WO2015011641A1

WO2015011641A1 - Semi rigid precast wall system

Info

Publication number: WO2015011641A1
Application number: PCT/IB2014/063303
Authority: WO
Inventors: Phillip Paul DOYLE
Original assignee: Doyle Phillip Paul
Priority date: 2013-07-24
Filing date: 2014-07-22
Publication date: 2015-01-29
Also published as: MY172102A

Abstract

A method of construction comprising the steps of erecting a first precast wall element, lowering a second precast wall element onto the first precast wall element such that their edge surfaces are spaced apart and oppose each other; the edge surface 5 of one of the precast wall elements being provided with support means extending therefrom for supporting the second precast wall element when it is lowered onto the first precast wall element, wherein a precast floor element is positioned on the upper surface of the first precast wall element, spaced from the second precast wall element, and concrete is poured onto the precast floor element and into the space 10 between the first and second precast wall elements.

Description

SEMI RIGID PRECAST WALL SYSTEM

Field of Invention

The invention relates to a method of construction, more specifically to a method of construction for an industrialised building system where the building components are precast structural components.

Background

An Industrialised Building System (IBS) refers to a technique of construction whereby components are manufactured in a controlled environment, typically offsite, then placed and assembled into construction works. IBS is also known as Pre- fabricated/Pre-Fab Construction.

A 'shear wall' structural design is more efficiently created in IBS (pre-cast concrete construction) by separating the upper and lower walls during the construction process, allowing sufficient reinforcement to be placed in the wall/floor joint for the loads to be transferred and distributed down through the structure. The reinforcement can be designed to meet a variety of structural design requirements, which is otherwise impossible in the conventional pre-cast concrete solution, where pre-cast walls are placed directly onto a mortar bed on the concrete floor. According to a prior art method, a first precast cementitious construction element is erected such that a second precast cementitious construction element can be lowered by a crane over its upper edge. Each of the elements is provided with metal plates extending from their edges, such that while the second element is supported by the crane and positioned at a distance above the first element, the plates of the two elements are welded together. When the weld is complete the second element can be released from the crane.

Thus the first and second elements are constructed to leave a space therebetween in which the ceiling and corresponding reinforcement is located. Typically a wooden ceiling is positioned before the second precast concrete construction element is lowered into position, whereafter steel reinforcement is placed and concrete is poured thereover to a depth determined by the structural engineer. After the concrete has set the wooden ceiling can be removed.

However, a disadvantage of the prior art system is that it takes around 7 days to perform the above steps, plus another 7 days for the concrete to cure. In particular the construction of the temporary wooden ceiling is a slow step. In addition, the crane has to support the second element for 20-30 minutes while it is welded to the first element. Furthermore the system is often not suitable for use in developing countries, as welding is a specialist skill that requires precision, and the relevant skilled workers are limited in such countries. In another prior art method, a first wall is provided with one or more protrusions on its upper surface, and a second wall is provided with a corresponding recess fitted with a plate, such that the second wall can be lowered onto the first wall via the corresponding protrusions and recesses, and the protrusion can be welded to the plate to secure the walls together. However, again this operation requires precision, as the tolerance to allow the protrusion to be welded to the plate is only about 3mm. If the gap between the plates is wider, the ends of a connecting bar can be welded to the respective plates to join the same, but this can lead to structural weakness. IBS is required in developing countries to keep up with the demand for housing, and Pre-cast concrete has been deemed to be an IBS by the local government. However, the costs of establishing factories to manufacture the pre-cast concrete elements, subsequent transportation thereof, the transportation infrastructure, and repairs due to handling issues can be prohibitive. In addition the use of timber formwork often leads to dimensional inaccuracies, and the conventional fixings between pre-cast concrete walls and concrete floor slabs are impractical as there is insufficient tolerance in these joints requiring expensive remedial action when the fixings cannot be aligned. An aim of the invention is to provide a method of construction which is easier and quicker to use in developing countries.

