GB2428434A

GB2428434A - Modular floor units

Info

Publication number: GB2428434A
Application number: GB0515075A
Authority: GB
Inventors: John Window
Original assignee: Henley Consultants Ltd
Current assignee: Henley Consultants Ltd
Priority date: 2005-07-22
Filing date: 2005-07-22
Publication date: 2007-01-31
Also published as: GB0515075D0

Abstract

The invention provides a modular solid concrete floor unit 1 for use in a prefabricated building system. An edge frame 2 is made from cold rolled C-section sheet metal members assembled in a factory to precise engineering dimensions. The grid of metal reinforcing rods 4 extends across the edge frame and is secured to the edge frame at each point of contact. The concrete slab is cast, using the edge frame as permanent shuttering. The grid covers the wire mesh and enters into the hollow interiors of the C-section edge members. When the concrete is set a floor unit is turned over so that the smooth bottom surface of the cast concrete slab forms the upper face of the reinforcing floor unit which has a continuous metal edge provided by the C-section sheet metal members.

Description

TITLE

Modular Floor Units

DESCRIPTION

Field of Invention

The invention relates to modular floor units, being components of modular building systems or of steel frame building systems for the rapid construction of buildings for use either as industrial or commercial premises or as dwellings. The invention also relates to a method for the manufacture of such modular floor units.

Background Art

Modular buildings can be constructed from prefabricated wall panels which are bolted or welded together on site to create the framework of a building.

The prefabricated wall panels can include pre-installed window frames, door frames, electrical connections and/or plumbing connections to reduce the building and finishing time on-site, and in a typical modular construction process are assembled on-site by being moved into position by a crane or other lifting equipment before being connected together to create a rigid structure. If the building is a steel-framed building then similarly the girders are lifted into position on-site and connected together to create the rigid framework of the building onto and into which are secured the desired external and internal wall panels.

The floors of such buildings can be hollow or solid. By "hollow floors" there is conventionally meant floors created from planks or panels, generally of timber or timber-based composite materials such as plywood, chipboard and oriented particle board, laid over a supporting structure such as timber joists or metal beams. By "solid floors" there is conventionally meant concrete floors.

Solid floors are often preferred for their better sound insulation properties, and are often specified for multi-occupancy buildings such as apartments, hotels and student accommodation and for industrial and commercial premises.

There are two basic methods of constructing solid floors in the above modular buildings. One is to pour wet concrete into an edge mould created from either temporary or permanent shuttering. That is the method almost universally used for ground-level flooring. The other method is to assemble the floor from pre-cast concrete flooring panels. Those panels are pre-cast in open moulds and generally incorporate metal reinforcement. They are often cast with longitudinal holes or channels to reduce the overall weight, and also are often cast with a slight convex shape which assists stress distribution in the final building. Ultimately however each array of pre-cast solid flooring panels is covered with a cement screed to smooth out the surface imperfections and irregularities. The screeded area must be kept clear of construction personnel while the cement screed dries and sets, and this of necessity slows down the construction process, requiring work on site to be stopped or diverted to other areas until the screed is sufficiently hard and durable to accept foot traffic without damage.

Pre-cast concrete flooring panels may be several metres in length but generally have a maximum width of about 500 mm. A system for the on-site casting of wider panels of solid flooring is commercially available under the Trade Mark HOLORIBTM. A concrete slab is cast on-site over a full width panel of sheet steel which is folded to create dovetail-section channels running longitudinally down the underside of the cast slab. Because of the re- entrant shape of the dovetail-section channels, the sheet steel panel forms an integral part of the cast slab, and provides longitudinal reinforcement to the concrete of the cast slab. Additional reinforcement (longitudinal or lateral) can be provided by embedded steel rods or wires in the concrete slab. The undersides of the HOLORIBIM cast flooring slabs are provided by the folded metal of the sheet steel, which supports the single span of concrete as it is setting. The edges are exposed concrete. When the HOLORIBTM cast flooring slabs are cast in position over a rigid structure of wall panels or of metal girders, the dovetail section recesses in the metal sheet cladding on the underside can receive retaining clips to hold in position electrical cables or plumbing pipework which can be received in the recesses or suspended beneath them, or may be used as anchorage points for a suspended ceiling suspended beneath the floor. A significant benefit of HOLORIB TM in situ cast floor slabs is that they can be made in widths of several metres, but disadvantages are the on-site casting and the high cost, which is a consequence of the full width panel of folded sheet steel which dads the underside. Also, the surface finish is such that even though a single cast slab may form the floor of a room of the building under construction, it is generally necessary to cover the floor with a cement screed laid on site.

