GB2427881A

GB2427881A - Support arrangement for casting foundation raft

Info

Publication number: GB2427881A
Application number: GB0513677A
Authority: GB
Inventors: Paul Kiss
Original assignee: Abbey Pynford Holdings Ltd
Current assignee: Abbey Pynford Holdings Ltd
Priority date: 2005-07-04
Filing date: 2005-07-04
Publication date: 2007-01-10
Anticipated expiration: 2025-07-04
Also published as: GB2427881B; GB0513677D0; EP1741840A3; EP1741840B1; EP1741840A2

Abstract

A support arrangement for use with a foundation raft 23 of settable material such as concrete comprises a base member 12, a support member 11 arranged at substantially 90 degrees to the base member and adapted to abut the concrete in use, and a cavity forming member 30 which with the base 12 and support 11 forms a cavity into which concrete can be placed, and a plurality of support ties 15 connected to the base member and extending from one side of the support 11 to the other and engaging the raft 23. After casting concrete a tied skirt of concrete 34 remains for supporting brickwork 40. An apertured cover may connect the top of member 40 to support 11, which may be apertured for passage of concrete (Fig 7, not shown); in an alternative version, (Fig 8, not shown) a stepped former temporarily attached to the ties 15 lies outside the raft 23 and the skirt 34 and can be removed after the concrete has set.

Description

I

SUPPORT ARRANGEMENT

This invention relates to a support arrangement for use with a foundation raft, typically formed of a settable material, and in particular, to foundation rafts which are spaced from the ground.

Then building on ground which is liable to subsidence or heave, it is well known to erect the building or other superstructure on a raft or beam, itself supported by piles, with the underside of the raft spaced above the ground by a void or compressible material. The raft or beam is typically cast in situ and is typically formed by pouring concrete or other settable material into formwork which defines the desired shape of the beam or raft. Typically this formwork takes the form of temporary shuttering, usually formed from wood or a metal such as stainless steel.

Once the settable material of the raft or beam has cured sufficiently, the shuttering is moved and a separate support angle is provided around the edge of the raft or beam such as that the appropriate wall or other b!ockwork can be built upon the support angle. The support angle itself is typically placed on timber decking on which the raft or beam has been constructed.

It has been found that, as the size of buildings increases, the size and strength of the support angle must also increase significantly in order that it can still adequately support the blockwork. However, as the support angles are typically formed from stainless steel, there is a significant cost increase as the thickness of the base member of the support angle has to increase to accommodate the load from taller and heavier buildings. A known support angle is disclosed in our earlier patent applications GB 0414203.0 and GB 0417485.0.

The present invention aims to provide a support arrangementwhich overcomes the problems described above and which improves on the arrangement disclosed in our earlier applications.

According to the present invention, there is provided a support arrangement for use with a foundation raft formed of a settable material, the support arrangement comprising: a base member; a support member arranged at substantially 90 with respect to the base member such that, in use, the support member is adjacent the foundation raft; a cavity forming member which, together with the base and support members, forms a cavity into which a settable material can be placed in use; and a plurality of support ties extending from one side of the support member to the other side of the support member for, in use, engagement with the foundation raft and the settable material in the cavity.

Thus, the present invention provides a cavity into which a settable material can be placed such that when bricks or other blockwork are laid on top of the cavity in order to build a wall or other structure, the load is carried not only by the base member but is transferred into the foundation raft via the plurality of support ties.

The cavity forming member preferably comprises a tray which envelops the base member and the lower portion of the support member. Alternatively, the cavity forming member may be substantially parallel to and on the opposite side of the base member from the support member. The support member itself may be corrugated, thereby increasing the strength and rigidity when it forms part of the shuttering retaining the settable material of the foundation raft during curing.

The lower portion of the support member is preferably provided with a plurality of holes through which, during formation of the foundation raft, settable material can be caused to flow into the cavity from the foundation raft.

The lower portion of the support member is preferably connected to the upper portion of the cavity forming member by a connecting element that is substantially parallel to the base member.

The support ties may pass through the support member and alternatively or additionally may be connected to the support member.

The support ties are preferably angled with respect to the base member such that an "elastic hinge" is formed at the point at which the support ties pass through the support member such that the loading mechanism on the support arrangement is that of a substantially vertical load from the brick or other blockwork and a substantially horizontal reaction force from the foundation raft, each acting around the hinge.

