For marine and other walls where flatness is not a prerequisite, an advanced design of circular SDM is disclosed. For walls which will be clad with lining board, an SDM consisting of a frame of vertical members (which in the cast wall provide flat vertical strips for attachment of the support'furring'channels supporting the lining board), is disclosed.

For applications requiring a solid wall, further modified SDMs support fibrecement sheets or a like, which become integral with the wall once the concrete is cast. This produces a high surface quality finished wall in a minimum of operations.

Background to the invention Traditionally formwork has consisted of plywood sheets, attached together and held in position by timber or metal bracing frames.

This traditional formwork is time consuming and expensive to erect, and on stripping, requires a finishing trade to apply render or sheeting to give a satisfactory finish. The alternative to concrete walls-block or brickworks have similar problems. They are also labour intensive and comparatively slow to erect.

Object of the Invention It is the object of the present invention to provide a formwork assembly with different shaped SDMs for different applications which overcome or substantially ameliorate the above disadvantages, increase the speed of construction, improve the sequence of activities, eliminate or reduce the number of trades involved and to lower the overall construction cost.

Summary of the Invention The concept of using Stress Distribution Members (SDMs) in the casting of concrete structures was disclosed by the author and granted a patent by Australian Industrial Property Organisation (AIPO patent No. 689156). That patent disclosed the general principle of using SDMs in conjunction with flexible formwork sheets to enclose a space for casting concrete. The particular SDM disclosed in that patent was circular, flat on the face confronting the membrane and with radial and circumferential ribs on its other face providing stiffness. In the first part of the current invention there is disclosed an SDM which is typically manufactured from pressed sheet metal which encompasses unique features in supporting the concrete and minimising the stresses in the flexible sheet.

The second component of this application discloses an SDM in the form of a rectangular grid of members which are specifically configured for the efficient casting of walls with flexible sheet membrane hereinafter referred to as'Flexwall', which will be subsequently clad with lining board supported on furring channels fixed to the concrete at regular intervals. These grid-shaped SDMs may be supported by ties passing through the concrete, or by support trusses which tie together above the level of the concrete and also at the bottom of the wall.

The third component of this application discloses a system referred to as'Finishwall'.

With this system, the formwork would consist of SDMs in the form of a rectangular grid of members supporting rigid sheets of fibrecement or similar material, and being in turn supported by a vertical tie frame with multiple ties passing through the concrete wall, or by strong back trusses which allow the number of ties passing through the concrete wall to be minimise. The rigid sheets may be used on both sides of the wall to provide finished plane surfaces, requiring only minor joint surfacing prior to painting. The rigid sheets, made from fibre-impregnated cementitous material would bond with the cement during the curing process and become an integral part of the concrete wall structure. Services may be laid within the panels prior to concreting. Doors and window frames may be assembled in the same operation as the formwork, allowing openings to be completed in one operation.

The fourth component of this application discloses a frame system comprising of horizontal top members fixed to vertical comer or side members, to provide a fixed framework to support SDMs, tie frame, strong back trusses, flexible and rigid sheets.

Brief description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a schematic cross-section plan of a formwork with circular SDMs prior to concreting; Figure 2 is a schematic cross-section plan of the Figure 1 after concreting and stripping of the formwork; Figure 3 is a schematic cross-section view of the opposite SDMs and arching effect; Figure 4 is a schematic perspective view of the framing system employed in the formwork of Figure 1; Figure 5 is a schematic view of the formwork of Figure 1, showing the framing system, flexible sheet and SDMs of circular configuration; Figure 6 is a cross-section plan of the formwork of Figure 1 employing SDMs of rectangular grid configuration used for'Flexwall'; Figure 7 is a schematic cross-section plan of the formwork of Figure 6 employing flexible sheet in one side and rigid discrete sheets on the other side of space to receive unset concrete; Figure 8 is a schematic cross-section plan of the formwork of Figure 7 after concreting, stripping the formwork, assembling services and lining board one side; Figure 9 is a schematic sectioned side elevation of the formwork of Figure 7; Figure 10 is a schematic elevation view of the SDMs of the formwork of figure 6; Figure 11 is a cross-section of the side frame, locking mechanism and associated truss used for'Flexwall' ; Figure 12 is a cross-section plan of the internal corner frame with locking mechanism and associated truss used for'Flexwall' ; Figure 13 is a side elevation of the internal comer frame in Figure 12; Figure 14 is a cross-section of the external corner frame with locking mechanism used for 'Flexwall' ; Figure 15 is a schematic cross-section plan of the'Finishwall'formwork with rigid sheets, rectangular grid SDMs, strong back trusses, and tie frames; Figure 16 is a schematic elevation view of the rectangular grid SDMs employed in the formwork of Figure 15;

