A FLOOR SLAB AND APPARATUS FOR FORMING SAME

Field of the Invention

The invention relates to floor slabs, and especially to concrete floor slabs for use in building construction.

Background and Prior Art Known to the Applicant

Suspended concrete floor systems have been part of the repertoire of building construction for many years, and a number of systems have been developed.

One such system, often known as a "beam and block" construction is illustrated in cross- section Figure 1. Elongate, generally T-section beams 1 are supported at each end, and optionally at other points along the length of the beam. The beams 1 are usually pre- stressed, or comprise e.g. steel reinforcing bars 2. Concrete blocks 3, are -then laid between the beams as illustrated, to form a floor/ceiling element. This construction defines a series of voids 11 between the beams 1.

Another such system, known as "HollowCore" is illustrated in cross-section Figure 2, and comprises a generally rectangular slab 4 of concrete, having a number of voids 5 running longitudinally through the slab 4. The voids may have a range of cross-sections aside from the square section illustrated; circular section voids are common. The use of voids such as this reduces the overall weight of the construction unit. The slab itself is typically pre-stressed with bars, strands or tendons 6 running through the slab 4. These are typically made of steel, but other materials may be used. The slabs are typically 1200mm wide but other widths are available, with slab depths typically ranging from 110mm to 400mm, and may have lengths up to around 10m or more, depending on the span to be bridged.

Figure 3 illustrates, in longitudinal cross-section, a hollowcore slab 4 initially positioned on bearing points 7. As a result of the pre-stressing of the concrete, the slab is initially bowed upwards with a deflection, or camber 8 that could be several tens of millimetres. The extent of the bowing illustrated in Figure 3 is exaggerated for the sake of clarity. As the weight of the slab 4 is released onto the bearing points 7, the bowing decreases. Ideally, the pre-stressing, and the slab weight would be so balanced that the slab would take up a flat conformation when in place. However, this is often not the case, and (as illustrated in Figure 4, again in longitudinal cross-section) a layer of screed 9 must normally added to the top surface to create a flat floor. It is sometimes necessary to use a structural topping in place of screed.

A yet further system, known as "Coffered Beams", is illustrated in perspective view in Figure 5. This system comprises an elongate beam 10 of a generally U-shaped section, defining a void 11 , running along the length of the beam 10. In many instances, the void 11 extends to the end of the beam 10 as illustrated. In an alternative embodiment, illustrated, again in perspective view, in Figure 6, the ends 12 of the beam 10 are closed, forming an open boxed-shaped structure. These coffered beams are often made of reinforced concrete.

In use, the coffered beams 10 are supported at each end and arranged in a side-by-side orientation with the voids 11 pointing downwards to form a floor, or deck, as illustrated in

schematic transverse cross-section in Figure 7. Often, a suspended ceiling 12 is fitted to the underside of the beams 10.

In all of these systems, voids 5, 11 are defined in the structure. These voids have the advantage of reducing the overall weight of the structure, although a relatively large depth of structure is still needed to provide the required structural stiffness. In principle, the voids could be used to house services such as water and gas pipework, ventilation ducting or cabling; in many instances this is the case, however the services can only run along the length of the beams 1, 4, 10, and not across; there is no connectivity between adjacent voids.

JP1083750A (Fudo Kenken KK) discloses a concrete floor plate not being designed to form a floor in itself, but requiring the introduction of a reinforced concrete layer, in order that a composite floor may be formed.

CH587988A5 (Freund) discloses a constructional element featuring angled metal ribs that protrude from the surface of the element. The invention there has the marked disadvantage of having a multi-piece construction; disadvantageous in terms of time, costs and energy which must be expended to make it.

It is amongst the objects of the present invention to address some of these problems.

Summary of the Invention

Accordingly, the invention provides a concrete floor slab comprising a substantially flat concrete panel and at least one rib located on the surface of said panel and wherein said rib (or ribs) does not extend to the edge of the panel. In preferred embodiments, the floor slab is suitable for creating a load-bearing floor in a building. It is preferable that the ends of the rib or ribs are at least 100mm from the edge of the panels, and more preferably 200mm or 300mm from the edge, to allow room for the panel to be supported at its edge, as well as providing a passage connecting the voids defined by adjacent ribs to allow services and the like to be installed.

Preferably the floor slab is of one piece concrete or reinforced concrete construction. Insofar as reinforced concrete embodiments of the inventions in this specification do feature elements of metal which act as reinforcers, they more preferably do not protrude from either the top or bottom in use surface of the floor panel.

Preferably, the floor slab has a plurality of ribs.

Included within the scope of the invention is a floor slab substantially as described herein, with reference to and as illustrated by any appropriate combination of Figures 8 to 11.