Summary of Invention In an aspect of the invention, there is provided a method of construction comprising the steps of:

erecting a first precast wall element;

lowering a precast floor element onto the first precast wall element, lowering a second precast wall element onto the first precast wall element such that their edge surfaces oppose each other;

the edge surface of one of the precast wall elements being provided with support means extending therefrom for supporting the second precast wall element when it is lowered onto the first precast wall element;

characterised in that the precast floor element is positioned on the upper surface of the first precast wall element, spaced from the second precast wall element, wherein concrete is poured onto the precast floor element and into the space between the first and second precast wall elements. Advantageously as part of the floor is precast, the time required to construct the concrete floor is significantly reduced. Furthermore the tolerances in this method are significantly larger, as there is no requirement for welding and the associated accuracy in the positioning of the respective parts to be welded. As such the method is suitable for developing countries where there is a shortage of skilled labour.

Typically the precast wall and/or floor elements comprise concrete. In one embodiment the concrete contains metal fibres (i.e. it is fibre-reinforced concrete) In one embodiment two precast floor elements are positioned such that their edges rest on the upper surface of the same first precast wall element. Typically the two precast floor elements are spaced apart from each other. In one embodiment a holding plate is secured over the edges of the floor element(s). This holds the floor element(s) to the first precast wall element while the structural topping is constructed on top of the precast floor elements. Typically the holding plate is secured via a nut connected to a threaded rod cast into the wall element. In one embodiment the holding plate is an angle typically made from steel.

Typically the precast floor elements are less than half the thickness of the overall concrete floor. Accordingly in the trade these are known as "half slabs". As such when the structural topping is constructed on the precast floor element the combined thickness of the floor element and concrete topping is reasonably close to a conventionally designed floor slab.

In one embodiment the support means comprises two or more bolts embedded in the wall element and extending from the edge surface thereof.

In one embodiment a plate is threadedly connected to the bolt, to allow the space between the wall elements to be adjusted. This allows a surveyor to ensure the wall elements at the specified level. In a further embodiment an elongate acorn nut is threadedly connected to the bolt. Typically the opposing edge surface is provided with a plate including a hemispherical recess in which the acorn nut may be located. This helps position the second precast wall element as it is lowered onto the first precast wall element, as the acorn nut locates in the hemispherical recess to retain the second precast wall element in position.

In a yet further embodiment one of the bolt and opposing edge surface is provided with a hemispherical protrusion and the other is provided with a hemispherical recess for locating the protrusion. Typically the protrusion is raised to allow the recess to mate with the same at a non-linear angle.

In one embodiment the plate on the opposing edge is moveable. Typically said moveable plate is welded to a bearing plate embedded in the wall element when both wall elements are aligned.

In one embodiment reinforced bars are embedded in the wall elements, portions of which extend from the edge surface of the wall elements. Typically the portions are U/hoop shaped. Thus when the concrete has set the reinforced bars are embedded therein to fix the walls and floor in position.

In one embodiment the floor element may be provided with guide means to guide the second precast wall element towards the first precast wall element. Typically the guide means comprises a steel rod fixed to the floor element via an angle. Typically a hooked bar is placed around a reinforced bar in the first precast wall element and threadedly connected to the angle such that the second precast wall element can be aligned with the first precast wall element by adjusting the position of a nut on the thread.

In one embodiment the second precast wall element is temporarily supported by a prop, which in turn is supported by the precast floor element. Typically a brace is placed on adjacent wall elements to support the same and allow the props to be removed while concrete is poured.

Therefore advantageously no welding is required, as the bolts support the second precast wall element, and unlike wooden formwork, the precast floor element is strong enough to resist the force from the prop due to any lateral motion of the second precast wall element. As such, once the prop is in place, support from the crane is no longer required, and the process is therefore faster as the crane can then be used for the next wall element. In addition, the system is suitable for use by unskilled workers in developing countries.

In one embodiment reinforced bars are positioned on the precast floor element so that they become fixed in place after the concrete is poured thereon. The amount of reinforcement in the critical wall/floor joint can be designed to mitigate against the stresses encountered in Zone III seismic zones. However, when fibre-reinforced concrete is used, the reinforced bars may not be required, advantageously thereby saving the time required to fit the bars. In one embodiment one or more brackets are provided in the face of the precast floor element. Typically hooked bars are provided to connect the brackets in the precast floor element to the support means and/or reinforced bars in the wall element. Typically the hooked bars are threaded such that the distance between the bracket and wall element can be adjusted by rotating a nut on the threaded part against the bracket.