Figure 17 is a schematic side elevation view of the strong back trusses employed in the formwork of Figure 15; Figure 18 is a schematic side elevation view of the tie frames employed in Figure 15; Figure 19 is a side elevation view of the split side member used for'Finishwall' ; Figure 20 is a cross-section plan of the split side frame of the Figure 19; Figure 21 is a side elevation of the top lock in Figures 17 and 18; Figure 22 is a side elevation view of a strap tie alternative used with strong back trusses.

Detailed Description of the preferred Embodiments Circular SDM As disclosed in patent 689156, formwork may be erected using a sheet of flexible fabric as the main containment material, with SDMs supporting this sheet and passing the concreting pressures via ties through the concrete either to remote anchorages or similar SDMs on the far side of the casting. The limiting feature of the flexible sheet is its membrane strength in tension, and in particular where the tie which passes through the sheet causes a discontinuity which would normally generate a high stress concentration.

The previous invention disclosed a disc which was flat on the side which confronted the membrane (and hence the concrete). The pressure of the cast concrete acting on the disc caused friction between the disc and the membrane which in turn reduced the membrane stresses in the fabric at the tiehole by allowing some of the stress to transfer as tensile stress in the SDM.

The current invention discloses in Figures 1 to 3 formwork assembly 1, and SDMs 2 which have a profile on the side confronting the membrane 3 and concrete 4 which has been configured to further reduce the membrane 3 stresses which pass in the region of the tiehole 5. This is achieved by ridge 6 around the circumference of the SDM 2. In particular when two SDMs 2 confront each other from opposing ends of tie 7, the concrete 4 tends to generate an arch action 8 between the ridges 6 which, by wedging action, tend to grip the membrane 3 preventing it from stretching away from the tiehole 5. By reducing this stretching, the stress in the membrane 3 is reduced.

Also disclosed in this configuration of SDM 2 is the central dished section 9. This shape is the result of innovative shape management followed by extensive computer analysis allowing the SDM 2 to transfer the large tensile forces from the tie 7 into balanced radial and circumferential stresses in the SDM 2 using cone action. The result is SDM 2 of minimum weight and maximum utilisation of material.

Figure 2 shows the cross-section plan of the Figure 1 after concreting and stripping of the formwork 1 components. A concrete surface with double curvature pattern 10 outside the SDMs area and circular curvature pattern 11 within the SDMs area is created.

Figure 4 Shows the frame system 15 of the formwork 1 in Figure 1, comprising top members 16 fixed to vertical side members 17 and bracing members 18 that hold and stabilize the said formwork 1 in predetermined position. Top members 16 can be secured to side members 17 anywhere along the length and height. Frameworks of variable heights and spans may be produced utilizing the same frame system 15 components.

Figure 5 Shows the frame system 15 employed in Figure 4 with flexible sheet 3 attached and suspended from top members 16, fixed and sealed to the floor by floor angle 20 and also fixed and locked to side frames 17. Trusses 21 are fixed to side frames 17 to enable side frames 17 to withstand concrete pressure. Assembling steps are: Setting out the location.

Providing and fixing corner and side frames and associated bracing to the floor.

Providing and fixing top members.

Providing and assembling reinforcing members.

Providing, attaching flexible sheet from top members followed by securing and sealing flexible sheet to the floor and side members.

