AU2010227010B2 - Method and Apparatus for Laying Concrete Reinforcement - Google Patents

Abstract

A method and an apparatus for laying reinforcement is disclosed. The method and the apparatus include the use of inflatable members that can be inflated and deflated selectively to raise and lower reinforcement that has been placed on a section of a construction site to facilitate supporting the reinforcement on bar chairs or other suitable supports for reinforcement on the section of the site. 4: "I AirIsdtboypia maon ubb o or w ork NtO 2 i, upyvarinidSi~n r wi - ~ I 2122 17 4

Description

- 2 - 2010227010 07 Oct 2010

METHOD AND APPARATUS FOR LAYING CONCRETE REINFORCEMENT

The present invention relates to concrete reinforcement. 5

The present invention relates particularly, although by no means exclusively, to laying concrete reinforcement on a construction site as a part of a method of forming a concrete slab (for example, for constructing a building) 10 or a concrete pavement (for exanqple, for constructing a road).

There are a number of forms of steel that are used as reinforcement in (a) concrete slabs which are cast on a 15 formwork and (b) concrete pavements which are cast on a sub-base on the ground.

Most commonly, the reinforcement is made up of two arrays of parallel bars placed transversely to each other. 20

The reinforcement can take the form of sheets of mesh formed by welding the above-described arrays of bars at the intersections of the bars. The bars are not necessarily evenly spaced or of equal diameter, length or 25 shape. Typically, the mesh sheets are lifted onto a formwork or a sub-base, as required.

The reinforcement can also take the form of single bars which are placed in a first array, i.e. layer, of 30 parallel bars and a second array, i.e. layer, of parallel bars positioned on the first array transversely (i.e. perpendicular to or at another angle except for parallel) to the first array. The bars may be joined on site at the intersections of the bars by means of tie wires at regular 35 or irregular intervals. The bars in this case are not necessarily evenly spaced or of equal diameter, length or shape. 2432353J (GHMatters) 7/10/10 - 3 - 2010227010 07 Oct 2010

The reinforcement can also take the form of a "carpet" of parallel bars interconnected by straps [for example, a product of this type that is commercially known 5 as BAMTEC carpets] which is rolled or pulled out into position on site firstly to form a first array, i.e. layer, and then a transverse array, i.e. layer, on the first array. 10 The position of reinforcement in concrete is very important. In Australia the distance of reinforcement from the top and the bottom of a concrete surface is governed by Australian Standard AS3600-2009. The standard defines "cover" as the distance from an outside surface of 15 reinforcement to the nearest permanent surface of a concrete slab or pavement. In particular, the standard specifies the "cover" of a concrete slab or pavement as 20, 25, 30, 35, 40 mm, etc subject to exposure conditions, concrete strength and compaction. 20

It is known to use bar chairs to support reinforcement above the surface of a formwork or a subbase of a concrete slab or pavement. The term "bar chairs" is understood herein to mean any element that can 2 5 support reinforcement above an underlying surface.

Bar chairs are commonly manufactured from steel, plastic or concrete and may be single or continuous chairs . 30

Single chairs are designed to be placed at the intersection of two bars or under a single bar at or between the intersections of the two bars. Continuous bar chairs are designed to support multiple bars that form a 35 first array of steel and which run parallel to each other. If mesh reinforcement is used, the bar chairs can support the second array as the two arrays are joined together. 2432353J (GHMatters) 7/10/10 - 4 - 2010227010 07 Oct 2010

Single bar chairs are designed to be placed before or after reinforcement is in position on a construction site. Continuous bar chairs are placed before reinforcement is 5 placed in position on site.

If single bar chairs are placed before reinforcement is in position, the reinforcement has to be positioned accurately to ensure it settles on the bar chairs. 10 Adjustment of bar chair positions is often required when using this method. Single bar chairs placed after reinforcement is in position are placed by lifting reinforcement, often whilst a steel fixer is standing on it, and then placing the bar chairs under the 15 reinforcement. If the transverse bars are placed far enough apart, the steel fixer may be able to walk between the bars and thus avoid lifting a proportion of his/her own mass as the bar chairs are placed. However, this can create a trip hazard. As a platform, reinforcement is 20 unstable and the steel fixer is required to bend and lift the mass of reinforcement etc thus creating a potential hazard. Some sheets of mesh can weigh as much as 160 kg and a large proportion of the sheet is lifted whilst placing bar chairs. Generally there are at least 4 bar 25 chairs per square metre of reinforcement.

