is fixed to the structural stud flanges 14 , whereby the whole containment sheet is assembled to be strong enough to withstand the pressure of the settable material, be it concrete or an alternative construction composite. [072] The above assembly process is repeated along the length of the row of vertical structural studs 10 and on both sides thereof, until both opposing sides of the structural studs 10 are completely covered with metal shutter strips 28 to form the composite wall formwork system 50 as shown in Figure 9.

[073] As seen in Figure 5, the outer, exposed surface 36 of the metal shutters is spaced away from the structural studs by a folded metal spacer 54, which connects flap 30 and channel 46. The void created by the spacer 54 serves to allow the uncured concrete to flow around the internal stud 10 , filling the gap 56 between flange 14 and metal strip internal surface 36, as well as the space 60 between adjacent studs 10 , without the need for holes 18 in the structural stud web 12 . Although there are holes 18 in the structural stud web 12, these are not necessary to let the concrete flow, but function to assist in reinforcement directed parallel to the general plane of the containment sheet, as described earlier.

[074] Spacer 54 is designed to space the shutter surface 36 from structural studs 10 for the following reasons:

1. To allow poured concrete to flow within the space between stud flanges 14 and the containment sheet having exterior surface 36;

2. To allow vertical stud 10 to have enough concrete cover to conform with applicable reinforced concrete structure standards so that the stud is considered a vertical reinforcement;

3. To protect the studs in the event of fire. As the gap between stud and containment sheet will be filled later with concrete, this layer of concrete will insulate the stud against fire and help preserve the structural integrity of the structure for fire rating purposes;

4. To allow for the fixings or fastenings (for example self-tapping screws or rivets) to be hidden behind the next higher-stacked nested strip 28 after its addition to the assembly, so that externally no fixings can be seen, improving the aesthetics of the structure;

5. To enable the internal components of the shutters to provide horizontal reinforcement for the structural walls; and 6. To allow the cross-sectional areas of the internal components of each shutter strip to contribute as horizontal reinforcement, namely flap 30, spacer 54, shelf 48, lip 42 and channel 46 (see Figure 5b).

[075] Although there is still a contact surface 62 between stud flanges 14 and flap 30 of the containment sheets, this contact surface is limited by the rectangular geometry of the interface. Referring to Figure 2, contact surface 62 is generally rectangular, its length corresponding to the length“F” of stud flange 14 and its width to the height“B” of the flap 30 in Figure 5(b). The contact surface area F*B is repeated only three or four times per meter length on the flanges 14. The total contact surface that could potentially transfer heat to the studs therefore is 12% to 16% of the total externally directed surface area of each stud flange 14. In the event of fire, external heat incident on the external surface of the wall system is transferred by conduction via flap 30 to spacer portion 54. The spacer has a very narrow geometry, having a sheet thickness of no more than about 1 mm. The limited conduction path via the spacer severely restricts the amount of thermal energy that can be transferred to the interior of the wall panel and to the stud. The configuration of the conduction path is designed to increase the time required for flap 30 to become hot enough to start transferring heat into the stud via the flange 14. As, the flap to flange contact surface area is limited to such a small percentage (12%-16%), heat transfer to the flanges 14 can be considered negligible. To improve the effectiveness of this restriction on heat transfer, a layer of thermal insulation may optionally be placed between the flap 30 and the flange 14 at interface 62. Generally, such a layer will not be needed, as the heat transfer to the studs will take a significant length of time to cause noticeable change in the mechanical properties of the structural stud.

[076] As shown in Figure 5(b) metal shutter strip 28 has on its inward surface, that is the surface opposite to exterior surface 36, at least one inwardly folded lengthwise corrugation 66 to give it extra stiffness. It will be appreciated by those skilled in the art that the shutter strip may vary to be of different profiles and may make use of one of many different clipping mechanisms to suit the intended application, while still adhering to principles set out in this disclosure.

[077] Figure 9 illustrates a complete wall formwork system 50, erected vertically perpendicular to slab 26. It has containment sheets secured on opposite sides of the row of studs, ready to receive between them the settable material, namely wet concrete in this embodiment. The formwork includes end caps 68 at its opposite ends to stop the settable concrete from escaping. Diagonal props (not shown here) are provided to support the wall in plumb orientation so that it stands vertically while receiving the poured concrete, as known in the art.

