BUILDING FLOOR STRUCTURE AND METHOD FOR LAYING DOWN THEREOF

The present invention relates to floor structures for civil and industrial buildings or the like, wherein a concrete slab is cast onto a carrying structure. Such floor structures may be laid down directly on site, or else they may be prefabricated separately and then installed as required; the present invention relates to both of these possibilities, and therefore, unless otherwise specified, the following description and the appended claims will refer to all alternatives. Moreover, it must be added that, although the invention is particularly suited to building floor structures, i.e. elements used for floor structures, it may however also be applied to vertical walls of buildings, in particular as a prefabricated panel, as detailed later.

It is known that an important requirement of floor structures is the relation between carrying capacity and weight; for this reason, there are many types of floor structures wherein light materials may be used, in particular polystyrene foam or polystyrene. i Some examples of these structures and of the components thereof are described in the English patent application GB 2355024 in the name of Roxbury Ltd. and in the Japanese one JPl 1036508 in the name of Shimizu Construction. The former describes a structure wherein a concrete slab is applied onto a polystyrene foam layer having a Greek fret profile section: in practice, the polystyrene panel is used as a formwork for the subsequent concrete cast, wherein also reinforcing rods are applied in order to improve the mechanical properties and the carrying capacity of the final floor structure so obtained. This solution offers the advantages of being easy to implement due to the fact that polystyrene is light, thermoinsulating material and at the same time can be used as a formwork for concrete.

However, the polystyrene layer itself cannot provide much strength and it is probably for this reason that, according to the Roxbury document, reinforcement rods are laid onto the valleys of the frets, buried in concrete.

However, this solution seems to be hardly feasible because in the first place it is not clear how the rods are kept in a position apart from the fret valleys, and secondly they do not seem to be connected to any reinforcement or any other external component, so that they cannot exert a very significant reinforcement action.

An improvement of this state of the art is represented by the aforementioned Japanese patent by Shimizu, wherein prismatic polystyrene blocks are inserted in the frets of a sheet metal; the latter has apertures and slots for the application of reinforcing rods, and the structure so obtained is interposed "sandwich-wise" between two concrete slabs.

In this case, the floor structure appears to be too complex, since it requires first the reinforcement rods to be assembled together with the sheet metal, and then the polystyrene blocks to be inserted in the spaces between the sheet metal and the rods. It follows that laying down a floor structure of this kind on site can be difficult in practice; however, even if the floor structure is prefabricated separately, assembling its components (manually, because it cannot be devised how to automate it) is not easy at all. The technical problem underlying the present invention therefore consists in providing a floor structure having structural and functional features which overcome the drawbacks described above, with reference to the state of the art taken into consideration.

The idea to solve said problem is to lay down a floor structure wherein concrete is cast onto a composite panel of the so-called "sandwich" type, which comprises a core made of an insulating material, usually a synthetic foam, interposed between two outer faces cooperating therewith, preferably made of sheet metal.

The synthetic foam is typically of the polyurethane type, as in insulating panels manufactured by the Applicant, whereas the panel may have both faces smooth or with frets, or else a smooth face and the other face with frets: this allows to

obtain floor structures having different thermal insulation and carrying capacity properties.

The features of the invention are set forth more specifically in the claims appended to this description; said features as well as the effects and the advantages deriving therefrom, will become more apparent from the following examples which disclose some preferred but not exclusive embodiments of the invention; in the drawings:

- Fig. 1 shows a perspective view of a first example of a floor structure according to the invention, with a portion removed; - Fig. 2 shows a cross section of the outer faces of a panel included in the floor structure of Fig. 1;

- Fig. 3 shows a cross section of the floor structure;

- Fig. 4 shows a sectional view of the floor structure along the line IV-IV of Fig. 3; - Fig. 5 shows a perspective view of a second example of a floor structure according to the invention, with a portion removed;

- Fig. 6 is a longitudinal section of the floor structure of Fig. 5.

In the drawings, reference numeral 1 designates as a whole a floor structure according to the invention, whose construction is shown in Figs. 1 and 3, comprises a "sandwich-type" composite panel 2 on which a concrete slab 3 is placed.

The latter may be provided with known reinforcement, e.g. iron rods, timber joists or other elements (not shown in the drawings), although, as better explained below, this is not necessary for the floor structure according to the invention.