The above issues with single bar chairs are not as relevant to continuous bar chairs. However, continuous bar chairs are expensive, limited in their height, and 30 often are required to be specially manufactured either off site or on site. Continuous bar chairs are also susceptible to damage from high point loads, eg when a BAMTEC carpet is placed on the bar chairs prior to being rolled out into position. Stronger and more expensive bar 35 chairs are therefore required at this position or special precautions must be taken to support such high forces, eg 2432353J (GHMatters) 7/10/10 - 5 - 2010227010 07 Oct 2010 by placing timber beside the continuous bar chairs to support the mass of the carpet.

Bar chairs are normally placed under the 5 reinforcement but are not fixed to the reinforcement.

However, there are bar chairs that can be clipped to the bars of reinforcement and are free to rotate about reinforcement. 10

It is known to use bar chairs that can be attached to bars of reinforcement and are free to rotate, thereby allowing reinforcement to be assembled on the back of a purpose built truck or other type of mobile platform and 15 placed on a construction site as a continuous mat. The following description focuses on the use of a truck for this purpose but also extends to other suitable mobile platforms. Longitudinal bars, which can take the form of loose bars for example, can be positioned in spaced apart 20 parallel relationship and fed from the truck as the truck moves along a section of a construction site. As the longitudinal bars are fed from the truck, the transverse bars are placed in position at required spacings along the length of the longitudinal bars. Steel fixers on the back 25 of the truck tie the transverse and longitudinal bars together at appropriate positions. As reinforcement is fed from the truck, the bar chairs are attached to the transverse bars and are allowed to swing into a vertical, self-supporting position. When a bar chair comes in 30 contact with a section of a sub-base it settles on the section and supports the reinforcement. The steel fixers also tie together successive longitudinal bars in each line of bars to form a continuous mat. The process for placing reinforcement in this manner is described in 35 Australian patent 752385 and International patent application PCT/AU2004/001504. 2432353_1 (GHMatters) 7/10/10 - 6 - 2010227010 07 Oct 2010

The process described in the preceding paragraph requires a large capital investment in a purpose built truck and is only suitable for relatively long straight concrete pavements such as continuously reinforced 5 concrete pavements (CRCPs), i.e. roadways.

Given the nature of the concrete market a number of trucks may be required in a geographical region to satisfy the demand for the above-described process. It is 10 necessary to disassemble, move, and reassemble the truck when there is an obstacle, such as a bridge or a roundabout, in a construction site or when moving between construction sites. During breaks in the construction due to weather or other reasons the trucks can be left idle 15 for long periods of time and it is not practical to move them between jobs to keep them fully utilised. The movement of the truck over the sub-base as the reinforcement is being placed can also cause damage to the sub-base itself or to the bond breaker on the surface of 20 the sub-base concrete, for example. The steel fixers are also required to bend over in an unsuitable position whilst tying the reinforcement. In addition, the steel fixers attaching the bar chairs are required to walk on reinforcement whilst it is being fed from the truck. This 25 is a significant safety issue.

The maximum length of straight bar available is 18 m. In order for the steel to move continuously from the truck onto a section of a construction site, the longitudinal 30 bars need to be tied together at the position they overlap. For CRCPs the concrete is often placed continuously using a slip-form paving machine. The force of the concrete mass causes reinforcement to move longitudinally. The resistance to this movement offered 35 by the mass of reinforcement on the bar chairs in contact with the sub-base can cause the reinforcement to buckle and form a wave, which is undesirable. To overcome this 2432353J (GHMatters) 7/10/10 - 7 - 2010227010 07 Oct 2010 problem the tie wires at the lap positions of the bars must be cut as concrete is being placed so the bars can move relative to each other and thereby avoid buckling the reinforcement. 5

The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere. 10 The present invention is an alternative option for laying reinforcement that addresses many of the problems with positioning conventional bar chairs, the cost of continuous bar chairs and the cost and issues associated with the method utilising the special truck or other types 15 of mobile platforms.

