ITCS20120037A1 - MIXED FLOOR IN GREEK SHEET AND CONCRETE FOR BUILDINGS - Google Patents

Description

Mixed slab in corrugated sheet metal and concrete for buildings

TECHNICAL FIELD OF THE PATENT.

This patent relates to a new type of mixed steel-concrete floor made with components widely available on the market but associated and connected together in such a way that the resulting product is highly innovative in terms of lightness and strength.

The invention is characterized by the original system of support, positioning and locking of the electro-welded meshes used in the construction of mixed steel-concrete floors.

In the present invention, only cold-shaped brackets with a length (Ls) shorter than the pitch of the corrugated sheet (plg) are provided (and a possible U-fork and / or a possible round bar, square or other profile) which make the connection between the following components:

- corrugated sheet,

- electrowelded mesh

- concrete (ordinary, light or ultralight).

In addition to satisfying the needs of corrugated sheet metal floors and ordinary concrete, it is the only system that can be industrialized to create very light slabs with the use of ultralight concrete.

The system of the present invention is indicated in the construction of buildings and in the renovation of old buildings as it allows to leave the old wooden beams, eliminating the heavy layers of filling between the planking and the floor. The lightening makes it the floor to be privileged in the reconstruction after seismic events as it reduces the exposure to seismic risk.

The use of high quantities of recycled polystyrene-polystyrene makes the present invention the most suitable for both the Green Building and for energy saving as well as the lightest concrete floor existing today. The lightness allows to eliminate the temporary shoring installed before the concrete casting, with obvious savings in purchase, transport, assembly, disassembly and storage.

Even more important is the benefit resulting from the elimination of shoring: - the construction of multi-storey buildings becomes very fast and less expensive,

- the programming of the casting of the floors can be in any order,

- if the attic on the top floor is laid first, the construction site is largely protected from rain,

- consequently the subsequent jets can also take place in the rain, respecting the contractual times,

- work safety problems decrease as the presence of men decreases today.

For large span corrugated sheet slabs with high loads, which require concrete in the compressed area with a strength greater than 25 MPa, it is possible to make a first casting in ultralight concrete (up to the plastic neutral axis that cuts the core of the brackets) and a second in ordinary concrete, up to cover the electro-welded mesh. In this case it is precisely the brackets that make the two jets integral and monolithic, maintaining both the qualities of lightness and resistance to large spans and high loads.

There are other benefits such as the surface roughness that allows the floors to grip well, the fire-fighting partition between the floors, the weight and cost savings of the load-bearing metal structures.

The mounting of the brackets is very quick: it takes place on site, with a vertical insertion of the tabs of the connectors in the slots or incisions on the corrugated sheet; the rotation and snap fastening of the harpoons follows.

Subsequently, it is possible to insert the U-forks and / or bars to block the electro-welded mesh, without any need to perform alignments, tracing, drilling, screwing, riveting, welding or other expensive site operation.

The bracket lends itself to easy post-production stacking and packaging which reduce the overall dimensions, transport and handling costs to the minimum possible levels.

STATE OF THE ART.

In corrugated sheet metal and ordinary concrete floors, the structural advantage brought about by the compressive strength of the concrete is largely diminished by the same weight of ordinary concrete. Remember that the variable or useful loads are present only in statistical percentage while the permanent structural ones, such as the floor, are always present.

To avoid problems of disconnection and â € œbuoyancyâ € between the concrete casting and the corrugated sheet, electro-welded meshes anchored in various ways to the corrugated sheet have always been used.

The remedies currently adopted are handcrafted and of little efficacy: round iron rods, profile pieces, etc. etc. However, these devices remain not connected either to the corrugated sheet or to the overlying electro-welded mesh.

The anchoring devices of the electro-welded mesh include:

- welding points or buttons performed manually, between mesh and corrugated sheet, with the electro-welded mesh in contact and coplanar to the corrugated sheet,

- L-shaped brackets fixed in the bottom of the rib channel, with screws or nails shot to the profiles of the steel structure (supporting the corrugated sheet); it would then be occasionally possible to connect the electro-welded mesh with manual binding to these L-shaped brackets.

The welding operation, with thousands of points or buttons, locally alters the galvanized protection of the corrugated sheet. If the electro-welded mesh is placed directly on the corrugated sheet, areas where the rods of the electro-welded mesh are not wrapped by the concrete arise with constancy, in alternating sections, such as the shaping of the corrugated elements; therefore the electro-welded mesh is badly connected to the concrete casting. Furthermore, the electro-welded mesh panels are free to move during the casting, therefore they must be tied together with iron wire, to guarantee the overlapping lengths between the various sheets.