[078] Referring again to the wall formwork system of Figure 6(a), which is shown with only one containment sheet in place, showing the internal structure. Horizontal rebars 20 are located lengthwise within wall formwork system 50 so that each will pass through one of the holes 18 of each consecutive structural stud 10. It will be appreciated by those skilled in the art that the number and size of the horizontal bars, the spacing between them and the configuration of holes 18 will be different from one wall formwork system size to another, based on the structural engineering design requirements. The formwork of Figure 6 may be laid horizontally so that it works as a reinforcement slab formwork for a floor, deck or roofing structure. The holes in the stud webs need not be exactly aligned from end to end of the formwork, but may be offset from one stud to the next, to enhance the cross-sectional structural strength of the studs through which the generally horizontal bars pass.

[079] In this floor slab embodiment, the horizontally laid structural studs 10 act as the main reinforcement elements of the slab once cast, and the optional reinforcement bars 20, penetrating the webs transversely to the studs through holes 18, offer reinforcement in the perpendicular direction. The slab formwork system is manufactured to the maximum possible dimensions that can be delivered, by forming modules of comprising the reinforced slab system formwork. These modules are then suitable to be set on multiple frames of support props that are erected on site. The modules are set edgewise adjacent each other in a tessellated manner to form the structural slab for each level in a multi-level building.

[080] The selection methodology for determining the structural stud size and its spacing in formwork embodiments disclosed herein is preferably implemented in the following steps:

1. Specification of wall thickness: The wall thickness specified by a structural engineer will determine the size of the structural stud 10 to be used. Different stud sizes have different dimensions. The overall wall thickness shown for example in the embodiment of Figure 2 read with Figure 3 and Figure 4 is the summation of: a) the length W of web 12; b) the length of spacer 54 (see Figure 5) of shutter strip 28 of the first side when assembled on flange 14; and c) the length of spacer 54 of the opposite side when assembled on flange 14; and d) the widths of channel 46 and ridge 52 of the strip on each side of the stud (unless these have already been included as part of spacer 54.

From the above it is obvious the that the stud size is always smaller than the overall wall thickness by at least the distance of spacer 54 from each side of the stud. This will ensure effective concrete flow around the stud without the need of openings in the stud web for this specific purpose. Also, this will allow use of thinner studs, which in turn means more economical use of materials.

Figure 6(b), Figure 7(b), Figure 8(b) shows an end cross-section of a structural stud 10 and containment sheets 28 in assembled configuration, that determines the overall wall thickness. Calculation of stud cross section:

The axial cross-sectional area of a structural stud having a hollow square C- shaped profile as shown in Figure 4 and Figure 2 is determined by applying the equation:

(L+F+W-H+F+L)*t

where;

• L is the structural stud lip length

• F is the flange length

• W is the web length

• H is the diameter of the hole that serves to reduce the effective web length

• T is the thickness of the metal used to roll form the profile of the

structural stud.

Specification of round bar reinforcement by diameter and spacing: Diameter will inform the cross-sectional area needed by a round bar and the spacing will tell how many bars are needed for a given length of the reinforced concrete wall. Determination of stud spacing:

The spacing between the structural studs is determined by comparing the stud cross sectional area with the specified round bar cross sectional area. The structural studs are placed apart to compensate for similar cross- sectional area for a given length of wall according to engineering specifications for round bars. Furthermore, the spacing between any two given structural studs 10 must not exceed the fixation requirements for the containment sheets to support the shutter strip against wet concrete pressure (or pressure of any other material used). a. If the equivalent structural stud spacing per given wall length to comply with structural engineering requirements is greater than the maximum spacing needed for the metal strip 28 to withstand the anticipated concrete pressure, then more structural studs will be added. The smaller the spacing necessary to withstand the concrete pressure, the greater the support available for the containment sheets 28 at each fixing point. b. Closer spacing between the structural studs means more reinforcement per given length than is strictly be needed according to the structural engineering design; hence a structurally stronger wall is achieved once the concrete is cured.

