EP1840291A2

EP1840291A2 - Reinforcing element for concrete structures and concrete structural element using said reinforcing element

Info

Publication number: EP1840291A2
Application number: EP07006679A
Authority: EP
Inventors: Giuseppe De Rossi
Original assignee: La Matassina Srl
Current assignee: La Matassina Srl
Priority date: 2006-03-31
Filing date: 2007-03-30
Publication date: 2007-10-03
Also published as: ITVI20060093A1; EP1840291A3

Abstract

The invention is a reinforcing element (1; 20) for concrete structures comprising a filiform body (2) having one shaped section (3; 21) in the vicinity of each end (2a) and part of the external surface (4) made rough by a plurality of ribs (5) delimiting recesses (6) created in the filiform body (2). The filiform body (2) is a flat strap (7) that defines a mainly longitudinal direction (X) and presents external surfaces (4) on which the ribs (5) ard the recesses (6) are created. The ribs (5) intersect one another.

Description

The invention concerns a reinforcing element for concrete structures and a concrete structural element using said reinforcing element.
It is known that reinforcing elements are usually included in the concrete mix in order to increase its mechanical characteristics.
Said reinforcing elements are commonly called "fibres" and are constituted by variously shaped filiform elements with reduced thickness, only a few centimetres long and made of steel or of a plastic material, which are included in the concrete mix, thus improving its resistance and its behaviour in case of shrinking and cracking.
Their presence also makes it possible to reduce and in some cases even to eliminate the use of metal reinforcements.
Inside the concrete mix the reinforcing elements deploy their characteristics of binding elements, thus improving the resistance of the mix, especially when the concrete matrix cracks.
For these reasons, the main applications of concrete with reinforcing elements, called "fibre-reinforced concrete", are represented by industrial floors, inside coverings of tunnel walls, consolidation of rocky walls and repair of dams and bridges.
A reinforcing element carried out according to the known art and widely used for making fibre-reinforced concrete is represented in Figure 1, where it is indicated as a whole by A.
It can be observed that it is constituted by a metallic filiform body B with mainly longitudinal development and circular cross section, which terminates with a shaped section C at each end.
The reinforcing elements of this kind have a smooth surface and are therefore characterized by limited resistance against the slipping effect generated in case of cracking of the concrete matrix in which they are dispersed.
As shown in Figure 1a, only the shaped sections C present at the ends guarantee resistance against slipping when the matrix M cracks, since the traction force F exerted along the filiform body B is counteracted by the reaction R of the concrete against the inclined side C' of the shaped section C.
Another reinforcing element belonging to the known art is represented in Figure 2, where it is indicated as a whole by D.
It comprises a filiform element E with mainly longitudinal development and circular cross section, provided with a plurality of waves G that follow one another on its entire length.
Reinforcing elements of the type described above, made of a metallic material like for example steel with low carbon percentage or a plastic material, develop higher resistance to slipping since each wave G counteracts the action of the concrete matrix M, thus generating the reactions R illustrated in Figure 2a.
However, they pose the drawback of being excessively elastic and deformable, just because of the presence of said waves G.
A further reinforcing element belonging to the known art is represented in Figure 3, where it is indicated as a whole by H and where it can be observed that it is constituted by a filiform flat strap L having smooth surfaces N.
Reinforcing elements of the type described above, made of a metallic material like for example steel with low carbon percentage or a plastic material, pose the drawback that the surfaces N, being smooth, do not develop any resistance against slipping out of the concrete matrix in case of cracking.
The present invention aims to overcome all the acknowledged drawbacks mentioned above, occurring in the reinforcing elements carried out according to the known art.
In particular, it is a first object of the invention to carry out a reinforcing element for concrete structures that features better resistance against slipping out of the concrete matrix than the reinforced elements of known type.
It is another object of the invention to carry out a reinforcing element where said improved resistance against slipping is not accompanied by higher, undesired elasticity and compliance of the reinforcing element in longitudinal direction.
The objects described above have been achieved through the construction of a reinforcing element for concrete structures that, according to the main claim, comprises a filiform body having at least one shaped section in the vicinity of each end and is characterized in that at least part of the external surface of the filiform body is made rough by a plurality of ribs delimiting recesses created in said filiform body.
According to the embodiment of the invention described herein, the filiform body is constituted by a flat strap that defines a mainly longitudinal direction and presents external surfaces provided with a plurality of recesses and ribs that intersect one another.
The shaped sections are two and each one of them is created in the vicinity of one end of the filiform body, where it defines a concavity delimited by a profile having an axis of symmetry orthogonal to the surface of the flat strap and to the longitudinal direction defined by said flat strap.
In each profile of each shaped section it is possible to identify two counteracting surfaces that generate reactions against the concrete matrix in case of cracking of the matrix itself.
The flat strap is made of a plastic polymeric material, but it can also be made of metal, preferably steel with low carbon percentage.
Advantageously, the reinforcing element that is the subject of the invention achieves higher anchorage capacity and higher resistance to slipping in the concrete matrix where it is immersed compared to reinforcing elements of known type with equal size, due to the presence of the ribs on its surface.
For this reason, the reinforcing element that is the subject of the invention features higher resistance to slipping in case of cracking of the concrete matrix compared to reinforcing elements of known type and consequently it increases the resistance to cracking of the concrete structure in which it is dispersed.
Still advantageously, a further increase in the resistance to slipping of the reinforced elements and thus in the mechanical resistance of the entire concrete structure is guaranteed by the terminal shaped sections whose profiles defining a concavity allow them to be better anchored to the concrete matrix.
Still advantageously, the presence of the ribs and recesses does not modify the elasticity of the reinforcing element that thus maintains the rigidity and resistance to elongation that are typical of the initial filiform element from which it derives.
The aims and advantages described above will be highlighted in greater detail in the description of a preferred embodiment of the invention, with reference to the attached drawings, wherein:

Figures from 1 to 3 show reinforcing elements carried out according to the known art;
Figures 1a and 2a show details of application of the reinforced elements belonging to the known art shown in Figures 1 and 2;
Figure 4 shows an axonometric view of the reinforcing element that is the subject of the invention;
Figure 4a shows an enlarged view of a detail of Figure 4;
Figure 5 shows an axonometric view of a construction variant of the reinforcing element that is the subject of the invention;
Figures 6 and 7 show two different enlarged details of the reinforcing element shown in Figure 4;
Figure 8 shows a concrete structural element while cracking, reinforced through the insertion of reinforcing elements carried out according to the invention.

The reinforcing element forming the subject of the invention is shown in the axonometric view of Figure 4, where it is indicated as a whole by 1.
It can be observed that it comprises a filiform body 2 having a shaped section 3 in the vicinity of each end.
According to the invention, at least part of the external surface 4 of the filiform body 2 is made rough by a plurality of ribs 5 that delimit recesses 6 created in the filiform body.
The ribs 5 intersect one another as illustrated in particular in Figure 6, which shows an enlarged detail of Figure 4.
As regards the filiform body 2, it can be observed that it consists of a flat strap 7 defining a mainly longitudinal direction X.
In this embodiment of the invention the flat strap has rectangular cross section and presents the external surface 4 provided with the ribs 5 and the recesses 6.
In other embodiments of the invention the filiform body, instead of comprising a flat strap with rectangular cross section, may comprise a thread with curved or circular cross section or any filiform element having any shape and section, provided that on at least part of its external surface there are said ribs and said recesses.
It can be observed in particular in Figure 6 that the recesses 6 have a substantially polygonal shape, in particular the shape of a quadrilateral.
It is obvious, however, that in different embodiments said recesses 6 may have any shape.
Indicatively, the ribs 5 and the recesses 6 can be obtained by forming the filiform body 2 with a shaped roller and according to the known technique.
As regards the shaped sections 3, in Figures 4a and 7 it can be observed that each of them defines a concavity 9 delimited by a profile 10 having an axis of symmetry Y that is orthogonal to the surface of the flat strap 7, as shown in the detail of Figure 7.
In particular, the concavities 9 of the shaped sections 3, as shown in Figure 4, are coplanar and face the same direction, while in a construction variant of the reinforced element indicated by 20 shown in Figure 5, the shaped sections 21 are still coplanar, but their concavities 22 face opposite directions.
In both embodiments the profile 10, 23 that delimits each concavity 9, 22 has the shape of a trapezium.
Obviously in other embodiments of the invention the profile that delimits each concavity can have another shape, for example curved or mixtilinear, not necessarily defining an axis of symmetry.
Reinforcing elements 1, 20 carried out according to any of the embodiments of the invention described herein are used to reinforce a concrete structural element 30 shown in Figure 8, in whose concrete matrix 31 a plurality of reinforcing elements 1, 20 subject of the invention are dispersed at random.
The reinforcing elements 1, 20 are firmly anchored inside the concrete matrix 31 owing to the presence of the ribs 5 and the recesses 6 that prevent any sliding and slipping when the concrete matrix 31 of the structural element 30 happens to crack as shown in Figure 8.
In this way the reinforcing elements 1, 20 that are the subject of the invention feature higher resistance to slipping than the reinforcing elements of known type, which are not provided with the ribs 5 and the recesses 6.
Furthermore, said higher resistance to sliding is obtained without modifying the elasticity of the reinforcing element 1, 20 in longitudinal direction when this is subjected to the traction generated when the concrete matrix 31 tends to crack as shown in Figure 8.
Higher resistance is also guaranteed by the profile of the shaped sections 3, 21 that define the concavities 9, 20.
In fact, with reference to the detail shown in Figure 4a, it can be observed that in the shaped section 3 the profile 10 that defines it comprises two counteracting surfaces 10a, 10b against which the reactions R are developed when, during the cracking of the matrix 31 shown in Figure 8, the filiform element is subjected to the traction force F.
In this way the reinforcing element that is the subject of the invention features the shaped sections that increase resistance in the concrete matrix, compared to the reinforcing elements belonging to the known art.
It is clear, therefore, that the reinforcing element that is the subject of the invention, in both the embodiments described, achieves all the set objects.
As regards the material of which the reinforcing element is made, it is preferably constituted by a polymeric plastic material that is easier to obtain and less expensive to produce.
It is evident, however, that the reinforcing element can also be made of any other material, for example ferrous metallic material with low carbon content.
In the construction phase the reinforcing element can be carried out with any shape and dimensions, as well as the profiles of the terminal shaped sections and of the ribs and recesses created thereon.
Further construction variants different from those described and illustrated in the attached drawings must be considered protected by the present patent, provided that they fall within the scope of the following claims.
Where technical features mentioned in any claim are followed by reference signs, those reference sings have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