The composite panel 2 is insulating and preferably of the type manufactured by the Applicant for the present application; in this regard, reference is to be made to the various patents obtained by the same Applicant, in particular to the European patent application EP 1485545 relating to continuous manufacturing of panels having both faces with deep frets, the contents thereof are fully drawn and incorporated herein by reference.

Of course, any other appropriate method for manufacturing "sandwich- structured" insulating panels may be used, also taking into account the various configurations of the panels themselves and of the faces thereof; thus, for example, in some cases the panels 2 may be manufactured through a discontinuous process by using moulds and presses, according to known technologies.

The panel 2 comprises an insulating core 5 interposed between two external sheet-metal faces 6 and 7; the insulating core is made of a synthetic foam, preferably a polyurethane foam, which adheres weE to the outer faces 6 and 7, so that they collaborate with the insulating core 5 to limit panel deformation under load.

As shown in the drawings, the sheets 6 and 7 are fretted with equal ribs 10, having a trapezoidal profile; in particular, pitch and profile of the ribs 10 and of the valleys 11 are equal. Furthermore, according to a preferred embodiment of the invention, the fretting is deep, i.e. the height H of the ribs from the bottom of the valleys 11 is greater than 30 mm and preferably greater than 50 mm for insulating core thicknesses S of approximately 60 mm. In order to promote the adhesion of concrete to the upper sheet metal 6, on the flanks of its ribs 10 there are prints 14 of the type already in use for sheets metals for floor structures, manufactured by the Applicant under the commercial name "Hi Bond"; thanks to said prints, it is no longer necessary to arrange falsework in concrete. Finally, in order to obtain a proper junction along the edges of adjacent panels in the floor structure, gaskets 16 made of rubber or other elastomers are used. The floor structure according to the invention may be laid down in situ, i.e. at the construction site, or it may be prefabricated separately as an industrial product. In the former case, the insulating panels 2 are first secured to the joists 17 of the warp supporting the floor structure; this operation may be carried out by

using any appropriate means depending on the type of joists used, e.g. by using screws or any other equivalent system.

Within this context, it should be specified that for some special applications, such as constructions including corbels 19 on bearing walls, the panel edge 20, which is transversal to the ribs 10, has a step-like design, as shown in Fig. 4. This is obtained by extending the sheet metal of the upper face 6 relative to the insulating core 5 and to the lower face 7; note that with such a joint support it is possible to support the panels 1 along the edges alone (i.e. without intermediate joists 17), provided that the distance between the ends of the panels is not excessive with respect to their inflectional rigidity.

After having laid down the panels as explained above, concrete is cast, possibly applying reinforcing rods; usual floor finishings can then be applied onto the floor structure so obtained. In the case of prefabricated floor structure, the insulating panels 2 are inserted into moulds (not shown in the drawings); concrete casting is then applied thereon and, once it has set, a modular prefabricated floor structure is obtained which can be transported to the construction site and then installed like existing prefabricated floor structures. The above description has clearly explained how the structure of the floor structure 1 solves the problem addressed by the invention.

In fact, as described, the invention is easy to implement both when working on site and when manufacturing a prefabricated floor structure separately. Another clear advantage is the fact that it is not necessary to fabricate any formwork for the concrete casting, since the panels 2 perform this function themselves.

From this point of view, it can therefore be stated that the building floor structure according to the invention has some analogies with the one described in the English patent application GB 2355024 to Roxbury; however, unlike the latter, the composite panel 2 of the present invention comprises, in addition to a synthetic-foam insulating core 5, also outer faces 6 and 7 collaborating therewith.

The panel 2 has therefore much better mechanical strength and carrying capacity proprieties than the simple polystyrene layer of Roxbury's patent. Furthermore, the carrying capacity of the panel 2 is such that it does not require any complex concrete reinforcement, thus avoiding all those problems highlighted by the Japanese patent JPl 1036508 by Shimizu Construction.