5. Once the structural studs have been spaced vertically and erected parallel to each other, the next step is to fix the shutter strips to the opposite sides of the studs.

[081] The assembly process to manufacture wall formwork system 50 shown in Figure 9 takes place in a factory environment, so that the formwork is delivered to site for erecting and filling with settable concrete only. The assembly process includes the following steps:

1. The vertical structural studs 10 are arranged in spaced apart relationship and are held in their relative positions until the assembly process of fixing the plurality of shutter strips 28 to the studs 10 has been completed.

2. The spacing between studs 10 is determined to conform with the same cross- sectional area as stipulated in the engineering calculations, and to comply with structural design standards for reinforced concrete.

3. The vertically placed studs are erected to the height specified in the plans for the wall formwork system 50. 4. The lowermost horizontal shutter strip 28 is fixed to the lowest available part of the structural studs at the contacting surfaces 62 (flange 14 with flap 30), visible in Figure 9.

5. Each flap 30 interfaces with each structural stud 10 at the contact surface 62 available on its flange 14, and is fixed to it by several screws. The number of screws or other fixing means will be determined by the load force that wet concrete pressure will exert on the containment sheets, which consequently transfer the load onto the fixing points at interfaces 62.

6. It will be appreciated that the less the spacing between the structural studs 10 the greater the number of studs per unit length of the wall and the more the available contacting interfaces 62. The more contacting interfaces means the same load (coming from hydrostatic pressure) being distributed over more of fixing points, leading to lessening of the load per fixing that comes from concrete pressure during pouring the settable material.

7. Steps 4,5,6 are repeated from the other side of the structural stud 10 on the opposite flange 14 with another layer of horizontal shutter strips 28.

8. If specified in the structural engineering design, any horizontal bars 20 required are inserted into the webbing holes 18 of the structural studs.

9. The next layer of metal strip shutters 28B is added above the lower metal shutters 28A already fixed to studs 10, by inserting lower lip 42 of strip 28B and sliding it into the channel available on the prior fixed shutter strip 28A.

10. Shutter strip 28B is secured in place as described at step 5 above.

11. The above steps are repeated until the row of structural studs 10 to form the wall of the design are covered with the shutter strips 28 from bottom to top on both sides, thereby forming the formwork wall formwork system 50, ready for filling with flowable concrete.

[082] The wall length, height and thickness are governed by the architectural design of the building and structural walls lay-out plans in the engineering drawings. In the case of an individual wall length being longer than the maximum length deliverable by truck, the wall may be manufactured in two or more modules and erected sequentially next to each other on site. The wall system may also have different windows and doors openings that will be catered for during the manufacturing and assembly process before delivery to site. It would be advantageous and economical to utilise available logistic capacity to the utmost and deliver walls in the largest possible dimensions that are practical, rather than to make multiple deliveries of smaller walls that will involve multiple crane lifts for erection to be achieved on-site.

[083] The side view of the formwork shown in Figures 6b, 7b, 8b shows how it is connected structurally with the structural slab 26 below. Normally dowel bars 70 are cast within the slab before the concrete is cured. The dowel bar diameters and spacing are specified by the structural engineer responsible. Once concrete slab 26 is cured with dowel bars 70 protruding partially, wall formwork system 50 is located to rest directly upon and perpendicular to the cured slab surface 80, allowing for the dowel bars 70 to enter into the void spaces between the structural studs 10 and between the staggered rows of horizontal bars 20 that pass through the holes 18 in the studs.

[084] Another aspect of the invention in this disclosure that is apparent in Figures 6d, 7d, 8d is the space 60 created by spacer 54 of shutter strip 28 when metal flap 30 rests against and is fixed by being screwed into stud flanges 14. A fillable void is thus established on both sides of structural studs 10, allowing for wet concrete to flow around each stud, without needing holes to be provided in the stud web 12 for this specific purpose. This provides for maximum cross-sectional or end elevational area of each stud 10 to be utilised for reinforcement functions and for protecting the structural stud against fire to comply with relevant standards.

