Cellular slab

The present invention relates to cellular slabs, particularly to a cellular slab, in which a cellular structure is formed by using intermediate plates to combine at least two slab elements forming the outer surfaces of the structure. The invention also relates to a method for manufacturing a cellular slab, as well as to uses of the cellular slab according to the invention. The invention relates especially to cellular slabs with a high loading resistance, which can be used in the building industry.

Cellular slabs can be manufactured, for example, by laser welding, gluing, riveting, or machine-seaming the slab elements to each other. Profile slabs can be set directly on top of each other or flat or profiled slabs can be attached to each other through the agency of intermediate plates. The drawbacks of such cellular slabs are high manufacturing costs and the several intermediate stages of manufacture. Laser welding also has the drawback that it can reduce the long-term corrosion resistance of galvanized-steel structures. The drawback with gluing is poor long-term durability, which particularly leads to splitting-off, due to variations in temperature and humidity conditions.

Slab structures are also known, in which two flat or profiled slab elements are attached to each other, for example, by means of insulating foam or wool, without separate intermediate plates. The stiffness of such constructions is not, however, sufficient for all of the most demanding building applications. When subject to alternating loading, the insulation will typically begin to detach form the slab elements, which further weakens the structure.

The invention is intended to eliminate the defects of the state of the art described above and for this purpose create a cellular slab construction that can be manufactured in a more practicable way compared to known cellular slabs, hi particular, the invention is intended to create a cellular slab and method for manufacturing a cellular slab suitable for roll- formed/roll-formable slabs.

The invention is based on the idea that the surface-slab elements and intermediate plates of

the cellular slab are attached to each other by means of a friction joint, a form-closed joint, or a combination of a friction joint and a form-closed joint. In that case, for example, folds are created during manufacture in a surface slab to be roll formed, which improves the bending strength of the structure and at the same time locks separate intermediate plates to the slab element by their first edges. The intermediate plates can be further attached by their second edges to a second surface-slab element, so that as a result a cellular slab is formed. Each individual cell is delimited by two adjacent intermediate plates and surface and bottom slabs, there being one cell, or typically several cells next to each other in the finished cellular slab.

The attachment to both slab elements preferably takes place with the aid of a form-closed friction joint. A friction joint refers to a joint, the force acting on which is transmitted from one joint surface another with the aid of friction between the joint surfaces. A form-closed joint refers to a joint, in which the shapes of the pieces limit their movement in at least one dimension and the force acting on the joint is transmitted from one joint surface to another by means of the normal strain between the joint surfaces. On the other hand, a form-closed joint can arise as a result of temporary or permanent deformation of the second or both joint surfaces. The term form-closed friction joint refers to a joint, in which the force acting on the joint is transmitted with the aid of both the friction between the joint surfaces and the normal strain between the joint surfaces.

According to a preferred embodiment, the cellular slab is based on slab elements, between which walls at right angles to the general plane of the cellular slab are installed. The thickness and cross-sectional shape of both the slab elements and the intermediate plates can always be altered according to the requirements of the planned purpose. For example, compression-loading capacity can be increased by altering both the material thickness and the cross-section. The slab elements and the intermediate plates are manufactured from thin sheet, preferably from thin steel sheet. The slab elements are preferably manufactured by roll-forming, for example, from thin sheet.

In the method according to the invention, the first and second slab elements are attached at a distance from each other with the aid of intermediate plates, in order to create a cellular

structure, with the aid of a friction joint or a form-closed joint, preferably a form-closed friction joint, between at least one slab element and an intermediate plate.

More specifically, the cellular slab according to the invention is characterized by what is stated in the characterizing portion of Claim 1. The method according to the invention is characterized by what is stated in the characterizing portion of Claim 25. The use according to the invention is characterized by what is stated in Claim 29.

The slab element of the cellular slab is preferably of thin sheet and most preferably of a profiled sheet manufactured by roll forming. The term a profiled sheet refers to a sheet, in which a corrugated basic shape, for example, has been profiled. Alternatively, the slab element can be manufactured, for example, by flanging.