It is an object of the invention to provide a pre-cast modular floor unit which overcomes the above disadvantages and which presents a smooth finish that does not require screeding, and to provide a method for the manufacture of such a floor unit.

The invention The invention provides a modular floor unit as defined in claim 1. The invention also provides a method for the manufacture of such a floor unit, as defined in claim 8.

Drawings Figure 1 is a perspective view of an edge frame and a lathce of reinforcing rods or wires secured thereto before being filled or partially filled with poured wet concrete; Figure 2 is a section through one edge frame cold-rolled C-section sheet metal edge member and reinforcing rod of the edge frame of Figure 1; Figure 3 is a section through another edge frame cold-rolled C-section sheet metal edge member and reinforcing rod or wire of the edge frame of Figure 1, showing a different method of securing the reinforcing rods to the edge frame under tension; Figure 4 is a detail of one lifting loop formed from the reinforcing rods or wires of Figure 1; Figure 5 is a detail of another form of lifting loop; Figure 6 is a perspective view similar to that of Figure 1 but showing the modular floor unit after filling the edge frame with concrete; Figure 7 is a sectional detail through one portion of an edge frame, with the set concrete having been poured and encasing the lattice of reinforcing rods or wires; and Figure 8 is a sectional detail through mutually abutting edge portions of two edge frames according to Figure 7, after being turned so that their smooth bottom surfaces face upwards, and with an upwardly facing recess being formed around the periphery of each floor unit.

To manufacture a modular floor unit according to the invention, first of all an edge frame 1 as shown in Figures 1 and 2 is constructed. Accurately sized and proportioned edge members 2 are cut from cold-rolled C-section sheet metal having the sectional shape shown in Figure 2 or Figure 3. That shape comprises a conventional C-section having a full height upright wall 2a, mutually parallel top and bottom walls 2b, and return flanges 2c spaced from but parallel to the wall 2a, but additionally having one or two out-turned flanges 2d along the mutually parallel facing edges of the top and bottom walls 2c. Figure 3 shows the C-section with one out-turned flange 2d, and Figure 2 shows the alternative C-section with two such out-turned flanges 2d.

The open mouth of the C-section is indicated as 3a in Figure 2, between the two out-turned flanges 2d and as 3b in Figure 3, between the one outturned flange 2d and the opposite return flange 2c.

The size and relative proportions of the edge members 2 is preferably such that together they accurately represent the floor dimensions of a room of the dwelling or other building in which they are ultimately to be used. The corners are mitred and welded or brazed together to form a continuous edge shuttering for the wet concrete that is going to be poured into the edge frame I as will be described later. The cutting of the mitre joints can be extremely accurately controlled with a CNC laser cutter, to provide a final edge frame that is dimensioned to a final accuracy that is well in excess of that which is normally expected in building constructional work where measurements are normally made on-site.

The open mouths 3a and 3b of the edge members 2 all face the centre of the assembled edge frame 1, and a lattice of metal rods or wires 4 is secured across that open centre extending from one side to the other. Figure 2 shows one method of securing the lattice. Each rod 4 of the lattice rests on the lower out-turned flange 2d of the C-section and is welded or brazed to that out- turned flange 2d where they are in contact. In an alternative modification of the construction (not illustrated) a second lattice of reinforcing rods or wires, similar to the first, could be welded or brazed to the upper out-turned flange 2d of figure 2 so that the two lattices are mutually spaced apart. This provides greater reinforcement when the wet concrete is poured into the edge shuttering, but does of course require a greater depth of concrete to cover both lattices. This greater level of reinforcement can be important when the floor unit is made of a dimension to form a continuous span across larger rooms.

