EP2636808A1

EP2636808A1 - Composite floor element for buildings made of corrugated metal sheet and concrete

Info

Publication number: EP2636808A1
Application number: EP13158200.9A
Authority: EP
Inventors: Giuseppe Grande
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-03-08
Filing date: 2013-03-07
Publication date: 2013-09-11

Abstract

Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), comprising the following components:
corrugated metal sheet (1), electrowelded wire mesh (3), concrete (4) wherein:
- between the corrugated metal sheet (1) and the electrowelded wire mesh (3) , above the corrugated metal sheet (1), stirrups (2) and/or profiles (2a, 2b) are positioned perpendicularly to corrugations of the corrugated metal sheet (1), with a calculated interval (ps), regularly throughout the whole floor surface;
-the concrete (4) is a light or extremely light concrete with a specific weight lighter than 1600Kg/mc;
-the stirrups (2) and/or the profiles (2a, 2b) have a length which is at least the same as the interval (pc) of the corrugations of the corrugated metal sheet (1),
-the stirrups (2) and/or the profiles (2a,2b) are mechanically fixed to the superior edge of the corrugated metal sheet (1),
-the electrowelded wire mesh (3) is kept apart from the corrugated metal sheet (1) by the presence of the stirrups (2) and/or of the profiles (2a, 2b) on said corrugated metal sheet (1),
-the concrete (4) fills the corrugations of the corrugated metal sheet up (1), covers the stirrups (2) and/ or the profiles (2a,2b) as well as the electrowelded wire mesh (3) with a suitable concrete cover,
-the creep strength between the concrete slab and the corrugated metal sheet (1) is given by the stirrups (2) and/or the profiles (2a, 2b) as well as by the channels of the corrugated metal sheet (1) and the adherence of the concrete (4) against the corrugated metal sheet (1),
-the electrowelded wire mesh (3), being supported by the stirrups (2) and/or by the profiles (2a,2b), works in a compression environment where the composite floor, made of corrugated metal sheet (1) and concrete (4), having a positive bending moment , in the middle part of the bearing beams, allowing for the first time to take full advantage of the structural contribution of the electrowelded wire mesh (3) in a compressed area, for checking positive moment, in floors made of corrugated metal sheets and concrete.
-the above structural position of the electrowelded wire mesh (3) in a compressed area, thru the use of light or extremely light concrete (4), determines a remarkable increase , from 200 to 300%, of the fully plastic moment of collapse, in comparison with the same loft's area without the electrowelded wire mesh (3) in the compressed area,
-the above structural position of the electrowelded wire mesh (3) in a compressed , with the use of light or extremely light concrete (4), allows, provided that the load is the same, a significant increase of the free span, from 25 to 50%, in comparison with spans which would be reachable using the traditional floors made of corrugated metal sheet (1) and ordinary concrete (4) or, assuming the same free span, an identical increase of the load.

Description

TECHNICAL FIELD OF THE PATENT

The present patent concerns a new type of mixed composite floor element, made of steel and light or ultralight concrete, realized with components which do have large scale diffusion in the market but at the same time connected and associated to each other so that the outcome is a final product significantly innovative and representing a breakthrough in terms of innovation, resistance and lightness.
The invention has as main peculiarity an original system which ensures the distance, the support as well as the blockage of the electrowelded wire mesh (used in the construction of mixed composite floor elements steel/concrete) such system, which is thoroughly described in this patent, allows for the first time to fully benefit from the structural resources of the electrowelded wire mesh in the compressed area of the slab made of light or ultralight concrete, where the composite floor element is particularly exposed to positive bending moment.
Throughout this patent, such distancing of the electrowelded wire mesh from the corrugated metal sheets takes place through two solutions (see Fig. 1-12):

A) U or L or C or Ω profiles, like in Fig. 2 and Fig. 3, of a minimal length equal to the width of the corrugated metal sheet, with a manual alignment to be carried out in the construction site: these profiles are installed with vertical or horizontal web, mechanically fixed upon the corrugated metal sheets (1) of normal industrial manufacturing,
B) U or L or C or Ω snaps stirrups, see Fig. 10 and Fig. 11, of minimal length (Ls) equal to the width of the corrugated metal sheet, with alignment already processed by the slots prebuilt on the corrugated metal sheet (1) at the building site, installed with vertical or horizontal web, snap fixed on the corrugated metal sheet (1) equipped of pre-cut slots.

The stirrups (2) of Fig. 11 have a length (Ls) which is inferior to the pitch of the corrugated metal sheet (plg) (and an hypothetic U fork and/or an eventual bar of round, square or other profile) which make possible the link amongst the following components:

corrugated metal sheet,
electrowelded wire mesh,
light or ultralight concrete.

The A) solution offered by this patent does not include any modification concerning the production of the corrugated metal sheet (1), seen that the simple production and the installation of U or L or C or Ω cold formed profiles above the corrugated metal sheets - before the assembling of the electrowelded wire mesh, would suffice.
The B) solution instead refers to an automated cutting out of the slots, necessary to receive connectors and spears of the snap stirrup (2), during the cold formed profiling of the corrugated metal sheets (1), with a station of coils fly punching, before entering in the profiling device.
It is the only system, suitable for industrialization, to realise extremely light composite floor elements with the use of ultralight concretes.
Such system is particularly suitable for the construction of new buildings and the refurbishment of old buildings because it permits to leave unchanged the old wooden beams, getting rid of the heavy "filling" layers between the floor and the planking. Such lightness makes this composite floor element, the one to be preferred when it comes to reconstruction after earthquakes because it drastically reduces the exposure to seismic risks.
The usage of high quantities of recycled polystyrene foam or polystyrene makes this invention the most suitable for the Green building as well as for the Energetic savings and also the lightest composite floor element today existing. The extreme lightness permits to eliminate the provisional shoring installed before the concrete casting, resulting in consistent savings in terms of purchasing costs, transport costs, assembling and storing.
Even more relevant and important is the benefit arising from the removal of the shoring :

the construction of buildings with many floors becomes quicker and less expensive,
the casting planning of composite floor elements can follow whichever order ,
if the last floor is casted at the beginning, the building site remains still well protected from the rain,
consequently, the following casting can take place even in condition of bad weather and the agreed contractual timelines will be respected,
safety issues at work decrease, since decreases the number of workers in the site.

