WO2000032888A1

WO2000032888A1 - Active formwork of concrete structures

Info

Publication number: WO2000032888A1
Application number: PCT/CZ1999/000045
Authority: WO
Inventors: Ondřej SOBOTKA
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-11-27
Filing date: 1999-11-26
Publication date: 2000-06-08
Anticipated expiration: 2001-05-27
Also published as: CZ390398A3; CZ286533B6; AU1258300A

Abstract

The invention concerns active formwork of concrete structures consisting of self-contained elements (1) made of thin-walled material, namely sheet metal, fitted with gang nails (2) oriented into the space to be filled with concrete mix. Individual elements (1) are self-supporting, three-dimensional hollow figures in the shape of the letter C, whose at least two sides contain gang nails (2) oriented into the concrete mix. The apertures arising at the points of gang nails (2) remain unblocked. Additional apertures (3) are made at the contact sides between individual elements (1). Adjacent self-contained elements (1) are interconnected by concrete passing through the apertures (3) to form a continuous concrete slab.

Description

Active formwork of concrete structures

Technical field

The given invention concerns active formwork of concrete structures, namely horizontal structures, but also vertical load-bearing structures. Active formwork consists of self-contained elements made of thin- walled material, mainly sheet metal, with gang nails oriented into the concrete mix.

Background of the invention

The methods of reinforcing concrete structures applied to date include dispersed reinforcement, concentric reinforcement and coupled reinforcement.

Dispersed reinforcement is produced by adding such particles into the concrete mix that are able to transfer the tensile stresses due to the bending moment. The main drawback of this solution is the fact that the reinforcing particles are found along the whole cross section, i.e. even in the points where their presence is unnecessary. In addition, the application of formwork or moulds is also necessary. Another disadvantage of this method consists in its rather complicated and demanding technology. In comparison with other types of reinforcement, the load-bearing capacity of dispersed reinforcement is low.

The application of concentric or member reinforcement consists in placing reinforcement inside a mould, subsequently filled with concrete. Among the drawbacks of this method there is the necessity of mould manufacture, which is expensive and complicated, the time consuming preparation for work and non-precise and unidentifiable position of reinforcement in the final product.

There also exists a reinforcing element, used for reinforcing porous concrete slabs, which is described in CS 219997. The method is based mainly on bonding porous concrete with its reinforcement. It combines all drawbacks of classic concrete structures, such as the necessity of formwork application, inaccuracy of the upper face etc. The principle of a coupled structure consists in fixing beams to the main girder grid. Both the beams and the girders are made of steel sections. The beams are usually one meter, but exceptionally up to three meters, apart. Profiled sheets laid on the top of the beams form permanent formwork. At pre-set distances, there are pins fixing the sheet metal to the bearing steel profiles. A specified concrete mix cover is applied on the profiled sheeting. The compressive stresses are taken over by the co-acting section of concrete around the pins. The disadvantage of this method is excessive consumption of steel pins. Only one direction of potential stress means another drawback. The used sheet metal has no other function. Manufacturing of such reinforcement is elaborate and costly. The given reinforcement has comparatively low fire resistance. It also relies on the usage of soffits, which means creating unused space. Another weak point of this structure is the Faraday cage phenomenon, resulting, among other things, in the lack of ionised air inside the building.

Another solution described e.g. in the CS 51917 file is focused on the construction of columns and girders and, above all, their bonding. The design also includes a steel channel that functions as a one-dimensional element or a member. Such channels could not act as a rigid floor slab, even if they were put closely side by side.

The CS 149428 file gives an example of a coupled building slab and the method of its manufacturing. It refers namely to the production of prefabricates which are not suitable for manufacturing monolithic structures. A potential bonding of individual slabs is provided by means of complicated details used in steel framing systems. The resulting structure designed in this way does not behave as a monolith.

Summary of the invention

The above mentioned disadvantages are eliminated to some extent by using active formwork of concrete structures. This invention consists of separate elements made of thin-walled material, mainly sheet metal, fitted with gang nails oriented into the space filled with the concrete mix. The invention is based on self-contained, self-supporting, three-dimensional elements in the shape of hollow "C"s, whose two (or more) sides are fitted with gang nails oriented into the concrete mix. The holes formed at the points where the gang nails are cut in metal remain unblocked. Additional apertures are made at the contact surfaces between individual elements. Adjacent elements are interconnected by concrete mix passing through the additional holes to form a continuous concrete slab.

The serviceable element is a hollow figure, whose profile resembles a horizontally positioned letter "C" opened upwards. The gang nails are situated at the longest side of the C-shaped element forming its bottom and at the short sides parallel to the longest side forming its upper face. Additional apertures at the lateral contact side of the element can be triangular or circular in shape. Additional apertures are used for mounting specially designed transversal reinforcement to form transversally reinforced concrete structures.

Another serviceable element takes the form of a C-shaped hollow figure opened sideways. The element is consists of lateral sides in the shape of longer bases which are fitted with gang nails and of a web, forming the contact side, which is fitted with additional apertures. Additional apertures are conveniently used for mounting transversal reinforcement.