The height of the profile groovel can be dimensioned in several ways. It can be made high in one of the slab elements of the cellular slab, in such a way that the profile groove extends to the surface level of the cellular slab. In that case, a separate supporting stiffener will not necessarily be required, because the intermediate plate will be supported directly on the support surface against the surface of the cellular slab. The profile groove can also be left to be lower than the surface level of the cellular slab. The profile grooves of the slab elements of the cellular slab can be equal in height, or the profile groove formed in one slab element can be high and the profile groove formed in the other slab element can be low. It is also possible to envisage that, instead of changing the height of the profile groove formed in the slab element, slab elements with a lower or higher profile height can be used, according to the intended use of the slab elements, in which case the profile grooves formed in the slab elements for the intermediate slabs can be of a standard height.

The internal diameter of the profile groove too can be dimensioned in several different ways. Preferably, the width of the internal diameter of the profile groove is of the same size or smaller than the thickness of the intermediate plate. On the other hand, it is possible to use an intermediate plate that is thicker than the width of the internal diameter of the profile groove, in which case a shape that narrows towards the narrower sides of the intermediate plate will be achieved. The friction of the friction joint between the

intermediate plate and the profile groove will then increase, because the intermediate plate will act as a wedge. In addition, the wedge-like shape of the intermediate plate will facilitate the installation of the intermediate plate.

Cellular slabs can be used for several different purposes. A cellular slab is suitable not only for floors, but also as a load-bearing structure for a ceiling, or as a load-bearing or non- load-bearing wall or ceiling element.

Considerable advantages are gained with the aid of the invention. With its aid, it is possible to manufacture an entire cellular slab with the aid of only friction joints, form-closed joints, or combinations of these. Welding or chemical adhesive substances are not required, because the friction/form of the joint of the slab element and the intermediate plate acts as an attachment, which simplified manufacture. Thus it is very suitable for mass production. On the other hand, in the case of form-closed joints, the form-closing not only simplifies manufacture, but also, thanks to the flanges and fold surfaces running at right-angles to the bending direction, it stiffens the structure particularly in the longitudinal direction, i.e. in the longitudinal direction of the folds of the profile shape of the slab elements. With the aid of form-closed joints, in addition to the above advantages it is also possible to reinforce the cellular slab in terms of strains parallel to the plane of the slab, as will hereinafter be described in greater detail.

The term form-closing refers to the fact that profile grooves, which can be folds, creases, or pleats, corresponding to the shapes of the intermediate plates, are made in the slab element. The profile grooves prevent the intermediate plates from moving freely, relative to the slab element, in at least one, preferably two, and typically in all three dimensions. It is typical of a fitting of this kind that the intermediate plates and slab elements are locked relative to each other by means of a form-closed friction joint, without a secondary attachment, such as machine seaming.

In the following, the invention is examined in greater detail with reference to the accompanying drawings, in which

Figure 1 shows a perspective view of a cellular structure according to one embodiment,

Figure 2 shows a cross-section of an I-shaped profile groove and an intermediate plate fitted to a profiled slab element,

Figure 3 shows a cross-section of a finished cellular structure manufactured with the aid of the construction of Figure 2,

Figure 4a shows a cross-section of a shallow L-shaped profile groove and an intermediate plate fitted to the profiled slab,

Figure 4b shows a cross-section of a shallow L-shaped profile groove and an intermediate plate fitted to a profiled slab element, in which there is a low profile height,

Figure 5 shows a cross-section of a cellular structure manufactured with the aid of the constructions of Figures 4a and 4b, and

Figure 6 shows a cellular slab, in which one of the slab elements is, for example, a slab for use in sandwich structures, in which there are fish-tail folds.

Figure 1 shows a cellular structure, in which there is a profiled bottom slab 11 and a profiled surface slab 12, as well as intermediate plates, i.e. web plates 13, connecting them. The web plates 13 are attached to profile grooves arranged in the bottom and surface slabs 11, 12. The profile grooves are formed in the bottoms of the corrugations of the corrugated general profile of the surface slabs. The corrugated profile of the profile slab determines the surface level of the cellular slab, in such a way that the surface of the cellular slab is considered the limit, beyond which the profile grooves located in the bottoms of the corrugations of the corrugated profile slab do not protrude. The joint between the web plates and the bottom and surface slabs is a form-closed friction joint.

Referring to Figure 2, the intermediate plate 23 can be essentially straight in the area of the joint and attached to the slab element 22 by fitting it into the essentially I-shaped profile groove 222 made in the plate element 22. The profile groove 222 is preferably manufactured in the bottom of the corrugated shape of the profile slab 221 of the slab element 22, so that it does not protrude from the surface plane of the slab. Figure 3 shows a structure, which is achieved by forming a corresponding form-closed friction joint with the intermediate plate 33 from both surfaces 31 and 32 of the cellular slab.