A mesh installed in the manner described does not help to counteract the shrinkage of the concrete, it is not placed in the area of the taut fibers (where the corrugated sheet rests on the beams and is characterized by a negative bending moment) nor is it effective to form (together to the corrugated sheet) the rigid surface so important and sought after in anti-seismic structures and required by the new technical standards.

THE ROLE OF ORDINARY CONCRETE AND ULTRALIGHT CONCRETE (polystyrene, polystyrene, polyurethane, recycled or not).

The concretes that can be used to build corrugated sheet slabs, in relation to their weight, can be classified as follows:

- Ordinary concretes: specific weight 2.300-2500 Kg / mc,

- Light concretes: specific weight 1.400-1600 Kg / mc, - <Ultra-light concretes: specific weight 200-800 Kg / mc.>

Passing from ordinary concretes to ultralight ones, there is a gradual replacement of traditional aggregates (sand and gravel) with those of a lighter type. In lightweight concretes the larger diameter aggregates are replaced by perlite or expanded clay, with the presence of sand again. In ultra-light concretes, also called so because they can float on water, the larger diameter aggregates are replaced by granules of sintered expanded polystyrene, expanded polystyrene, cork, wood shavings, etc. etc.

The polystyrene and polystyrene foams can also be of the recycled type, obtained from packaging or insulation reduced to chips and granules of various shapes.

On the contrary, they are preferable as they have a shape that allows them to “mesh” better in the cement paste and avoid segregation with floating. In ultralight concretes, the sand remains in the high weight range, between 500 Kg / mc and 800 Kg / mc.

The main purpose of the sand is to allow the workability of the ultra-light concrete by the vibrators which, with very short interventions, here and there, of one or two seconds each, quickly make the concrete pour into the channels of the corrugated sheet.

Under the weight of 500 kg / mc, only water, foaming surfactants, cement, hyperplasticizers and polystyrene-polystyrene granules are used to make ultra-light concretes.

If you want to reach the maximum strengths allowed for the category of ultralight concretes, it is necessary to add silica fume or silica fume, essentially silicon dioxide SiO2 â € œamorphousâ € that is without a crystalline lattice. In this form, silicon oxide is extremely reactive at room temperature and easily combines with secondary calcium hydroxide, residual product of the main but incomplete reaction of hydrated calcium silicates, forming further fibers or microscopic needles of hydrated calcium silicates. This secondary reaction (in quantitative and temporal terms) also known as pozzolanic, allows to originate a much denser structure of needles that intertwine with each other giving rise to the resistances traditionally measured on the cubes in a free crushing test. Furthermore, the dimensions of the silica smoke of a few nanometers allow it to be placed inside the structure of hydrated calcium silicates, which has voids of a few tens of nanometers, making the overall structure more dense, impenetrable and resistant. Another advantage of these concretes is the medium-high quantity of CS (calcium silicates) which allows, once hydrated, to develop a considerable quantity of chemical bonds towards the Fe-Zn alloy of which the corrugated sheet of the floors is made. resulting in good structural adhesion.

DESCRIPTION OF THE INVENTION, OF THE FIGURES AND OF A FAVORITE WAY OF REALIZING THE INVENTION.

The mixed floor made of corrugated sheet metal and concrete object of the present invention comprises a bracket which constitutes a connection device between the corrugated sheet and the electro-welded mesh of the floors (Fig. 1 Tav.1).

It constitutes a radical innovation, both for highly industrialized production and for the elimination of all accessory processes, subjections and additional building site costs.

It consists of a profile whose literal measures are shown in Fig. 2 Table 1:

- <Ls: bracket length (2),>

- <Lb: length of round or other profile (5b),>

- <Фb: diameter of (5b) if in round profile;>

- <hb: height of (5b) if different from round profile,>

- <pf: hole pitch of any forks (5a) for anchoring the electrowelded mesh (3),>

- <pr: electro-welded mesh pitch (3) of any size without any limitation,>

- <prc: welded mesh pitch (3) coordinated with the connectors pitch (pc),>

- <pc: connector pitch and / or anti-extraction harpoon pitch, coinciding with that of the slots> printed on the corrugated sheet (see also Fig. 7 Table 2) and therefore also with the Greek pitch (see also Fig. 3 Table 1) ,

- <plg: corrugated sheet pitch (see also Fig. 7 Table 2).>

In Fig. 5 Sect. B-B Tab.1 and Fig.7 Tab.2:

- <ps: stirrup pitch (or incision pitch, if smaller).>

In Fig. 6 Table 2:

- <a: connector to be inserted in rotation in the slots of the corrugated sheet,>

- <b: upper wing of the bracket,>

- <bcâ € ™: width of connectors (a) and harpoons (c + d) coordinated in tolerance with (bc) of Fig. 7 Tab.>

2,

- <B: lower wing of the bracket,>

- <c: height of the anti-extraction plate of the snap harpoon,>

- <d: height of the snap harpoon,>

- <h: height of the bracket (2),>

- <hf: projected height of any U-shaped fork (5a),>

- <Î ±: angle between the two plates (c) and (d) of the snap harpoon,>

- <β: angle between the two branches of the locking fork (5a) of the electrowelded mesh,>

- <у: angle between the upper wing (b) and the core of the bracket (h), if greater than 90 ° it allows>

great savings in packaging, transport and handling,

- <Фa: diameter of the holes on the upper wing of the bracket, in which to insert the U-fork of>

locking of the electro-welded mesh,

- <Фf: round diameter of the U-shaped fork (5a) for locking the electrowelded mesh,> - <pf: pitch of the mesh anchoring holes for inserting U-shaped forks (5a),>

- <pc: connectors and harpoons step which can also coincide with the Greek step,>

- <t: thickness of the plate of the bracket (2),>

- <tlg: slack between the lower edges (a) and (B) of the bracket (2), to allow snap-in installation.>

In Fig. 7 Tab. 2:

- <bc: base slots (6) or incisions (7) for inserting the rotating connectors (a) and the harpoons>

(c + d),

- <hc: height of the buttonholes (6) or incisions (7),>

- <ic: center distance between the slots (6) or incisions (7).>

The brackets (2) of Fig. 2 have a length (Ls) that does not exceed the pitch of the corrugated sheet (plg).

In this way there are no more constraints on the mounting of the stirrups. Each bracket â € œserveâ € only a predetermined sheet of sheet metal and there is no need for alignment with the brackets of the adjacent sheets of corrugated sheet. The brackets can also have a length (Ls) which is a submultiple of the pitch of the corrugated sheet, up to a minimum number which is that of the Greek elements contained in the pitch (plg) as can be seen in the third sheet of metal a right of Fig. 2, in Fig. 3 Sect. A-A a.g. (before casting) and in Fig. 4 Sect. A-A p.g. (post cast).

Each bracket is equipped with a certain number of rotating connectors and another number of harpoons (four shown: but their number may be different, depending on the structural calculation). The bracket is installed as follows:

- <the tabs of the connectors (a) of Fig. 6 are inserted vertically into the slots (6) or> incisions (7) of Fig. 7, present on the upper part of the corrugated sheet,

- <the bracket is rotated until the harpoons made up of sheets (c) and (d) enter the> slots (6) or incisions (7) of Fig. 7, arranged in step (ic),

- the bracket is forced to enter the aforementioned slots (6) or incisions (7) with the possible help of a rubber hammer,

- at the click of the four harpoons (or other number) the bracket is installed.

The pitch (ic) of the slots is particularly designed to allow first insertion and then snap locking. In this way the installation of the bracket is immediate, it does not require special tools, just the pressure between the profile and the corrugated sheet of the floor is enough.

The tabs of the connectors (a) and of the harpoons (c + d) of Fig. 6 prevent them from being extracted from their seats once inserted, thus guaranteeing the structural mechanism against sliding and detachment of the slab. If you want a higher level of structural constraint of the tabs and hooks of the brackets, it is possible to replace the aforementioned slots (6) with engraved impressions (7), which are easy to cross on site. In this case the corrugated sheet is imprinted and cut (see the four groups of eight incisions each in the drawing Fig. 7 Tab. 2) but no sheet metal element is removed. This choice has the economic advantage of having very small pitches (ps) between the groups of slots-engravings with an electro-welded mesh on a smaller span, with larger meshes, with rounds of smaller diameter and with a lower cost.

The incisions (7) of Fig. 7 instead of the slots (6) of Fig. 7, have the advantage of not letting the cement paste of the fresh concrete run down in the event that you do not want to install any bracket on a certain number of engravings on the corrugated sheet.

Furthermore, during casting, the slots (6) and / or incisions (7) become clogged with very fine cementitious paste which â € œseatâ € and stiffly blocks any residual play between the bracket and the corrugated sheet.