There are other beneficial impacts such as the roughness of the working surfaces, which provides for an ideal grip on the floor, the possibility to designate ant fire areas, the saving on the weight and the general cost of the metallic supporting structures and of the groundwork.
The assembling of the snap stirrups (2) Fig. 10 and Fig. 11 of the B) solution is extremely swift: it takes place in the building site, without alignment operations, with processes of vertical insertion of the connectors' flaps inside the slots or other intended incisions in the corrugated metal sheet; following step is the rotation and the snap fixing of the spears.
Then can be also possible an eventual insertion of the U forks 5a of Fig. 7 and/or of the bars of Fig. 7 in order to block the electrowelded wire mesh , without requirement for alignments, punching holes, screwing in, welding, riveting or any other demanding site operations.
The profiles (2a and 2b) of Fig. 2 and Fig.3 as well as the snap stirrup (2) of Fig. 11 are particularly suitable for post-production stacking processes and packaging, which reduces drastically the space required and transport costs.

STATE OF THE ART AND PROPOSED INVENTION

Since the late 40's, after the experiences of Winter in America, the corrugated metal sheet found widespread usage for roofing and walls.
In the following years, corrugated metal sheets were produced for composite floor elements, of height between 55 mm and 200 mm, on which the casting of traditional concrete of 2400 Kg/mc is executed.
The thickness of such casting is generally included between 40mm and 100mm outside the corrugation: this means between the upper thread of the corrugated metal sheet and the upper thread of the final concrete casting.
The usage of mixed composite floors made of corrugated metal sheet and concrete is shown in WO-A-8900223 , which describes a floor composite element intended for buildings and made of corrugated metal sheet and concrete, comprehensive of an electrowelded wire mesh placed above the corrugated metal sheet, in which we can find - perpendicularly to the corrugations several connectors for the shear. These connectors are placed where the shear is maximum, only on the steel beam and not throughout the whole surface of the composite floor, with the only aim to create a beneficial situation for the beam, not for composite floor in corrugated metal sheet.
In order to avoid problems of disconnection and "floating" between the concrete casting and the corrugated metal sheet, always electrowelded wire mesh are used and fixed in various ways to the corrugated metal sheet.
The currently used "homemade" remedies turn out to be quite inefficient round bar, pieces of profile and so on. Such processes are in any case not linked directly to the corrugated metal sheet and not even to the aforementioned electrowelded wire mesh
Amongst the devices intended for the fixing of the electrowelded wire mesh appear:

stitches or welding buttons manually inserted, between the mesh and the corrugated metal sheet, with the electrowelded wire mesh itself in direct contact and coplanar with the corrugated metal sheet
L type stirrups fixed to the bottom of the corrugation channel, with screws or nails shot in the sections of the steel structure (with supporting function to the corrugated metal sheet); to these L stirrups would be eventually feasible to link- with manual connection- directly the electrowelded wire mesh.

The process of welding , with thousands of stitches, can locally alter the protection given to the corrugated metal sheet by the zinc coating.
In order to prevents the tendency of "cooperative" concrete plate toward a sliding effect, it is common practice to insert several cold drawing points- a few millimetres deep-at the side of the corrugated metal sheet.
In this way it is possible to obtain a higher resistance of the composite floor in comparison to the resistance offered by the corrugated metal sheet alone, realising at the same time a mixed structure steel/concrete.
When the electrowelded wire mesh leans directly against the corrugated metal sheet , we observe the creation - constantly but in accordance with the shaping of the corrugations - of areas of non-wrapping of the round bar of the electrowelded wire mesh from the concrete; therefore the electrowelded wire mesh is badly connected to the concrete casting.
Furthermore the panels of the electrowelded wire mesh are free to move during the casting, consequently they need to be tied up with iron wire, to guarantee the lengths of overlapping amongst the various sheets.
A wire mesh of this kind does not help toward the shrinkage of the concrete, does not place itself in the area of the stretched fibres (where the corrugated sheet leans over the beams and is characterized by a negative bending moment) and is not even efficient to give shape (together with the corrugated metal sheet) to the rigid plan which is crucial for antiseismic structures as well as being required by law in accordance with the new technical rules, but more importantly does not contribute structurally toward the compressed area where the composite floor works with positive bending moment.
As it turns out from the catalogues of the main companies active in the field , the ordinary weight, after casting, of these composite floor made of corrugated metal sheet and concrete is as follows:

165 Kg/m² with corrugated metal sheet 55 mm high and slab of 35 mm;
240 Kg/ m² with corrugated metal sheet 55 mm high and slab of 65 mm:
175 Kg/ m² with corrugated metal sheet 75 mm high and slab of 45 mm;
250 Kg/ m² with corrugated metal sheet 75 mm high and slab of 75 mm.

