GB2584095A - Corner shutter member - Google Patents

Abstract

A corner shutter member for retaining a settable material comprises a sheet of material shaped and folded to define an upright retaining wall. The retaining wall has a line of weakness 21 extending vertically across it to define first and second retaining wall portions 28a/b. Each of the first and second portions has a respective first or second base portion 29a/b extending orthogonally from a lower edge to keep the retaining wall substantially upright. The shutter member is bent on site to form either an internal or external corner, and the base portions are shaped so as to not obstruct each other. The first and second portions may have an orthogonal lip portion 30a/b extending from an upper edge to resist distortion. The shutter members may be transported flat. A plurality of ties 33 may link the base portions to corresponding wall portions and may be stamped or cut into the portions. The line of weakness may be a row of apertures or may be thinner than the rest of the shutter member. Also claimed is a method of forming a concrete slab by folding a shutter member and pouring concrete over the base portions.

Description

Corner Shutter Member The present invention relates to a corner shutter member suitable for use in a shutter system for supporting concrete or other settable material, and particularly, but not exclusively, for use during the construction of a structure such as a foundation raft, slab or low level beam.

In the building industry, it is known to erect a building or other structure on a raft, slab or beam, which may be supported by piles or cast directly on a suitably prepared piece of ground. This method of construction is particularly useful when building on ground that is liable to subsidence or heave, for example. The underside of the raft may be spaced above the ground by a void or compressible material. When using this method of construction, the raft or beam is typically cast in situ by pouring concrete or other settable material into formwork which defines the desired shape of the beam or raft. A shutter system suitable for such an application is disclosed in UK Patent Application Publication Number GB 2522887 and a corner shutter member in accordance with the present invention is particularly applicable to a shutter system such as the shutter system disclosed in that patent application.

Shutter systems as disclosed in UK Patent Application Publication Number GB 2522887 employ a number of linear sections formed of sheet steel, one of which is illustrated in attached Figures 1 and 2 of this specification. A number of such sections may be joined together to form a shutter to define an edge of a poured concrete slab, slab or the like.

Linear sections of a shuttering system, such as disclosed in UK Patent Application Publication No GB 2522887 and the attached Figures 1 and 2, as well as other such systems have proved very successful. However, at a corner of a building if it is often necessary to accurately cut linear sections at an angle of forty five degrees, abut these together and subsequently weld them together to provide a corner shutter member. This is time consuming to do on site and may require equipment such as mitres or table saws, to ensure that the angles are correctly cut. This is in addition to welding equipment and a skilled welder who will need to be present on site.

In order to avoid the problems outlined above, preconstructed corner shutter members may be provided which are prefabricated in a factory and supplied to a site. Unfortunately, unlike the linear edge shutter members, these cannot be nested together for transportation, or for ease of distribution on site. Thus, corner shutter members, of which there may be many in a multi-storey building, have to be transported as individual items. This not only makes them bulky and therefore difficult to transport, either to a site or around a site but, unless appropriately packaged (which further adds to the bulk of such items) they are more prone to damage than their nested linear counterparts.

The present invention aims to provide an improved corner shutter member which may be suitable for use with the aforementioned type of shutter system, but which may also find use in other applications.

According to the first aspect of the present invention there is provided a corner shutter member for retaining concrete or other settable material, the shutter member comprising a single sheet of material shaped and folded to define, in use, an upstanding retaining wall arranged to retain concrete or other settable material, the retaining wall having a line of weakness extending substantially vertically across it to define first and second portions of the retaining wall to either side of the line of weakness, each of the first and second portions of the retaining wall having a respective first or second base portion extending substantially orthogonally from a lower edge and arranged to, in use, support the shutter member on a substrate and maintain the retaining wall in an upstanding position, wherein the line of weakness is arranged to permit the shutter member to be bent on site to form either an internal corner or an external corner, as desired, and wherein the first and second base portions are shaped so as not to obstruct each other when the shutter member is bent to form either an internal corner or an external corner shutter member.