[085] Once the wall formwork system 50 has been erected, the concrete is poured on site. The plurality of structural studs 10 and shutter strips 28 of the containment sheets, together with the concrete when cured, become a very strong composite structural section, found to be much stronger than the conventional cast in-situ wall having round bar reinforcement.

[086] Figure 10 shows various formwork units, made according to methods in this disclosure, being assembled to form a building structure. Each of the walls 50 are seated on a common slab 26, which has dowel bars 70 protruding through the void between the pairs of opposing containment sheets. Each wall is erected in place and supported by props 90 to stand plumb, in readiness for receiving the settable material, in this case concrete. Once the concrete has cured, props 90 may be removed. Details of wall intersections at a 90° corner, or T-intersection, are illustrated in Figures 12, 13, 16, 17 and 18 and will be discussed below.

[087] As illustrated in Figure 10, the studs 10 may be selected to extend above the height of the containment sheets of the vertical formwork of which they form part, so that the extended portions 72 act as a form of edge protection mitigating against fall risk, for site safety. This is particularly useful if the wall is at the edge of a construction site, with the extended height being specified to comply with health and safety regulations.

[088] At each otherwise open end of each wall formwork system 50, an end cap 68 is located to stop the flowable poured concrete escaping. Temporary fixing brackets 74 are screwed into the concrete slab 26 and the wall formwork system 50 to prevent the panel from movement until the settable material has been received and cured. Any downpipes or conduits 130 are accommodated inside the void of the formwork system 50, between studs 10 and sheets 28.

[089] While undergoing factory manufacture and assembly, the formwork system will have all door and window openings catered for at their specified locations before delivery to site.

[090] The exposed surface 36 of formwork system 50 can be left as it is or be covered by different shutters or render finishes, according to the surface finish specified in the architectural plans. Different wall finish specifications and installation procedures are determined by product manufacturers to comply with relevant codes.

[091] Referring to Figure 1 1 , the formwork system already described is applied in the building of a lift shaft 200 comprising four wall systems 50, intersecting to define four corners. The figure illustrates two levels of the shaft only - not the shaft for the entire structure - for simplicity. Essentially the same steps will be repeated for the superseding levels, including for buildings considered“skyscrapers”.

[092] For forming the lift shaft, the wall of each formwork system 50 is built to the full height of two levels, where it is logistically possible to do so. In these cases, each wall formwork system must allow for a structural slab connection at the middle between the levels where they interface (or as may otherwise be specified). To this end, a plate 202 is fixed at the interface to the structural studs 10 in a gap left between two of the shutter strips 28, where the slab will be connected during site construction to the wall formwork system 50. As seen in Figure 15, plate 202 has holes punched to receive and locate ferrules 76 in position in the stud by means of welding or any other suitable fixing method. The number of ferrules needed and the spacing between them will be specified in the relevant structural engineering plans for slab connection. This will apply to each of the four wall systems 50 of the lift shaft where connected to the surrounding slab around the shaft. Another way to connect the slab to the wall system is shown in Figure 18, using an L-bar connector 206 welded to the web 12 of stud 10.

[093] Referring to Figurel 1 Figure12, Figure 13 and Figure 15, the walls are connected at the corners using either a hook bar connector 204 as in Figure 13, or an L-bar connector 206, seen in Figures 12. Each corner will be covered after erection of wall formwork system 50 with a 90° corner cap 208, which is fixed with screws into the two intersecting walls along the wall height, to stop concrete escaping out of the corner connections, as illustrated in Figures 13 and 14. All lift shaft door openings will be covered by end caps 68 to prevent poured concrete escaping outside the wall formwork system 50. The process will be repeated for all the superseding levels of the building.

[094] Once the two intersecting wall formwork systems have been erected on site and before the concrete is poured, the L-bar 206 or hook bar 204 connectors are operatively applied to connect the two wall forms together and are then covered with a corner cap 208, screwed externally into the plurality of shutter strips 28 on the overlapping contacting surfaces of the corner cap 208 and metal strips 28.

[095] The connection is now sufficiently sealed and ready to receive the poured concrete without it spilling from the connection. Once the concrete is cured, the two walls are structurally connected. The number of connector bars 204,206 per unit length will be specified in the structural engineering design to comply with load limits.