The base member may be decking or other support material on which the foundation raft is formed or alternatively may be a separate element which may be formed integrally with either the support member, the cavity forming member or both.

The support member and the cavity forming member may also be integrally formed as a former which, after the foundation raft has been formed, may be removed.

The support ties are not necessarily connected to the base member, but may be connected in certain embodiments to provide additional support. However, it is preferred that the support ties do not connect to the base member, especially when the support ties do not pass through the support member, as this allows the former to be removed once the settable material has set.

The support ties may be formed of any suitable material, just so long as they are capable of withstanding tension. The support ties may be metal strips, rods or even cable or string type material.

When the support ties are rigid, one or both ends may be shaped, e.g. corrugated, or provided with projecting portions in the form of ribs, prongs or the like which engage with the surrounding settable material in use to increase the retention of the support tie within that material. The support ties may be welded to the base member and or to the support member, but alternatively any form of suitable engagement means, such as screws, bolts or the like may be used.

In the arrangement in which the support ties are connected to the base member, the base member preferably includes a plurality of slots, each slot being associated with a respective support tie which, in use, extends into the slot. The support tie may pass through the base member and may be provided with a support plate extending substantially parallel to and on the under, outer side of the base member. Such a support plate may be integrally formed with the support tie or, alternatively, may be a separate element engaged, typically by welding, to the support tie. This additional support plate provides additional support to the base member and helps ensure that the thickness of the base member can be minimised.

The base member, support member and cavity forming member are typically formed from ito 4 mm thick stainless steel, although other thicknesses and/or suitable materials can be utilized. For example a plastic material could be used for any part that in use does not require welding. As the load of the brickwork is taken by the support ties, and not by the base member, support member or cavity forming member, these elements are not structural. The base member, support member and cavity forming member are preferably formed as a single element.

The support member may be tack welded to the base member or, in an embodiment in which the support member does not directly contact the base member, additional webs or ties may be provided to support the support member during curing of the settable material of the foundation raft. The webs or ties are preferably connected between the support member and the base member, the base member extending underneath the foundation raft which is curing.

It is also important to prevent air being trapped in the cavity by the flow of concrete. If this occurs, the air serves to prevent the concrete fully occupying the cavity and is thus structurally unacceptable. In order to prevent air being trapped, one or more air vent holes can be provided in the cavity forming member. However, during use the concrete may also fTow into the air hole. Whilst this may not be a problem when the former is intended to remain in place, it can be a problem when the former is to be removed as, once cured, the concrete which has passed through the air holes will contact and flow over the outer side of the cavity forming member, thereby preventing or hindering the removal of the former.

Thus, the air holes are preferably covered by a perforate membrane which allows the air to escape the cavity. Any concrete that might pas through the membrane can easily be wiped away, thereby ensuring that no concrete contacts the former preventing removal after curing.

Examples of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a known support angle with reinforcing tie; Figure 2 shows a first example of the present invention; Figure 3 shows a second example of a support arrangement according to the present invention; Figure 4 shows the loads represented on the arrangement of Figure 3; Figure 5 shows a perspective view of the arrangement of Figure 3; Figures 6A, 6B and 6C show a third example of a support arrangement according to the present invention; Figure 7 shows a perspective view of the third example; Figures 8A, 8B and 8C show a third example of a support arrangement according to the present invention; and Figures 9A, 9B and 9C show the provision of air vent holes in the present invention.

Figure 1 shows a known support angle and support gussets, as described in our own earlier applications GB 0414203.0 and GB 0417485.0. A support angle 10 comprises a support member 11 integrally formed along its longer edge with a base member 12. The base member is provided with a plurality of holes 13 through which suitable fixing means such as screws or nails can be inserted to assist in fixing the base member 12 to, for example, timber decking (not shown).

The support member 11 is provided with a number of slots 14 through which a respective support tie 15 passes from one side 16 to the other side 17 of the support member 11. The support ties are typically elongate in shape and are, for example, welded at 18 to the base member 12 and to the support member at slots 14. Each support tie has, at the opposite end to point 18, a securing portion 19 which, in use, passes into and engages with the low level beam or foundation raft which is being constructed.