Typically the reinforcing rods or wires of the lattice are welded or brazed together at each intersection. Panels of pre-welded mesh can be used, or the rods can be secured in place individually and then welded at each crossing point. The rods can be smooth profiled or shaped for a better key to the concrete that is eventually to cover and encase them.

Figure 3 illustrates an alternative means of securing the rods or wires of the lattice 4 to the edge frame I. Each rod or wire rests on the outturned flange 2d but continues across the centre of the C-section profile to pass through a hole formed in the outer upright wall 2a. The individual wires or rods are welded or brazed to the edge frame I where they pass through the outer wall 2a, and are then cut off after welding or brazing, and the connection smoothed with an angle grinder. If desired, further welds or brazed connections can be made where the individual wires or rods pass over the out-turned flanges 2d, as in Figure 2.

The advantage of this method of construction is that the wires or rods of the lattice can be pre-tensioned before or during the step of connecting them to the edge frame, to create a pre-tension in the internal reinforcement of the concrete that is subsequently cast in the edge shuttering created by the edge frame 1.

One important and preferred feature of the lattice 4 is that at a few mutually spaced locations the wires or rods of the lattice extend upwardly into a loop 5 as shown in Figures 1, 2 and 4. The number of such spaced locations is a matter of design choice, and depends on the intended function of the loops 5 in the final modular floor unit. The loops 5 are always used for lifting and handling the complete modular floor unit, but it is possible that a greater number of such loops 5 could be specified for the establishment of anchorage points for hanging a suspended ceiling beneath the floor unit in the final building.

The loops 5 could be made from a simple bend in a continuous length of rod or wire as in Figure 4, or could be formed separately and wrapped around or wired to or welded or brazed to the rod or wire lattice as in Figure 5.

When the edge frame 1 is complete, it is placed on a smooth level surface that has been coated with a mould release agent such as an oil film. The smooth level surface may be a solid concrete surface covered with a cladding of boarding or metal, or simply painted with an impervious paint that together with the mould release agent avoids the adherence to the surface of the wet concrete that is poured into the edge shuttering provided by the edge frame 1.

Concrete is poured to a depth sufficient to cover the or each lattice 4 of reinforcing rods or wires, but not sufficient to cover the upstanding loops 5. A line L in Figure 2 indicates a typical pouring depth. The concrete spills over into the hollow interior of the C-section profiles of the edge members 2 and reinforces the edge frame 1 against accidental damage during its subsequent handling. If desired, conventional vibrator tools can be used to assist in the complete and uniform filling of the mould and to expel entrained air.

When the concrete has set, the floor unit is as shown in Figure 6. The edge frame 1 is an integral part of the cast structure, which therefore has the finished outer dimensions which are a characteristic of the accurate fabrication of the edge frame. A number of loops 5 extend up and out of the cast concrete. The floor unit can be picked up using lifting equipment such as a crane using these loops 5 as carrying points, and is then inverted, probably on-site, so that the loops 5 go to the bottom of the floor unit and the top surface has the smooth and flat finish that is a characteristic of the smooth level surface on which the edge frame I was positioned while the concrete was poured. This smooth level surface requires no screeding on-site and is a smoother and flatter floor finish than any that are attainable by conventional building methods. Moreover it can be continuous across the entire footprint of the room, or alternatively if a number of smaller floor units are placed together side by side to form the floor of the room they will butt together to create a smooth and flat floor because the junction between adjacent floor units are established by smooth metal-to-metal contact of adjacent edge members 2.

Around the edge of the floor unit is a continuous rim of steel, provided by the edge frame 1. That can be shaped or apertured during fabrication (i.e. prior to pouring the concrete) if required to create accurately positioned anchorage points for prefabricated wall units of the building to the constructed.

Alternatively the wall units can be connected on site by riveting, screwing, welding or brazing to the edge frame 1. To assist connection onsite by screwing, an insert of timber 6 could if desired be placed in the bottom of each edge member 2 as shown in Figure 3, so that a self-tapping screw can be inserted through the top edge of the edge frame 1 on-site and into the timber 6.

