WO2013171437A1

WO2013171437A1 - Improved-grip reinforcing bar and method of producing same

Info

Publication number: WO2013171437A1
Application number: PCT/FR2013/051097
Authority: WO
Inventors: Marcel Matiere
Original assignee: Societe Civile De Brevets Matiere
Priority date: 2012-05-18
Filing date: 2013-05-17
Publication date: 2013-11-21
Also published as: EP2850259B1; PT2850259T; PL2850259T3; ES2604470T3; US20150135629A1; EP2850259A1; FR2990710A1; FR2990710B1; DK2850259T3

Abstract

The present invention relates to an improved-grip reinforcing bar for a reinforced concrete component, which is composed of a metal profile section (1) in the form of a flattened strip of rectangular cross section with two opposite wide faces (10, 10') on which longitudinally separated projecting anchoring portions are formed.

Description

ENHANCED ADHESIVE ARMATURE BAR AND METHOD OF MAKING SAME

The invention relates to an improved adhesion reinforcing bar for a reinforced concrete part, in particular a beam, a slab or a column and also covers the reinforcement cages using such bars and their methods of production.

It is known that the principle of reinforced concrete consists in combining the qualities of compressive strength of concrete and tensile strength of metal reinforcements. A reinforced concrete construction element behaves in fact like a composite part in which the reinforcing bars and the concrete, which have neighboring expansion coefficients, deform in the same way under the effect of the applied stresses, at least up to a limit effort.

In the case, for example, of a reinforced concrete part subjected to bending forces, it is usually considered, for the calculation of reinforcement, that this part comprises, on either side of a neutral axis, two parts subjected, respectively, to compressive forces received by the concrete and to tensile stresses concealed mainly by the longitudinal reinforcing bars. It is therefore determined by calculation the cross section that should be given to each bar tense to withstand the forces applied, given the distance between the facing face of the compressed part and the center of gravity of the bar.

Generally, the entire reinforcement of a reinforced concrete element has the shape of a cage consisting of two layers of longitudinal bars, respectively active and passive, interconnected by transverse stirrups that allow the manipulation and implementation of the entire cage and resist, on the other hand, sharp forces.

As the external forces that solicit a reinforced concrete element are generally applied on the concrete, it is the bonding bond at the steel-concrete interface, that is to say the concrete sheath surrounding each bar, which allows the loading of reinforcement, necessary for the normal operation of the structure. The transfer capacity of the forces between the concrete and the rebar depends, therefore, on the quality of this bonding bond.

It is known that, when the tensile force applied in the tensioned part of a reinforced concrete part increases, firstly there is an almost linear phase during which the tensile force is transferred into each bar by the steel-concrete interface which is progressively degraded until the appearance, in the concrete, of microcracks caused by small displacements between the bar and the concrete which surrounds it. If tensile forces continue to increase, this first quasi-linear phase is followed by a non-linear phase during which the microcracks are located in fewer and larger macrofissures, which form a network of "fishbones", with a loss of adhesion and rigidity of the interface.

These macrocracks allow the penetration of moisture and aggressive agents in contact with the frame. As they appear, in the first place, on the side where the coating is less important, it is necessary to leave a minimum coating distance between a reinforcing bar and the corresponding facing face of the part to prevent corrosion of the coating. bar and bursting of the concrete. This coating distance imposed by the regulations may be, for example, 30 mm.

Long ago, it has been proposed in document FR-A-765,943 to improve the strength of a reinforced concrete beam, by replacing circular round-section bars usually used as reinforcements, by bars. flat shaped metal strips rectangular section, while maintaining this minimum distance imposed.

In such an arrangement, in fact, the width and the thickness of each flat bar can be chosen so as to present the cross section determined by the calculation in the usual way in order to withstand the forces applied. Such flat reinforcing bars are, therefore, of equal section, equivalent to the round bars usually used but, for the same coating distance, the axis of the flat bar is farther from the center of gravity of the beam than that a round bar of the same section and the resistance of the beam can, thus, be improved.

Similarly, with equal strength, the use of flat reinforcing bars makes it possible to reduce the overall thickness of the reinforcement cage and, consequently, of the concrete part, while maintaining the same lever between the bars. stretched and opposite face facing.