A corner shutter member in accordance with the present invention enables the corner shutter member to be supplied as a linear unit and, subsequently, to be bent on site (normally by hand) into a corner shape, normally by being bent at right angles to form a right angled corner shutter member. However, other corner shapes may be constructed other than right angled corners.

An additional feature of the invention is that it may enable a corner shutter member to be fabricated merely by a stamping and folding process, without the need for any welding or any other fabrication steps to be performed in the factory.

A particular advantage of the present invention is that it enables a single corner shutter member to bent on site to form either an internal corner shutter member or an external corner shutter member. This is of particular advantage because it avoids having to provide two specific corner shutter member types, to form both internal and external corner shutter members and avoids having to correctly distribute these to and around a site. This also greatly simplifies the ordering of corner shutter members for a site, for all that is required is to know the total number of corners, avoiding any confusion which may otherwise arise from having to specify, separately, the required number of internal corner shutter members and the required number of external corner shutter members.

It is particularly advantageous if the corner shutter member is arranged to be bent to form either an internal corner shutter member or an external corner shutter member which can have any desired corner angle in the range of 90° to 340°. Indeed, this range may be extended depending on the configuration of the corner member. An advantage of this is that it permits a single corner member to be bent to form any desired corner, not just an internal or external right angled corner.

Preferably, the first and second base portions are shaped such that they may permit the corner shutter member to be bent to form either an internal or an external corner shutter member, without the base portions overlapping. This may require that the base portions be "cut" away in the region of the line of weakness to avoid the base portions interfering with each other when forming an internal corner shutter member, (as these base portions may otherwise restrict the bending of the corner shutter member, as these base portions will normally lie in the same plane). This issue does not arise when bending the corner shutter member to form an external corner shutter member.

The amount that the base portions are cut away may determine the minimum angle of corner that may be formed. That is to say, the more the base portions are cut away, the closer the first and second portions of the retaining wall may be brought together and thus the smaller the angle between them and thus the smaller the angle of the corner to be formed.

It may be desirable to reinforce the top edge of each retaining wall portion, in order to prevent the retaining wall portions being distorted by the weight of concrete present on only one side of the retaining wall. This reinforcing will normally be provided in the form of a lip which will normally extend to the same side of the retaining wall as the base portion extends and lie in a plane parallel to the base portion. Thus, it is necessary that the lip portions are also shaped so as not to obstruct each other when the shutter member is bent to form either an internal or external corner.

Preferably, the first and second lip portions are shaped such that they may permit the shutter to be bent to form either an internal or external corner, without the first and second lip portions overlapping.

Preferably, each lip portion has a downwardly extending distal edge, such that the top edge of each of the first and second portions of the retaining wall, together with their associated lip portions, define n-shaped channels along the top of the corner shutter member. The n-shaped profile at the top edges of the retaining wall portions provides a convenient way of significantly strengthening the retaining wall, permitting a thinner grade of sheet material to be used for constructing the corner shutter member than may otherwise be required.

The corner shutter member may be formed from a sheet which is cut or stamped and machine folded to have a number of linear fold lines which are all parallel to one another and which extend in a longitudinal direction of the shutter member to define at least the upwardly extending retaining wall and each of the first and second base portions extending substantially orthogonally from the retaining wall, permitting the corner shutter member to be transported in a generally linear configuration, where multiple corner shutter members may be nested together, where the first and second portions of the retaining wall lie in the same plane and where the line of weakness is arranged to permit the first and second portions of the retaining wall of the shutter member to be bent relative to each other, onsite and possibly by hand, in either a forward direction or a backwards direction, such that the first and second portions of the retaining walls lie in substantially orthogonal planes, with the corner shutter member forming either an internal or external corner.