In this connection, it should also be pointed out that the insulating panels 2 laid down on the joists 17 of the floor structure or supported along the edge 20, represent themselves a carrying surface suitable for bearing people's weight, thereby facilitating the laying. In this particular example of the invention, the configuration of the panels themselves is also advantageous, in that their upper and lower faces 6 and 7 have both deep frets; this feature, as explained in the aforementioned European patent application EP 1485545, is not usually applied to insulating panels due to reasons related to the production process. It is however able to provide the panels with much strength and, moreover, the presence of ribs 10 and valleys 11 having the same profile ensures a more even behaviour of the panels 2 under the loads applied to the faces thereof. Within this context, it should also be pointed out that since the panel 2 has the same fretting on both faces 6, 7, with the ribs 10 and the valleys 11 having the same profile, the thickness S+H of the insulating core 5 is substantially constant, thus ensuring an even behaviour as concerns thermal insulation from heat transmission by conduction.

Finally, it will be appreciated that, compared to the aforementioned prior art, this example of a building floor structure according to the invention is suitable for the application of finishing panels, as indicated with a dashed-dotted line in Fig. 1.

These finishing panels may belong to false ceilings used for covering plumbing, raceways, wirings, sheaths or other elements, which are easily placed in the valleys 11 of the lower face 7 of the panel 2, as generically indicated with dashed line circles E in Fig. 3.

Of course, many changes may be made to the above-described invention; in this regard, it has already been said at the beginning that, though the invention is particularly suited to building floor structures, it may even be applied to vertical walls. In other words, it is conceivable to use the aforementioned prefabricated floor structures as curtain elements for buildings; in such a case, variants might be studied in order to obtain lighter prefabricated elements, e.g. by reducing the thickness of the composite panel 2 or of the slab 3.

It should also be emphasised that, notwithstanding polyurethane foam is the preferred material for providing the insulating core 5 of the panel 2, it might however be replaced with alternative materials, among others including polystyrene foam.

In this frame, whatever the material used for the insulating core 5 of the panels

2, what matters is that it is integral with the upper and lower walls 6 and 7 so as to collaborate therewith in providing adequate mechanical strength to bear the weight of concrete and to form the desired floor structure.

Many variants are possible also as regards the shape of the insulating panel 2 and the manufacturing method thereof.

As already mentioned, it may be manufactured through a continuous or discontinuous process; in addition, independently of the manufacturing process employed, it may also have configurations other than that with both faces 6, 7 with frets.

An example of such an alternative configuration is shown in Fig. 5, wherein for sake of simplicity the same numbering has been used for elements being equivalent to those previously described, with the addition of an apostrophe.

As shown, in this case the insulating panel 2' has frets 10' on its upper face 6' only, whereas the lower face T has micro-ribs; the concrete slab 3' is then applied onto the panel.

Also in this variant of the invention, the floor structure may be fabricated in situ, i.e. by casting the concrete directly onto the previously laid panels 2', or else it may be prefabricated separately; in the former case, it is also possible to

use the step-like edge 20' for providing a joint in the corbel 19', as mentioned above.

Further possible variants of the invention as described so far, may be obtained by using materials other than those taken into consideration. It has already been mentioned that the polyurethane foam of the insulating core 2, 2' may be replaced, for example, with polystyrene foam or the like: the important thing is that polystyrene or other materials adhere to the outer faces 6, 7 and 6', T of the panels, so as to collaborate therewith like polyurethane foam does. Moreover, it should be pointed out that the insulating core 5 of the panels may also include a mineral wool layer, in combination with the synthetic foam, like in some special applications provided by the present Applicant, commercially known as Firemet ®. Materials other than sheet metal may then be used for the upper faces 6, 6' and the lower faces 7, 7' of the panels 2, 2'; thus, for example, one may use plastic materials (polycarbonates, PVC, polyethylene, etc.), composite materials like carbon fibres (aramidic fibres) and glass fibres (fibreglass reinforced plastic), or even materials like panel-shaped laminated wood (marine plywood, various types of laminated wood, etc.). Of course, the choice among these different materials will depend on various factors, such as the cost and weight of the panels, the loads to be borne, the thicknesses to be used, and so on.

It is also clear that combinations of different materials may even be employed for the upper and lower faces: for example, in the case of Fig. 5, the upper face 6' might be made of sheet metal in order to create the ribs 10' more easily, whereas the lower one T might be made of plastic, or carbon fibre, or wood. Finally, it should be pointed out that variants are conceivable for the concrete as well; in fact, in general it is possible to use any construction mix based not only on cement, but also on resins or the like. All of these variants still fall within the scope of the following claims.