The method and the apparatus of the present invention include the use of inflatable members that can be inflated and deflated selectively to raise and lower reinforcement 20 that has been placed on a section of a construction site to facilitate supporting the reinforcement on bar chairs or other suitable supports for reinforcement on the section of the site. More particularly, the inflatable members lift the reinforcement to an elevated position. 25 Bar chairs or other suitable reinforcement supports are then positioned in relation to the raised reinforcement so that the reinforcement is supported by the bar chairs when the inflatable members are deflated. 30 In accordance with the present invention, there is provided a method of laying reinforcement in which: (a) reinforcement is placed directly on one or more than one inflatable member, such as an elongate tube, in a 35 deflated state on a section of a construction site, 2432353_1 (GHMatters) 7/10/10 - 8 - 2010227010 07 Oct 2010 (b) bar chairs that can rotate about the reinforcement are coupled to the reinforcement, (c) the inflatable member or members are inflated 5 and raise the reinforcement into an elevated position that allows the bar chairs to rotate into a vertical self-supporting position, and (d) the inflatable member or members are deflated 10 and thereby lower the reinforcement until the bar chairs contact the section of the construction site and support the reinforcement.

In one embodiment, after the reinforcement has been 15 placed directly on the inflatable member or members in the deflated state in step (a), rotatable bar chairs are coupled to the reinforcement in step (b) by being clipped or otherwise positioned on bars of the reinforcement. The inflatable member or members are then inflated and raise 20 the reinforcement into an elevated position in step (c) so that the bar chairs rotate to the above-mentioned self-supporting position. When the bar chairs are in the self-supporting position, the inflated member or members are deflated in step (d) and thereby lower the reinforcement 25 until the bar chairs contact the section of the construction site and the reinforcement settles on the bar chairs. The deflated member or members are then repositioned on another section of the construction site and the above sequence is repeated. 30

In another, although not the only other, embodiment after the reinforcement has been placed directly on the inflatable member or members in the deflated state in step (a), the inflatable member or members are partially 35 inflated before the bar chairs are coupled to the reinforcement in step (b). The partial inflation of the inflatable member or members makes it easier to couple the 2432353_1 (GHMatters) 7/10/10 - 9 - 2010227010 07 Oct 2010 bar chairs to the reinforcement in some situations. Steps (c) and (d) can then be carried out as described above.

In accordance with the present invention, there is 5 also provided a method of laying reinforcement in which: (a) reinforcement is placed directly on one or more than one inflatable member, such as an elongate tube, in a deflated state on a section of a construction site, 10 (b) the inflatable member or members are inflated and raise the reinforcement into an elevated position, (c) bar chairs are positioned in relation to the 15 reinforcement; and (d) the inflatable member or members are deflated so that the reinforcement is supported by the bar chairs on the section of the construction site and the bar chairs 20 support the reinforcement.

In one embodiment, the step of raising the reinforcement using the inflatable member or members allows the bar chairs, either single or continuous, to be 25 placed on the section of the construction site underneath the raised reinforcement in vertical alignment with the reinforcement. With this arrangement, deflating the inflatable member or members lowers the reinforcement onto the bar chairs, whereby the bar chairs support the 30 reinforcement. The deflated member or members are then repositioned on another section of the construction site and the above sequence is repeated.

In another, although not the only other, embodiment, 35 the step of raising the reinforcement using the inflatable member or members allows the bar chairs, either single or continuous bar chairs, to be coupled (for example by being 2432353J (GHMatters) 7/10/10 - 10 - 2010227010 07 Oct 2010 clipped) to the reinforcement in the raised position, whereby the bar chairs are supported by the reinforcement above the section of the construction site. With this arrangement, deflating the inflatable member or members 5 lowers the reinforcement and the bar chairs so that the bar chairs contact the section of the construction site and the reinforcement is supported by the bar chairs. The deflated member or members are then repositioned on another section of the construction site and the above 10 sequence is repeated.

The above-described methods make it possible to lay reinforcement quickly with minimal safety risks for steel fixers who are tasked with connecting the bar chairs to 15 the reinforcement.