The above arrangement may be advantageous because it permits a relatively thick sheet of material, typically a steel sheet, to be used to form the corner shutter member, for this will be folded by machine. This will thus provide a shutter member, once machine folded, with a significant resilience along the machine fold lines between the base portions and the retaining wall portions. This is desirable as these fold lines act to maintain the retaining wall portions in an upright configuration, due to the inherent strength of the folded sheet. Additionally the greater the thickness of the sheet used, the greater the resilience of the retaining wall portion to flexing in use. However, the line of weakness permits the corner shutter member to be bent on site, normally by hand, to the shape of the desired corner shutter member, thus to form either an internal corner shutter member or an external corner shutter member.

As an alternative to the above however, the corner shutter member may be cut or stamped and additionally formed with a plurality of pre-weakened fold lines, which are all parallel to one another and which extend in a longitudinal direction of the shutter member, permitting the shutter member to be transported flat, where multiple corner shutter members, in the form of multiple flat sheets, may be stacked one upon another, where the plurality of pre-weakened fold lines are arranged to permit the corner member to be folded on site, possibly by hand, to define, in use, at least the upwardly extending retaining wall and each of the first and second base portions extending substantially orthogonally from the retaining wall.

The complete corner shutter member can be formed in a factory simply by stamping or cutting the sheet to the desired shape and optionally machine folding the sheet so that it has a uniform linear profile (except in those sections which were the sheet has been cut away beforehand), or forming it with a number of pre-weakened fold lines, to permit the sheet to be folded by hand on site. The fold lines may be pre-weakened in the same manner as the line of weakness is formed and there may be no distinction between these, other than the fold lines are substantially horizontal and are to define the linear profile of the corner shutter member, while the "line of weakness" defines a substantially vertical line about which the two retaining wall portions are bent to form a corner having a desired angle.

It is particularly advantageous if the corner shutter member is formed entirely from a single flat sheet of metal, by cutting or stamping and subsequently folding, without any welding or fastenings, for this results in a corner shutter member which is relatively easy and inexpensive to fabricate. Furthermore, the linear configuration permits a number of such corner shutter members to be easily stacked, or nested, and packaged in the factory prior to transportation to a site.

On site the line of weakness permits the corner member to bent by hand, to form the desired corner shape, where the line of weakness will then form the apex of the corner. However the relative lack of strength of the sheet to flexing about the line of weakness is acceptable, for this is not necessary to retain the angle of the corner, for instead this may be maintained by the base portions of the corner member being anchored to a substrate on which the concrete or other settable material is to be poured.

The corner shutter member may comprise a plurality of ties, each linking a respective base portion to a corresponding retaining wall portion in order to, in use, restrain the retaining wall portion. The ties in use will exert a tensile force between the base which will be either anchored to the substrate or retained in place by the weight of concrete upon the base portion. It is particularly advantageous if the first and second portions of the retaining wall and the first and second base portions all have portions of a tie stamped or cut in them, wherein each portion of a tie in a retaining wall portion is arranged to engage with a corresponding portion of a tie in a corresponding base portion to form a tie, to link the base portion to the retaining wall portion and to restrain the retaining wall portion. This enables the ties to be formed integrally from the sheet material without any additional processes, the portions of the ties then being pushed out of the sheet on site and engaged with each other, so that the ties do not interfere with the nesting of the corner members while being transported.

The line of weakness preferably comprises a linear row of apertures through the sheet material. However, alternatively the line of weakness may advantageously comprise a line in a material, possibly produced by partial stamping into the sheet of material, where the sheet of material is thinner than it is for the remainder of the sheet.

