Background of the invention For the installation of plaster covered boards for suspended ceilings several known problems arise.

In fact, the plaster suspended ceilings require metallic frameworks to which plaster covered boards are connected by means of self tapping screws. The frameworks are in turn screwed to the floors by means of screw anchors. In particular, it is difficult the drilling of concrete beams or other structural elements, usually in reinforced concrete. Furthermore it is in any case difficult to arrange metallic frameworks for supporting plaster suspended ceilings.

An important aspect of the construction of floors is the so called"vapour barrier", i. e. an insulation from humidity and vapour in gaseous phase that can give condensate water. In theory, the vapour barrier should be made at the lowermost surface of the floor. However, with traditional techniques of construction of floors the vapour barrier is made over the upper level of the floor, leaving not protected all the layer of the floor. This fact involves high costs in creating the insulating pack of the floor.

The vapour barrier normally is a sheet of aluminium integrated to a waterproof membrane. A typical floor, then, starting from the above towards below has a concrete casting with pavement, a waterproof membrane, an heat insulation, the vapour barrier by means of membrane with a sheet of aluminium, a primer, a reinforced concrete and hollow tiles mixed floor, and, at the lowermost surface, a plaster coating.

Therefore, it would be advantageous to move the vapour barrier towards below, eliminating the membrane with the sheet of aluminium and using plaster covered boards with integrated a sheet of aluminium or other equivalent vapour barrier. It is, however, complicated as above described to install plaster suspended ceilings in a way that is quick and not expensive on the floors lower surfaces.

Summary of the invention It is therefore object of the present invention to provide a structural element such as a ceiling beam or girder or pre-stressed concrete beam and similar, for making floors, roofs, etc., which makes remarkably easier the application of plaster suspended ceilings, without reducing the resistance of the final structure.

It is another object of the invention to provide a method for the production of this structural element.

It is a particular object of the present invention to provide a structural element for making floors, peaked roofs, etc., that is made not in plain concrete or tile- like material, which is, at the same time, self- supporting, and that allows the application of plaster suspended ceilings.

It is another particular object of the present invention to provide a plurality of elements associated to said structural element that allow the application of plaster suspended ceilings.

Hereinafter, with the term structural element a desired ceiling beam, girder or the like for floors is intended to define an element that achieves the principles according to the invention as described and claimed below.

According to a first aspect of the invention, a structural element has a lower side wall that can be perforated by screws, for making easier the installation of plaster suspended ceilings and for supporting their weight.

The layer that can be perforated by screws can be advantageously formed by a sheet section in which a layer is present of light material that is set between structural element and the sheet section.

The metal sheet section, filled with the layer of light material, when the structural element is laid, is oriented towards below the floor or roof pitch and allows thus the easy application of the screws, which cross both the plaster suspended ceilings and the metal sheet and can pierce all the layer of light material without hitting against concrete portions. This way, a plaster suspended ceiling can be made directly connected to the floor.

The light material can be chosen among polystyrene foam, polyurethan foam, wood, etc.

In a first embodiment of the invention, said structural element comprises a concrete casting and said layer that can be perforated by the screws is integrated to a lower wall of said concrete casting.

The layer that can be perforated by screws can be integrated to the concrete at casting the concrete.

Alternatively, the layer that can be perforated can be connected to the casting by means of screws or riveting after the casting, through brackets embedded in the casting same. The light material can, in this second case, be integrated at the moment of the casting or at the moment of the fastening of the sheet section to the

casting.

The concrete casting can be made with free or pre- stressed reinforcement bars, in order to obtain in the first case a girder for building industry and in the second case a concrete pre-stressed beam.

In a second embodiment of the invention, said structural element comprises a self-supporting framework as an elongated girder, but without concrete castings.

Under the elongated girder said metal sheet box-shaped section is arranged, which envelopes the elongated framework and in which said light material layer is present between the structural element and the metal sheet.

