AU2007335186A1

AU2007335186A1 - Bar chairs

Info

Publication number: AU2007335186A1
Application number: AU2007335186A
Authority: AU
Inventors: John Dennis Collins; David Tarabay
Original assignee: OneSteel Reinforcing Pty Ltd
Current assignee: OneSteel Reinforcing Pty Ltd
Priority date: 2006-12-21
Filing date: 2007-12-21
Publication date: 2008-06-26
Also published as: AU2010100548B4; AU2014227536A1; AU2010100548A4; WO2008074092A1; AU2006252206A1; AU2018247320B2; AU2017200462A1; AU2018247320A1

Description

WO 2008/074092 PCT/AU2007/001992 BAR CHAIRS The present invention relates to bar chairs and bar chair modules that comprise at least two bar chairs 5 that are coupled together. Bar chairs are used in the construction of reinforced concrete structures, such as slabs or beams, to support steel reinforcing within structures at a desired 10 height or heights above or below top or bottom surfaces of the structures. Reinforcing can take the form of individual bars or mesh made from longitudinal and transverse bars welded 15 together at intersections of the bars. Hereinafter, reinforcing is described as being in the form of a "mat" of reinforcing. A mat can be made up of one or more layers of reinforcing. 20 In use, bar chairs are positioned on a formwork or on a sub-base of the structure in selected positions and reinforcing is then positioned on the bar chairs and is supported by the bar chairs. The positions of known 25 bar chairs and reinforcing is illustrated diagrammatically, by way of example, in Figures 1[a] and 1[b]. Figure l[a] illustrates a situation in which a 30 single mat 3 of reinforcing positioned on a plurality of bar chairs 7 is required. Figure 1[b] illustrates a situation in which two mats 3, 5 of reinforcing are on a plurality of different sized bar chairs 7, 9 required. 35 Two or more mats of reinforcing may be required for concrete structures that are between -200 and 2000 mm thick.

