EP1092817A2

EP1092817A2 - Improved formwork for the construction of floors, roofings and the like

Info

Publication number: EP1092817A2
Application number: EP00119093A
Authority: EP
Inventors: Roberto Il Grande
Original assignee: Daliform SRL
Current assignee: Daliform SRL
Priority date: 1999-10-12
Filing date: 2000-09-02
Publication date: 2001-04-18
Also published as: IT248147Y1; EP1092817A3; ITPN990041V0; ITPN990041U1

Abstract

Formwork for containing a concrete casting, adapted to form the resting surface for a floor, roofing or similar structure of a building. The formwork is made up by stool-shaped elements (15) which are moulded out of plastic material and are joined to each other by allowing their side edges to overlap, while leaving vertical cavities (16) open between contiguous elements.

These cavities are then closed on top by means of stoppage elements (18) adapted to prevent the cast concrete from penetrating them.

Description

The present invention refers to an improved formwork adapted to contain a concrete casting for the construction of resting surfaces to lay floors, roofings and similar structures thereupon.
In building constructions, the surface or floor resting against the ground is quite often constituted by a constant-thickness concrete casting, which discharges its weight, as well as the use or working overload, in a spot-by-spot or locally concentrated manner. Such a concrete casting, which represents the actual support for the floor, is contained between the actual load-bearing structures of the building, such as the foundations on which pillars or walls of reinforced concrete, stones or bricks are raised. These foundations have the task of distributing the load of the building on to the ground. In practice, however, the problem arises of the greater pressure that is exerted by the foundations as compared with the one exerted by the intermediate casting supporting the floor. Owing to this difference in the pressures, the ground tends to yield to a greater extent under the foundations and the intermediate casting tends therefore to gradually deform up to the point at which it breaks off along various lines. A first known solution adopted to do away with this problem calls for the intermediate casting to be reinforced by embedding an electro-welded grid therein or through the use of prestressed concrete.
This solution, however, proves effective in reaching its aim only under certain conditions of the ground and the load of the building.
Another solution known in the art calls for a reinforced concrete slab to be cast so as to rest, ie. lay upon formworks of the lost material, ie. unrecoverable type made of such materials as polystyrene or cardboard honeycomb structure. These formworks are approached to each other, ie. set close to each other to form a continuous structure. In the course of the time, the material thereof dissolves, thereby leaving a void gap between the foundations. In more recent years, the formworks are constructed by making use of stool-like elements, which are made of rigid plastic material and are joined to each other by the overlapping of their respective side edges. Elements of this kind are described for instance in the Italian patent no. 1253374.
Such a solution is very effective in solving the problem of creating a hollow aeration space under the floor, but does not yet prove fully satisfactory in its ability of evenly absorbing the strains and deformations deriving from the differentiated pressures or loads imparted on to the ground by the foundations and the floor support casting. In fact, the stool-like elements, which are usually provided with a dome of a circular shape, leave vertical gaps or cavities open between them, into which the concrete casting is therefore able to flow and set, thereby forming a kind of solid legs. These solid legs, therefore, eventually act as further points of concentrated and differentiated pressure exerted on to the ground.
It therefore is a main purpose of the present invention to provide an improved formwork for the construction of floors, roofings or the like, which enables the foundations and the concrete slab of the floor resting against the ground to be constructed in such a manner as to ensure that the load of the building rising thereupon is distributed evenly on the same, so as to prevent the slab and the floor laid thereupon from breaking off or splitting in the course of the time.
According to the present invention, this and further aims are reached in a formwork embodying the characteristics recited in the appended claims and more thoroughly illustrated in the description that is given below with reference to the accompanying drawings, in which:

Figures 1A-1C are diagrammatical views of the traditional building method;
Figures 2A-2C are diagrammatical views of the building method making use of an improved formwork according to the present invention;
Figure 3 is an exploded perspective view of a detail of a formwork made according to the present invention; and
Figures 4A-4F partial cross-sectional diagrammatical views of different types of slabs constructed with the use of formworks according to the present invention.