Providing and putting ties in tie holes already manufactured in the flexible sheet.

Providing and putting SDMs, into the position with ties connected and secured..

Casting concrete into the formwork.

Rectangular grid SDM-Flexwall The construction industry presently uses brick or concrete block walls as load bearing walls which are cement rendered or clad with lining board. The present invention now explains another method for construction of load bearing walls utilizing SDMs and flexible sheets called'Flexwall'. Here SDMs with rectangular grid configurations are designed to provide flat vertical strips on the surface of the concrete wall that are spaced along the length, to allow the fixing of furring channels for lining board.

Figure 6 shows a cross-section plan of the formwork 1 in Figure 1, but with rectangular grid SDMs 25, that are positioned over the side of the flexible sheet 3 that does not confront the space 26 to receive unset concrete. Assembling steps are similar to the assembling steps for circular SDMs explained before. The frame system similar to the frame system 15 in the figure 4 is used (not shown). Several ties 27 are connected to and secured to each associated SDM 25 (unlike the circular SDMs that usually one tie is connected and secured to one SDM at each end). SDMs may be assembled or fixed to strong back trusses, as an alternative to eliminate or reduce the number of intermediate ties connected thereto (not shown).

Figure 7 shows a cross-section plan of formwork 1 in Figure 6, but with flexible sheet 3 in one side and rigid sheets 28 like fibrecement sheets on other side of the space 26 to receive unset concrete.

Figure 8 shows the cross-section plan of wall in Figure 7 after casting the concrete 30 into the space 26 and stripping of the formwork 1. Flat vertical strips 31 are created at regular spacings, to allow fixing of furring channels 32 for lining board 33. Services utilities 34 are assembled prior to assembling lining board 33. The space 35 also would increase sound rating effectively.

Figure 9 shows a sectioned side elevation of the formwork 1 in the Figure 7. Opposite rectangular grid SDMs 25 are connected by the intermediate ties 27 which cross through the space 26 to receive unset concrete, and also through the tie 38, which connects opposite SDMs 25 together above the concrete level. Tie 38 that is located above concrete level

hereinafter is called'Top lock'. Top lock 38 can be made to become a permanent part of the SDMs 25 and can rotate to occupy less space during storage. Figure 9 also show the sleeve or pocket 39 in the flexible sheet 40, to accommodate top member 41. Here top member 41 is made from rectangular hollow sections. Reinforcing members 42 in form of bars or mesh are also shown extending up, to be used as a starter bar for the subsequent wall constructed on the next higher floor.

Figure 10 shows a face view of rectangular grid SDMs 25 used in Figures 6 to 9. The center vertical members 45 will provide the flat vertical strips on the concrete surface.

Four numbers of intermediate ties will be connected to the SDM 25 shown in the Figure 10 and will be secured at tie locations 46 on the SDM 25.

Figure 11 shows a cross-section plan of side member 50 with flexible sheet 3 secured and locked through the locking mechanism consisting of long triangular shape side pieces 51, central piece 52 and tightening bolt 53. After flexible sheet 3 is placed into the position through the route shown, the nut 55 is tightened to push central piece 52 forward to push and lock flexible sheet 3 against side pieces 51. Truss 54 assembled to central piece 52 used to enable side frame 50 to withstand concrete pressure.

Figure 12 shows the cross-section plan of internal comer frame 60 with a similar locking mechanism and truss 61 used for side frame 50 in Figure 11.

Figure 13 shows the side elevation view of the internal corner frame 60 in the Figure 12.

Figure 14 shows cross-section plan of external corner frame 65 using the similar locking mechanism used to lock flexible sheets 3 in the Figure 11.

Rectangular grid SDM-Finishwall One of the major problems in the building industry is the number of trades and time required to construct load bearing walls. Conventional bricks and block walls would require block layers trade, followed by infill concrete into the blocks and then the lining board trade.

The present invention discloses the method used to construct walls with finished surfaces in one operation called'Finishwall'.'Finishwall'is a reinforced concrete wall surfaced by fibrecement sheets or a like, wherein the concrete is cast against the fibrecement sheets and cures to produce a solid wall with an integral high quality surface finish.