If the mixed section structural calculation requires the mesh to have a free length of deflection with limited compression, it is possible to install a U, L or any other shaped fork or bars in round, square or another profile that has the functions of anchoring reinforcement typical of reinforced concrete constructions.

A U-shaped drawing of this fork (5a) is attached in Fig. 6, exemplifying and not limiting or exhaustive of the case studies that can be adopted. Also of the bars (5b) are attached the front view in Fig. 2 and the transversal view in Fig. 6 of round profile of length (Lb) and diameter (Φb) exemplary and not limitative of the case studies that can be adopted. In the case of using the bars (5b) alone or in combination with the forks (5a), the pitch of the electro-welded mesh cannot be any longer any (pr) of Fig. 2 but must be coordinated, (prc) of Fig. 2, with the pitch (pc) of the frets of the corrugated sheet.

The harpoon (c + d) can also be made by simply embossing the sheet thickness (t) of the bracket (2) without any sheet metal flap.

The system described up to now retains all the functional and structural validities even in the case of ordinary concrete castings, it lends itself well to improve the sliding resistance on medium-large spans and lends itself to the best possible use of the compression resistances, however reachable also by ultralight concretes.

In fact, with nanotechnology operations, using SiO2amorphous silicon dioxide (in the form of silica smoke or silica fume) and acrylic hyperplasticizers, it is possible to increase the resistance of the calcium hydrosilicates, of which the cement paste is made, up to very high values and such to compensate for the voids originated by polystyrene granules or other light aggregates, by drawing on the ultra-light concrete values of breaking strength by crushing in free test on a 25 MPa cube, like ordinary concrete.

The system described can use the modest but not negligible compressive strengths of ultralight concretes due to the specificity of the mechanism identified by this patent: the bending of the entire floor determines compression thrusts in the concrete (in the middle area) which are also collected through the electro-welded mesh (3) and transferred to the support brackets (2), to counteract the traction that originates in the corrugated sheet.

The balance between traction and compression occurs by means of the sliding mechanism prevented by the presence of the brackets installed perpendicularly to the direction of the corrugated sheet metal corrugations. The viscous flow of ultralight concretes is the lowest of all concrete slabs as the water / cement ratio is approximately 0.28-0.30.

Consequently, they are much more stable over time than floors in corrugated sheet metal and ordinary concrete (made with water / cement ratios of 0.6-0.7) and do not have the same deferred lowering. Therefore, in the case of ultralight concretes, it is allowed to design mixed steel-concrete sections as long as the following occur:

- the contact pressures between concrete (4) and brackets (2) Fig. 5 Sect. B-B, in the action of contrasting the compression thrust, coming from the electro-welded mesh (3), carried out by the entire vertical side (h) of Fig.6 of the bracket (2);

- the shear stress on the connectors (a) and on the harpoons (c + d) Fig. 6 that join the brackets (2) to the corrugated sheet (1), which transfer and cancel the corrugated sheet, due to prevented sliding, the compression coming from the concrete.

In Fig. 5 Sect. B-B you see:

- three brackets with fork (5a),

- a bracket with eyelet for housing the locking bar (5b) of the electrowelded mesh (3), enlarged in Part. a of Fig. 6,

- a bracket with fold for housing the locking bar (5b) of the electro-welded mesh (3), enlarged in Part. b of Fig. 6.

Furthermore, the aforementioned bracket can also be produced in die-cast alloys.

CASTING AND HARDENING OF ULTRALIGHT CONCRETE.

In the case of corrugated sheet slabs with medium-large spans, the use of ultra-light concretes avoids the installation of temporary shoring as the lowering is 70% lower than ordinary concrete slabs.

The electro-welded mesh (3) has the function of limiting the shrinkage of the concrete, avoiding surface lesions of the screed and the separation of the concrete (4) from the corrugated sheet (1) of Fig. 2.

The electro-welded mesh (3) supports, with modest deflection between the brackets (2), the first team of workers, who advances distributing and vibrating the concrete on the floor, and the second team, who level the concrete. The operation of vibrating and then leveling the ultra-light concrete is particularly productive and fast, due to the lightness and spreadability of the ultra-light concrete, reducing the fatigue of the workers, the leveling times and occupational diseases (white finger) related to vibration of concrete on site. After the concrete has hardened, a light and quick torching with propane gas allows the polystyrene granules emerging on the surface to evaporate. Thousands of pits and vacuoles originate in this way. This preparation makes the floor very rough and offers excellent adhesion to the mortar or glue of the tiles or other flooring.