With reference to Figures 1A through to 1C, these can be noticed to schematically illustrate a building 10 which is raised on a ground 11. The building 10 is sustained by foundations 12, such as pillars or the like, which are sunk into the ground 11. Furthermore, the building 10 rests on the same ground with a ground floor 13 laid upon it. This floor 13 is usually constituted by a reinforced or prestressed concrete casting. It has been found and demonstrated that the load of the building 10 exerts onto the ground 11, in correspondence of the foundations 12, a pressure that is greater than the pressure exerted by the floor 13. As a result, in the course of the time the ground tends to yield to a much greater extent under the foundations 12, while the floor 13 is correspondingly stressed by such an upwardly directed pushing force as to be able to bring about considerable cracks and breakages 14 that start from the extrados of the floor and may even extend throughout the same floor (Figure 1C).
In the building solution according to the present invention, which is illustrated schematically in Figures 2A through to 2C, said floor 13 laid against the ground can be noticed as being cast on a lost-material formwork 15 that rests directly on the ground. The formwork 15 is constituted by elements in the form of a stool, which are moulded out of plastic material and are connected to each other by the overlapping of their respective side edges (Figure 3).
These stool-like elements are usually provided with a top surface of a circular shape. As a result, when joined together, the same elements practically form upwardly open cavities 16 therebetween (Figure 3), which extend vertically down to the feet of the elements themselves. In order to prevent the cast concrete from entering such cavities 16, thereby forming pillars through which a part of the load of the building would then be able to discharge itself with a locally concentrated pressure, the use is proposed of stoppage elements 18.
The most rational configuration for such a stoppage element 18 is represented by a rigid diaphragm that is appropriately shaped so as to be able to fittingly conform to the opening of the cavity 16, in such a manner as to create a formwork 15 featuring a continuous tread-on surface. Upon such a surface the reinforcing iron rods of the slab can be appropriately arranged in view of the subsequent concrete casting.
The above described solution allows for different types of slabs to be made through the use of formworks according to the present invention, as schematically illustrated by the respective partially cross-sectional views appearing in Figures 4A through to 4F.
In a first example of possible embodiment, Figure 4A illustrates, as a cross-sectional view of the top portion of the elements forming the formwork 15, a ceiling floor with lacunar intrados formed by: an upper reinforcement 20 embedded in a concrete casting 21, a layer of insulating material 22 provided therebelow, and a lower cross reinforcement 23 embedded in a lower extension of the concrete casting that is contained and limited downwards by the stoppage element 18. Figure 4B is a cross-sectional view of the same ceiling floor at the foot portion of the elements of the formwork 15.
In a second example of possible embodiment, Figures 4C and 4D are cross-sectional views, at the top portion and the foot portion of the elements of the formwork 15, respectively, of a reinforced slab with lacunar intrados similar to the one shown with reference to the ceiling illustrated in Figures 4A and 4B. The corresponding elements that form the two structures are indicated with the same numerical references.
In a third example of possible embodiment, Figures 4E and 4F are cross-sectional views, at the top portion and the foot portion of the elements of the formwork 15, respectively, of a reinforced slab with undulating intrados, which is shown to simply comprise an upper reinforcement 20 embedded in a concrete casting 21, and a lower cross reinforcement 23 laid directly upon the stoppage element 18.
As a result, with the use of the formwork according to the present invention buildings 10 can be constructed, in which between the foundations 12 there are inserted reinforced slabs 13 which, further to featuring an aeration hollow space provided therebelow, will in the course of the time settle into the ground jointly with the foundations without breaking or splitting off. This settling of the foundations and the slabs will in fact only cause the legs of the stool-like elements forming the formwork 15 to crush and break down. Anyway, the formwork 15 itself constitutes a lost-material fade-away structure, so that its gradual destruction in the course of the time will not affect the stability and integrity of the building to any extent. The formworks 15 with the stoppage elements 18 enable therefore the slabs to be supported in the phases during which the concrete is cast, and until such concrete castings become fully consolidated, in a simple and effective manner and at certainly competitive costs as compared with traditional solutions. Furthermore, they ensure a desired continuity of the slab between the foundations and the impermeableness of the intrados thereof.

Claims

Formwork for containing a concrete casting, adapted to form a resting surface for a floor, roof or similar structure of a building, said formwork being constituted by elements moulded out of plastic material in the form of a stool, which are joined to each other by the overlapping of the respective side edges, thereby leaving vertical cavities open between contiguous elements, said formwork being characterized in that stoppage elements (18) are further provided to close said vertical cavities (16) between the elements of the formwork (15), in such a manner as to prevent the cast concrete from entering said cavities to form corresponding solid legs through which a part of the load of the building would then be able to discharge itself on to the ground with a locally concentrated pressure.
Formwork according to claim 1, characterized in that said stoppage elements (18) are constituted by shaped rigid diaphragms, in such a manner as to turn the upper surface of the formwork into a continuous tread-on surface.