The main advantages of the above described method are: simple preparation of active formwork elements for bearing structures, fast and simple concreting and a high-precision surface attained by screeding along the upper edge. Another advantage is optimal consumption of steel, lower in comparison with commonly used methods. The gang nails are easy to manufacture by pressing, while the strength of the basic sheet metal remains undiminished, and together with concrete they produce a solid continuous structure. The apertures at the lateral sides of elements make the sheet metal lighter, decrease its consumption, increase its rigidity, allowing, at the same time, for mounting transversal reinforcement or for connecting to the adjacent element of active formwork. The active formwork of this design allows for two-way stress, and each individual element may be positioned with perfect precision. Another advantage consists in the fact that no moulds are needed, except for supporting tapes. Active formwork of this design allows for easy finishing. And to conclude, it is universally applicable - active formwork may be combined with any other systems to speed up production and increase its efficiency. Active formwork of this design allows for on-site assembly, which eliminates high costs for transport. Material waste is minimized, and the manufacturing of active formwork and its application can be performed by less qualified labour. Active formwork of concrete structures is applicable not only in horizontal bearing structures, but also in vertical bearing structures. Its design allows for the application of any plaster material. Active formwork of concrete structures according to this invention provides a solution combining reinforcement and formwork in one element.

Brief description of the drawings

The invention in question will be described in a greater detail using a particular example of implementation illustrated by the enclosed drawings. Figure n. 1 depicts an example of an element of active formwork of concrete structures in the shape of a horizontally positioned letter "C" in front view. Figure n. 2 displays the same element in plan view, and figure n. 3 shows the element in side view. Figure n. 4 shows the arrangement of active formwork elements, forming a two-way reinforced floor element in axonometric view, while figure n. 5 gives axonometric view of active formwork elements mounted on supports.

Detailed description of the preferred embodiments

A model application of active formwork of concrete structures consists of self- contained elements I made of thin- walled plate metal, fitted with gang nails 2 oriented into the concrete mix space. Individual elements 1 are self-supporting, three-dimensional hollow figures in the shape of the letter C opened upwards. The hollow element I is fitted with gang nails 2 at the longest side 7 of the letter C that forms its bottom and at the short sides 8 parallel to the longest side 7, which form its upper face. The gang nails 2 are oriented into the concrete mix. The holes arising at the points of gang nails 2 remain unblocked. Additional apertures 3 are made at the contact sides of individual elements 1. Adjacent self-contained elements I are interconnected by concrete passing through the additional apertures 3 to form a continuous concrete slab. Additional apertures 3 at the lateral contact side 9 of the element 1 are circular in shape. Additional apertures 3 serve for mounting transversal reinforcement 5 in order to form a transversally reinforced concrete structure.

Another example of implementation shows the element I in the shape of a hollow figure resembling the letter C, open towards its side. The element I consists of lateral contact sides 9 in the form of longer bases fitted with gang nails 2 and a web forming the contact side fitted with additional apertures 3. Additional apertures 3 serve for mounting transversal reinforcement 5.

The gang nails applied in all examples are oblong-shaped with their sides in 1: 10 scale.

The lateral sides of elements I are fitted with additional circular apertures 3 with a diameter of 160 mm. The apertures are 198 mm apart, and they serve for mounting transversal reinforcement 5. Individual elements I are placed in the bearing structure side by side to form active formwork, the inside of the elements I being subsequently filled with concrete mix. The basic dimensions are: width = 600 mm, height = 200 mm, length = 6000 mm. The joint between the plate of the elements I and concrete is secured by gang nails 2 pressed in the plate. The apertures appearing in the plate as a result of pressing the gang nails 2 allow, to a certain extent, for concrete leakage to form small corpuscules, important for further processing. When dried, the corpuscules form a dense grid - depending on the quantity and size of the apertures - which facilitates the finishing of the lower face by spatula or classic plastering.

Industrial applications

Active formwork of concrete structures of this design will find its place mainly in the construction of new buildings, but also during the reconstruction of the existing buildings.

Claims

P A T E N T C L A I M S

1. Active formwork of concrete structures, consisting of self-contained elements made of thin-walled material, mainly sheet metal fitted with gang nails oriented into the concrete mix, is characterised in that individual elements (1) are self-supporting, three-dimensional hollow figures in the shape of the letter C, whose at least two sides are fitted with gang nails (2) oriented into the concrete mixture, the apertures arising at the points of gang nails (2) remain unblocked, additional apertures (3) are made at the contact sides of individual elements (1), and adjacent self-contained elements (1) are interconnected by concrete passing through the apertures (3) to form a continuous concrete slab.

2. Active formwork according to claim 1, characterised in that the element (1) resembling a hollow figure in the shape of a horizontally positioned letter C, opened upwards, is fitted with gang nails (2) at the longest side (7) of the letter C forming the bottom and at its short sides (8), parallel to the longest side (7), which form the upper face.

3. Active formwork according to claim 2, characterised in that additional apertures (3) at the lateral contact side (9) of the element (1) are of circular shape.

4. Active formwork according to claim 2, characterised in that additional apertures (3) in the lateral contact side (9) of the element (1) are of triangular shape (4).

5. Active formwork according to claim 3 or 4, characterised in that transversal reinforcement (5) is mounted in additional apertures (3) to form a transversally reinforced concrete structure.

6. Active formwork according to claim 1, characterised in that the element (1) resembling a hollow figure in the form of the letter C, opened sideways, consists of lateral sides (9) in the form of longer bases fitted with gang nails (2) and a web forming the contact side fitted with additional apertures (3).

7. Active formwork according to claim 6, characterised in that additional apertures (3) are used for mounting transversal reinforcement (5).