According to a second aspect of the present invention there is provided a method of forming a concrete slab or structure, the method comprising forming, by cutting or stamping and folding, a corner shutter member as described above, transporting it to a site with other corner shutter members in a nested linear transport configuration, bending a corner shutter member about its line of weakness to form either an internal or external corner shutter member, securing the base portions of the corner shutter member to a substrate at a desired position and pouring concrete or other settable material over the base portions.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a perspective view of a portion of a known linear shutter member which, together with other such shutter members, will form a shutter for forming a concrete slab or similar structure; Figure 2 shows, in cross-section, the shutter member of Figure 1 retaining a concrete slab; Figure 3 is a plan view of a stamped metal sheet to be formed into a corner shutter member in accordance with the present invention; Figure 4 is a plan view of the metal sheet of Figure 3 when folded along the fold lines indicated by the broken lines in Figure 3 to form a corner shutter member in accordance with the present invention; Figure 5 is a front elevation of the corner shutter member of Figure 4; Figure 6 is an end elevation of the corner shutter member of Figures 4;and 5; Figure 7 shows the corner shutter member of Figures 4 to 6 bent to form an external corner shutter member; Figure 8 shows the shutter member of Figures 4 to 6 bent to form an internal corner shutter member; Figure 9 is a perspective view corresponding to Figures 4 to 6 of the corner member in a linear configuration prior to bending, but shows the ties assembled; Figure 10 corresponds to Figure 9 but shows the corner shutter member after it has been bent to form an external corner shutter member; Figure 11 corresponds to Figure 9 but shows the corner shutter member after it has been bent to form an internal corner shutter member; and Figure 12 is a cross-section through a portion of one of the corner shutter members of Figures 9 to 11, showing the corner shutter member secured to a substrate onto which concrete has been poured and which is retained by the corner shutter member.

Referring to Figures 1 and 2, theses illustrate, in perspective view and in cross-section respectively, a portion of a linear shutter member of the type disclosed in UK Patent Application, Publication Number GB 2522887. The linear shutter member is indicated generally as 1 and will typically be between one and two metres in length, such that it may be easily handled and positioned at a desired location on site. The linear shutter member 1 comprises a base 2 and a retaining wall 3, the retaining wall 3 having a lip 4 along an upper edge folded to form an n-shaped channel 5 to stiffen the upper edge of the retaining wall.

The linear shutter member 1 may be formed from a sheet of steel which is folded to the profile shown. A number of such linear shutter members 1 may be fabricated in a factory and shipped in a nested configuration to a site. On site these will normally be anchored, by fasteners 6 extending through holes 7, to a substrate 27. These will then define the edges of a concrete raft or similar structure that is to be formed, with joining strips 8 adjoining adjacent linear shutter members 1 to form a continuous shutter along each edge of the raft to be formed.

Previously, in order to form a corner shutter member for a raft, the ends of two linear shutter members 1 would each be cut at 45°, abutted together and then welded on site to form a corner shutter member, requiring a welder to be present on site.

Once the linear shutter members 1 and any required corner shutter members have been formed and anchored to the substrate 27, as shown in Figure 2 and any reinforcing bars 9 laid, concrete 10 or some other settable material is then poured to the level of the top of the shutter members 1 to form the raft or similar structure.

As will be appreciated from Figure 2, until it sets, the mass of the concrete 10 acting only on one side of the retaining wall 3 will exert a significant strain on the retaining wall 3. To counter this, in this embodiment, prior to the linear shutter members 1 being fastened to the substrate 27, L-shaped brackets 11 are clipped in place on the retaining wall 3 via apertures 12 in the retaining wall 3. These brackets 11 and are then affixed to the base 6 and substrate 27 by the fasteners 6. These brackets 11 can thus be inserted on site as required, permitting the linear shutter members to be transported to the site in the nested configuration.

Although in the embodiment illustrated in Figures 1 and 2, the retaining wall is restrained by the L-shaped brackets 11, other means may be provided to retain the retaining wall 3 in an upright configuration, particularly the ties described later in this application, in respect of the corner shutter member of the present invention, could for example be employed as one alternative for the L-shaped brackets 11.

The corner shutter member of the present invention, described below with reference to Figures 3 to 12, is suitable for use with linear shutters members, for example such as those described with reference to Figures 1 and 2. Corner shutter members in accordance with the present invention, when used together with such linear shutter members, may provide a complete shutter system for forming a concrete raft or similar structure. This may enable a shutter for a raft to be assembled which will define the complete raft, including the corners and it may be possible to assemble this without the use of specialist tools, such as welding equipment.