[096] Figures 14 and 15 show sectional side views of wall formwork systems of the disclosure connected to slab 26. The wall systems can be either a factory assembly of single level wall height or of multiple levels’ height, depending on delivery logistics and site conditions. In case of a single level height wall, the slab connection details shown in Figure 14 will be used to connect the slab 26 into the wall formwork system 50. Normally, in this situation, the formwork system would be erected on site before concrete is poured (first stage pour), allowing for L-bars 206 to be part of this pour. The slab reinforcement can thereafter be connected into the L-bar arrangement, hence connecting the wall reinforcement structural stud 10 into the slab 26 reinforcement. Once the concrete has been poured for the slab 26 (second stage pour) and allowed to cure, the slab 26 is levelled to receive the next wall formwork system 50, superimposed on top of the slab. The connection between slab 26 and the superimposed wall formwork system of the next level. If the wall formwork system 50, external surface is exposed being a fagade, the wall surface can have a finish 92 applied, the finish could be render or paint or the whole external can use the previous concept explained as per figure 8 where the board will be the finished surface.

[097] Figure 15 shows an embodiment in which a wall of height sufficient to accommodate two or more levels is being constructed. To connect the wall formwork system 50 into each slab 26, a plate 202 having ferrule-accommodating holes is located against stud 10 with welded ferrules 76 fixed to it. The plate 202 is placed at the exact slab height for the relevant level. The formwork for wall formwork system 50 is erected on-site and concrete is poured into it (first stage pour). Reinforcement for the proposed slab is connected to the wall formwork system 50 at each level by means of the ferrules 76, each of which has an internal thread to be connected to a threaded bar with the slab reinforcement. Thereafter, the second stage concrete pouring, this time of the slab, takes place. The process is repeated at each slab level where connection with wall formwork system 50 is required.

[098] Figure 16 shows, applying like numbering from previous figures, different options of connecting a slab 26 to wall form 50, using either:

1. In (a), an extended reinforcement bar 20 that is fixed to the structural stud 10 of the lower wall;

2. An extended reinforcement bar 20 that is fixed to the structural stud 10 of the lower wall and another L-bar 74, which is connected to the slab; or

3. A smaller size structural stud 10 A that is connected to structural stud 10 the lower wall formwork system 50. The smaller stud 10A is connected to the lowers stud 10 and the upper stud 10 through the slab by the mean of bolts 78

[099] In each of the above cases the building procedure is as follows:

1. The lower wall formwork system 50 is erected on site including the connection bars 20,74 and structural studs 10;

2. Concrete is poured for the lower wall formwork system 50; 3. The concrete of slab 26 is poured for the upper level;

4. A superimposed wall formwork system 50 is erected on the top of concrete slab 26 where bars 20 and structural studs 10 along the wall length sit inside the intermural void of the superimposed wall formwork system of the upper level;

5. Concrete is then poured for the wall formwork system 50 of the upper level; and

6. These steps are repeated until the superstructure is completely built.

[0100] Another connection detail is explained with reference to Figures 17 and 18, when a wall formwork system 122 is extended perpendicularly from another wall formwork system 124, forming a T-wall intersection. To connect the two structural walls 122, 124 together, a series of L-bars 206 are used go through the holes 18 punched along the length of at least one structural stud 10 in each of the two perpendicularly intersecting wall systems. Once the two wall formwork systems have been erected, abutting each other, an equal angle bracket 58 is screwed from each side to secure them together at the intersection corners and to inhibit concrete leakage during pouring. Props 90 and brackets 74 of the type shown in Figure 10 are then added further to stabilize the structure, to ready it for receiving the settable material, concrete in this example.

[0101] Figure 19 illustrate the system of the invention being used in fabricating modular structural columns out of the system components. Each columns contains a row of structural studs 10 (whether C-, Z- or other profile), each of which has a series of holes 18 along its web 12 as shown in Figures 3 &4 for horizontal bar 20 to penetrate through, thereby to connecting to all, so as to form what is known in the structural engineering profession as a“blade column”. Strips 28 are fixed to either side of the row of studs and end walls are provided each end by an end cap 68, thereby to form a fillable space to receive concrete for curing. Each column, when cured, may be applied as a construction element in creating a larger walled structure.