Specifically, the inflatable member or members can be positioned on the section of the construction site quickly and the bar chairs can be safely and conveniently coupled, 20 for example by being clipped, to the reinforcement or positioned underneath the reinforcement while the reinforcement is securely and safely supported by the inflatable member or members directly on the section of the construction site. 25

Moreover, in particular, the steps of inflating and then deflating the inflatable member or members and lowering the reinforcement and the bar chairs until the bar chairs contact the ground and support the 30 reinforcement are quick and safe steps.

The method may include repositioning the inflatable member or members successively on adjacent sections of the construction site and repeating the above sequence. 35

Alternatively, the method may include leaving the inflatable members in place and in an inflated state and 2432353_1 (GHMatters) 7/10/10 - 11 - 2010227010 07 Oct 2010 thereafter pouring concrete to form a reinforced concrete slab or a reinforced concrete pavement on the construction site, whereby the inflated members define voids for the provision of services . 5

The inflatable members could be supplemented by other smaller diameter inflatable members as required to provide services . 10 The use of inflatable members described in the two preceding paragraphs could replace "waffle" pods in house construction and also allow the formation of ducting for the provision of services as well as heating and/or cooling for example in a slab. 15

Preferably the inflatable member or members are in the form of an elongate tube or tubes.

Preferably step (a) described above further includes 20 a subsequent step of positioning a plurality of the inflatable members in the form of tubes in a parallel array with the tubes being transverse to the lower or the first layer of reinforcement if the reinforcement is in the form of loose bars or in either direction if the 25 reinforcement is in the form of a mesh. Specifically, the tubes are preferably transverse to and not parallel to the first layer of reinforcement, i.e. they could be at 45 degrees for example. 30 According to the present invention there is also provided an apparatus for laying reinforcement on a construction site which includes: (a) a plurality of inflatable members, and 35 2432353J (GHMatters) 7/10/10 - 12 - 2010227010 07 Oct 2010 (b) an assembly for supplying and releasing fluid from the inflatable members to inflate or deflate the members . 5 Preferably the assembly includes a fluid source, a regulator for regulating the flow of fluid into the members, and a relief valve for controlling the pressure in the members . 10 According to the present invention there is also provided a method of constructing a concrete slab or a concrete pavement which includes; (a) one or other of the above-described methods of 15 laying reinforcement on a section of a construction site; and (b) pouring concrete onto the section of the construction site to form the concrete slab or the 2 0 concrete pavement or a section of the concrete slab or the concrete pavement.

Preferably the method includes repeating steps (a) and (b) to form successive sections of the concrete slab 25 or the concrete pavement.

The present invention is described further with reference to the accompanying drawings, of which: 30 Figure 1 is a top plan view of a section of a construction site which illustrates a first step of an embodiment of a method of laying reinforcement on the section of the construction site; and 35 Figures 2 to 6 are top plan views of the same section of the construction site shown in Figure 1 which illustrate the subsequent steps of the method. 2432353J (GHMatters) 7/10/10 - 13 - 2010227010 07 Oct 2010

With reference to Figure 1, a first step of the method illustrated in the drawings is to position a series of parallel inflatable members in the form of inflatable 5 tubes 3 that are in a deflated state onto a section 7 of a construction site. The inflatable tubes 3 may be of any suitable size and shape and may be made from any suitable material. 10 The section 7 of the construction site may be a part of a sub-base for forming a concrete pavement or a part of a formwork for a concrete slab.

The inflatable tubes 3 are positioned to extend 15 parallel to a direction of forming the concrete pavement or the concrete slab. (It is noted that the tubes 3 can be transverse to the direction of forming but the subsequent repositioning of the tubes 3 is not so easy.) This direction is illustrated by the arrow A in the 20 drawings. Generally, the orientation of the inflatable tubes 3 should be selected to be transverse to the required orientation of the bottom layer of reinforcement that is subsequently positioned on the tubes 3. 25 The inflatable tubes 3 are connected to a fluid source (not shown), such as an air or a water source, via a manifold 9 and a regulator (not shown) and this assembly is adapted to supply fluid to the tubes 3 and thereby inflate the tubes 3. The assembly is also formed to allow 30 fluid to be released from the tubes 3. The assembly also includes a relief valve (not shown) which limits the pressure in the tubes 3.