In a second, and unified aspect, the invention also provides apparatus for manufacturing a floor slab as described herein comprising: table portions arranged in a spaced apart fashion, and having top surfaces aligned in substantially the same plane; side bars, located on said table portions, and spaced apart from each other; end inserts, located between said side bars; and a profiled tray, extending between said table portions; whereby said table portions, side bars, end insert and profiled tray define a mould, so shaped as to form said floor slab.

Preferably, said side bars (with or without the table portions) are moveably mounted so that the spaced-apart separation may be varied. In this way, the same apparatus may be readily reconfigured to produce floor slabs of differing sizes and configurations.

Preferably also, said side bars (with or without the table portions) are moveably mounted so that the side bars may be positioned to define a tapering mould. Also included in the scope of the invention is apparatus for manufacturing a floor slab (as described herein) substantially as described herein, with reference to and as illustrated by any appropriate combination of Figures 9 to 16.

Brief Description of the Drawings

The invention will be described with reference to the accompanying drawings, in which:

Figures 1-7 are illustrations of floor slabs known in the prior art;

Figure 8 is a perspective view of a floor slab according to the present invention; Figure 9 is a plan view of an array of such floor slabs;

Figures 10 and 11 show plan and cross-sectional views of a floor slab according to the present invention; Figures 12-16 show plan and cross-sectional views of apparatus for manufacturing floor slabs of the present invention.

Description of Preferred Embodiments

Figure 8 shows, in perspective, a floor slab according to the present invention, generally indicated by 13. The slab 13 comprises a substantially flat elongate panel 14, on one surface of which is located a rib 15. The rib 15 gives structural rigidity to slab 13, resisting bending moments when in use, and under load. It can be seen that the rib runs along the length of the panel 14, but does not extend to the ends 16. In preferred embodiments, the slab 13 is constructed as a single piece concrete casting. In order to give additional strength, the concrete casting is preferably reinforced with steel in a generally conventional manner, or in combination with steel fibres incorporated in to the concrete for added strength.

In use, the panel may be suspended from each end and oriented with the rib facing downwards, giving a substantially flat upper surface. Figure 9 is a plan view of the underside of a deck constructed using the elements 13. Four such slabs 13 are illustrated. The location of the bearing points 7 for each end of the slabs 13 are illustrated by the double dashed lines. It can be seen from this illustration, that the particular construction of the slabs 13 allows connectivity between the voids defined by adjacent ribs 15. In this way, services such as cables, pipes and ducts may be run in either direction e.g. as illustrated by the path 17 running both along and across the floor slabs 13.

Figure 10 illustrates in more detail an embodiment of the invention. Figure 10a is a transverse cross-section of a floor slab 13, along line AA of Figure 10c, identifying the rib depth 18, and showing a profiled edge 19 of the panel 14. The rib depth 18 may be varied according to the structural stiffness needed to meet the required load-bearing capacity of the floor slab 13. It is envisaged that rib depths of approximately 50, 100, 150, 200, 250

or 300mm would provide a range of structural stiffness to suit most applications, although other greater, smaller or intermediate rib depths are contemplated (ranging from 50mm to 2000mm). As a general principle, rib depths up to approximately five times the depth of the panel are particularly preferred. The profiled edge 19 comprises a concave channel running along the edge of the panel 14; the top (in use) edge of the channel is set slightly inside the bottom edge, i.e. the width of the top (in use) face is slightly less than the width of the bottom (in use) face. This allows the panels to be butted together along their lower faces, leaving a channel, defined by adjacent profiled edges 19, which may be grouted after positioning of the slabs 13 to add further structural rigidity to the whole assembly.

It is envisaged that slabs 13 could be of varying length depending on the span to be bridged, e.g. for most applications from approximately 2.5m up to approximately 7.5m long. Other smaller or greater lengths are also contemplated, ranging e.g. from Im to 48m.

It can be seen in Figure 10 that each end of the rib 15 has an angled profile. This improves the efficiency of slab 13 slightly by omitting a portion of the rib at each end in the area where it would be structurally least effective.

Figure 10b is a longitudinal cross-section of a floor slab 13, along the line BB of

Figure 10c or 1Od. The figure identifies the depth 20 of the slab, or panel 14 of the floor slab 13. It is envisaged that panel depths 20 of 100, 150 or 200mm would provide a range of structural stiffness to suit most applications, but other greater, smaller or intermediate panel depths are contemplated ranging from 50-400mm.

Figure 10c is a plan view of the underside (in use) of a floor slab 13 of the present invention and identifies the panel width 21. It is envisaged that panel widths 21 in the range of 350-750mm would provide a range of sizes to suit most applications, but other greater, smaller or intermediate panel widths are contemplated, ranging from 0.15m to 2.5m for a single rib construction and from 0.3m to 5m for a double rib construction.