The support member 11 provides support to the concrete or other settable material of the foundation raft in the temporary condition before curing, the concrete being located on side 16 of the support member 11. The substantially horizontal base member 12 is used to secure the support angle 10 in the construction phase via holes 13 and provides permanent support to the brickwork of a building. When bricks or other blockwork are loaded on the base member 12 to build a walt or other structure, the load of the wall or structure is taken by the base member 12, but is also transferred along the support ties 15 into the concrete of the foundation raft (not shown).

Figure 2 shows a first example of the present invention and is similar to that shown in Figure 1. The difference between the present invention and Figure 1 is the provision of a tray 20 which surrounds the base member 12 and the lower portion of the support member 11 to define a cavity 21 into which a settable material such as concrete can be placed. The cavity is approximately 75mm deep and the base member is preferably approximately 125mm wide. By doing this, the support tie 15 does not necessarily need to engage with the base member 12, but simply engages with the concrete in cavity 21. The upper surface of the settable material is smoothed such that, in use, bricks or other b!ockwork (not shown) can be laid on top of the concrete within the cavity 21. Support is provided as the load generated by the bricks or other blockwork is transferred into the concrete of the cavity, which is connected to the supporting tie, and then subsequently into the foundation raft 23. The weight of the bricks or other blockwork is balanced by a reaction force from the concrete of the foundation raft 23, as well as by other decking material (not shown) beneath the base member and the foundation raft.

Adjacent, support ties are typically spaced by 225mm, the size of a standard house brick, but could be other dimensions to accommodate other sized blockwork.

A second example of the present invention is shown in Figures 3 to 5. In this example, the support member 11 is corrugated, as shown in Figure 5, and this allows the use of thinner material to provide an adequate support to the concrete of the foundation raft during curing. In addition, the support member Ills separate from the base member 12 which is itself formed integrally with a cavity forming member 30. The separate support member 11 and integral base member and cavity forming member define a cavity 31 into which settable material can be inserted in use. In the example in Figure 3, the support tie 15 takes the form of a thin rod of metal or other suitable material, but could be any shape, material or construction, so long as the tie is able to withstand a tensile toad. The support member 11 is located and secured to the base member 12 by tack welding or other suitable means. The support tie 15 is passed through a hole 33 in the support member 11 and is allowed to rest on base member 12.

Preferably, the connecting tie 15 is fixed to the support member 11 by welding or other means and then concrete 34 is poured, both for the foundation raft and into the cavity, and allowed to cure. Subsequently, and as shown in Figure 4, brick work 40 and other load bearing materials 41 are placed on the cured concrete 34 in the cavity or foundation raft. In this example, the base member is preferably 120 mm.

The load W from brick work 40 causes a tensile load T together with a bending moment in the support tie 15. At point H, an "elastic hinge" forms and the loading mechanism becomes that of a couple about hinge H, with forces W being the load of the brickwork and R being the reaction load from the foundation raft. The support tie is thus designed to accommodate the formation of hinge H and the tensile load T. Figures 6A to C and 7 show a third example of the present invention. In this arrangement, the cavity forming member 30 is provided with a number of connecting webs 35 which extend between the upper portion of the vertical section 36 of the cavity forming member and the support member 11.

The lower portion of the support member 11 is provided with openings 37 through which, in use, concrete which has been poured on side 16 of support member 11 is caused to flow into the cavity 31. Openings 38 in the upper surface of the cavity enable air from within the cavity to be expelled as the concrete flows from side 16 through openings 37 into the cavity 31.

The support element 11 may have additional webs 39 to secure the upper portion of the support element against the concrete pressure P during curing.

Openings 37 and 38 are sized to allow concrete to flow through opening 37, for air to escape the cavity 31 via openings 38, but opening 38 is sized to prevent significant overflow of the concrete outside of the cavity 31.

In the arrangements described above, the former remains in situ after curing of the foundation raft has finished and during subsequent building.

Figures 8A, SB and 8C show a further example of a support arrangement 40 according to the present invention. In this example, a removable former 41 supports the foundation raft 51 during curing. The former 41 is comprised of a support member 42, a cavity forming member 43 and a foot portion 44. In this arrangement, a cavity 45 is formed by the cavity forming member 43 and the decking 46 on which the foundation raft 51 is formed. The foot portion 44 of the former 41 extends outside the cavity 45.