In the composite floors made of corrugated metal sheets and ordinary concrete the structural advantage generated by the compression resistance of the concrete is mainly lessened by the weight of the ordinary concrete itself, because a remarkable part of the load on the composite floor is represented exactly by the weight of the ordinary concrete.
The structural engineer must therefore pay particular attention to the entity of the structural bearing loads (G1 according to EC3) and to the entity of the non structural supported loads (G2 according to EC3): in fact while the variable load or load capacity Q is only statistically present, the permanent loads (G1 and G2) are always present.
Generally speaking, loads G1 and G2 influence the cost of the structure of the building and most of all of the foundations works.
Through the two A) and B) solutions, described in this patent, it is possible to overcome the problems of the composite floors made of corrugated metal sheet.
Based upon the following comparisons, it is possible to clearly determine one of the advantages of this patent: a consistent saving in terms of weight of the composite floor.
1^st COMPARISON: between a composite floor of corrugated metal sheet 55 mm high 8/10 mm thick, pitch of the corrugations 150 mm and ordinary concrete with γ_cls,ord = 2.400 Kg/ m³ and a composite floor with the same corrugated metal sheets and super light concrete with γ_cls,ult = 600 Kg/m³.
In both cases assuming that the thickness of the slab (concrete out of the corrugation) will be 50 mm.
Each channel of the corrugated metal sheet, without concrete, has the following volume: $V_{c} = ((0, 089 + 0, 061) / 2) * 0, 055 = 0, 00413 m^{3} / m^{2} .$
Adding the volume of each base weighing on each corrugation of 150 mm: $V_{s} = 0, 05 * 0, 15 = 0, 0075 m^{3} / m^{2} .$
Weight of a traditional composite floor of corrugated metal sheet and ordinary concrete:

- concrete weight:

(V_c + V_s) * γ_cls,ord = (0,00413+0,0075)*(1/0,15)*2.400 = 186 Kg/ m² +

- corrugated metal sheet weight 11 Kg/ m² =

Total weight of the composite floor: 197 K g/ m²
Weight of composite floor described in this patent made of corrugated metal sheet and ultra light concrete:

- concrete weight:

(V_c + V_s) * γ_cls,ord = (0,00413+0,0075)*(1/0,15)*2.400 = 47 Kg/ m² +

- corrugated metal sheet weight 11 Kg/ m² =

Total weight of the composite floor: 58 K g/ m²
The composite floor of this patent weights: 58/197 = 0,294, indeed 29% of the weight of a traditional composite floor made of corrugated metal sheet and ordinary concrete.
2^nd COMPARISON: between a composite floor of corrugated metal sheet 75 mm high, 8/10 mm thick, pitch of the corrugations 190 mm and traditional concrete with γ_cls,ord = 2.400 Kg/m³ and a composite floor with the same corrugated metal sheet and super light concrete with γ_cls,ult = 600 Kg/m³.
The assumption is that the slab (the concrete outside the corrugation) in both cases will have a thickness of 50 mm.
Each channel of the corrugated metal sheet, without concrete, has the following volume: $V_{c} = ((0, 064 + 0, 046) / 2) * 0, 075 = 0, 00413 m^{3} / m^{2} .$
Adding the volume of the weighing base on each pitch of circa 190 mm: $V_{s} = 0, 05 * 0, 19 = 0, 0095 m^{3} / m^{2} .$
Weight of the traditional composite floor of corrugated metal sheet and ordinary concrete:

- concrete weight

(V_c + V_s) * γ_cls,ord = (0,00413+0,0095)*(1/0,19)*2.400 = 172 Kg/m² +

- corrugated metal sheet weight: 11 Kg/m² =

Total weight of composite floor 183 Kg/m²
Weight composite floor described in this patent made of corrugated metal sheet and ultra light concrete:

- concrete weight:

(V_c + V_s) * γ_cls,ult = (0,00413+0,0095)*(1/0,19)*600 = 43 Kg/ m² +

- corrugated metal sheet weight: 11 Kg/ m² =

Total weight of composite floor: 54 Kg/ m²
The composite floor described on this patent weights: 54/183 = 0,295, which means 30% of the weight of the composite floor made of traditional corrugated metal sheet.
Furthermore the composite floors in corrugated metal sheet, electrowelded wire mesh and ultra light concrete, as long as they are equipped with the profiles (2a or 2b) Fig.2 or with the snap stirrups described in this patent, in comparison with the composite floors in corrugated metal sheets and ordinary concrete, have the following characteristics:

plastic resistant moment of the composite section equal or superior,
significantly superior clear span, even more than 50%,
no intermediary shoring even with a composite floor having a clear span of 4-8 ml.

ROLE OF THE ULTRA LIGHT CONCRETE (in polystyrene, polystyrene foam, polyurethane, recycled and not) AND LIGHT CONCRETE.
The concretes which can be used to build composite floors, according to their weight can be classified as follows:

- Ordinary concrete: specific weight 2.300-2500 Kg/m³,

- Light concrete: specific weight 1.400-1600 Kg/m³,

- Ultra light concrete: specific weight 200-800 Kg/m³.
As we go from the ordinary concretes to the ultralight ones, a gradual replacement of the traditional aggregates (sand and gravel) with lighter aggregates takes place. In the light concretes, the aggregates of bigger diameter are replaced by perlite or expanded clay, while sand is still present. In the ultralight concretes, so defined as they can even float on the water, the aggregates with bigger diameter are replaced by expanded polystyrene grains, expanded polystyrene, cork and wood chipboard and so on.
The expanded polystyrene foam and polystyrene can also be of recycled type, obtained from packaging or agglomerated of chipboard and grains of various entity.
In reality they are even to be preferred because they present a form which allows them to have a better grip onto the cement paste avoiding disintegration and floating in the water. In the ultralight concretes the sand remains instead in the high band of weight, between 500 Kg/m³ and 800 Kg/m³.
The main scope of the sand is to allow an optimal intervention on the concrete by the vibrators which, with extremely short interventions all over the place of circa 1 or 2 seconds each, make the concrete pour quickly into the channels of the corrugated metal sheet.
Below the weight of 500Kg/mc, to produce ultralight concretes only water, surfactant foaming agents, cement, fluidizers and polystyrene or polystyrene foam grains are to be used. Since the aim is reaching the highest resistances allowed for the category of the ultralight concretes, it is necessary to add silica fume, which basically is silica dioxide SiO₂ "amorphous" and as such without any crystal lattice.
In such a form the silica dioxide becomes extremely reactive at room temperature combining itself easily with secondary calcium hydroxide, residual product from the main reaction, although incomplete, creating further fibres or microscopic needles of silicate calcium hydrate.
Such secondary reaction (in terms of quantities and time) also called pozzolanic reaction, provides the creation of a much thicker structure of needles which weaving amongst themselves create the resistances which are traditionally measured on the cubes with free trials of crushing.
Furthermore the dimensions of the silica fume being just of few nanometres, make sure that it can insert itself within the structure of the silicate calcium hydrate, which presents some empty spaces of several nanometres, making the whole structure thicker, more resistant and impenetrable.
Another advantage of these concretes is represented by the medium/high quantity of CS (calcium silicates) which allows, once hydrated, to develop a remarkable quantity of chemical bonds in comparison with the alloy Fe-Zn, of which the corrugated metal sheet of the composite floors is made out, originating a strong structural adhesion.

TECHNICAL PECULIARITIES AND COMMON ADVANTAGES OF THE TWO A) AND B) SOLUTIONS OF THIS PATENT

The two A) and B) types of composite floor described in this patent, present the following common peculiarities(Fig. 1-12):

the corrugated metal sheet (1) for composite floors possibly with the sides of the corrugations equipped with cold drawing or fold or spoors randomly placed to allow a better anchoring between the corrugated metal sheet (1) and light or ultra light concrete (4);
the profiles (2a or 2b) of Fig.2 or of the snap stirrups (2) of the Fig. 11 are installed on the superior edge of the corrugations (1),
the profiles (2a or 2b) of Fig.2 or of the snap stirrups (2) of the Fig. 11 are installed perpendicularly to the corrugations,
the profiles (2a or 2b) of Fig.2 or the snap stirrups (2) of the Fig.11 having a minimal length (Ls) which is equal to the width of the superior part of the corrugation, as shown in Fig. 7,
the profiles (2a or 2b) of the Fig.2 or of the snap stirrups (2) of the Fig. 11 have the objective of distancing the electrowelded wire mesh (3) from the corrugated metal sheet and supporting it, to avoid that the mesh is crushed against the corrugated metal sheet (1) of the workers' team walking on the electrowelded wire mesh (3) during the preparation of the composite floor and during the casting of the ultralight concrete (4);
the electrowelded wire mesh (3) is installed at last, just before the casting; it must sustain the two teams of workers who alternating want to ensure, the first team the casting through hosepipe on the composite floor, the second team the levelling and the shaving of the concrete just casted; in order to support these workers with the least possible deflection of the electrowelded wire mesh, it is necessary that the distance between the profiles (2a or 2b) of Fig. 2 or between the snap stirrups (2) of the Fig.11, is no more than one meter or according to the structural calculation; this type of installation of the electrowelded wire mesh on the profiles (2a or 2b) of Fig.2 or on the snap stirrups (2) of the Fig.11 enhances the productivity of the building site for the installation of composite floors;
the corrugated metal sheet (1) during the casting of the concrete, supports the provisional loads of the building site which are the workforce and the materials which will need to be installed on the composite floor;
the ultralight concrete (4) holds the following structural functions:
- vertically distributing the loads to the electrowelded wire mesh and then to the corrugated metal sheet;
- horizontally distributing, together with the electrowelded wire mesh, the stresses of shear and sliding to the profiles (2a or 2b) of Fig.2 or to the snap stirrups (2) of the Fig. 11 and to the corrugated metal sheet (1),
- originating compressed connecting rods which initiate from the compressed area of the ultralight concrete (4) and of the electro welded mesh wire (3), arriving up to the bottom of the channels of the corrugated metal sheet (1);
the corrugated metal sheet (1) after the casting of the ultralight concrete, after the process of hardening, cooperates with the electrowelded wire mesh (3) and with the ultralight compressed concrete (4) to create a composite section constituted by:
- steel of the corrugated metal sheet,
- steel of the electrowelded wire mesh ,
- compressed concrete,
which will have the definitive bearing structural function to support the future loads as planned by the structural project.

DESCRIPTION OF THE INVENTION, OF THE FIGURES AND OF AN EMBODIMENT OF THE A) SOLUTION WITH A HOLLOW PUNCHED U PROFILE.

With reference to the figures 1, 2, 3, 4a, 5a and 5b and the type A) solution, apart from the elements already described in the previous chapter which are common to the two A) and B) solutions, it is defined and described as follows:

simple or hollow punched U profile (2a, 2b) of Fig.2 installed with perpendicular direction toward the corrugations of the corrugated metal sheet (1) ;
fixed by means of screws or structural rivets on the corrugated metal sheet (1);
such profile (2a, 2b) can also have other shapes of the section: L, C, Ω or T shape and so on, with vertical and horizontal web of the profiles, what really matters however is the function which keeps the distance between corrugated metal sheet and electrowelded wire mesh as well as the linear and diffuse link between the two structural elements;
the slot or hollow punch (5) of the above metioned profiles (2a, 2b) are enough deep to allow the overlap and anchoring of the sheets of the electrowelded wire mesh ;
the slot or hollow punch (5) are blanked on the profiles (2a, 2b) with a single modular pitch "p"; for example a pitch with module m=50 mm allows the acceptance of electrowelded wire mesh with pitch round bar of 50 mm or of 100 mm or 150 mm or 200 mm;
the slot or hollow punch (5) are blanked on the profiles (2a,2b) with double modular pitches "p+q"; for example a pitch with module m = 40 mm + q =50 permits the acceptance of electrowelded wire mesh with pitch round bar of 50 mm or of 80 mm or 100 mm or 120 mm or 150 mm or 160 mm or 200 mm.