The next step in the method is to lay reinforcement 35 on the section of the construction site transverse to and on top of the tubes 3. 2432353J (GHMatters) 7/10/10 - 14 - 2010227010 07 Oct 2010

The reinforcement may be in the form of individual bars, BAMTEC carpets, mesh or any other suitable reinforcement. 5 The drawings illustrate the use of loose bars or rolls of BAMTEC carpets. When BAMTEC carpets are used in the form of separate "carpets" of parallel bars 11 and 12 the bars are interconnected by straps made from steel or other materials (not shown). 10

Loose bars are placed in position or the BAMTEC carpets are rolled or pulled out into position firstly to form a first array, i.e. layer, of parallel bars 11 (Figure 2) and then to form a transverse second array, 15 i.e. layer, of parallel bars 12 on the first array (Figure 3). In Figure 2, the reinforcement is positioned so that the bars 11 are transverse to the tubes 3. To simplify the drawings the straps connecting the reinforcement are not shown. In Figure 3, the second layer of reinforcement 20 is positioned so that the bars 12 are perpendicular to the first layer of reinforcement and therefore are parallel to the tubes 3. Again, the straps connecting the reinforcement are not shown to simplify the drawings. 25 Instead of loose bars and BAMTEC carpets, the reinforcement could take the form of sheets of mesh whereby bars 11 and 12 are connected by welding during manufacture. The reinforcement could also take the form of a combination of loose bars, BAMTEC carpets, and mesh 30 sheets.

With reference to Figure 4, the next step in the method is to clip bar chairs 13 onto bars 11 (the transverse bars) of the reinforcement at positions that 35 are selected from the viewpoint of subsequently supporting the reinforcement. Given that the reinforcement is essentially on the ground at this point, the bar chairs 13 2432353_1 (GHMatters) 7/10/10 - 15 - 2010227010 07 Oct 2010 extend from one or other of the sides of the bars 11. It is noted that, at this stage the tubes 3 could be partially inflated to raise the bars just above the subbase to aid the attachment of the bar chairs 13. 5

When clipping the bar chairs 13 to the reinforcement is completed, air, water or other suitable gas or fluid is forced into the tubes 3 and expands the tubes 3 and raises the reinforcement above the ground. As the reinforcement 10 rises, ultimately the bar chairs 13 rotate downwardly into self-supporting, i.e. vertical, positions. This is illustrated in Figure 5 by the change of shape of the bar chairs 13 when compared to Figure 4. 15 Once the bar chairs 13 are in self-supporting positions, air or water is released from the tubes 3 and the tubes 3 deflate so that the bar chairs 13 contact the ground and support the reinforcement. This is illustrated in Figure 6. 20

In the deflated state, the tubes 3 are well clear of and no longer supporting the reinforcement and can be pulled away from the section of the construction site and then positioned on another section of the construction 25 site and the above-described method can be repeated on this and successive sections.

Alternatively, the tubes 3 are not deflated entirely and are only deflated to the extent required to bring the 30 bar chairs 13 into self-supporting positions. The partially deflated tubes 3 are retained in position and form voids in a subsequently formed concrete pavement or concrete slab. 35 Using the above-described method it is possible to install large or small areas of reinforcement without the need for incurring the high capital cost of a special 2432353_1 (GHMatters) 7/10/10 - 16 - 2010227010 07 Oct 2010 truck and without the safety risks involved in placing reinforcement using the conventional methods or a special truck. 5 It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention. 10 By way of example, the present invention is not confined to the particular parallel pattern of inflatable tubes 3 shown in the drawings.