However, in order to prevent slippage of the concrete with respect to the bar, it has been envisaged, in document FR-A-765.943, to provide, on one side of the bar, a series of indentations made by rolling and each corresponding to a protruding boss on the other side. These bosses and cavities formed, respectively, on the two broad faces of the bar, have a high height, of the same order as the thickness of the strip, in order to achieve a perfect connection between the bar and the concrete, preventing any slippage. from one to the other.

However, to allow the formation of such bosses, they must be spaced from each other by a distance of the same order as the width of the flat bar and therefore exert on the concrete coating, point abutment efforts, separated from each other, which, from a certain level of traction, can cause the appearance of macrofissures more open, with a risk of bursting of the concrete.

Such an arrangement therefore allows no progressiveness in the transmission of forces between the bar and the concrete sheath which remain perfectly secured to a tensile force limit, from which the bar may come off abruptly from the concrete.

Furthermore, the production of a series of bosses on one face and cavities on the other face, gives the flat bar, in its central part, a corrugated profile comprising, in the longitudinal direction, a succession of narrowing in thickness which are weaknesses detrimental to the resistance to tensile stresses and which can cause a break in the bar for an effort much lower than the theoretically applicable limit force. Moreover, the provisions of this patent, published in 1934, have never been applied in practice.

The object of the invention is to solve such problems and thus avoid the disadvantages of this ancient technique while benefiting, however, from all the advantages brought by the use of flat bars with improved adhesion as reinforcements of reinforced concrete.

The present invention thus relates, in a general manner, to the production of an improved adhesion reinforcing bar for a reinforced concrete part, consisting of a metal profile extending in a longitudinal direction, having the form of a flattened strip of substantially rectangular cross-section, with two opposite broad faces extending between two lateral sides and having a plurality of protruding anchoring portions spaced longitudinally from each other and bearing on the concrete in a direction opposite to a tensile force applied to the bar.

According to the invention, each of the two broad faces of the strip is provided with a series of elongated lock-shaped anchoring portions separated from one another by groove-shaped hollow portions and extending transversely over any the width of the strip, substantially to the lateral sides thereof, and each of said elongated locks protrudes over a small height, not exceeding one quarter of the thickness of the strip and has, in cross section , a substantially trapezoidal profile, with a relief face of small width relative to its length and two inclined connecting flanks with the elongate bottom of the adjacent grooves which constitute, for each latch, two inclined bearing faces, each in one direction , on the encasement concrete, said inclined faces each having an elongated shape extending between the two sides of the strip, so as to distribute the support forces over the entire width of the strip. the latter.

Thanks to such arrangements, it becomes possible to ensure an excellent distribution of support forces over the entire rectangular perimeter of the bar, without risk of embrittlement thereof and with the maintenance, throughout its length, of a cross section as constant as possible, in order to withstand in the best conditions applied traction forces.

Particularly advantageously, the elongate locks on each side of the strip are spaced from each other by a constant pitch not exceeding half the width of the strip and preferably between one and three times the thickness of the strip.

Preferably, the locks formed respectively on the two broad faces of the strip are parallel and the locks on one side are offset longitudinally by half a step with respect to the locks on the opposite face, so that the bottom of each groove of a first face is substantially in line with a lock of the second face.

In a preferred embodiment, the elongated locks formed respectively on the two faces of the strip, extend transversely in directions inclined at a non-zero angle with respect to the longitudinal axis of the strip.

According to another preferred feature, the elongate locks formed respectively on the two faces of the strip are inclined symmetrically, in opposite directions, with respect to the longitudinal axis.

Advantageously, on each face of the strip, the angle β of inclination of the locks relative to the axis is between 35 ° and 75 °. In a particular embodiment, the anchor locks provided on each broad face of the strip are in the form of interlocking V-shaped chevrons, with two straight portions inclined symmetrically on either side of the longitudinal axis of the strip.

In another embodiment, the anchor locks have an undulating shape, symmetrical with respect to the longitudinal axis of the band.

According to another preferred feature, the locks provided on each broad face of the strip extend to a short distance from each of the lateral edges thereof, so as to leave, along each of said edges, a flat part. smooth having a small width, of the order of 0.2 e, e being the average thickness of the strip.

Advantageously, on each of the two broad faces of the strip, the raised faces of the elongated locks and the bottoms of the grooves are situated, respectively, in two parallel planes extending on either side of an average plane in which are placed the two flats extending respectively along the two side edges of the strip.