WO 2008/074092 PCT/AU2007/001992 -2 As is shown in Figure 1[b], where the structures are less than - 500 mm thick and two mats 3,5 of reinforcing are required, conventional bar chairs 7 of a s selected size can be used to support reinforcing at one height and different-sized, in this case larger, conventional bar chairs 9 can be used to support reinforcing at the other height. Both types of conventional bar chairs can be placed on the formwork (not 10 shown) or on the sub-base - as shown in the Figure. This same process of using different-sized bar chairs for supporting reinforcing at different heights, with the bar chairs being placed on the formwork or on the is sub-base, can be repeated to create more than two mats of reinforcing. However, when concrete structures exceed - 500 mm thickness, conventional bar chairs that are positioned on 20 the formwork or on the sub-base can no longer be used. Typically, the process of using bar chairs on the formwork or on the sub-base of such structures leads to over crowding of the bar chairs and/or to the use of bar chairs that are relatively small but are not of sufficient height 25 and/or strength to support the reinforcing properly. Known alternative bar chairs to these conventional bar chairs 7, 9 are shown in Figure 2. 30 The known bar chair 11 shown in Figure 2[a] is manufactured from bar that may vary in diameter from between 10 and 20 mm. The known bar chairs 13, 15 shown in Figures 2[b] and 2[c] are manufactured by bending mesh into the shapes shown in the Figures. 35 The known bar chair shown in Figure 2[a] is an example of a widely used type of bar chair. The bar chair WO 2008/074092 PCT/AU2007/001992 -3 is manufactured by first forming a "U" shape as shown in Figures 3[a] and 5[a]. This first shape may be manufactured automatically on bar processing equipment. In a second step, carried out manually, one leg 17 (Figure 5 3[b]) and then the other leg 19 (Figure 3[c]) are bent outwardly in oppositely facing directions to create a bar chair of an appropriate height "H" with oppositely extending feet of length "L" that can support the bar chair - Figures 2[a], 3[c], 4 and 4[a]. 10 In use, a plurality of the bar chair 11 shown in Figures 2[a], 3[c], 4 and 4[a] is positioned to sit on an existing mat 23 of reinforcing (or on a sub-base of the structure - not shown) as illustrated in Figures 4 and is 4[a], with the oppositely extending feet of the bar chairs resting on and tied to the reinforcing. In the case of Figure 4, parallel pairs of bars 25 are then positioned on and tied to the bar chairs 11 and form a layer of reinforcing. In the case of Figure 4[a], "dummy" bars 27 20 are then positioned on and tied to the bar chairs 11 and a layer of reinforcing (not shown) is then placed on the "dummy" bars. In practice, it is found that the bar chair 11 25 shown in Figures 2[a], 3[c], 4 and 4[a] tends to be unstable when placed on a layer of reinforcing and, typically, one or more of the horizontal legs must be tied to the reinforcing as shown in Figures 4 and 4[a]. 30 In addition to the above-mentioned stability issue, manufacturing the bar chair 11 shown in Figures 2[a], 3[c], 4 and 4 [a] by the method shown in Figure 3 potentially places an operator of a manual bender at risk of crush injury to his/her hands or fingers. 35 Furthermore, the method of manufacture is expensive and slow and the irregular 3-dimensional shape WO 2008/074092 PCT/AU2007/001992 -4 of the finished product is difficult to pack, store and transport, further adding to the cost of the bar chair. The above description of the prior art is not to 5 be taken as a description of the common general knowledge in Australia or elsewhere. The method of the present invention, described hereinafter, improves manufacturing safety, reduces 10 manufacturing costs, and improves packing, storage and transport of bar chairs. According to a first aspect of the present invention there is provided a bar chair for supporting 15 reinforcing in a reinforced concrete structure, which bar chair comprises an assembly of (a) a base member that is essentially a 2-dimensional member and can be positioned horizontally on an underlying support such as a sub-base of the structure or a layer of reinforcing that is already 20 in position and (b) an upright member that is essentially a 2-dimensional member and can be coupled to the base member to extend upwardly from the base member and define a support for a new layer of reinforcing spaced above the sub-base or the existing layer of reinforcing. 25 Preferably the base member comprises a bar and a centrally located socket or other suitable member extending outwardly from the bar to receive a section of the upright member and thereby couple the base member and 30 the upright member together to form the assembly. The socket may be welded or otherwise securely connected to the bar. 35 Alternatively, the socket may be formed as a separate component that can be removably coupled to the bar. For example, the socket may have a first opening for WO 2008/074092 PCT/AU2007/001992 -5 receiving the upright member and a second transverse opening for receiving the bar and allowing the socket to be slid along the bar to a selected location on the bar. The construction of the bar and the socket as separate 5 components has advantages in terms of manufacture and allowing a range of different forms of the base member to be assembled on a site to suit particular conditions on the site. 10 Preferably the upright member includes a "U" shaped section with two parallel legs and an interconnecting web, and wherein at least one of the legs of the "U" can be positioned to extend into the socket of the base member to thereby couple the two members together 15 to form the assembly. In one embodiment, the assembly comprises two base members, and both legs of the "U" of the upright member can be positioned to extend into the sockets of the 20 base members to thereby couple the three members together to form the assembly. The "fit" of the leg or legs of the "U" of the upright member in the socket of the base member may be a 25 tight fit or one that allows relative rotation of the components to facilitate adjustment of the shape of the bar chair to avoid obstructions. In another, although not the only other, 30 embodiment, the upright member comprises the "U" shaped section and an arm section extending outwardly from an end of one leg of the "U" shaped section. With this arrangement, the assembly comprises the upright member and a single base member. An end of the free leg of the "U" 35 shaped section can be positioned in the socket of the base member to form the assembly. The assembly can be positioned with the base member and the arm section of the WO 2008/074092 PCT/AU2007/001992 -6 upright member resting on the sub-base of the structure or on the existing layer of reinforcing and the upright member extending upwardly. 