Referring now to Figure 3, here there is shown a flat steel sheet 13 which has been cut (possibly by stamping or laser cutting for example) to provide the shape shown and to provide the cut lines represented by the solid lines within the outline of the shape. The dashed lines 14 to 19 are, in this embodiment, indicative only of where the sheet 13 is to be subsequently folded and do not appear on the actual sheet.

The sheet 13 is cut to provide an outer perimeter, as shown, and to provide a vertical linear array of slots 20 which define a vertical line of weakness 21. Although the line of weakness 21, in this embodiment, is formed by the linear array of slots 20, this could be formed by any other appropriate means, such as by the sheet being thinner along the line of weakness 21, or being structurally weakened by an appropriate process being applied to the material of the sheet along the line of weakness 21.

The cuts also form a number of apertures 22 arranged to receive fastenings, as describe later and to also form four first portions 23 of respective ties and four corresponding second portions 24 of those ties. The first portions 23 of the ties are formed with tabs 25a at their ends and the second portions 24 have apertures 25b at their ends to receive the tabs 25a, as described later.

In this embodiment, the sheet 13 of Figure 1 is folded through 90°, out of the paper as shown, along each of the fold lines 14 to 19, to provide a corner shutter member 26 as shown in top elevation in Figure 4, in front elevation in Figure 5 and in end elevation in Figure 6. It may also be useful to refer to the corresponding perspective view of Figure 9, noting that Figure 9 shows the ties after they have been assembled, which is described below with reference to Figure 9.

The folding process, together with the slots 20 defining the line of weakness 21, create a corner shutter member 26 as shown in Figures 4 to 6. This has an essentially flat, or linear, configuration enabling multiple ones of such corner shutter members 26 to be stacked or nested together for transportation to a site.

Only on site need the corner shutter members 26 be subsequently bent (normally by hand) about their line of weakness 21, in order to form corner shutter members each having a desired corner shape to form corner shutter members for a raft or similar structure to be formed.

In an alternative embodiment, the dashed lines 14 to 19 of Figure 3 may be preweakened fold lines, preweakened by the sheet being thinner along these lines, structurally weakened by an appropriate process being applied to the material of the sheet along these lines, or by the lines comprising a linear array of apertures through the sheet. These may then avoid the need to machine fold the sheet, but instead permit the shaped sheet to be transported flat to site, where the folds may then be created by hand, to form the linear profile of the sheet, before bending to form a desired internal or external corner having a desired corner angle.

Referring to Figures 4 to 6, the corner shutter member 26 comprises an upright retaining wall 28 comprising a first portion 28a and a second portion 28b defined by the line of weakness 21 separating the two portions 28a and 28b.

The corner shutter member 26 has a first base portion 29a and a second base portion 29b, each extending orthogonally inward from a bottom edge of a respective retaining wall portion 28a or 28b. Along the top edges of the first and second retaining wall portions 28a and 28b are first and second lip portions 30a and 30b respectively, each of the first and second lip portions 30a and 30b extending orthogonally inward from a top edge of a respective retaining wall portion 28a or 28b. Each of the first and second lip portions 30a, 30b have a downwardly protruding distal end portion 31a or 31b, with the respective retaining wall portions 28a, 28b, lip portions 30a, 30b and distal end portions 31a, 31b defining respective n -shaped channels 32a and 32b which stiffen the top edges of the retaining wall portions 28a, 28b.

As mentioned above, multiple corner shutter members 26, in the linear or transport configuration illustrated in plan view in Figure 4, may be nested or stacked to assist in packaging and transportation to a site. On site, a corner shutter member 26 may then be bent to form an external corner shutter member as shown in Figure 7 or an internal corner shutter member as shown in Figure 8, with the corner shutter member 26 being bent along the line of weakness 21. Although shown bent to form a right angle external corner in Figure 7 and a right angle internal corner in Figure 8, the corner shutter member 26 could be bent to form any angle between 90° and 360°, as will be appreciated from a review of Figures 7 and 8.