Advantageously this arrangement provides additional resilience in respect of lateral movement during construction and is useful in seismic zones.

In one embodiment the wall elements are provided with plates to which an angle can be secured via angles, bolts and/or welds to secure the wall elements together. In a further embodiment the wall elements are provided with U-shaped elements which may be joined by a further U-shaped element.

In one embodiment a lightweight infill is placed in the non-structural section of one or more wall elements. Advantageously this reduces the weight and hence cost of the wall elements.

In a further aspect of the invention, there is provided a precast wall element for use in an industrialised building system, the edge surface of which is provided with at least one bolt extending therefrom for supporting a further precast wall element when it is lowered thereonto, characterised in that a section with a hemispherical protrusion or recess is threadedly connected to the bolt for engaging a corresponding hemispherical recess or protrusion in the surface of an opposing precast wall element, to facilitate alignment of the precast wall elements.

In a further aspect of the invention, there is provided a method of manufacturing a precast element comprising:

fitting edge boards to a first level of a casting bed;

casting a precast element on the first level;

fitting edge boards to a second level of a casting bed;

casting a precast element on the second level;

characterised in that the edge boards from the first level can be removed before the precast element at that level has fully cured, and fitted to a third level; In one embodiment the edge boards are removed after one hour from casting the precast element.

Advantageously the edge boards from the lower levels can be re-used to create the elements at higher levels. In contrast, the existing systems use wooden formwork wherein the lower sections must be retained to support the higher sections.

In one embodiment the casting bed and/or edge boards are made from fibre- reinforced plastic. Typically the edge boards split into two or more pieces longitudinally to facilitate removal thereof. This is advantageous as the wooden formwork must be broken to remove the same, and it is discarded after use which is wasteful.

In one embodiment the edge board is cleaned before it is re-fitted. This allows it to be used 50-100 times.

In one embodiment the edge boards are configured as a C-shape to allow U-bars to protrude therebetween into the space defined between the arms of the C-shape. The edge boards have holes to allow the U-bars to protrude, and it is a simple task to see if they are aligned by holding a straight edge against the same.

Typically a T-piece is used to keep the two edge boards together while a spacer is used to maintain the arms of the C-shape apart. In one embodiment the edge boards are maintained in position relative to the casting bed with a combination of Z-shaped connectors, U-shaped brackets and/or wedges.

In a yet further aspect of the invention, there is provided apparatus for manufacturing a precast element comprising:

a casting bed

a plurality of edge boards for fitting to the casting bed;

characterised in that the edge boards are made from fibre-reinforced plastic and can split into two or more pieces longitudinally to facilitate removal thereof. Brief Description of Drawings

It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention. It should be noted that measurements indicated in the following Figures are for example only and are not intended to be limiting.

Figure 1 illustrates a schematic cross-sectional view of a shear wall being constructed using the method according to an embodiment of the invention.

Figure 2 illustrates a further schematic cross-sectional view of a shear wall being constructed using the method according to an embodiment of the invention (a) from the side (b) from the front; (c) in an alternative configuration from the side.

Figure 3 illustrates a schematic cross-sectional view of a shear wall constructed using the method according to an embodiment of the invention.

Figure 4 illustrates a schematic cross-sectional view of the precast floor elements being positioned (a) showing the U-bars (b) showing the guides.

Figure 5 illustrates a schematic cross-sectional view of the precast floor elements being secured. Figure 6 illustrates a schematic cross- sectional view of the precast wall elements being secured.

Figure 7 illustrates a shear wall being constructed using the method according to a further embodiment of the invention (a) schematic cross-sectional view prior to the second precast wall element being lowered; (b) schematic cross-sectional view after the second precast wall element has been lowered; (c) schematic plan view; (d) schematic cross-sectional view of an alternative embodiment prior to the second precast wall element being lowered; (e) partial view indicating tolerances of the alternative embodiment.

Figure 8 illustrates a schematic plan view of the secured precast wall element.