5 According to a second aspect of the present invention there is provided a bar chair for supporting reinforcing in a reinforced concrete structure, which bar chair comprises an upright member that includes at least one leg and a coupling member mounted to an end of the 10 leg, whereby the coupling member is adapted to connect the upright member to (a) an underlying support such as a sub base of the structure, (b) a layer of reinforcing that is already in position, or (c) a base member. 15 Preferably the upright member includes a "U" shaped section with two parallel legs and an interconnecting web, and wherein the coupling member is mounted to the free end of one or both legs of the "U"'. 20 Preferably the coupling member is mounted for rotation about the lengthwise extending axis of the leg. According to a third aspect of the present invention there is provided a bar chair module for 25 supporting reinforcing in a reinforced concrete structure, which bar chair module comprises (a) at least two of the above-described bar chair of the first or the second aspects of the present invention and (b) at least two parallel spaced-apart elongate members that are coupled to 30 the bar chairs and interconnect the bar chairs together so that the bar chairs are parallel to each other and are spaced-apart and can be moved between (i) a generally flat folded storage position and (b) an outwardly folded operative position in which the planes of the bar chairs 35 are transverse to the axes of the elongate members. Preferably the elongate members are coupled to WO 2008/074092 PCT/AU2007/001992 7 the upright members of the bar chairs. According to a fourth aspect of the present invention there is provided a reinforced concrete 5 structure that comprises reinforcing supported on one or more of the bar chair of the above-described bar chair or bar chair module. The present invention is described further by way 10 of example with reference to the accompanying drawings, of which: Figures 1 to 4 show a series of known bar chairs, as described above; 15 Figures 5 to 9 show one embodiment of a bar chair in accordance with a first aspect of the present invention; 20 Figures 10 and 11 show another embodiment of a bar chair in accordance with the first aspect of the present invention; Figure 12 shows the versatility of the two bar 25 chairs shown in Figures 5 to 11; Figure 13 shows 4 different embodiments of base members that can be used in embodiments of a bar chair in accordance with the first aspect of the present invention; 30 Figure 14 shows an embodiment a bar chair in accordance with a second aspect of the present invention; Figure 15 shows an embodiment of a bar chair 35 module in accordance with the present invention in a folded storage position; and WO 2008/074092 PCT/AU2007/001992 -8 Figure 16 shows the embodiment of the bar chair module shown in Figure 15 in an operative position. The bar chair of the first aspect of the present s invention is an assembly of two basic components, namely a base member 31 and an upright member 33, each of which is straight forward to manufacture, can be packed and transported flat, and can be conveniently assembled on site to form a bar chair. Two embodiments of the bar 10 chair are shown in Figures 5-11. In the embodiment shown in Figures 5-9, the upright member 33 is a "U" shaped member and the base member 31 (referred to hereinafter as a "O"-shaped based is member) is a short length of bar 35 with a centrally located socket 37 extending outwardly from the bar and capable of receiving an end of one of the legs of the "U" shaped upright member 33. As viewed in Figures 5-9, the "$"-shaped base member 31 has a shape of an inverted "T". 20 A first step in manufacturing the Figures 5-9 bar chair includes manufacturing the "U" shaped member 33 shown in Figure 5[b] as previously described, typically on automatic equipment. As illustrated in Figure 5, the legs 25 "H1" of the "U" shaped upright member - see Figure 5[b] can be made shorter than the combined length of the members "H" and "L" of the legs of the conventional "U" shaped member - see Figure 5[a]. 30 A second step in manufacturing the Figures 5-9 bar chair includes manufacturing two "P" shaped base members 31. With reference to Figure 6, each "S3" shaped base 35 member 31 is manufactured from a short length of bar 35 of a suitable diameter and a short length of tubing 37 that defines a socket. The bar could be flat, rectangular, WO 2008/074092 PCT/AU2007/001992 -9 round, square etc and the tubing could be square, round, rectangular etc and can vary in length from 20-100 mm, but is more preferably 50 mm in length. 5 As can best be seen in Figure 6, the "D" shaped base member 33 is manufactured by welding the tubing centrally to the bar 35 and at 90* to the bar to form a socket that extends transversely to the bar. 10 Alternatively, the socket 37 could be in the form of a short length of tubing that has aligned transverse openings in the wall of the tubing 37 so that the tubing can be slid onto the bar 35 and positioned as required along the length of the bar 35, with the main opening in is the tubing 37 extending perpendicular to the axis of the bar 35. In this context, it is relevant to note that there will be situations in which it is not necessary that the socket 37 be positioned centrally of the bar 35. 20 The position of the tubing 37 along the length of the bar 35 is not critical. However, a position near the centre is preferred. The bar should be long enough to span between the bars in a layer of reinforcing on which the bar chair sits plus approximately 100 mm overhang. A 25 bar of 400 mm would be suitable for most applications. The "f3" shaped base member 33 could be manufactured from injection moulded plastic, cast metals, pressed metal or other suitable materials, such that the 30 tubing 37 is integral to the bar and does not have to be joined to the bar in a separate operation. Alternatively, tubing 37 manufactured from injection moulded plastic, cast metals, pressed metal or other suitable materials could be clipped onto a suitable bar made from any of the 35 materials mentioned. On site, the "0" shaped base member 31 is placed WO 2008/074092 PCT/AU2007/001992 - 10 on a sub-base of a structure to be constructed or on the first, second or third etc., layers of reinforcing and, if required, is tied in position to hold the tubing of the member in a vertical position, as shown in Figure 7. One 5 leg of the "U" shaped upright member is then inserted into the tubing as shown in Figure 