In addition, the present invention is not confined to 15 the use of inflatable tubes 3 and extends to the use of any suitably-shaped and sized inflatable members or members that can be varied in height by mechanical or electrical means that can support reinforcement. 20 In addition, the present invention is not confined to clipping or otherwise securing the bar chairs 13 onto the reinforcement before the inflatable tubes 3 have been inflated. Specifically, the present invention extends to a method that includes clipping or otherwise securing the 25 bar chairs 13 onto the reinforcement after the inflatable tubes 3 have been inflated, and thereafter deflating the inflatable tubes 3 and lowering the reinforcement until the bar chairs 13 contact the section of the construction site and support the reinforcement. 30

In addition, the present invention extends to a method that includes positioning the bar chairs 13 in relation to the inflated tubes 3 without clipping or otherwise securing the bar chairs 13 to the reinforcement. 35 This method includes positioning the bar chairs 13 beneath the raised reinforcement in vertical alignment with the 2432353J (GHMatters) 7/10/10 2010227010 07 Oct 2010 - 17 - reinforcement. Deflating the tubes 3 lowers the reinforcement onto the bar chairs 13. 2432353_1 (GHMatters) 7/10/10

Claims (12)

1. A method of laying reinforcement in which: (a) reinforcement is placed directly on one or more than one inflatable member in a deflated state on a section of a construction site, (b) bar chairs that can rotate about the reinforcement are coupled to the reinforcement, (c) the inflatable member or members are inflated and raise the reinforcement into an elevated position that allows the bar chairs to rotate into a vertical selfsupporting position, and (d) the inflatable member or members are deflated and thereby lower the reinforcement until the bar chairs contact the section of the construction site and support the reinforcement.

2. The method defined in claim 1 wherein, after the reinforcement has been placed directly on the inflatable member or members in the deflated state in step (a), rotatable bar chairs are coupled to the reinforcement in step (b) by being clipped or otherwise positioned on bars of the reinforcement, the inflatable member or members are then inflated and raise the reinforcement into the elevated position in step (c) so that the bar chairs rotate to the self-supporting position, the inflated member or members are deflated in step (d) when the bar chairs are in the self-supporting position and thereby lower the reinforcement until the bar chairs contact the section of the construction site and the reinforcement settles on the bar chairs.

3. The method defined in claim 1 wherein, after the reinforcement has been placed directly on the inflatable member or members in the deflated state in step (a), the inflatable member or members are partially inflated before the bar chairs are coupled to the reinforcement in step (b) ,

4. A method of laying reinforcement in which: (a) reinforcement is placed directly on one or more than one inflatable member in a deflated state on a section of a construction site, (b) the inflatable member or members are inflated and raise the reinforcement into an elevated position, (c) bar chairs are positioned in relation to the reinforcement; and (d) the inflatable member or members are deflated so that the reinforcement is supported by the bar chairs on the section of the construction site and the bar chairs support the reinforcement.

5. The method defined in claim 4 wherein the bar chairs, either single or continuous, are placed on the section of the construction site underneath the raised reinforcement in vertical alignment with the reinforcement.

6. The method defined in claim 4 wherein the bar chairs, either single or continuous bar chairs, are coupled (for example by being clipped) to the reinforcement in step (c) when the reinforcement is in the elevated position, whereby the bar chairs are supported by the reinforcement above the section of the construction site.

7. The method defined in any one of the preceding claims wherein the deflated member or members are repositioned on another section of the construction site at the end of step (d) and the sequence of steps (a) to (d) is repeated at another section of the site.

8. The method defined in any one of claims 1 to 6 includes leaving the inflatable members in place and in an inflated state at the end of step (d) and thereafter pouring concrete to form a reinforced concrete slab or a reinforced concrete pavement on the construction site, whereby the inflated members define voids for the provision of services .

9. The method defined in any one of the preceding claims wherein the inflatable member or members are in the form of an elongate tube or tubes.

10. A method of constructing a concrete slab or a concrete pavement which includes; (a) the method of laying reinforcement on a section of a construction site defined in any one of claims 1 to 9; and (b) pouring concrete onto the section of the construction site to form the concrete slab or the concrete pavement or a section of the concrete slab or the concrete pavement.

11. The method defined in claim 10 includes repeating steps (a) and (b) to form successive sections of the concrete slab or the concrete pavement.

12. A method of laying reinforcement in which inflatable members are inflated and deflated to raise and lower reinforcement on a section of a construction site to facilitate positioning reinforcement on bar chairs or other suitable supports for reinforcement on the section of the site.