[0102] In the case when a full structural column is fabricated out of wall system components including reinforcement structural studs 10 and shutter strips 28, there are at least two sets of staggered holes 18 in the webs of the studs to receive the equally sized legs of a U-bar 82, which penetrates through two holes in each of the webs to create what is called a concrete confinement reinforcement (or ligature) that will withstand structural loads applied on the structural column. Once the plurality of equal leg U-bars penetrate through the holes 18, they can be welded from the side at which the free ends of the legs are positioned, by connectors 84. This builds the ligature shape along the whole length of the module, the length of which is defined by the row of structural studs 10. Again, the spacing between structural studs 10 will be governed by the criteria mentioned earlier.

[0103] One skilled in the art will appreciate that the formwork of the invention presents dual functionality, the metal formwork operating as formwork as well as reinforcement. It may be manufactured in a customised fashion to suit each building project. The present invention stands alone in eliminating the need for conventional reinforcement by using the structural studs of the formwork to provide all necessary vertical reinforcement while the spacing of the cladding allows for required settable material thickness around the stud, as for example the deformed bars specified by structural engineers in building skyscrapers.

[0104] It is intended that a table of calculated cross section areas for each size of structural stud to be manufactured for use according to the invention will be supplied to structural engineers, so they can rely on and to be used in their calculations for reinforcement of wall, column, slab and like designs.

[0105] The system of the invention is directed to providing a permanent formwork system compromising metal structural studs and metal shutters. It does not need to be stripped away or otherwise removed once the concrete or other settable material within has set. The description and drawings are illustrative of the disclosure and are not to be constructed necessarily as limiting the scope thereof. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure. The skilled reader will be able to envisage other embodiments not herein disclosed, but which utilise the principles and novel concepts discussed above.

Claims

1. Permanent hollow panel formwork comprising a containment sheet and an elongate reinforcing member connected to the sheet in spaced relationship to define a gap between them, the gap being sufficient in width for protecting the reinforcing member against degradation from external conflagration when filled with a cured construction composition.

2. The formwork of claim 1 wherein the reinforcing member is connected in axially parallel orientation in relation to the containment sheet.

3. Formwork according to claim 1 or 2 wherein the reinforcing member comprises an elongate web having opposite major elongate edges and a flange extending from each.

4. The formwork of claim 3 wherein the web has a keyed surface.

5. The formwork of claim 4 wherein the surface is keyed by ribbing.

6. Formwork according to any one of claims 3 to 5, wherein the web is adapted to support a generally horizontally disposed reinforcing bar.

7. The formwork of claim 6, wherein the web is adapted to have an aperture into which a reinforcing bar is supportively receivable.

8. The formwork of claim 7, wherein the aperture is a hole having a flared rim.

9. The formwork according to any one of the preceding claims, wherein the sheet comprises a plurality of nestable strips.

10. The formwork of claim 9 wherein the strips have a first portion comprising a channel and a second portion configured to fit into the channel of a strip located adjacent to it.

11. The formwork of claim 9 or 10 wherein the strips comprise a spacer projecting from the sheet and configured to abut the reinforcing member.

12. The formwork of claim 11 wherein the spacer comprises an extending fin by which it is connected to the reinforcing member.

13. The formwork of claim 12 wherein the fin extends generally parallel with the sheet, defining an interface through which the spacer is fastenable to the reinforcing member by a fastening device.

14. A structural slab comprising a cured composition at least partially shaped by permanent formwork having a containment sheet supporting the composition and a plurality of elongate structural reinforcement members connected to be spaced from the sheet by a gap of minimum width sufficient for protecting the reinforcing member against degradation from external conflagration when filled with a cured construction composition.

15. The structural slab of claim 14 having spacers arranged at intervals along the member to space the sheet from the member and define the fillable gap.

16. The structural slab of claim 15 wherein the spacers are adapted to interact with the elongate reinforcement member and to connect with the sheet.

17. The structural slab of claim 15 wherein said spacer is adapted to receive a reinforcement member in the form of a bar and to be fixed to the sheet.