DESCRIPTION OF THE INVENTION , OF THE FIGURES AND OF AN EMBODIMENT OF THE B) SOLUTION WITH THE SNAP STIRRUP

With reference to the figures 6, 7, 8, 9, 10, 11 and 12 the B) solution, as well as the elements described on the previous chapter and common to the two A) and B) solutions, are defined by the following.
It is constituted by a profile whose literal measures are reported in the Fig. 7:

Ls: stirrup length (2)
Lb: length of round or other profile (5b),
φb:diameter of (5b) if in round profile;
hb: height of (5b) if different from the round profile,
pf: pitch holes of the eventual anchoring forks (5a) of the electrowelded wire mesh (3),
pr; pitch of the electrowelded wire mesh (3) of any measure without limitations,
prc: pitch of the electrowelded wire mesh (3) coordinated with the pitch of the connectors (pc),
pc: pitch connectors and/or pitch spears anti extraction, coinciding with the one of the loops printed above the corrugated metal sheet (see also Fig. 12) and therefore also with the pitch of the corrugations (see also Fig. 8),
plg: pitch corrugated metal sheet (see also Fig. 12).

In the Fig. 10 Sec. B-B and Fig. 12:

ps: pitch stirrups (or pitch incisions, in case of inferior measure).

In the Fig. 11:

a: connector to be inserted, on a rotation basis, onto the loops of the corrugated metal sheet,
b: superior flange of the stirrup,
bc': width connectors (a) and spears (c+d) coordinated with tolerance to (bc) of Fig. 12,
B: superior flange of the stirrup ,
c: height of the anti-extraction metal sheet of the snap spear,
d: height of the snap spear,
h: height of the stirrup (2),
hf: projected height of the eventual U fork (5a),
α: angle between the two metal sheets (c) and (d) of the snap spear,
β: angle between the two branches of the blocking fork (5a) of the electrowelded wire mesh,
γ: angle comprised between the superior flange (b) and the web of the stirrup (h), if more than 90 degrees allows significant packaging, transport and movement economies,
φa: diameter of the holes on the superior flange of the stirrup, in which must be inserted the U blocking fork of the electrowelded wire mesh,
φf: diameter of round bar of the U blocking fork of the electrowelded wire mesh,
pf: pitch of the anchoring holes of the mesh for insertion of the U forks (5a),
pc: pitch of the connectors and spears which can correspond with the pitch of the corrugations,
t: thickness of the metal sheet of the stirrup (2),
tlg: backlash between the stirrup's (2) lower sides (a) and (B) , to facilitate the snap installation,

In Fig. 12:

bc: base of slots (6) or incisions (7) for the insertion of the connectors (a) with rotation of the spears (c+d),
hc: height of the slots (6) or incisions (7),
ic: distance between the slots (6) or incisions (7).

The stirrups (2) in Fig.7 have a length (Ls) which does not goes beyond the length of the pitch of corrugated metal sheet (plg).
In this way there is no limitation to the assembling of the stirrups.
Each stirrup "serves" solely a unique sheet of corrugated metal sheet and there is no need for alignment with the stirrups belonging to the adjacent sheets.
The stirrups can also have a length (Ls) which is a submultiple of the pitch of the corrugated metal sheets, but not less than a minimum number represented by the number of corrugations contained in the pitch (plg) as displayed in the third metal sheet on the right of Fig.7, Fig. 8 Sec. A-A a.c. (before casting) and Fig. 9 Sec. A-A p.c. (after casting).
Each stirrup is equipped with a certain number of rotating connectors and another number of snap spears (four are displayed here, but their number can vary depending on the structural calculation).
The stirrup is assembled in the following way:

the flaps of the connectors (a) of the Fig. 11 are vertically inserted in the slot (6) or incisions (7) of the Fig. 12, present on the superior part of the corrugated metal sheet,
the stirrup undergoes a rotation until when the spears, constituted by the corrugated metal sheet (c) and (d), enter the slot (6) or incisions (7) of Fig. 12, placed according to the pitch (ic),
the stirrup is forced to enter the aforementioned slot (6) or incisions (7) with the aid of a rubber hammer,
the noise of the snap of the four spears (or another number) indicates that the snap stirrup is installed.

The pitch (ic) of the slots is particularly studied to allow first the insertion and then the snap blockage.
In this way it is possible to obtain an immediate installation of the stirrup without any requirement for special tools, being the pressure between profile and corrugated metal sheet enough.
The flaps of the connector (a) and of the spears (c+d) in Fig. 11 avoid that, once inserted, may be removed ensuring the structural mechanism against the sliding and the detachment of the flap.
If a higher impact of the structural constraints of the flaps and of the spears of the stirrups is required it is possible to replace the above mentioned slots (6) with cavity incised (7), easy to manage in the building site.
In this case the corrugated metal sheet is cavity incised and cut (refer to the four groups, each with 8 incisions, see Fig. 12) but no material of the corrugated metal sheet is taken away.
This particular choice presents an economical advantage, because the pitches (ps) are extremely shortened in the slots-incisions also with an electrowelded wire mesh less extended, with larger cells and with inferior diameters at lower costs.
The incisions (7) of Fig. 12 in place of the slots (6) of Fig.12, are able to block a leaking of fresh past of cement of the fresh concrete in case the assembling of a stirrup is not required over a certain number of slots on the corrugated metal sheet.
Furthermore during the casting, the slot (6) and/or the incisions (7) are getting filled up with fine past of cement which blocks and "welds" any possible gap between stirrup and corrugated metal sheet.
If the structural calculation with composite section requires that the mesh has a free interval of movement with limited compression, it is also possible to install a U or L fork or of any other shape, or some round bars, or even square or any other profile, which realizes an "anchoring" function which is typical of the constructions in reinforced concrete.
A representation of such U fork (5a) is attached, see Fig.11; this is a simplification and the example is not exhaustive of all the cases.
A frontal view of the bars (5b) is also attached, see Fig.7, as well as a transversal view in Fig. 11, with round profile and length (Lb) and diameter (φb): again the example is a simplification and not exhaustive.
In case of use of bars (5b), alone or in combination with the forks (5a), the pitch of the electrowelded wire mesh cannot be as we like (pr), see Fig. 7, but will need to be coordinated, (prc) see Fig.7, with the pitch (pc) of the corrugations of the corrugated metal sheet.
The spear (c+d) can be realised also through simple embossing of the corrugated metal sheet of thickness (t) of the stirrup (2) without any flap in the corrugated metal sheet.
In the Fig. 10 Sec. B-B are shown:

three stirrups with fork (5a),
a stirrup with buttonhole suitable for insertion of the blocking bar (5b) of the electrowelded wire mesh (3): it can better be seen in the Part. a of the Fig.11a,
a stirrup with flap for reception of the blocking bar (5b) of the electrowelded wire mesh (3), it can better be seen in the Part. b of the Fig.11b,

Furthermore such bar can also be produced through die-cast alloys.

ADVANTAGE OF THE A) AND B) SOLUTIONS OF THIS PATENT

The described solutions :

A) U, L, C, Ω profiles manually aligned and manually fixed in the building site on the corrugated metal sheet,
B) snap stirrups with U, L, C, Ω profiles, assembled in slot industrially set up and pre aligned on the corrugated metal sheet,

are particularly suitable for the best possible usage of the compressions' resistances reachable through the ultralight concretes and present also significant advantages related to the functionalities and the quality of the operations in the building site.
The B) solution represents a radical innovation, for the highly industrialized production as well as well as for the reduction of any further successive working process and the building site's costs.
The profiles (2a,2b) of Fig.2 or the snap stirrups (2) of Fig. 11, whilst distancing the electrowelded wire mesh from the corrugated metal sheet (1) avoid the blockage of the concrete (4), which could be trapped and create enclaves of air in case the electrowelded wire mesh is leaned directly against the corrugated metal sheet (1).
The round bars of the electrowelded wire mesh (3) are very well wrapped and covered by the concrete (4) without areas of missing adherence, which is normally the case for mesh which leans directly against the corrugated metal sheet (1).
The profiles (2a, 2b) of Fig.2 or the snap stirrups (2) of Fig. 11, allow the ideal structural position of the electrowelded wire mesh (3) in the area of "best structural performance", but also in the points where the electro welded wire mesh is particularly tense (therefore where the composite floor works with a negative bending moment) and also in the points where the electro welded mesh wire is particularly compressed (therefore where the composite floor works with a positive bending moment).
The electrowelded wire mesh (3) has, as well in case of this patent, the usual function of avoiding a shrinkage of the concrete, avoiding superficial damages of the concrete and also avoiding the separation of the concrete from the corrugated metal sheet (1) Fig. 5a, of Fig. 5b and of Fig.9.
The electrowelded wire mesh (3) separated from the corrugated metal sheet (1) from the profiles (2a, 2b) of Fig. 2 or from the snap stirrups (2) of Fig.11, shows a modest inflexion under the weight pressure of the first team of workers (which comes for distributing and vibrating the concrete on the composite floor) and the second team of workers, which level the concrete distributing it equally with suitable machines with rolling blades.
The pitch between the profiles (2a, 2b) of Fig. 2 or the snap stirrups (2) of Fig. 11 must be calculated by the structural designer in order to avoid the elastic lowering of the electrowelded wire mesh, so that after the transit of the team of workers the net can be back exactly to a flat position and as such ready to receive again compressions as a consequence of the composite section made of corrugated metal sheet and ultralight concrete.
Thanks to the limited pitch between spacers (2a,2b) of Fig.2 or snap stirrups (2) of Fig.11, the electrowelded wire mesh does not incur in particular deformations which normally takes place during the assembling of panels of electrowelded wire mesh or at a later stage during the casting of the concrete, this means that the rounds of the mesh remain perfectly aligned and able to resist to the compression.
The described system can use the modest but not insignificant compression's resistance of the ultralight concretes exactly for the peculiarities disclosed by this patent: the general deflexion of the entire composite floor generates compressions in the concrete ( median strip area) which are collected also through the electrowelded wire mesh (3) and transferred to the profiles (2a, 2b) of Fig. 2 or to the snap stirrups (2) of Fig. 11, to counteract the traction which originates in the corrugated metal sheet (1).
The balance between traction and compression takes place through mechanisms of sliding inhibited by the presence of the profiles (2a ,2b) of the Fig. 2 or of the snap stirrups (2) of Fig. 11, installed perpendicularly in comparison to the corrugations of the corrugated metal sheet.
The creep of the ultralight concretes is absolutely the lowest amongst all the composite floors which can be made with concrete, because the ratio water/cement is about 0,28-0,30.
Therefore said ultralight concretes can be considered much more stable in the long run in comparison with the composite floors made of corrugated metal sheet and ordinary concrete (where the ratio water/cement is 0,6-0,7) and do not give any sign of the same deferred lowering.
Therefore the ultralight concretes are suitable for the creation of composite sections steel-concrete provided that the following conditions are met:

the contact pressure between concrete (4) and the profiles (2a, 2b) of Fig. 2 or the snap stirrups (2) of Fig. 11, when inhibiting the compression thrust coming from the compressed base and from the electrowelded wire mesh (3), function carried out by the flanges of the U profile of Fig. 3 or by the web (h) of the stirrup (2) of Fig.11;
the shearing stress on the connectors between the U profiles and the corrugated metal sheet (1) of Fig. 4a and Fig. 4b or on the connectors (a) and on the spears (c+d) Fig. 11 which connect the stirrups (2) to the corrugated metal sheet (1), transferring and nullifying on the corrugated metal sheet, for impeded sliding, the compressing stress coming from the concrete.