Figure 9 illustrates a schematic cross-sectional side view of the relative positions of various components.

Figure 10 illustrates a schematic cross- sectional plan view of two wall elements fixed together (a) at a corner; (b) on a straight section; (c) at the top of a wall junction. Figure 11 illustrates a schematic cross- sectional plan view of two wall elements fixed together in an alternative arrangement.

Figure 12 illustrates a schematic cross-sectional plan view of two wall elements secured temporarily by an angular steel cap. Figure 13 illustrates a schematic cross-sectional view of the internal floor element (a) supporting a cantilever external floor slab, which is constructed in situ; (b) showing an edge form; (c) showing an alternative edge form.

Figure 14 illustrates a method of construction according to an embodiment of the invention.

Figure 15 illustrates a schematic cross-sectional plan view of a casting bed for use in a method of manufacturing a precast element according to an embodiment of the invention.

Figure 16 illustrates a schematic cross-sectional partial side view of a casting bed.

Figure 17 illustrates a schematic cross-sectional partial view of a casting bed while a precast element is being manufactured.

Figure 18 illustrates a schematic cross-sectional side view of a wedge.

Figure 19 illustrates a schematic cross-sectional side view of two edge boards separated by a spacer.

Figure 20 illustrates a schematic plan view of two edge boards held together with T- piece. Figure 21 illustrates a cross section through the edge boards and first cast wall slab, with an angle for supporting the next slab. Figure 22 illustrates how adjacent edge boards are held together at corners.

Figure 23 illustrates a view of the edge boards which can be adjusted to different sized slabs (a) in plan (b) in sectional elevation. Figure 24 illustrates a cross-section view of a wall panel comprising a lightweight infill.

Detailed Description With reference to Figure 1 there is illustrated a cross-section through a shear wall 2 under construction, comprising a first precast wall element 4 from which support means extend in the form of two steel bolts 8. The end of each bolt is threaded 10, and a flat plate 12 is connected thereto via an elongated nut 14. The nut 14 is 50mm and adjustable to provide a tolerance of +/- 10mm. The plates on the ends of the bolts support a second precast wall element 6, such that a space is created between the wall elements.

In this embodiment the second precast wall element 6 is provided with a plate 36 and reinforced bar running therethrough for additional structural integrity. With regard to Figures 2a-b, the first precast wall element 4 further comprises a plurality of reinforced bars 16 which are substantially U-shaped protruding from the upper edge surface. These are aligned around 32mm off the longitudinal central axis 20 of the second precast wall element 6 for alignment with corresponding U-shaped reinforcing members (U bars) 18 protruding from the lower edge surface of the second precast wall element 6 which are aligned with the longitudinal central axis 20. The size, shape and location of the U bars 16, 18 are standardized for specific categories of residential buildings and can be aligned in different ways to suit requirements. Two precast floor elements 26, 28 are positioned such that their edges rest on the upper surface of the same first precast wall element 4, as will be described hereunder.

With reference to Figure 2c, an alternative configuration is illustrated in which the U-bars are aligned on the longitudinal central axis, and upper and lower U-bars are alternated therein to avoid clashing with each other. This configuration is useful for lighter loads.

With reference to Figure 3, the floor structure 22 has been constructed in the aforementioned space. In this embodiment helix reinforcement 24 is provided around the support bolt 8 to alleviate problems that may occur locally during the temporary propping of the lower wall prior to pouring the concrete on the floor slab as hereinafter described . With regard to Figure 4a, two precast floor elements 26, 28 are positioned with a crane such that their edges rest on the upper surface of the same first precast wall element 4. The two precast floor elements are spaced apart from each other and the U-bars by a distance defined by the structural requirements and governing codes.

With further reference to Figure 4b, the upper wall 6 may be lowered down into position with the aid of a guide, a steel rod 180 welded to an angle 182. The angle 182 is fixed to the precast floor element 28 by a threaded steel rod 186 with a steel bar welded to it. A nut 188 is screwed down to keep the steel angle 182 from being rotated when the upper wall 6 is lowered. A hooked bar 190 is placed around a steel bar 178 which has been cast into the lower wall 4. The hooked bar is threaded on the opposite end and fixed to the steel angle 182 with a nut 184, such that if the steel rod 180 is deflected outwardly by the wall 6 as it is lowered, the nut 184 can be tightened to bring the wall back into alignment.