As is perhaps most clearly evident form a comparison of Figures 3 and 9, it is the original cutting or shaping of the steel sheet 13 which results in the first and second base portions 30a and 30b and the first and second lip portions 30a and 30b having the shape shown. This enables the corner shutter member 26 to be bent to form either an external corner shutter member, as shown in Figure 7,or an internal corner shutter member, as shown in Figure 8, without these portions obstructing one another.

With reference now to Figure 9, prior to the corner shutter member 26 being bent on site to form either an external corner shutter member, as shown in Figure 7, or an internal corner shutter member, as shown in Figure 8, the first portions 23 and the second portions 24 of the ties 33 are pushed inward until they meet, as shown in Figure 9, with the first and second portions 23 and 24 then being joined by passing the tabs 25a on the end of the first portions 23 through the apertures 25b on the end of the corresponding second portions 24 and bending the tabs 25a, as shown, to form the respective ties 33.

Alternatively the corner shutter member 26 could be bent first to form either an internal or external corner shutter member, with the ties then subsequently being assembled.

Once the corner shutter members 26 have been assembled and bent to form either, external corner shutter members, as illustrated in Figure 10, or internal corner shutter members as illustrated in Figure 11, these may then be fixed to a substrate 34 as shown in Figure 12 to define the corners for a raft or similar structure to be subsequently formed. The corner shutter members 26 would be joined to adjacent linear shutter members, for example linear shutter members 1, as illustrated with reference to Figures 1 and 2, to define a shutter extending about the raft or similar structure that is to be formed. Any reinforcing bars 35 would also be placed with spacers on the substrate 34. Concrete or another settable material 36 may then be poured until it reaches the level of the top of the linear shutter members and corner shutter members 26, as shown in Figure 12. Thus the base portions 29a, 29b of the corner shutter members 26 and any ties 33 or other brackets 11 for supporting the retaining wall portions 28a, 28b are encapsulating in the concrete 36 or other settable material. This leaves a clean outer face 37, avoiding the need to subsequently remove the shutter members. Furthermore, from Figure 12 it will be appreciated that the mass of the concrete 36, or other settable material, acting on the base portions 29a and 29b will act to retain the base portions 29a and 29b in position and thus retain the retaining wall portions 28a and 28b in an upright position, reducing the stress on the fastenings 26.

The above embodiment of the invention has been described by way of example only and it will be appreciated that many variations may be made which will fall within the scope of the invention, as defined by the following claims.

Particularly, the ties illustrated could be replaced with other reinforcing means such as the L-shaped brackets of Figure 1 for example. Alternatively, depending on the dimensions of the corner shutter member 26 and particularly the thickness and strength of the sheet material forming the corner shutter member 26, the ties may not be necessary. Additionally, the line of weakness has been shown as being created by a line of apertures. However, the line of weakness, established to permit bending of the two halves of the corner shutter member, could be created by any suitable means, for example the two halves of the shutter member may be separate and joined to each other by any form of hinge attached to each of the two halves, or multiple hinges attached to each of the two halves. However, it is much preferred that the line of weakness is formed by either the disclosed line of apertures or a line of thinner material or structurally weakened material, for this may be formed integrally with the sheet forming the corner shutter member, avoiding the need for additional components or fastenings.

Claims (15)