With reference to Figures 4a and 4b, the intermediate plate 43 can have a joint area that is

essentially L-shape and attached to the plate elements 41, and 42 by fitting it into the L- shaped profile groove 442, 444 respectively made in the slab elements 41, 42. In this case too, the profile groove 442, 444 is preferably manufactured in the corrugated shape 441, 443 of the slab elements 41, 42, in such a way that it does not protrude from the surface level of the slab.

According to the preferred embodiment according to Figure 4b, the horizontal part of the L-shaped profile slab of the intermediate plate 43 is essentially on the same plane as the surface level of the profile slab. This improves the load-bearing capacity of the slab.

Figure 5 shows a stiff cellular slab, achieved with the aid of the constructions of Figures 4a and 4b. A web plate that has primarily a U-shaped cross-section is fitted into profile grooves that have an L-shaped joint surface.

As will be noted from the abovementioned figures, the present joint is particularly effective in the case of corrugated surface slabs. In this case, at least one, and preferably both of the surface-slab elements comprise a profiled sheet, which comprises bottoms extending in the direction of the intermediate plates and protrusions extending in the opposite direction, so that the intermediate plates are attached in each case with the aid of form-closed friction joints made in the said bottoms. The profiling of the bottom and surface slabs increases the surface area and stiffness of the bottom and surface slabs and permits the profile grooves to be left at, or below the plane of the surface level of the slab.

According to one preferred embodiment, the intermediate plates are thermo-perforated, in order to increase their thermal insulating value. The thermo-perforation technique is, as such, known in the art.

The features affecting the properties of the surface and bottom slabs, such as material thickness, cross-sectional shape of the profile, and the material used, can be selected according to the intended use. Similarly, the material thickness, cross-sectional shape of the profile, and other features of the web plates can be selected to be suitable for the intended use. The flat web plate 13 shown in Figure 1 can also be replaced with profiled

web plates, such as profiles with a σ-shaped (sigma-shaped) profile, which will increase the stiffness of the structure. On the other hand, instead of using a flat web plate 13, it is also possible to use a web plate with a primarily Z-shaped cross-section. In that case, the profile grooves formed in the surface of bottom slabs have joint surfaces that are primarily L-shaped, but either the bottom or surface plate's L-shape is in the opposite direction to that of the profile groove of the other bottom or surface slab. The web plate can also have a raised pattern, so that as the load-bearing surface area of the web increases, the stiffness of the entire structure also increases. On the other hand, the portion of the web plate that is set into the profile groove can also be at a different angle, compared to the rest of the web plate. In that case, the angle between the web portion of the web plate and the portion delimited by the joint surfaces will be less than 180° and more than 90°. On the other hand, the profile groove made in the surface slab can be at an angle other than 90° relative to the straight direction of the bottom on the corrugation of the profile shape of the surface slab. By using web plates, or a profile-groove angle of this kind, it is possible to construct a cellular slab, in which the cells are primarily δ-shaped (triangularly-shaped), or trapezium- shaped.

The intermediate plates are preferably manufactured from a metal material, the thickness of which is greater than, typically at least twice the thickness of the material thickness of the slab elements.

The distance of the surface-slab elements from each other at the locations of the web plates can be, for example, 5 - 20 cm.

The present structure can be implemented in such a way that the intermediate plates are attached to the slab elements essentially entirely with the aid of a form-closed joint, or friction joint, or preferably a form-closed friction joint between the surface-slab elements and the intermediate plates, without separate attachment means, such as welding, adhesive substances, or machine seaming. This makes the production process highly streamlined.

In addition to purely form-closing and friction, it is possible to use a secondary mechanical attachment to reinforce the joint, for instance, adhesive substances, welding, for example,

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laser welding, heating, riveting, or local deformations in the area of the joint, such a rivetless riveting, or an attachment implemented with the aid of local protrusions and corresponding holes or recesses, or similar. Rivetless riveting refers to, for example, the local penetration of the joint, or local deformation, for example, depressions or folds, so that local structures increasing the durability of the joint are created in the joint. Combinations of different secondary attachment methods are also possible.