With the precast floor elements in position, the second precast wall element 6 can then be provided with a prop (not shown), the floor elements being strong enough to resist the force from the prop due to any lateral motion of the second precast wall element 6, while steel reinforcement bars 30 are positioned and a structural topping of concrete 32 is poured in the remaining space. It should be noted that if fibre- reinforced concrete is used, the steel reinforcement bars 30 may not be required as the strength is provided by the fibre-reinforced concrete instead, thereby speeding up the construction process as time is not required to fit the bars.. With reference to Figure 5, it can be seen that the ends of the floor elements are held down by a holding plate 48 comprising a steel angle 46. A steel rod 38 is cast into the first precast wall element 4, extending thereabove and through a hole in the holding plate 48. A washer 44 is placed on the rod 38, and the end includes a thread 40 to allow a nut 42 to be screwed thereonto to secure the arrangement. This helps prevent movement of the floor and wall elements during the construction process.

With regard to Figure 6, a hooked bar 50 is placed around the U bar 18 protruding from the second precast wall element 6. The other end of the hooked bar 50 is provided with a thread which is passed through a bracket 58 secured to a plate 54 in the floor element 28, which in turn is welded to a shaped steel rod 52. A nut 56 is screwed onto the thread of the hooked bar 50 so that the lateral position of the second precast wall element can be adjusted and/or secured in position. With respect to Figure 7a, an alternative support for the upper wall element is illustrated, wherein a bolt 66 embedded in the upper wall element 6 is provided with an elongate acorn nut 70 connected thereto, comprising a hemispherical end 72. The bolt is provided with helix reinforcement 68 to alleviate problems that may occur locally during the temporary propping of the lower wall prior to pouring the concrete on the floor slab. The lower wall element 4 is provided with a bearing plate 62 secured to the wall element 4 via a steel rod 60. A moveable plate 64 is placed on the bearing plate 62, and includes a hemispherical recess 74. The upper wall can then be lowered such that the end 72 fits into the recess 74, as illustrated in Figure 7b. The vertical alignment of the wall can then be adjusted, and the moveable plate welded 76 to the bearing plate to secure the same in position, as indicated in Figure 7c.

Figure 7d illustrates a similar arrangement but where the end 72' of the nut 70' contains a hemispherical recess and the plate 64' is provided with the corresponding hemispherical section. As can be seen from figure 7e, the hemispherical section on the plate 64' includes a 5mm tolerance which allows the two parts to mate together even if one is at a slight angle, due to the mating curved surfaces. Sprung steel 69 can be used to ensure the end 72' and plate 64' lock together, the lower arm of the sprung steel 69 being fitted into a hole in the plate 64' .

With regard to Figure 8, a schematic plan view of the arrangement is illustrated, including the alternative support, as described above, and the holding plate 48, which is angled slightly to ensure that it fits between the U-bars.

With respect to Figure 9, the relative positions of the U-bars 18, support bolts 66, and holding plates 48 are indicated in a typical upper wall element 6.

With regard to Figures lOa-b, two wall elements 6, 6' can be temporarily fixed together, by using a fibre reinforced plastic angle 276 fixed thereto using bolts 278 and/or welding. The bolts are secured with a nut 284, a washer 282 and a wedge 280. Cement mortar 286 with a waterproof additive is poured into the formed recesses. Thus the walls are held together so that the props can be removed during concreting operations. The walls are firmly anchored in position through the U bars after concreting has completed.

With reference to Figure 10c, a steel angle 290 is used to form a brace at the top of the junction of walls 6 and 6' to keep them vertically aligned and secure during laying of and tying of steel and concreting operations for the structural topping. The push/pull props will be removed upon the fixing of the brace 290 and the vertical formwork 276 to the corners, to facilitate the operations to construct the structural topping. The steel angle brace 290 is secured in position by a wedge 296 driven between a washer with a raised section 294 at the centre, and a steel stopper 292 welded to the angle 290.