The system described up to now retains all the functional and structural validities even in the case of ordinary concrete castings. It improves the sliding resistance of traditional floors in corrugated sheet metal and ordinary concrete designed in a mixed steel-concrete system, especially for large spans in corrugated sheet metal-concrete.

The invention, well understood, is not limited to the representation given by the figures, but can receive improvements and modifications by the man of the trade without leaving the framework of the patent. The present invention allows numerous advantages and to overcome difficulties that could not be overcome with the systems currently on the market.

Claims (1)

CLAIMS 1. <Mixed floor in corrugated sheet metal (1) and concrete (4) for buildings including an> electro-welded mesh (3) placed over the corrugated sheet (1) in which the concrete (4) fills the corrugated sheet corrugations (1) and covers the electro-welded mesh (3), characterized by the fact that above the corrugated sheet (1), in a direction perpendicular to the ribs and with a regular pitch (ps), brackets (2) of length (Ls) are fixed for the entire length surface of the floor, on which it is possible to place and / or block the electro-welded mesh (3) by means of U-shaped round forks (5a) or other shape, shape and profile or other reinforced concrete rods as well as by means of bars (5b) of round, square or other profiles and that the bracket (2) is profiled or stamped in sheet metal or die-cast in aluminum or other alloy. 2. <Mixed floor slab made of corrugated sheet metal (1) and concrete (4) for buildings, according to> claim 1, characterized in that the profiles of the brackets (2) are C or L-shaped profiles with flaps which form connector tabs (a) and harpoons (c + d), with holes (Φa) on the upper wing (b) of said brackets (2) to block the electro-welded mesh (3) with the insertion of reinforced concrete rods (5a, 5b) of round, square or other profile in order to make the electro-welded mesh participate in the compressive stresses in the middle of the span of the floor. 3. <Mixed floor slab in corrugated sheet (1) and concrete (4) for buildings, according to> claim 2, characterized by the fact that the flaps that constitute the tabs of the connectors (a) and of the harpoons (c + d), are profiles and / or press-folded and / or embossed and / or cut-molded with indentations of width (bcâ € ™) and pitches (ic) and (pc) for hooking on slots or incisions existing on the corrugated sheet, parallel or perpendicular to the longitudinal direction of the corrugated sheet metal. 4. <Mixed floor in corrugated sheet (1) and concrete (4) for buildings, according to> claim 1, characterized in that the support brackets (2) are timed and organized on a single sheet of corrugated sheet (1 ) with pitch (ps) and that slots (6) present on the corrugated sheet (1) are replaced by incisions (7). 5. <Mixed floor slab in corrugated sheet (1) and concrete (4) for buildings, according to> claim 4, characterized in that the support brackets (2) have the upper flange (b) with a greater angle у 90 ° with respect to the core (h). 6. <Mixed floor slab in corrugated sheet (1) and concrete (4) for buildings, according to> claim 1, characterized by the fact that no marking is required on site, no alignment of the brackets (2) as these must be mounted only in the slots (6) or incisions (7) industrially prepared on the corrugated sheet, therefore with millimeter precision and that the mounting of the brackets (2) is quick and that no drilling, screwing, riveting, welding operations are required to fix the brackets (2) to the corrugated sheet (1). 7. <Mixed floor slab in corrugated sheet (1) and concrete (4) for buildings, according to> claim 1, characterized in that the brackets (2) have the upper wing (b) with an eyelet (6a) or fold (6b) to accommodate a bar (5b) of round iron, square or other profile to hold the electro-welded mesh alternatively or together with the forks (5a) and that eyelet (6c) or fold (6d) can be arranged on the opposite side with respect to the upper wing (b) and that the eyelets or folds (6 a, b, c and d) and the holes (Фa) on the upper wing (b) for the upper wing can coexist on the same bracket ™ insertion of the forks (5a). 8. <Mixed slab in corrugated sheet (1) and concrete (4) for buildings according to> claims 1, 2, 3 or 4, characterized in that the concrete is a lightweight concrete with a specific weight of less than 1600 Kg / mc. 9. <Mixed floor in corrugated sheet metal (1) and concrete (4) for buildings according to> claims 1, 2, 3 or 4, characterized in that the concrete is an ultra-light concrete with a specific weight of less than 800 Kg / mc. 10. <Mixed floor in corrugated sheet (1) and concrete (4) for buildings according to> claim 8 or 9, characterized in that the concrete is added with silicon dioxide SiO2amorph and acrylic hyperplasticizers.