8. A second "1" shaped member 31 is then placed under the second leg of the "U" shaped member to complete assembling the bar chair with the bar chair being thereby supported on the layer of 10 reinforcing. This is illustrated in Figure 9. The above sequence of placement steps is not critical and, by way of example, the components of the bar chair could be assembled together completely before 15 placing the bar chair on the sub-base of a structure to be constructed or on the first, second or third etc., layers of reinforcing. Figures 10 and 11 illustrate another, although 20 not the only possible other, embodiment of the bar chair of the first aspect of the present invention. The bar chair of this embodiment includes (a) a different shaped upright member 41 to the "U" shaped upright member 33 of the Figures 5-9 embodiment of the bar chair described 25 above and (b) a single "1" shaped base member. Specifically, the "U" upright member 41 of the bar chair shown in Figures 10 and 11 includes a "U" shaped section 43 and an arm part 45 that extends outwardly from 30 one end of one leg of the "U" shaped section parallel to the web of the "U" shaped section. The length "H2" of one leg may be different to the length "Hi" of the other leg to take into account the bend radius forming this leg and the difference in height resulting from not using a second 35 "1" shaped member to support the leg "H2". In use, on site the "U" shaped upright member is WO 2008/074092 PCT/AU2007/001992 - 11 positioned in a similar manner to that shown in Figure 8 but without the need for the second " '" shaped base member, as illustrated in Figure 9. The use of this shape is illustrated in Figure 11. 5 With reference to Figure 12, both embodiments of the bar chairs of the first aspect of the present invention are formed so that the legs of the "U" shaped upright members that extend into the sockets of the base 10 members are free to rotate within the sockets. Being able to rotate the "" shaped base member allows the assembly to be positioned on site in irregular arrangements to avoid obstructions 47 - as shown in Figure 12. 15 When assembled prior to placing a bar chair on reinforcing, the legs of the "U" shaped upright members 33, 41 of both embodiments of the first aspect of the present invention could be secured in the sockets of the base members to prevent the assembly falling apart. By 20 way of example, the sockets could have an indent, and integral clip or a weld bead etc., that allows the "U" shaped upright members 33, 41 to be inserted and held with sufficient force to prevent the parts separating and preferably allow the legs of the "U" shaped members 33, 41 25 to rotate in the sockets . This would allow the bar chairs to be assembled at a manufacturing site and packed flat for storage and transport to the site. On site the assemblies shown in Figures 9 and 11 would be created by simply rotating the "" shaped base members through 90*. 30 Being manufactured as separate components that can be assembled off-site or on-site as described above allows the bar chair of the first aspect of the present invention to be manufactured more safely and improves 35 production efficiency. The elimination of the bending process to form the legs "L" is also a major advantage. The bar chair also has the advantage of being able to WO 2008/074092 PCT/AU2007/001992 - 12 utilise scrap reinforcing to manufacture the "Q0" shaped base member 33, 41. The value of the steel manufactured component that utilises scrap is approximately 4 times the value of the scrap value of the component. The financial 5 benefit of utilising scrap is quite significant. The design of the bar chair also improves the handling, storage and freight of the bar chair. Other embodiments of the base member are shown in 10 Figure 13. Each of these alternatives, which are not the only possible alternatives, is the same conceptually as the "0" shaped base member 33, 41 shown in Figures 5-11. Each of these alternatives is essentially a two dimensional member that is an assembly of (a) bars that i form particular shapes as shown in the Figure and (b) a plurality of sockets extending from the bars. A plate support (not shown) is a further alternative, although this is less preferred as it would 20 have limitations in application. Some of these do not allow a pre-assembled bar chair to be packed as a flat pack. The bar chair of the second aspect of the present 25 invention is a single component, which is straight forward to manufacture, can be packed and transported flat, and can be conveniently assembled on site to form a bar chair. One embodiment of the bar chair is shown in Figure 14. 30 With reference to Figure 14, the embodiment of the bar chair of the second aspect of the present invention shown in the Figure comprises the bar chair of the first aspect of the invention, modified by replacing one or both "P" shaped base members by a socket 49 that is 35 mounted to an end of the leg 63 of the "U" shaped upright member 61 and is free to rotate about the axis of the leg 63 and can be clipped onto a bar (not shown) in the WO 2008/074092 PCT/AU2007/001992 - 13 reinforcing supporting the bar chair or onto a short length of bar that does not include the tubular section. Figure 15 shows an embodiment of a bar chair 5 module 51 in accordance with a third aspect of the present invention. The module 51 comprises: (a) two bar chairs, in accordance with the first aspect of the present invention (but could also be io in accordance with the second aspect), and (b) a pair of parallel bars 53 coupled to and thereby interconnecting the bar chairs so that the bar chairs are parallel to each other and are spaced-apart. 15 The bar chairs and the bars are coupled together by means of universal joints (not shown) that allow the bar chairs to be moved from the folded storage position shown in Figure 15 to the expanded operative position shown in Figure 16. 20 The module can be pre-assembled at a manufacturing site and stored and delivered in the flat pack form shown in Figure 15 and can be readily manipulated on site into the operative position shown in 25 Figure 16. Many modifications may be made to the embodiments of the present invention described above without departing from the spirit and scope of the invention. 30 By way of example, whilst the embodiment of the bar chair in accordance with the first and second aspects of the present invention and the bar chair of the bar chair module in accordance with the third aspect of the 35 present invention include sockets 37, 49, the present invention is not so limited and extends to any suitable member to couple together the two components of the bar WO 2008/074092 PCT/AU2007/001992 Cha~. 14

