GB2070097A - Floor support system comprising channelled lightweight concrete beams - Google Patents

Abstract

Channelled beams 2 of moulded lightweight foam concrete are secured together by dowels 14 each in a pair of overlying crossed slots 12a and 12b in juxtaposed beam flanges 6 and 8. The concrete of density 600-1500 Kg/m<3> is foamed using aqueous foaming agent, and the beams can be easily cut with conventional woodworking tools. Cables and pipes in notches 18 and channels 10 are concealed by floor decking 16 nailed to the flanges; or a floor surface may be formed from lightweight concrete screed on a support over the beams, or by filling the channels with lightweight concrete. <IMAGE>

Description

SPECIFICATION Floor support system This invention concerns floor support systems.

It is known to support flooring, in the form of planks or panels of wood material, by parallel timber joists or beams 3 to 5 meters in length and of 50 x 200 mm. cross-section and spaced apart by 400 to 600 mm. An advantage of timber is that it can receive nails and be sawn easily. A disadvantage is that timber prices have risen substantially and it can be difficuit to obtain beams of sufficient size and quality to satisfy modern building regulations. As an alternative units up to 7 metres long of precast conventional concrete have been used disposed side by side and fromed with channels and voids to lighten their weight. Services such a pipes and cables are located in the chanels which are filled with concrete screed to from a floor surface or on the surface of the units for later burying in the screed.

Burying such services in concrete screed is not always desirable, but the use of screed is a convenient way to provide the floor surface since hammering nails into conventional concrete by hand to secure floor boards or panels is extremely difficult if not impossibte. Also the precast units must be formed exactly to size since they cannot be cut or at least only with great difficulty.

According to the invention a floor support system coinpnses a plurality of substantially parallel, juxtaposed beams formed with channels, said beams being secured one to another by shear connectors, and said beams being formed of lightweight foam concrete.

Lightweight foam concrete is concrete formed by a method comprising mixing water, aqueous foaming agent, air, cement and filler.

Foam may be generated in a foam generator, known per se, in which aqueous foaming agent, water and air are mixed to form foam which is supplied to a concrete mixing machine, for example a ribbon blender, in which the foam is mixed with the cement and filler to produce a substantially even spread of foam throughout the mix. Before addition of the foam the cement and filler may be first mixed together in a substantially dry state. The aqueous foaming agent is preferably of a kind producing a stable consistent foam such as used, for example, in fire-fighting. The filler may be, for example, sand, stonedust, or perferably pulverised fuel ash. The cement and filler may be in proportion, for example, of about one part cement to three parts filler.

The mixing may be carried out using an AERCRETE (Trade Mark) machine manufactured by Master Engirieering Limited or Robertsebridge, Essex, or other comparable machine.

Preferably the mixed concrete is allowed to dry and set in air at normal atmospheric temperature.

The foam concrete has a structure in the form of a mass of tiny bubbles and a density of the order of 600-1 500 Kg/m3. It is stronger than another lightweight concrete called "aerated" concrete in which bubbles are produced chemically using aluminium powder in the mix which is set and dried in an autoclave.

In contrast to conventional concrete, lightweight foam concrete can relatively easily receive nails and be cut by conventional wood working tools, for example, saws.

The beams of lighweight foam concrete are formed with channels extending therealong, preferably using moulds which are vibrated.

The beams have side flanges in which spaced openings are formed for example by moulding.

These openings may be lined with plastics material. When the beams are disposed side by side with the open sides of the channels uppermost, the openings in a flange in one beam coincide with the openings in the adjacent flange of the next beam. Dowels which may be of plastics or comprise an outer layer of plastics are inserted into pairs of these coincident openings to connect the beams together. This connection is a shear connection which resists forces applied in shear tending to displace one beam relatively to another.

Each beam may be formed with a plurality of longitudinal channels spaced one from another by ribs extending upwards from a web interconnecting the side flanges.

The flanges and ribs can be formed with voids or notches, which may be moulded and lined with plastics material, to allow ease of passage of services through the flanges and ribs onto which decking, for example chipboard panels, can be nailed to form the floor surface.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a fragmentary perspective view of a floor support system formed according to the invention provided with decking; Fig. 2 is a side view of a beam supported at each end, used in the- system in Fig. 1; Fig. 3 is an enlarged fragment of a side flange of a beam in Fig. 1 to show on larger scale a shear joint; Fig. 4 is a perspective view of another embodiment of beam which can be used in a floor support system formed according to the invention;; Figs. 5 and 6 are perspective views of fragments of floor support systems formed according to the invention using beams which are modifications of those in Fig. 1, and Fig. 7 is a diagrammatic elevational view partly in section of another embodiment of shear connector for use in a floor support system formed according to the invention.