With respect to Figure 11, an alternative arrangement for fixing wall elements 6, 6' is indicated. A shaped recess 86 and 88 is formed in a vertical plane at the end of each of the walls 6 and 6' . A plurality of reinforcing bars 90 which are substantially U shaped protrude from the recess in wall 6. These are aligned around a line running through the centre of wall 6' for alignment with corresponding U-shaped bars (U bars) 92 protruding from the formed recess 88 in wall 6' . A steel reinforcing U-bar 94, is placed over the Protruding U bars 90 and 92 linking them together.. A backing rod 96 is placed in the space between the walls nearest the external surface. A mastic joint 98 is applied to the backing rod and the wall surfaces of 6 and 6' . A waterproof mortar is placed into the vertical space 100 between the walls 6 and 6', encompassing the U bars 90 and 92 and link bars 94. and tamped into position With regard to Figure 12, another alternative arrangement for fixing wall elements 6, 6' is indicated. A cap brace 100 is placed on the adjacent upper walls to secure the same. The cap brace 100 comprises an external angle 102, joined to an internal angle 108 by welding two top plates 104 and 106 to the tops of the angles. The cap brace is fixed to the walls 6,6', through bolts 110 fitted to ferrules cast into the wall.

With respect to Figure 13a, a cantilever floor element 112 is created externally, by extending the top reinforcement 116 and bottom reinforcement 118, 120 from the structural topping 114 covering the internal precast concrete floor element 26, under the suspended wall 6 to the formed area for the cantilever slab 112, which is reinforced in the manner of cantilever construction, and the concrete cast in-situ.

With regard to Figure 13b, the method of construction is shown wherein an edge board 206 is held in place by a J bolt 194 to form a drop down for a wet area, cantilever or architectural feature. The edge board prevents spillage while pouring the concrete. The J bolt has a flat disc 204 pressing against edge board 260. A second disc 196 is screw fixed in place to even the distribution of pressure on the top curve of the J bar 194. The J bar goes through a hole 192 formed in the bottom of the wall 6 and is secured by a nut 202 and washer 204. The configuration of the J bolt may be maintained by inserting fibre reinforced plastic and/or wedges (not shown) in the gap between the edge board 206 and the J-bolt 194.

With respect to Figure 13c a similar arrangement is illustrated in which a larger edge board 200 is utilised, extending between the wall elements 4, 6. With regard to Figure 14, a method of construction according to an embodiment of the invention is illustrated, comprising the steps of:

erecting a first precast wall element 4 as a lower wall, with a steel plate 62 cast into the top thereof for supporting an upper wall 6;

placing precast floor elements 26 and 28, in the form of half-slabs on the lower wall, and securing the same with a holding plate in the form of a steel angle 46;

lowering a second precast wall element 6 with a steel plate cast thereinto onto the lower wall, forming an upper wall;

placing prop to brace the upper wall against the half-slab;

bracing the tops of adjacent walls to each other;

removing the props and pouring concrete onto the half slabs to form the floor structure; and

allowing the concrete to cure.

Steel reinforcement may be laid after the props are removed and before the concrete is poured, for strength. Alternatively, fibre-reinforced concrete may be poured. Figure 15 illustrates a plan view of the casting bed 126, which is made from fibre reinforced plastic (FRP). The casting bed 126 is comprised of I beams 128 as the main support members which are placed on a level surface adjacent to the structure where the precast elements that are manufactured on the bed, are to be used. Box sections 130 are placed on the I beams and pin fixed to them. The casting plate 132 is placed on top of the box sections and pin fixed to them.

Figure 16, illustrates a cross section through the casting bed 126 showing an I beam 128 on which an H section 216 is fixed by a pin 218 to keep the box section bearer 222 in its specified location.

With reference to Figure 17, a Z shape connector 244 is used to connect edge boards 230, 232 to a casting plate 242 laid on the bearers 222. The edge boards are clamped into position with a wedge 234, illustrated end-on. A U shaped bracket 248 is used to clamp the Z shape section to the casting plate 242. The U shape bracket is tightened with the use of a wedge 234 against the casting plate 242. Alternatively the Z shaped connector 244 is fixed to the casting plate 242 and bearer 222 with a G clamp (not shown).