Reinforcing element (1; 20) for concrete structures, comprising a filiform body (2) having at least one shaped section (3; 21) in the vicinity of each end (2a), characterized in that at least part of the external surface (4) of said filiform body (2) is made rough by a plurality of ribs (5) delimiting recesses (6) created in said filiform body (2).
Reinforcing element (1; 20) according to claim 1), characterized in that said ribs (5) intersect one another.
Reinforcing element (1; 20) according to claim 1), characterized in that said filiform body (2) is a flat strap (7) that defines a mainly longitudinal direction (X) and presents external surfaces (4) on at least one of which said ribs (5) and said recesses (6) are created.
Reinforcing element according to claim 1), characterized in that said filiform body (2) is a thread with substantially circular cross section defining a mainly longitudinal direction and provided with said ribs and said recesses on at least one part of its side surface.
Reinforcing element (1; 20) according to any of the claims from 1) to 4), characterized in that said recesses (6) have a substantially polygonal shape.
Reinforcing element (1; 20) according to claim 1), characterized in that said shaped sections (3; 21) are two and each one of them defines a concavity (9; 22) delimited by a profile (10; 23) having an axis of symmetry.
Reinforcing element (1) according to claim 6), characterized in that said concavities (9) are coplanar and face the same direction.
Reinforcing element (20) according to claim 6), characterized in that said concavities (22) are coplanar and face opposite directions.
Reinforcing element (1; 20) according to claim 6), characterized in that said profile (10; 23) has the shape of a trapezium.
Reinforcing element (1; 20) according to any of the preceding claims, characterized in that it is made of a synthetic material.
Reinforcing element (1; 20) according to claim 10), characterized in that said synthetic material is a polymer.
Reinforcing element (1; 20) according to any of the claims from 1) to 10), characterized in that it is made of a metallic material.
Reinforcing element (1; 20) according to claim 12), characterized in that said metallic material is steel with low carbon percentage.
Concrete structural element (30) using a plurality of reinforcing elements (1; 20), each one comprising a filiform body (2) having at least one shaped section (3; 21) in the vicinity of each end (2a), characterized in that at least part of the external surface (4) of said filiform body (2) is made rough by protruding ribs (5) delimited by recesses (6).
Concrete structural element (30) according to claim 14), characterized in that said filiform body (2) is a flat strap (7) made of a polymeric synthetic material, wherein said shaped sections (3; 21) are two and each one of them defines a concavity (9; 22) delimited by a trapezoidal profile (10; 23) having an axis of symmetry (Y).