Furthermore, with operations of nanotechnology, using silicon dioxide SiO₂ , amorphous (in the shape of silica fume) and acrylic hyper-fluidizers it is possible to raise the resistance of the hydro silicates of calcium, which are the main element of the paste of cement, up to extreme high values, so high which can actually compensate the vacuum originated by the polystyrene grains, making sure that the ultralight concrete obtains a level of tolerance and resistance to the breaking on a free trial with a concrete cube of 25 MPs, which equals the values of an ordinary concrete.
In case of composite floors in corrugated metal sheet of span medium-large, the usage of ultralight concretes prevents the installation of provisional shoring, because the decrease results to be inferior to 70% in comparison with composite floors in ordinary concrete.
The process of vibration, levelling and grinding of the ultralight concrete is particularly productive and fast, for the qualities of lightness and spread ability of the ultra light concrete, which permits to reduce the efforts of the workers , the levelling times and professional diseases (white finger) directly linked to the vibrations of the concretes in the building site.
In a moment successive to the hardening of the concrete, a light and quick flaming of gas propane permits the evaporation of the possible residual grains of polystyrene which pop up on the surface.
In this way thousands of vacuoles originate.
This process ensures that the composite floor becomes extremely rough and offers an exceptional grip to mortar or tiles or to any other adhesive or floor.
The system, so far described, keeps its characteristics also in the case of casting of ordinary concrete.
It improves creep strength of the traditional composite floors made of corrugated metal sheet and ordinary concrete, planned as a system of composite steel-concrete floor, especially for large span of composite floor made of corrugated metal sheet-concrete.
In conclusion there are the following advantages:

1. weight of the composite floor reduced of 30% in comparison with the weight of the a composite floor in corrugated metal sheet and ordinary concrete,
2. fully plastic moment of collapse of the composite section equal or superior,
3. span considerably superior even up to the 50%,
4. full elimination of intermediate shoring even with span between 4 and 8 ml.

ORIGINALITY OF THE STRUCTURAL MECHANISM OF THE A) AND B) SYSTEMS OF THE PRESENT PATENT

The strongly innovative originality of this patent consists in having highlighted the following structural mechanism:

in the compressed slab with ordinary concrete the structural presence of the electrowelded wire mesh, with the foreseen concrete cover, does not modify as a matter of fact the fully plastic moment of collapse, calculated according to the assumption stress-block EC2-EC4;
the same composite floor in corrugated metal sheet with an ultra light concrete would show a fully plastic moment of collapse only of a third or a fourth in comparison with the moment of a composite floor with ordinary concrete,
therefore in the composite floor made of corrugated metal sheet and ultra light concret, the electrowelded wire mesh will be considered in the calculations;
consequently in the compressed slab with ultra light concrete , the structural presence of the electrowelded wire mesh, with the foreseen concrete cover, makes increase the fully plastic moment of collapse, calculated assuming the hypothesis stress-block EC2-EC4, of values included between 250% and 300%, in other words 2,5-3 times (which can reach and even overcome the moment of the composite floors made of corrugated metal sheet and ordinary concrete), thanks to the relevant compression-absorbing action carried out by the electrowelded wire mesh , discharging the slab of ultra light concrete from the compressions,
in order to ensure that the electrowelded wire mesh can absorb such consistent load of compression, it is necessary that it will be positioned in the highest possible part of the compressed slab, at the distance of the concrete cover chosen by the structural designer of the composite floor made of corrugated metal sheet; such positioning is achieved for the first time through the A) and B) solutions of this patent;
to preserve this important contribution of the electrowelded wire mesh, it is fundamental that the electrowelded wire mesh itself is protected against possible phenomenon of buckling;
such a phenomenon of instability of the rounds bar of the electrowelded wire mesh can be normally ruled out because the load normally pushes against the floor, then on the concrete cover and finally on the electrowelded wire mesh itself, preventing any phenomenon of buckling;
in several circumstances of concentrated loads (i.e. a corridor with two heavy libraries or industrial racks placed at the third or fifth central part of the span) it is possible that a phenomenon of buckling of the round bar of the electrowelded wire mesh will take place in the central part of the composite floor, which is free from any load,
in such case the profiles (2a, 2b) of Fig. 2 or the snap stirrups (2) of Fig. 11, entail ligatures and forks which constrain the electrowelded wire mesh avoiding buckling;
it is up to the designer to establish the pitch that the profiles (2a,2b) of Fig.2 or the snap stirrups (2) of Fig. 11 must have, in the area of maximal compression of the base, where the composite floor works with positive bending moment, so that also this limited possibility of risk could be ruled out.

The invention, it should be noted, is not limited to the representations given in the figures, but may be perfected and modified by those skilled in the art without, however, exceeding the limits of patent.
The invention permits numerous advantages, and to overcome difficulties that could not otherwise have been overcome with the systems on sale at present.