Thus the edge forms 230,232 are held firmly in place during the placement of the reinforcement and concrete operations to the wall panel. The wall panel is constructed on the casting plate between the edge forms. Circular openings are made between the two edge forms 230,232 for the insertion of the U bars and temporary supports for the walls, which extend into the space defined between the arms of the C-shape created by the edge forms.

With reference to Figure 18, a wedge 234 comprising a rubber centre piece with steel plates vulcanized on the top 236, bottom 238 and sides of the rubber section, and a gap on the back side to allow compression of the wedge. The wedge 234 is used to tighten precast elements together, the plates allowing the wedge to be driven into position more easily (rubber alone would have too much friction). The Z shaped connector 244 and U shaped bracket 248 are longitudinally angled (not shown), and therefore the wedge is correspondingly angled to ensure contact along the length thereof.

With regard to Figure 19 a metal spacer 240 is placed in position at the end of the edge boards 230, 232 to prevent the arms of the C-shape formed thereby from moving and coming closer together.

With reference to Figure 20 a T piece 224 passes through slots 226 and 228 cut in the edge boards 230 and 232 respectively, with the edge boards being clamped together by a wedge 234 passing through the T piece.

Thus the T-piece keeps the two parts of the C-shape together while the spacer maintains the arms of the C-shape apart and prevents collapse thereof.

The precast wall elements are manufactured by casting them one upon the other in a stack up to ten number high, on a casting bed made from fibre reinforced plastic (FRP), The edge boards, also made of FRP, are in two pieces to facilitate their removal after the concrete has been placed, where the U/hoop bars protrude from the upper and lower edges of the walls. The length of the vertical edge forms is fixed in accordance with the floor to ceiling height of the project. The length of the horizontal wall forms is the length of the longest wall in the project.

With regard to Figure 21, an angle 252 is fixed to the cast wall with a bolt 254 that has already been cast into the wall to be the holding bolt for the half slab, and tightened using nut 258 and plate 256. The bottom edge board 232 is placed on the angle 252 and secured with a U section 250 and a wedge 234. The U bars and BRC mesh is laid and fixed in position and the top edge board 230 is fixed on top of the lower edge board by means of the T plate 224 and the spacer 240.

With reference to Figure 22 a steel angle 260 is placed on top of the perimeter edge boards 264, 230, 232 at the corner. The top leg is fixed to the edge board 264 with a pin 266.A wedge 234 is driven horizontally between the edge boards 230 and 232 and the vertical leg 262 of the angle to hold the edge boards in position.

With reference to Figures 23a-b, a vertically aligned steel plate 268 with two plates 270 and 276 welded on either side of it is used to keep the moveable edge board 264 in its specified place during concreting operations. The horizontal steel plate 270 is fixed to the moveable edge board 264 with a pin 272. The edge boards 232 and 230 are aligned with the moveable edge board 264 with a wedge 234 placed between the edge boards 232 and 230 and a sloping plate 274 welded to the vertical plate 268. The moveable edge board 266 is horizontally aligned with the edge boards 232 and 230 are pushed down against the casting plate 238 with a wedge 234 pushed between the sloping plate 262 and the edge boards. The sloping plate 262 is welded to the vertical plate 268. The vertical plate 268 is held in position against the casting bed 238 with a G clamp 278.

This arrangement allows the edge boards to be configured to suit different sized walls. The sectional elevation shows the vertical plate 268 with the edge boards 232 and 230 together with the moveable edge board 264 being pushed down onto the casting plate 238 with a wedge 234 secured in a sloping steel plate 274, which in turn is welded to the vertical steel plate 268. The edge boards 232 and 230 are pushed against the moveable edge board 264 with a wedge 234 contained by a vertical (tapered) steel plate 262 welded to the vertical steel plate 268.