During formation of the foundation raft, the concrete or other settable material flows into the cavity 45 from the main body of the foundation raft and is retained by the former 41 for curing. Support ties 47 extend from the main body of the foundation raft 51 into the cavity 45 at an angle to the horizontal and are connected to the lower portion of the support member 42 or the cavity forming member 43 by means of plastic (or other suitable material) cable ties 48 which can be cut once the foundation raft 51 has cured to enable the former 41 to be removed.

The former 41 is also provided with a plurality of support gussets 49 which provide additional strength and support during curing of the foundation raft 51. In this example, the foot portion 44 is connected to the decking 46 by means of screws 50, but other suitable fixing means could be utilised.

Figures 9A, 9B and 9C shows the provision of one or more holes 52 in the cavity forming member 43 to permit air to escape from the cavity 45 whilst the concrete is entering the cavity. The holes are preferably in the upper surface of the cavity forming member 43. The holes are covered, on the inner side 43A of the cavity forming member by a membrane 53, e.g. aluminium foil or other suitable material, having a single, relatively large hole 54 (approximately 5mm diameter) therethrough.

The hole or holes should be sized to allow the air to pass easily from the cavity without restricting the flow of the concrete. Alternatively, the membrane may have a plurality of much smaller holes, such that air, but not concrete, can pass through the holes.

During pouring of the concrete, air is fully displaced from the cavity 45 and concrete can pass through the hole 54 in the membrane 53. The viscosity of the concrete is such that flow is restricted through the hole and the concrete forms a small mound 55 around the hole, but does not enter into contact with the cavity forming member 43.

If any concrete did come into contact with the cavity forming member, it can easily be washed away from the cavity forming member without causing undue damage to the concrete in the cavity. Once the concrete has cured, the former 41 is easily removed as it is not restrained by any concrete. The membrane 53 simply tears from the former and, when reusing the former, the membrane can be replaced.

Claims

1. A support arrangement for use with a foundation raft formed of a settable material, the support arrangement comprising: a base member; a support member arranged at substantially 90 with respect to the base member such that, in use, the support member is adjacent the foundation raft; and a cavity forming member which, together with the base and support members, forms a cavity into which a settable material can be placed in use; and a plurality of support ties connected to the base member and extending from one side of the support member to the other side of the support member for, in use, engagement with the foundation raft.

2. A support arrangement according to claim 1, wherein the cavity forming member comprises a tray which envelopes the base member and the lower portion of the support member.

3. A support arrangement according to claim 1, wherein the cavity forming member is substantially parallel to and on the opposite side of the base member from the support member.

4. A support arrangement according to any one of the preceding claims, wherein the support member is corrugated.

5. A support arrangement according to any one of the preceding claims, wherein the lower portion of the support member is provided with a plurality of holes through which, in use, settable material can be caused to flow into the cavity.

6. A support arrangement according to any one of the preceding claims, wherein the lower portion of the support member is connected to the upper portion of the cavity forming member by a connecting element that is substantially parallel to the base member.

7. A support arrangement according to any one of the preceding claims, in which the support ties are angled with respect to the base member.

8. A support arrangement according to any one of the preceding claims, in which the support ties are connected to the base member.

9. A support arrangement according to any one of the preceding claims, in which the support ties pass through the support member.

10. A support arrangement according to any one of the preceding claims, wherein the support tie is positioned such that an elastic hinge is formed so that, in use, any loading on the base member is balanced by a reaction from the foundation raft.

11. A support arrangement according to claim 1, wherein the base member is formed integrally with either or both of the support member and the cavity forming member.

12. A support arrangement according to claim 1, wherein the support member and cavity forming member are integrally formed as a former such that, in use, after the foundation raft has been formed, the former can be removed.

13. A support arrangement according to claim 12, wherein the support ties are connected to the support member by means of temporary connecting means which can be cut, after use, to enable removal of the former.

14. A support arrangement according to any one of the preceding claims, wherein the cavity forming member is provided with one or more holes through which, in use, air can escape the cavity when settable material flows into the cavity.

15. A support arrangement according to claim 14, wherein each hole is covered by a perforate membrane.