Preferably, said structural element is formed by at least a couple of stiff parallel boards, which extend for all the length, joined to each other by a plurality of spaced transversal brackets. The boards and the brackets can be in construction material such as steel, iron, aluminium, wood, and can be joined to each other for riveting, bolting, welding or gluing, according to the material of which they are made. The structural element, when it is laid, is used as a desired self-supporting girder, and is filled of plain concrete when casting the floor. After the casting, the layer that can be perforated by the screws allows to fasten plaster boards in the way above described.

According to another aspect of the present invention, a method for the production of a structural element for making floors has the characteristic that it comprises the following steps: - pre-arranging a box-shaped metal sheet section, in which a light material layer is present, - association of said metal sheet section to a structural element, whereby, in use, the lower side of said metal sheet section is a wall integrated to said structural element and that can be perforated by the screws.

In a first embodiment of the method, the structural

element is formed by a concrete casting, and for its production, in integration to the metal sheet section that contains the layer of light material, the steps are provided of:: - prearranging a concrete mould or equivalent material for casting the structural element; - arranging in said mould a reinforcement of the structural element, for example of iron bars; - arranging always in said mould, a fastening for said sheet in which a layer of light material has been pre- arranged.

In a first embodiment, the steps are provided of - introducing in the mould said sheet section having a flat face oriented towards below that lays on the bottom of the mould, in said sheet section a layer of light material being pre-arranged; - casting concrete in said mould incorporating said sheet section, said layer and at least part of said reinforcement; - extracting the structural element after hardening comprising a lower face of sheet section and the layer in light material integrated to the concrete and to the relative reinforcement that is embedded between the concrete and the sheet section.

In a second embodiment, the steps are provided of - introducing in the mould brackets oriented towards below and capable of protruding from the concrete after the casting; - casting concrete in said mould incorporating part of said reinforcement and of said brackets; - after hardening, fastening by means of screws or rivets said sheet section to said brackets, said sheet section having a flat face oriented towards below.

The light material can, in this second case, be preferably integrated at the moment of the casting,

arranged between the brackets. Alternatively, it can be connected at the moment of fastening the sheet section to the casting.

The length of the sheet section can in a first case extend for all the length of the structural element. In this case, the sheet section has the lower flat face that covers all the bottom face of the concrete casting, whereby the lower face of the structural element is completely a sheet section.

Alternatively, a plurality of portions of said sheet section arranged is provided aligned longitudinally, spaced and centred transversally. The width of the portions can be also less than the width of the casting, whereby the lower face of the structural element is made of concrete with at the centre a row of spaced portions of sheet section. It is also possible that the sheet section is continuous instead of discontinuous and of width less than the girder.

Advantageously, the sheet section is U-shaped. In it the light material lays, in such a way that the wings of the sheet section protrude from the layer of said light material. In the first embodiment, the protruding wings allow to the whole support, consisting in the sheet section and in the polystyrene foam layer, of being connected by means of screws directly to the wall side of the beam. In the second embodiment, the protruding wings offer a steadier fastening to the concrete.

In a further embodiment of the method, the structural element is formed by a self-supporting framework, without concrete portions, and for making it integral to the metal sheet section, that contains the layer of light material, the steps are provided of: - arranging a couple of stiff parallel boards, which extend for all the length of the structural element; - joining said boards by means of a plurality of spaced transversal brackets;

- fastening said metal sheet section, in which said light material layer is arranged, to said self-supporting structure formed by said boards and said brackets.

Before the union of the boards with the brackets, can be inserted a metal welded framework element, useful for forming the reinforcement of the floor.

According to the invention, the plaster suspended ceilings are screwed to the sheet section. In fact, the screws penetrate directly through the plaster board and through the surface of the sheet section into the light material in it contained.

In particular, floors made with concrete beams according to the invention, allow a quick installation of the plaster suspended ceilings. In fact, the plaster covered boards are directly connected to the beams of the floor in a steady way and adhere directly to the floor lower surface. With such an installation the working costs mainly given to the installation of a metal framework are eliminated.