The slab elements and the web plate can also be locked longitudinally to each other, by creating a corrugated shape in the web plate and profile groove of the surface slab in the longitudinal direction, or by using lateral end folds. Longitudinal locking will improve the shear-resistance between the slab elements and the intermediate plates and when using the slab elements as a sandwich construction the joint effect between the surface slab and the concrete will improve.

According to a preferred embodiment, the cellular element is filled with an insulating material, such PUR, EPS, XPS or wool insulation. So-called hard insulations (e.g., PUR, EPS, XPS) are especially advantageous, as they retain their shape under stress. The insulation can also form adhesion with the slab elements. The insulating material not only improves the thermal, sound, and fire resistance of the structure, but also increases the torsion-resistance of the web plates, thus improving the durability of the entire structure. In particular, insulators like polyurethane and similar prevent, by their own compressive effect, the torsion or buckling of the web plate, so that the durability of the entire structure improves. On the other hand, the web plates prevent most of the deflection of the structure, which means that the polyurethane does not try to tear off the surface slabs. Most of the strain is taken by the steel. Thus, good and diverse long-term resistance is achieved, because the surface slabs remain together and retain their shape, despite the loading. For its part, the durability also improves the form-locked joint, as described above.

According to one embodiment, raised patterns or spikes are created in the slab elements forming one or both of the surfaces of the cellular slab. The raised patterns or spikes can be created in the flat surface of the surface slabs either so that they protrude from all of the planes formed by the corrugated profile, or from only some of the planes formed by the

corrugated profile. Preferably, the raised patterns or spikes protrude from planes deviating from the planes parallel to the broken line of the corrugated profile of the surface slab in Figure 4b. The protruding raised patterns or spikes improve the joint effect of the surface slab significantly, when the cellular slab is used as a sandwich slab or slab and concrete is cast on top of the surface slab, in which the raised patterns or spikes are formed.

The intermediate plates are preferably fitted detachably to a sandwich slab. Thus, the cellular slab can be used during concrete casting as a temporary support, from which the lower layers, i.e. the bottom slab and web plates, can be removed once the concrete has cured. This will create a considerable increase, up to 20 cm, in room height under the concrete, if the cellular slab is used to make an intermediate floor. Alternatively, the cellular slab can be left in the intermediate floor to improve the sound or thermal insulation of the structure, or its fire resistance or load-bearing capacity. On the other hand, the stiffness of the cellular slab is better than that of similar known appliances, so that the number of casting supports can be significantly reduced.

The web plate need not necessarily be vertical between the surface and bottom slab, but can also be at a slant, for example, to form crosses.

The support reaction of a cellular slab can be further increased by using thicker web-plate steel, or several web plates in specific parts of the cellular slab, which are designed to provide support at the locations of other supports, such as load-bearing walls, or temporary columns. Several web plates can be located, for example, as a wedge at the location of a support point, to locally reinforce the structure in areas of high stress.

With reference to Figure 6, according to one embodiment the slab elements 62 forming one surface of the cellular slab comprise a composite slab for making concrete composite structures, in which case the intermediate plates are form-fitted to the composite slab. Typically, there is a trapezium, i.e. fish-tail-shaped profile groove in the sandwich slab, to which the web plates can be attached by form-closing. The form-closed joint with the composite slab can also be designed to be such that it provides an improved adhesion profile on the concrete-side surface of the sandwich slab, hi that case, the form fitting will

create a pattern improving adhesion in the upper surface of the slab. An implementation of this kind can be created with the aid of form locking made with the aid of, for example, an L-shaped profile groove, in which case the horizontal part of the L profile will form a peak, under which the concrete will, however, penetrate, hi the surface of the concrete side of the profile groove, there can also be secondary patterning, for example, raised patterning, in order to improve adhesion.

Structures according to the present invention and its embodiments can be used, as either permanent or temporary supports in, for example, ceiling, intermediate floor, wall and base floorstructures. On the other hand, they can also act as casting formwork, in which case the structure is set vertically and filled, for example, with concrete. When filled with sand, a corresponding structure can also be used, for example, as noise barrier or bullet shield.

The cellular slab can be implemented as a unit structure, in which case several cellular slabs can be easily joined together, to create a cellular structure with a large surface area.

The slab elements and/or intermediate plates of the cellular slabs are preferably manufactured from steel, most preferably from galvanized or stainless steel, but other materials too, such as aluminium, can be used in special applications.