With reference to Figure 24, a lightweight polystyrene panel 298 may be positioned in the non-loadbearing section of the wall, 6 and 6'. The polystyrene may be porous or comprise interconnecting channels so that the concrete is distributed throughout for additional strength when poured therearound. Beam reinforcement 302 and column reinforcement 300 is designed and positioned in accordance with an engineer's calculations. Advantageously this reduces the weight and hence cost of the wall It will be appreciated by persons skilled in the art that the present invention may also include further additional modifications which do not affect the overall function.

Claims

1. A method of construction comprising the steps of:

erecting a first precast wall element;

lowering a precast floor element onto the first precast wall element;

lowering a second precast wall element onto the first precast wall element such that their edge surfaces oppose each other;

characterised in that the precast floor element is positioned on the upper surface of the first precast wall element, spaced from the second precast wall element, wherein concrete is poured onto the precast floor element and into the space between the first and second precast wall elements.

2. A method of construction according to claim 1 wherein the precast wall and/or floor elements comprise concrete or fibre-reinforced concrete.

A method of construction according to claim 1 or 2 wherein two precast floor elements are positioned such that their edges rest on the upper surface of the same first precast wall element.

4. A method of construction according to claim 3 wherein a holding plate is secured over the edges of the floor element(s).

A method of construction according to any preceding claim wherein the support means comprises a two or more bolts embedded in the wall element and extending from the edge surface thereof.

A method of construction according to claim 5 wherein a plate is threadedly connected to the bolt, to allow the space between the wall elements to be adjusted

A method of construction according to claim 5 wherein anut is threadedly connected to the bolt and comprises a portion with a hemispherical protrusion or recess.

A method of construction according to claim 7 wherein the opposing edge surface is provided with a plate including a hemispherical recess or protrusion for engaging the corresponding nut section.

9. A method of construction according to claim 8 wherein the plate on the opposition edge is moveable, but is welded to a bearing plate embedded in the wall element when both wall elements are aligned.

10. A method of construction according to any preceding claim wherein reinforced bars are embedded in the wall elements, portions of which extend from the edge surface of the wall elements.

A method of construction according to any preceding claim wherein the second precast wall element is braced against the precast floor element using one or more props.

A method of construction according to claim 11 wherein a brace is placed on adjacent wall elements to support the same and allow the props to be removed while concrete is poured.

A method of construction according to any preceding claim wherein reinforced bars are positioned on the precast floor element so that they become fixed in place after the concrete is poured thereon.

A method of construction according to claim 13 wherein the reinforced bars are extended between the first and second precast wall elements for supporting a cantilever element.

15. A method of construction according to any preceding claim wherein

more brackets are provided in the face of the precast floor element.

16. A method of construction according to claim 15 wherein hooked bars are provided to connect the brackets in the precast floor element to the support means and/or reinforced bars in the wall element.

A method of construction according to claim 16 wherein the hooked bars are threaded such that the distance between the bracket and wall element can be adjusted by rotating a nut on the threaded part against the bracket.

A method of construction according to any preceding claim wherein a lightweight infill is placed in the non-structural section of one or more of the wall elements.

A precast wall element for use in an industrialised building system, the edge surface of which is provided with at least one bolt extending therefrom for supporting a further precast wall element when it is lowered thereonto,

characterised in that a section with a hemispherical protrusion or recess is threadedly connected to the bolt for engaging a corresponding hemispherical recess or protrusion in the surface of an opposing precast wall element to facilitate alignment of the precast wall elements.

A method of manufacturing a precast element comprising:

fitting edge boards to a first level of a casting bed;

casting a precast element on the first level;

fitting edge boards to a second level of a casting bed; casting a precast element on the second level;

characterised in that the edge boards from the first level can be removed before the precast element at that level has fully cured, and fitted to a third level;

21. A method of manufacturing according to claim 20 wherein the edge boards split into two or more pieces longitudinally to facilitate removal thereof.

A method of manufacturing according to claim 20 or 21 wherein the edge boards are configured as a C- shape to allow U-bars to protrude therebetween into the space defined between the arms of the C-shape

Apparatus for manufacturing a precast element comprising:

a casting bed;

a plurality of edge boards for fitting to the casting bed;

characterised in that the edge boards are made from fibre-reinforced plastic and can split into two or more pieces longitudinally to facilitate removal thereof