Another use of timber during the construction of the floor unit is illustrated in Figures 7 and 8. During the concrete pouring step the entire edge frame I could be raised above the smooth level casting surface on an edge frame of timber 7. That timber 7 would have to be braced and anchored to prevent it from bowing outwardly under the pressure of the wet concrete, but once the concrete has set can be removed to create an edge channel 8 around the periphery of the top surface of the finished floor unit. Figure 8 shows two such edge channels 8 located side by side between adjacent floor units.

Those edge channels can be used to assist in the location of partition walls in the building under construction or can be filled with a screed or grout of mortar on-site, to create a smooth transition between adjacent floor units. That is important in those cases where the floor units do not span the complete length and width of a room, or when they form the floors of corridors which are too long or too complex in shape to have a floor provided by a single prefabricated floor unit, it will of course be appreciated that the simple grouting of recesses 8 on-site is a significantly less intrusive and obstructive site operation than the laying of a complete cement screed across the entire floor of a building, as at present.

Because the edge frame I is made to precise dimensions using CNC cutting equipment, it is feasible to incorporate into the edge frame apertures for the location of the ends of pipes or conduits which can be positioned across the edge frame 1 before the concrete is poured. Such pipes or conduits in adjacent floor units in the final building are in precise register due to the accuracy of the fabrication of the edge frames 1, and can act as trunking for - -9-.

electrical cables or even as water or heating pipes (optionally after lining them in the final building with a continuous pipe liner).

Claims

1. A modular floor unit for creating a solid floor of a building, comprising; an edge frame made from cold-rolled C-section sheet metal edge members welded or brazed together to form an accurately sized and proportioned edge shuttering for the floor unit, with the open mouth of each C- section edge member facing the centre of the edge frame; a plurality of metal reinforcing rods or wires extending in a lattice from each side of the edge frame to an opposite side, and welded or brazed to the C-section edge members of the edge frame at each point of contact therewith; and a concrete slab cast within the edge frame and encasing the reinforcing rods or wires, the concrete slab filling at least a part of the hollow interiors of the C-section edge members and being cast over a smooth base to which a mould release agent has been applied, the resulting smooth bottom surface of the cast concrete slab forming the upper face of the resulting floor unit.

2. A modular floor unit according to claim 1, wherein the lattice of metal reinforcing rods or wires is provided with an array of hanging or lifting eyelets which extend upwardly out of the concrete slab during casting and which depend from the underside of the modular floor unit in use.

3. A modular floor unit according to claim 1 or claim 2, in which the lattice of metal reinforcing rods or wires is a grid of rods welded or brazed together at their intersections.

4. A modular floor unit according to claim 1 or claim 2, wherein the lattice of metal reinforcing rods or wires is a lattice of rods or wires pre-tensioned between the C-section edge members of the edge frame, before the concrete slab is cast.

5. A modular floor unit according to any preceding claim, wherein two mutually spaced lattices of metal reinforcing rods or wires extend across the edge frame, both being welded or brazed to the C-section edge members of the edge frame at each point of contact therewith; encased within the concrete slab as reinforcement for the concrete.

6. A modular floor unit according to any preceding claim, provided with an edge rebate along one or more top edges of the floor unit.

7. A modular floor unit according to any preceding claim, provided with a timber infill located at the bottom of each of the C-section internal cavities of the edge members during casting of the concrete slab.

8. A method for the manufacture of a modular floor unit for a solid floor of a building, comprising: creating an edge frame from edge members of cold rolled C-section sheet metal welded or brazed together to form an accurately sized and proportioned edge shuttering for the floor unit, with the open mouth of each C- section edge member facing the centre of the edge frame; securing a plurality of reinforcing rods or wires to extend in a lattice formation from each side of the edge frame to an opposite side, by welding or brazing each reinforcing rod or wire to the C-section edge members at each point of contact therewith; placing the assembled edge frame and supported reinforcing lattice on a smooth flat surface that has been coated with a mould release agent; pouring wet concrete into the space defined by the edge frame, to a depth sufficient to cover and encase the lattice of reinforcing rods or wires and partially to fill the central cavities of the C-section edge members; allowing the concrete to set into a cast slab bounded by the edge frame; and lifting the cast slab together with the edge frame from the smooth flat surface on which it has been cast, and inverting the cast slab to present its smooth face, being the bottom face during casting, as the top face of the resulting modular floor unit.