Claims

Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), comprising the following components:
- corrugated metal sheet (1)

- electrowelded wire mesh (3)

- concrete (4)
Characterized by the fact that:

- between the corrugated metal sheet (1) and the electrowelded wire mesh (3) , above the corrugated metal sheet (1), stirrups (2) and/or profiles (2a, 2b) are positioned perpendicularly to corrugations of the corrugated metal sheet (1), with a calculated interval (ps), regularly throughout the whole floor surface;

- the concrete (4) is a light or extremely light concrete with a specific weight lighter than 1600Kg/mc;

- the stirrups (2) and/or the profiles (2a, 2b) have a length which is at least the same as the interval (pc) of the corrugations of the corrugated metal sheet (1),

- the stirrups (2) and/or the profiles (2a,2b) are mechanically fixed to the superior edge of the corrugated metal sheet (1),

- the electrowelded wire mesh (3) is kept apart from the corrugated metal sheet (1) by the presence of the stirrups (2) and/or of the profiles (2a, 2b) on said corrugated metal sheet (1),

- the concrete (4) fills the corrugations of the corrugated metal sheet up (1), covers the stirrups (2) and/ or the profiles (2a,2b) as well as the electrowelded wire mesh (3) with a suitable concrete cover,

- the creep strength between the concrete slab and the corrugated metal sheet (1) is given by the stirrups (2) and/or the profiles (2a, 2b) as well as by the channels of the corrugated metal sheet (1) and the adherence of the concrete (4) against the corrugated metal sheet (1),

- the electrowelded wire mesh (3), being supported by the stirrups (2) and/or by the profiles (2a,2b), works in a compression environment where the composite floor, made of corrugated metal sheet (1) and concrete (4), having a positive bending moment , in the middle part of the bearing beams, allowing for the first time to take full advantage of the structural contribution of the electrowelded wire mesh (3) in a compressed area, for checking positive moment, in floors made of corrugated metal sheets and concrete.

- the above structural position of the electrowelded wire mesh (3) in a compressed area, thru the use of light or extremely light concrete (4), determines a remarkable increase , from 200 to 300%, of the fully plastic moment of collapse, in comparison with the same loft's area without the electrowelded wire mesh (3) in the compressed area,

- the above structural position of the electrowelded wire mesh (3) in a compressed , with the use of light or extremely light concrete (4), allows, provided that the load is the same, a significant increase of the free span, from 25 to 50%, in comparison with spans which would be reachable using the traditional floors made of corrugated metal sheet (1) and ordinary concrete (4) or, assuming the same free span, an identical increase of the load.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1, characterized by the fact that the electrowelded wire mesh (3) is bound to the stirrups (2) and/or the profiles (2a,2b) throughout binding or other structural connections, in order to avoid cases of buckling of the round bars of the electrowelded wire mesh (3), which are parallel to the corrugations of the corrugated metal sheet and which are compressed in the middle of the span.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 2 characterized by the fact that the stirrups (2) and/or the profiles (2a,2b), supporting the electrowelded wire mesh (3) situated in the middle of the floor are equidistantly positioned, in order to avoid cases of buckling of the round bars of the electrowelded wire mesh (3), which are parallel to the corrugations of the corrugated metal sheet and which are compressed in the middle of the span.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to the previous claims characterized by the fact that the stirrups (2) and/or the profiles (2a, 2b) are fixed to the higher edge of the corrugated metal sheet (1) through structural connectors completely or at least partly resistant to the effects of shear and sliding, calculated in accordance to the Science of the Constructions.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1, characterized by the fact that the profiles (2a , 2b) and/or (2) are respectively U, L,C or Ω profiles.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to a previous claim characterized by the fact that the stirrups (2) and/or the profiles (2a, 2b) present some slot or socket punch (5) as well as holes (φa) to receive and block the electrowelded wire mesh (3) .
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1 characterized by the fact that the electro welded net(3) is leaning or it is even fixed against the stirrups (2) thanks to several forks (5a), which present a U round or any other shape, profile and form or another bracing of reinforced concrete as well as through several bars (5b) of round, square or other section and that the stirrup (2) is outlined in metal sheet or alternatively die cast in aluminium or other alloy.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1 characterized by the fact that the profiles of the stirrups (2) are C, L or Ω profiles, with flaps which represent some reeds of spear-like (c+d) connectors (a) , with holes (φa) on the higher wing (b) of said stirrups (2) , finalized to block the electrowelded wire mesh (3) with the insertion of bracing suitable for round reinforced concrete (5a, 5b) , or square or whichever other profile in order to fully involve the electro welded net in the compressing contractions in the median strip of the loft's span.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 8 characterized by the fact that the flaps representing the reeds of the connectors (a) and of the spears (c+d) , are profiled and/or folding pressed and/or embossed and or cut with plate marks of width (bc) and intervals (ic) and (pc) to provide ideal coupling on the loop (6) or incisions (7) existing on the corrugated metal sheet (1), which are either parallel or perpendicular toward the longitudinal direction of the fretted metal sheet.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1 characterized by the fact that the supporting stirrups (2) are disposed and organised over a single corrugated metal sheet (1) with a given interval (ps) and that the slots (6) which are on the corrugated metal sheet (1) are replaced by incisions.
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1 characterized by the fact that the supporting stirrups (2) have a superior wing (b) with an angle γ greater than 90 degrees wider in comparison with the core (h).
Composite floor element for buildings made of corrugated metal sheet (1) and concrete (4), according to claim 1 characterized by the fact that the stirrups (2) present on the superior wing (b) with a slot (6a) or flap (6b) to make room for a round iron bar (5b), which can also be square or of any other shape, to keep the electro welded mesh in alternative or together with the forks (5a) and that the slot (6c) or the flap (6d) can be positioned over the opposite side of the superior wing (b) and that on the same stirrup (2) there can be both, the slots or the flaps (6a, 6b, 6c e 6d), as well as the holes (φa) on the superior wing (b) for the insertion of the forks (5a).