1. Claims 1. A corner shutter member for retaining concrete or other settable material, the corner shutter member comprising a single sheet of material shaped and folded to define, in use, an upwardly extending retaining wall arranged to retain concrete or other settable material, the retaining wall having a line of weakness extending substantially vertically across it to define first and second portions of the retaining wall to either side of the line of weakness, each of the first and second portions of the retaining wall having a respective first or second base portion extending substantially orthogonally from a lower edge and arranged to, in use, support the corner shutter member on a substrate and act to retain the retaining wall substantially upright, wherein the line of weakness is arranged to permit the corner shutter member to be bent on site to form either an internal corner shutter member or an external corner shutter member, as desired, and wherein the first and second base portions are shaped so as not to obstruct each other when the corner shutter member is bent to form either an internal corner shutter member or an external corner shutter member.
2. 2. A corner shutter member as claimed in Claim 1, wherein the first and 20 second base portions are shaped such that they permit the corner shutter member to be bent to form either an internal or an external corner shutter member without the first and second base portions overlapping.
3. 3. A corner shutter member as claimed in Claim 1 or 2, wherein each of the first and second portions of the retaining wall has a respective first or second lip portion extending orthogonally from an upper edge and arranged to stiffen the top of the retaining wall to help resist, in use, distortion caused by the mass of wet concrete or other settable material being present on only one side of the retaining wall, and wherein the first and second lip portions are shaped so as not to obstruct each other when the corner shutter member is bent to form either an internal or external corner shutter member.
4. 4. A corner shutter member as claimed in Claim 3, wherein the first and second lip portions are shaped such that they permit the corner shutter member to be bent to form either an internal or an external corner shutter member, without the first and second lip portions overlapping.
5. 5. A corner shutter member as claimed in Claim 3 or 4, wherein each lip portion has a downwardly extending distal edge such that the top edge of each of the first and second portions of the retaining wall, together with their associated lip portions, define n-shaped channels along the top of the corner shutter member.
6. 6. A corner shutter member as claimed in any preceding claim, which is cut or stamped and machine folded to have a plurality of fold lines which are all parallel to one another, which fold lines extend in a longitudinal direction of the shutter member and which define at least the upwardly extending retaining wall and each of the first and second base portions extending substantially orthogonally from the retaining wall, permitting the shutter member to be transported in a generally linear configuration, where multiple corner shutter members may be nested together, where the first and second portions of the retaining wall lie in the same plane.
7. 7. A corner shutter member as claimed in any one of claims 1 to 5 which is cut or stamped and additionally formed with a plurality of pre-weakened fold lines which are all parallel to one another and which extend in a longitudinal direction of the shutter member, permitting the corner shutter member to be transported flat, where multiple corner shutter members, in the form of multiple flat sheets, may be stacked one upon another, where the plurality of pre-weakened fold lines are arranged to permit the corner member to be folded on site to define, in use, at least the upwardly extending retaining wall and each of the first and second base portions extending substantially orthogonally from the retaining wall.
8. 8. A corner shutter member as claimed in any preceding claim, formed entirely from a single flat sheet of metal by cutting or stamping and subsequently folding, without any welding or fastenings.
9. 9. A corner shutter member as claimed in any preceding claim, comprising a plurality of ties, each linking a respective base portion to a corresponding retaining wall portion in order to, in use, restrain the retaining wall portion.
10. 10. A corner shutter member as claimed in Claim 9, wherein the first and second portions of the retaining wall and the first and second base portions all have portions of a tie stamped or cut in them, wherein each portion of a tie in a retaining wall portion is arranged to engage with a corresponding portion of a tie in a corresponding base portion to form a tie to link the base portion to the retaining wall portion and to restrain the retaining wall portion.
11. 11. A corner shutter member as claimed in any preceding claim, wherein the line of weakness comprises a linear row of apertures through the sheet of material.
12. 12. A corner shutter member as claimed in any one of Claims 1 to 10, wherein the line of weakness comprises a line where the sheet material is thinner than it is for the remainder of the sheet.
13. 13. A corner shutter member as claimed in any one of Claims 1 to 10, wherein the line of weakness comprises a line along which the sheet material has been treated to weaken the structural properties of the sheet.
14. 14. A corner shutter member as claimed in any preceding claim, which is arranged to be bent to form either an internal or external corner shutter member having any desired corner angle in the range of 90° to 340°.
15. 15. A method of forming a concrete slab or structure comprising forming, by cutting or stamping and folding, a corner shutter member as claimed in any preceding claim, transporting it to site with other corner shutter members in a nested linear transport configuration, bending a corner shutter member about its line of weakness to form either an internal or external corner shutter member, securing the base portions to a substrate at a desired position and pouring concrete or other settable material over the base portions.