Claims

1. A bar chair for supporting reinforcing in a 5 reinforced concrete structure, which bar chair comprises an assembly of (a) a base member that is essentially a 2 dimensional member and can be positioned horizontally on an underlying support such as a sub-base of the structure or a layer of reinforcing that is already in position and 10 (b) an upright member that is essentially a 2-dimensional member and can be coupled to the base member to extend upwardly from the base member and define a support for a new layer of reinforcing spaced above the sub-base or the existing layer of reinforcing. 15

2. The bar chair defined in claim 1 wherein the base member comprises a bar and a centrally located socket extending outwardly from the bar to receive a section of the upright member and thereby couple the base member and 20 the upright member together to form the assembly.

3. The bar chair defined in claim 2 wherein the upright member includes a "U" shaped section with two parallel legs and an interconnecting web, and wherein at 25 least one of the legs of the "U" can be positioned to extend into the socket of the base member to thereby couple the two members together to form the assembly.

4. The bar chair defined in claim 3 wherein the 30 assembly comprises two base members, and both legs of the "U" of the upright member can be positioned to extend into the sockets of the base members to thereby couple the three members together to form the assembly. 35

5. The bar chair defined in claim 3 or claim 4 wherein the "fit" of the leg or legs of the "U" of the upright member in the socket of the base member is a tight WO 2008/074092 PCT/AU2007/001992 - 16 fit or one that allows relative rotation of the components to facilitate adjustment of the shape of the bar chair to avoid obstructions. s

6. The bar chair defined in claim 2 wherein the upright member comprises a "U" shaped section and an arm section extending outwardly from an end of one leg of the "U" shaped section, and the assembly comprises the upright member and a single said base member and an end of the 10 free leg of the "U' shaped section can be positioned in the socket of the base member to form the assembly.

7. A bar chair for supporting reinforcing in a reinforced concrete structure, which bar chair comprises 15 an upright member that includes at least one leg and a coupling member mounted to an end of the leg, whereby the coupling member is adapted to connect the upright member to (a) an underlying support such as a sub-base of the structure, (b) a layer of reinforcing that is already in 20 position, or (c) a base member.

8. The bar chair defined in claim 7 wherein the upright member includes a "U" shaped section with two parallel legs and an interconnecting web, and wherein the 25 coupling member is mounted to the free end of one or both legs of the "U".

9. The bar chair defined in claim 7 or claim 8 wherein the coupling member is mounted for rotation about 30 the lengthwise extending axis of the leg.

10. A bar chair module for supporting reinforcing in a reinforced concrete structure, which bar chair module comprises (a) at least two of the bar chair defined in any 35 one of the preceding claims and (b) at least two parallel spaced-apart elongate members that are coupled to the bar chairs and interconnect the bar chairs together so that WO 2008/074092 PCT/AU2007/001992 - 17 the bar chairs are parallel to each other and are spaced apart and can be moved between (i) a generally flat folded storage position and (b) an outwardly folded operative position in which the planes of the bar chairs are 5 transverse to the axes of the elongate members.

11. The bar chair module defined in claim 10 wherein the elongate members are coupled to the upright members of the bar chairs. 10

12. A bar chair substantially as hereinbefore described with reference to the accompanying drawings.

13. A bar chair module substantially as hereinbefore 15 described with reference to the accompanying drawings.