Figure 1 Od is a plan view of the underside (in use) of a further embodiment of the invention. In this embodiment, the slab 13 tapers from one end 16 to the other. In this

way, an assembly of side-by-side tapering slabs can be formed into a curved deck, or form elements of a circular structure supported at its centre and perimeter.

Figure 11 illustrates a further embodiment of the invention wherein two ribs 15 are located on the surface of the panel 14. Figure 1 Ia is a transverse cross-section of a floor slab 13 along the line AA of Figure l ie showing the location of the two ribs 15 on the panel 14. Again, the panel has a profiled edge 19, as described above.

Figure 1 Ib is a longitudinal cross-section along the line BB of Figure l ie. Figure 1 Ic is a plan view of the underside (in use) of the floor slab 13, again showing the two ribs 15.

Figure 12 illustrates, in plan view, apparatus for manufacturing floor slab 13 according to the present invention, generally indicated by 100. The manufacturing apparatus, 101, comprises table portions 102 with a pair of side bars 103, extending vertically upwards (in use) from the table portions 102, and defining the edges of a floor slab 13 to be manufactured. The two table portions 102 are located with their upper faces lying in substantially the same plane and, in preferred embodiments, the table portions 102 and/or the side bars 103 may be moved apart from each other in order allow floor slabs 13 of differing widths to be cast in the mould defined by the side bars 103, the table portions 102 and the end inserts 104, described below.

End inserts 104 are located between the side bars 103, again extending vertically upwards (in use) from the table portions 102, and defining the ends of the floor slab 13 to be manufactured. The end inserts 104 are slideable within the side bars, so that varying lengths of floor slabs 13 may be formed on the same apparatus. The length of the slab 13 to be cast is identified by 105.

Resting on the table portions 102 is a shaped rib tray 106 to form the projecting rib or ribs 15. The tray 106 is held in position by a number of studs 107. These slabs are more clearly illustrated in the accompanying cross-sectional views. By moving the side bars 103, with or without the table portions 102, relative to each other, floor slabs 13 of differing width 108 may be manufactured.

Figure 13 is a transverse cross-sectional view of apparatus 100 along the line AA of Figure 12. Illustrated are two table portions 102, manufactured from a concrete-resistant material such as stainless steel. The side bars 103 are formed of angle-section steel and may be moved relative to each other as indicated by the arrows 109. The side bars 103 have angled profiles 1 10 to their inner edges, to create the grouting channel described above. Located between the two table portions 102 is a rib tray 111, constructed from stainless steel, or another concrete-resistant material such as plastics. In this preferred embodiment, the rib tray 111 is removable, and is located on the table portions 102 by means of upwardly facing studs 112. The rib tray 111 defines the depth of rib 15 to be formed on the floor slab 13, and differing depths of rib tray 111 may be provided so that a range of specification of floor slab 13 may be cast, as indicated by the dimensions 113, and corresponding rib-forming portions of the rib tray 11 , shown in dotted outline. The rib trays may be formed with differently shaped profiles in both transverse cross-section and in longitudinal cross-section to enable the manufacture of floor slabs incorporating ribs with bespoke shapes to meet varying visual and structural requirements.

In use, a concrete premix slurry 114, either reinforced conventionally (e.g. with steel bars) or in combination with steel fibres is introduced into the mould defined by the table portions 102, the side bars 103, the end inserts 104 and the rib tray 111, and allowed to harden to form the floor slab 13. The slab 13 may then be removed from the mould for final curing and eventual use.

Optionally, additional fittings 115 such as fillets and fixing channels, such as those sold under the Registered Trade Mark Halfen®, may be cast into the floor slab 13 as indicated.

Figure 14 is a plan view, using reference numbers as used in Figure 12, to illustrate an embodiment of manufacturing apparatus 100 for form a floor slab 13 having two ribs 15.

Figure 15 is a transverse cross-sectional view of the apparatus of Figure 14, along the line AA. Elements are as numbered and described in Figure 13. This apparatus is configured to cast a floor slab 13 having two ribs. To achieve this, two rib trays 111 , 111 a are provided. An infill plate 116 may be used to fill the gap between the two rib trays 111,

11 Ia ₅ supported on intermediate supports 117. Alternatively, a single rib tray defining two ribs 15 may be used.

Figure 16 illustrates apparatus 100 for manufacturing a floor slab 13 having a longitudinally tapered profile. The elements are as numbered and described in Figure 12. In this embodiment, the side bars 103 are adjustable, to allow them to be angled with respect to each other in order to define a tapering mould in which to cast a floor slab 13.

By "floor slab" it is meant a slab which by virtue of its form and strength is suitable for forming a structural floor member without further additions. It is also meant that the floor slab is capable of bearing a load functionally commensurate with its role as a floor slab.