If the plaster suspended ceilings are to be replace or removed, it is sufficient to release the plaster covered boards from the floor lower surface, without affecting further the ceiling beam.

A further advantage is that of providing a vapour barrier near the lower level of the floor. In this case, plaster suspended ceilings may be used equipped with a sheet in aluminium.

Furthermore being the girder according to the invention pierceable by the screws, it is possible to bolt it directly to the principal steel structures of the building, such as for example to the steel beams, or it can be connected by epoxy resins.

Advantageously, the lower parts of the sheet section can be coated of a insulating layer, for example, but not exclusively, adhesive layer of cellular polyethylene with

a layer of some mm.

Brief description of the drawings Further characteristics and the advantages of the structural element according to the present invention will be made clearer with the following description of an embodiment thereof, exemplifying but not limitative, with reference to the attached drawings, wherein: - figure 1 shows a sectional view of a portion of floor in direct phase of installation with two structural elements according to the invention; - figure 2 shows a perspective view of the floor of figure 1 after the application of an plaster covered board; - figure 3 shows a perspective view of a mould of casting of a structural element according to the invention with pre-arranged a sheet section and a layer of light material; - figure 4 shows a sectional view of the mould of figure 3 after the casting; - figure 5 shows an elevational longitudinal view of the structural element according to the invention as resulting after the casting; - figure 6 shows a perspective view of a mould of casting of a structural element according to the invention with pre-arranged a plurality of sheet section discontinued portions and inside layers of light material; - figure 7 shows a sectional view of the mould of figure 6 after the casting; - figure 8 shows a plan view from below of a different embodiment of the structural element according to the invention as resulting after the casting according to figures 6 and 7; - figures 9a and 9b show an elevational view, respectively frontal and longitudinal, of a reinforcement equipped with brackets concerning a different embodiment

of the invention; - figures 10a and 10b show an elevational view, respectively frontal and longitudinal, of the reinforcement of figures 9a and 9b after the application of a layer of light material; - figures lla llb show an elevational view, respectively frontal and longitudinal, of the reinforcement of figure 10a and 10b after casting of the concrete ; - figures 12a and 12b show an elevational view, respectively frontal and longitudinal, of the ceiling beam of figure lla llb to whose base a sheet section has been attached; - figures 13a and 13b show an elevational view, respectively frontal and longitudinal, of a ceiling beam of pre-stressed concrete to whose base a sheet section has been mounted; - figures 14 and 15 show respectively a structural element according to the invention in reinforced concrete and in pre-stressed concrete after the fastening to a steel structural beam; - figure 16 shows a perspective view of a structural element according to a second embodiment of the invention,; - figure 17 is an enlarged partial view of the structural element of figure 16; - figure 18 is a cross sectional view of the structural element of figure 16; - figures from 19 to 23 are cross sections of different embodiments of the structural element of figure 16; - figure 24 is a top plan view of a floor with structural elements like figure 16 and other auxiliary elements forming the span of the floor; - figures 25a and 25b show a side and perspective view of an auxiliary element to be arranged next to the structural elements at the zone of casting of the main girders;

- figure 26 is a top plan view of a floor with structural elements as that of figure 16 and other auxiliary elements forming the span of the floor; - figures 27a and 27b show a side and cross sectional view of an auxiliary element arranged next to the structural elements at the zone of casting of the main girders; - figures 28,29 and 30 show structural elements similar to that of figure 16 and respectively with end board, with end board and side bracket, with side bracket and side boards; - figure 31 is a sectional view of scaffold for casting a floor that exploits the structural elements according to the invention; - figure 32 is a partial view of a floor at casting with the structural element according to the invention and spanning elements in light foam material; - figure 33 is a cross sectional view of a floor like that of figure 32.

Description of a preferred embodiment With reference to figures 1 and 2, a structural element 1 according to the invention is used for making a floor 2 of known type in combination with hollow tiles 3.