A formwork system for casting'finishwall'is now described with reference to the drawings; Figure 15 shows a cross-section plan of the formwork 70 used to construct the 'Finishwall'. The formwork 70 components are: A frame system similar to the frame system 15 in the Figure 4 is used comprising of horizontal top members fixed to vertical comer or side members, to provide a fixed framework to support rigid sheets 71 located on the either sides of the space 72 to receive unset concrete. (Frame system is not shown).

Spaced discrete rectangular grid SDMs 73 located on the outer surface of the rigid sheets 71.

Strong back trusses 74 located on the outer surface of the rigid sheets 71 and between the SDMs 73, and preferably aligned with the joins 76 of the fibrecement sheets 71. Strong back trusses 74 would eliminate or reduce the number of intermediate ties connected thereto.

Tie frames 85 can also be used as an alternative to replace strong back trusses 74, where having several ties 81 connected to the tie frame 85 is a preferred method.

Rectangular grid SDMs 73 design is further changed to eliminate ties to be connected thereto, and SDMs 73 have no mechanical connection to the rigid sheets 71. Instead horizontal beams 75 are used to support SDMs 73 and transmit the load from SDMs 73 to strong back trusses 74 or tie frames 85.

'Finishwall'can be transformed to'Flexwall'by replacing rigid sheets 71 with the flexible sheet membrane (not shown).

Figure 16 shows a view of the rectangular grid SDMs 73 with no tie hole locations.

Vertical members 78 are closely spaced to reduce bending stresses in the rigid sheets 71.

Figure 17 shows a side view of the strong back trusses 74 employed in the formwork 70 of Figure 15. Seats 80 are fabricated to accommodate the horizontal beams 75 and also to transmit load from beams 75 to strong back trusses 74. Tie 81 is used to connect opposite strong back trusses 74 at the bottom. Top lock tie 82 is used to connect opposite strong backs 74 at the top above concrete level.

Figure 18 shows a side view of tie frame 85 employed in the formwork 70 of Figure 15, which is used as an alternative to replace strong back trusses 74. Several ties 81 are connected to tie frame 85 along the height in areas close to the horizontal beam 75 seats 80, to transmit the loads. Tie frames 85 are also preferably aligned with joins 76 of the fibrecement sheets 71 of the Figure 15.

Figure 19 shows an elevation view of split side member 90 consisting of pieces 91 and 92, bolted together by bolts 96, and can be modified for variable wall-thickness required. Top members 93 will sit on the seats 94. Horizontal beams 75 in the Figure 15 also terminate and sit on seats 95 of the side member 90.

Figure 20 shows a cross-section plan of side member 90 in the Figure 19 showing extension piece 98 that may be located between the pieces 91 and 92 to increase the wall thickness provided by the side member 90. Figure 20 also shows fibrecement sheets 99 edges located within the webs 100 of the side member 90.

Figure 21 shows a side elevation view of the top lock 82 in the Figures 17 and 18. Top lock 82 is adjustable in length and is fixed to the upper section of tie frames 85 and strong back trusses 74. Top lock 82 can rotate and will be secured to tie frame 85 and strong backs 74 during transportation and storage. Barrier 105 is used to connect and hold tie frame 85 and strong back 74 to the top member 93.

Figure 22 shows a side elevation view of a strap tie 108 secured to the bottom part of the strong back truss 74 in the Figure 15. The locking mechanism 109 is used to stretch and lock strap tie 108 in place.

Assembling of formwork components for'firishwall'consists of some or all the steps of : Setting out the location.

Providing and fixing corner and side members and associated bracing to the floor.

Providing and positioning reinforcing members.

Providing and assembling rigid sheets, clamping sheets to top members.

Providing and positioning tie spacers and tie-rods in place.

Providing and positioning strong back trusses or tie frames in place and securing ties thereto.

Providing and positioning SDMs in between the strong back trusses or tie frames, followed by horizontal beams spanning between the adjacent strong back trusses or tie frames.