In the Figs. like reference numerals refer to like parts.

In Fig. 1 a plurality of horizontal parallel juxtaposed lightweight foam concrete beams 2 are shown.

Each beam has a horizontal soffit or base web 4 and upstanding side flanges 6 and 8 having sloping inner side faces 6d and 8d between which is defined an open topped channel which tapers slightly towards the web.

At spaced intervals each flange 6 has through elongate openings or slots 1 2a opposite corresponding through elongate openings or slots 1 2b in the flange 8 of the same beam. The openings 1 2a which are rectangular are all similarly inclined at a slight angle to the horizontal, whilst the openings 1 2b are also rectangular and similarly inclined but in the opposite direction to the openings 12a.

To lock two adjacent beams together dowels are used, a dowel 14 being driven as in interference fit into one opening 1 2b in a flange 8 which is next to the flange 6 of the next beam having an opening 1 2a alongside the said opening 1 2b so that the opening 1 2a receives the same dowel as an interference fit. This locking provides a shear connection resistant to vertically or horizontally directed shear forces attempting to move one beam relatively to those immediately adjacent and accordingly the beams provide a firm support for floor decking 1 6, for example chipboard panels which may be nailed to the flanges 6, 8.

Because the openings 12a, 12b are elongated and inclined in opposite directions, adjacent beams need not be exactly aligned since it is only necessary for an opening T2a receiving the same dowel as an opening 1 2b to cross somwhere along the length of each opening in order that both accommodate the dowel.

The dowels 14 may be tubes (Fig. 3) and may be formed of thermoplastic plastics material. The plastics material may be for example polyvinylchloride, which when heated becomes more easily deformable to facilitate insertion into a pair of openings 12a, 12b.

Alternatively the dowels 14 may be of thermo-setting plastics which can be heated to reder them deformable for insertion and thereafter set in wedged state in the corresponding pairs of openings 12a, 12b.

After the dowels have been inserted, the remaining space felt in the openings 12a, 12b may be filled with grout which may be expanding plastics material.

The side flanges are also formed with voids or notches 1 8 which allow services, for example piping and cables to transfer from one channel 10 to another or extend transverseiy to the beams as exemplified by pipe 20.

Each beam is formed on a mould which preferably vibrates slightly, a former being used to define channel 10. The openings 12a, 12b and the notches 1 8 are formed as part of the moulding operation using formers to which may be applied thin liner members, of, for example, hard plastics which line the openings and notches in the moulded beam. The concrete may include reinforcements 22 and/or 24.

Reinforcement 22 may be a rod of, for example steel, and reinforcement 24 may be a sheet-like or steel, plastics or fibre glass in the form, for example of a grid.

With reference to Fig. 2, each beam 2 can be supported at its ends on ledges 22' between which and the beam, felt pads (not shown) may be disposed. Preferably the openings 1 2a and their corresponding opposite openings 1 2b are located at positions from each end of the beam of about one third of the total beam length. However beams formed in a variety standard predetermined lengths may be cut to size to suit a particular location.

Using panels 1 6, or alternatively floorboards as decking permits removal of the decking for access to the services, and the channel 10 can provide ventilation.

As an alternative, the panels 1 6 may be replaced by decking comprising less dense lightweight concrete screed, which may be a foam concrete, on a support, for example a steel or plastics mesh, over flanges 6, 8.

Lightweight foam concrete has excellent sound and heat insulation properties. If these are desired to a particularly high level the channels 10 may be filled with such concrete, after installation of the services. The top surface of this filling may form the floor surface.

If desired the panels 1 6 or the concrete floor surface may be covered by floor finishing material, for example carpet tiles or polyvinychloride tiles.

In Fig. 4 the beam 2 has two channels 10 divided by a central rib 26 of the lightweight conctete.

Because of their lightness beams formed as described above may be relatively easily manhandled.

Examples of dimensions of beams 2 which may be made are listed below.

Flange 6,8 Web 4 Weight in Width Depth or rib 26 thickness thickness Lenght Type Kg/M. length in mm. in mm. in mm. at upper end in mm. in M. Domestic (Fig. 1) 38 400 188 72 32 4.5 Office type A 40 400 188 74 36 4.0 (Fig. 1) Office type B 44 400 210 74 48 5.0 (Fig. 1) Office type C 66 600 210 74 48 8.0 (Fig. 4)

The width of slot 12a, 12b may be about 1 8 mm, and the inner and outer diameters of dowel tube 14 about 12 and 18 mm. respectively.