In particular, is shown a hollow tile 3 resting on two structural elements 1. In the building industry, the structural element of figure 1 is normally defined as "girder", whereas the structural element of figure 2 is normally defined as"ceiling beam"in pre-stressed concrete.

According to the invention, each structural element 1 consists in a reinforcement 4 and by a sheet section 5, embedded in a concrete casting 6. The sheet section 5 is filled with a layer of light material 8 that is set between the concrete 6 and the sheet section 5 and is oriented in use towards below of the floor for application of plaster suspended ceilings 9 (figure 2).

In fact, since the sheet section 5 can be easily

perforated, for example with self tapping screws 10, and since the light material 8 allows free penetration, the plaster suspended ceilings 9 are easily screwed to the structural elements 1. More precisely, the screws 10 cross in turn the plaster board 9, the lower face of the sheet section 5 and penetrate all the layer of the light material 8 without forcing, unless at the end of the movement, against concrete 6. This way a floor lower surface made of plaster board is created directly connected to the concrete beams of floor 2.

With reference to figures 3 and 4, to make the girder 1 according to the invention, which can be seen in longitudinal vista also in figure 5, it is sufficient to provide a mould 7 for casting concrete. In a first step the sheet section 5 with a face 5a oriented towards below is laid onto the base 7a of mould 7. Over base 7a of mould 7, the reinforcement 4 is arranged that, after the casting of concrete 6, becomes the reinforcement of the structural element 1.

In the embodiment of figures from 1 to 5, the length of the sheet section 5 extends for all the length of the structural element 2.

Advantageously, the side walls 11 of the sheet section 5 are slightly higher of the layer of the light material 8 in it contained, creating thus two protruding wings lla. Such protruding wings lla allow to the sheet section 5 and to the light material 8 to be connected by means of screws 12 directly to the wall side of the floor beam 2 (figure 2 and 5) by means of pins not shown, previously inserted in the mould.

With reference to figures from 6 to 8, in a second embodiment of the invention, the structural element 1' comprises a plurality of portions 5'of sheet section arranged aligned longitudinally, spaced and centred

transversally for a width less than that of the structural element 1'. The portions of sheet section 5'are inserted in the mould 7 alternated before casting the concrete (figure 6 and 7). This way, a structural element is obtained that has a lower face in concrete 6 (figure 8), discontinued by the portions of sheet section 5', which can be used for fastening plaster covered boards.

Figures from 9A to 11B show in turn the steps of a further embodiment of the invention. With reference to figures 9A and 9B, respectively in front and longitudinal view, a reinforcement 4 is arranged, of traditional type, to which brackets 13 are welded. Blades 14 are also provided that define the position of the sheet of light material 8 (Figure 10A and 10B). In particular, the brackets 13 are welded to reinforcement 4 spaced as shown in figure 9B.

As shown in figures 11A and 11B it is sufficient to put the reinforcement thus equipped in a mould for casting the concrete 6. To make the base in sheet section on the girder 1, as shown in figure 12A and 12B, it is sufficient to fasten by means of screws 12 the sheet section 5, which is put on the floor beam, causing the self tapping screws 12 to penetrate brackets 13 and then blades 14.

Lo same method can be can be used for making a floor beam of pre-stressed concrete 1", shown in figures 13A and 13B.

Structural elements 1,1'or 1'', thus made, can be easily connected to a structural H beam 16 of steel, as shown in figures 14 and 15. In fact, it is sufficient to use screws 15 that penetrate the sheet section 5.

Structural elements 1 thus made allow a quick fastening of the ceiling of plaster covered boards 9 directly to the lower surface of the floor. This way, it is not necessary to install additional frameworks to the

plaster suspended ceilings 9.

The possibility of coating the lower surface of the floor with plaster covered boards 9 connected with screws 10 (figure 2) is particularly advantageous, since the traditional concrete beams of reinforced concrete cannot be pierced by the screws. The advantages are not only in quicker installation, but also in a less operative work, with a subsequent reduction of the costs of construction.