18. A prefabricated permanent formwork system defining a space for filling with a settable filler to form a reinforced wall of said filler when set, the system comprising: a. an internal structure comprising a row of elongate spaced structural studs having their elongate axes in parallel spaced relationship; and b. an outer skin extending along the row in parallel to and spaced from the studs to define gaps between the studs and the skin for receiving said filler; wherein the studs are configured to vertically reinforce the skin to required construction standards without requiring additional reinforcement means.

19. The formwork system of claim 18, comprising fixing means operable to fix the skin to the studs.

20. The system of claim 18 or 19, wherein the studs comprise an elongate web having opposite elongate edges and a flange connected to each opposite edge.

21. The system of claim 20, wherein the web is adapted to support a horizontally disposed reinforcing bar.

22. The system of claim 21 , wherein the web is adapted to include an aperture sized to receive a reinforcing bar for the bar to be supported by a rim of the aperture.

23. The system of claim 22, wherein the aperture is a flared hole configured for promoting keying between a settable material and the web.

24. A system according to any one of claims 20 to 23, wherein the web has a keyed surface.

25. A system according to any one of claims 18 to 24, wherein the skin comprises parallel overlapping elongate strips.

26. The system of claim 25 wherein the strips have elongate edges configured for nesting.

27. A system according to any one of claims 18 to 26, wherein the filler is of lower thermal conductivity than the skin.

28. A method of constructing a structural panel comprising a settable structural composition, the method comprising the steps of: a. Providing permanent formwork configured for containment of a settable composition, the formwork comprising a row of elongate reinforcement members connected to a flanking containment sheet that is spaced from the members by a gap into which the settable composition is receivable, the gap being of width such that when filled with settable material allows the composition to form a cured body effective to protect the reinforcement members from degradation due to external conflagration; b. Introducing a settable composition into the formwork; and c. Allowing the composition to cure.

29. The method of claim 28 wherein steps a and b are performed at different localities.

30. The method of claim 29, including the step of providing a second containment sheet and connecting the second sheet to the reinforcement members on a side of the row opposite to the already-connected sheet in corresponding spaced relationship.

31. A method according to any of claims 28 to 30 wherein the member has a keyed surface suitable for locking with the settable composition.

32. A method of reinforcing a wall panel comprising the steps of: a. providing a permanent formwork structure comprising opposed sheets separated by a row of upright studs, b. causing the studs to be spaced from the sheets therefore to define a

fillable space for receiving a settable material between the studs and sheets, and c. filling the space with settable material to envelop the studs.

33. The method of claim 32 including causing the studs to be enveloped by the settable material to a thickness that, when set, is effective to protect the studs against thermal degradation caused by external conflagration.

34. The method of claim 33 including providing the studs with a keyed surface for contacting the settable material in mechanical locking relationship when set.

35. An elongate stud for upright erection in a hollow panel wall formwork structure, the stud having a ridged surface and flanges with stiffening lips and a web between the flanges, the web having a plurality of holes formed therethrough for a settable structural composition to fill to set in locked relationship with the web.

36. Hollow panel formwork in kit form, comprising a containment sheet and an elongate reinforcing member connected in spaced relationship to the sheet to define a gap between them, the gap being sufficient for receiving therein a settable construction composite for setting to a structurally effective thickness for protecting the reinforcing member from degradation from external conflagration.

37. Formwork according to claim 36 wherein the reinforcing member is adapted to support a horizontally disposed reinforcing bar.

38. Formwork according to claim 37 wherein the reinforcing member is adapted to include an aperture.

39. Formwork according to claim 38, wherein the aperture comprises a hole adapted for keying with the fillable material.

40. Formwork according to claim 39, wherein the hole has a flared rim.

41. Formwork according to any one of claims 38 to 40, wherein the reinforcing member comprises a web through which a plurality of apertures pass, the total area of the apertures not exceeding 7% of the cross-sectional area of the member.

42. Formwork according to any one of claims 36 to 41 , wherein the reinforcing member has a surface keyed for mechanical locking with the settable material.

43. Formwork according to claim 42 wherein the surface is keyed by having ribbing.

44. Use of the formwork kit of any one of claims 36 to 43 in the construction of a column.