In the modification shown in Fig. 5 outer faces 6a, 8a of the side flages 6, 8 of each beam are chamferred so that those outer faces of a said beam are upwardly convergent thus leaving between each two adjacent beams an open-topped groove 28 of V-shaped section which may be filled with filler 30.

The uppermost part of each outer side 6b, 8b in the arrangement in Fig. 6 is rebated at 6c, 8c, thus leaving between each two adjacent beams an open-topped groove 28a of substantially rectangular cross-section which may be filled with filler 30.

Filler 30 may be adhesive, for example cement mortar, and can provide a positive seal against ingress between the beams of air or water and aid the shear connectors 14 in the transfer of forces between the beams.

Instead of the shear connectors or dowels 14 being tubular they can be solid rods of any suitable cross-section, for example circular of diameter substantially equal to the width of slot 12a, 12b or substantially square of side length substantially equal to the width of the slot.

In an alternative embodiment of shear connector or dowel indicated at 14' in Fig. 7, the dowel comprises a metal core formed by a steel bolt 32 with a head 34 and a nut 36. The bolt shank is surrounded by a sleeve 1 4a of thermoplastic or thermo-setting plastics material having an internal diameter greater than the diameter of the bolt shank. Beyond each end of sleeve 1 4a the bolt shank carries washers 38. These may have a chamferred face 38a to conform with slope of inner faces 6d and 8d of two adjacent flanges 6 and 8 shown in phantom lines in Fig. 7. The overall initial length of sleeve 1 4a is greater than the combined thickness of the two flanges 6 and 8 where the dowel passes through them.

The dowel 14' is inserted in a pair of adjacent openings 12a, 12b. Then the nut 36 is tightened to longitudinally compress the sleeve 1 4a between the washers. This causes the sleeve to expand radially or transversely to the bolt axis and jams the sleeve firmly in the openings 12a, 12b. To facilitate this deformation of the sleeve it may be heated by heat from the bolt which can be heated by any suitable technique. For example the bolt may be temporarily connected in an electrical circuit in which the bolt acts as an electrical resistance heater.

As with the previous dowels described herein, the external cross-section of the sleeve 1 4a may be of any desired shape.

In use the dowel 14' can ensure a good positve seal between itself and the sides of the openings 12a, 12b so that adjacent beams are held firmly together to ensure positive transfer of shear and other forces throughout the system of connected beams.

In a particular example intended to fit in slots 12a, 12b of about 1 8 mm. wide, the sleeve 1 4a may have an external diameter of about 18 mm. and an internal diameter of about 12 mm., the bolt shank diameter being about 10 mm.

Claims (14)

1. A floor support system comprising a plurality of substantially parallel, juxtaposed beams formed with channels, said beams being secured one to another by shear connectors, and said beams being formed of lighweight foam concrete.

2. A system as claimed in claim 1, in which said beams comprise flanges formed with openings receiving the shear connectors.

3. A system as claimed in claim 2, in which the openings are slots.

4. A system as claimed in claim 3, in which a said flange of a first beam of first and second said juxtaposed beams is adjacent a said flange of the second beam, a said slot in one of these flanges extends crosswise to a said slot in the other of these flanges, and a said shear connector extends through both slots where they cross.

5. A system as claimed in any one preceding claim, in which a said shear connector is a dowel.

6. A system as claimed in claim 5, in which the dowel is a tube or rod of plastics material.

7. A system as claimed in claim 5, in which the dowel comprises an inner metal part surrounded by plastics material.

8. A system as calimed in claim 7, in which the dowel comprises a sleeve of plastics material on a metal bolt and the sleeve is longitudinally compressible between a bolt head and a nut on the bolt.

9. A system as claimed in claim 2, or as claimed in any one of claims 3 to 8 when appended to claim 2, in which the flanges extend upwardly from bases of the beams and have voids or notches in their upper faces.

10. A system as claimed in claim 2 or claim 9, or as claimed in any one of claims 3 to 8 when appended to claim 2, in which sides to two adjacent said flanges on two juxtaposed said beams define a groove between said sides.

11. A system as claimed in claim 10, in which the groove contains material which when initially introduced into the groove has adhesive properties.

1 2. A system as claimed in claim 11, in which the groove contains cement mortar.

13. A system as claimed in any one preceding claim, in which the channels and beams are covered by decking forming a floor.

14. A system as claimed in claim 13, in which the decking is nailed to the beams.

1 5. A system as claimed in claim 13, in which the decking is lightweight concrete screed on a support over the beams.

1 6. A system as claimed in any one of claims 1 to 12, in which the channels are filled -with lightweight concrete forming a floor surface.

1 7. A floor support system substantially as hereinbefore described with reference to the accompanying drawings.