A further advantage, furthermore is the possibility of using plaster covered boards 9 with embedded sheet of aluminium to provide the vapour barrier at the lowermost level of the floor.

In a way not shown, finally, the lower face of the sheet section 5 may be coated with an insulating layer, in species cellular polyethylene some mm thick. This way, the heat bridge that usually affect floors near the beams is eliminated, caused by the higher heat conductivity of the concrete beams with respect to the rest of the floor, which comprises hollow tiles.

With reference to figures 16,17 and 18, according to another embodiment, a structural element 21 according to the invention is formed by a self-supporting framework, without concrete portions.

For its production integral to metal sheet section 25, that contains the layer of light material 28, two parallel stiff boards 22,23 are provided, which extend for all the length of the structural element 21. The stiff boards are joined and kept integral to each other by means of a plurality of transversal spaced brackets 24. The metal sheet section 25, in which the layer is arranged of light material 28, is fixed to the self-supporting structure 21 formed by boards 22,23 and by brackets 24.

Before the union of the boards 22,23 with the brackets 24, an metal framework 4 is inserted, useful for the reinforcement of the floor.

In figure 16,17 and 18 a section 29 is also shown that insulates heat transfer through boards 22 and 23 with respect to elements that rest on the boards same for spanning the floor, as shown hereinafter.

Figures from 19 to 23 are cross sections of other embodiments of the structural element, featuring respectively: - absence of section 29, for example when boards 22 and 23 are in insulating material, for example wood, or when the thermal insulation is not necessary; - presence of a transversal tube 26 that crosses the structural element 21 and allows the passage through it of installation cables or tubes; - bracket 24 extending up to the upper edge of boards 22 and 23; - element 21 having different size, depending on the needs, with corresponding different shape of bracket 24; - structural element 21 with fastening screws 50 of two brackets 24.

With reference to figure 24, a floor with structural elements like that of figure 16 can also be made with the aid of auxiliary elements 34 and other light elements 40 that are arranged to span the floor.

In figure 24 three structural elements 21 are provided to whose end auxiliary elements 34 are connected, arranged also laterally, resting on side boards 32. The auxiliary elements 34 have brackets 39 with protruding elements 39a (figure 25a and 25b) suitable for sinking in the concrete of the floor casting. Brackets 39 can be pierced by the screws. Therefore, by arranging a scaffold boarding 42, according to a rectangle among four upright columns 43, it is possible to cast the main girders on the scaffold boarding 42 with integration of auxiliary elements 34. This way, under the final main girders plaster suspended ceilings can be fastened by piercing brackets 39.

In a similar way, in figure 26 a floor provides structural elements 21, with auxiliary elements 30 and 34, arranged respectively at the ends and at the sides of

structural elements 21. For making, instead, surfaces that can be pierced for fastening the plaster suspended ceilings, are boards 36 are provided having hollow frames 37 (figures 27a and 27b).

Auxiliary elements 30 and 34 are better shown in figures 28,29 and 30. More precisely to the structural element of figure 16 are respectively connected: an end board 30, by means of rivets 31; an end board 30 with side bracket 32, connected with rivets 33; as well as a side bracket 32 with side boards 34 connected with screws 35.

A scaffold similar to that shown in figures 24 or 26 is shown in figure 31, using stays 46 for supporting the scaffold boarding 42. The hollow tiles 40 and the structural elements 21 span the floor and support casting in plain concrete 45.

In figure 32 how a floor 45 is made is shown using the structural elements 21 and hollow tiles 40, for example in polystyrene, resting on boards 41, or continuous spanning elements 50, in foam material, for example polystyrene.

Figure 33 is a cross sectional view of the floor as that of figure 32, with continuous spanning elements of polystyrene 40 resting on boards 41. There are also: plaster suspended ceilings 9, installations 51, which pass through channels 38 between the structural elements 21, upper layers 47 and 48 of the floor.

The foregoing description of a specific embodiment will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason,

departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.