Preferably, the two planes in which the raised faces of the bolts and the bottoms of the grooves are situated, respectively, are spaced apart by a height h which can range from 0.08 e to 0.24 e, e being the thickness average of the band.

Furthermore, the connecting flanks between the raised faces of the bolts and the bottom of the corresponding grooves, which constitute, for each latch, two elongated bearing faces, each in one direction, on the concrete, are inclined at an angle at least 45 °, with respect to the raised face of said lock.

The invention also covers a reinforcement cage for a reinforced concrete part, comprising two layers of reinforcing bars connected by stirrups and extending at a short coating distance, respectively, from two facing faces spaced apart from the room.

According to the invention, at least one of the two plies of the cage consists of such flat bars with improved adhesion and the stirrups are also formed of flat metal strips, alternately welded on the raised faces of the elongated anchoring locks formed on each of the broad faces of said flat bars.

But the invention also covers a method of making such reinforcing bars with improved adhesion. According to the invention, first of all a metal strip in the form of a flattened strip having two opposite large faces and centered on a longitudinal axis is produced first, then this flattened strip is subjected to a rolling pass between two rollers rotating around axes. parallel and orthogonal to the longitudinal axis of the strip, said rollers being provided on their periphery with spaced-apart impressions, for the formation, by rolling, of elongate locks separated by parallel grooves, on each of the two broad faces of the strip. bandaged.

These two rolling rolls are each provided, on their periphery, with an alternation of cavities and teeth intended to form, respectively, the locks and the grooves on each of the broad faces of the band and extending between two smooth portions. of small width, for the formation of two flats along the two lateral sides of the strip.

Normally, these lock formation impressions are regularly spaced along the periphery of each of the rolling rolls, so as to form locks. away from a constant step. But in some cases, the impressions may be distributed along the periphery of each of the rolling rolls, so as to periodically vary the spacings of the locks made on each broad side of the strip.

But the invention will be better understood from the detailed description which follows of some preferred embodiments, given as simple examples and shown in the accompanying drawings.

Figure 1 shows schematically, in perspective, a reinforcing bar according to the invention, provided with locks orthogonal to its longitudinal axis.

Figure 2 shows schematically, in two embodiments, the effect of a tensile force applied to such a bar.

Figure 3 is a partial view, in perspective, of a reinforcing bar provided with latches inclined relative to its longitudinal axis.

Figure 4 is a schematic view of such a bar, in section through a plane orthogonal to its longitudinal axis.

Figure 5 is a top view of a bar provided on its two faces, locks inclined in opposite directions.

Figure 6 is a view of a bar of Figure 5, in section through a plane orthogonal to its longitudinal axis.

Figure 7 is a detailed view of this bar, in section through a plane parallel to its longitudinal axis.

Figure 8 is a schematic detail view of a reinforcement cage using longitudinal bars according to the invention.

Figure 9 shows, in top view, two embodiments of a reinforcing bar according to the invention.

Figure 10 schematically shows the steps of making a reinforcing bar.

Figure 11 is a detailed view of the rolling rolls, in section along the line 1-l of Figure 10.

Fig. 12 is a cross-sectional view of another embodiment of a flattened bar.

In Figure 1 which is a half-view of detail in longitudinal section, there is shown, in perspective, a first embodiment of a reinforcing bar according to the invention consisting of a flat metal strip 1 centered on a longitudinal axis x 'x and having a rectangular cross section with two opposite large faces, respectively upper and lower 10', extending between two lateral sides 1 1.

Each of the two wide faces 10, 10 'of the strip 1 is provided with a series of regularly spaced elongated protruding portions 2.2', separated from each other by groove shaped portions 3, 3 '.

Each projecting portion 2,2 'thus forms an elongate lock which has, in cross section to its direction, a substantially trapezoidal profile with a raised face 21 and two inclined flanks 22, 23 for connection with the rectangular bottom 31 of the two grooves 32.33 extending respectively on either side of the latch 2. These latches 2 extend transversely over almost the entire width I of the strip 1, substantially to the lateral sides 1 1 thereof and are relatively close together. others, the pitch c spacing between two successive locks being at most equal to half the width I of the band.

For a reinforced concrete reinforcing bar, the ratio of the nominal width to the nominal thickness is normally between 4.5 and 6. Preferably, the spacing pitch of the locks will therefore be between one and three times the thickness of the band.

The bolts 2 thus brought together, as well as the grooves 3 which surround them, therefore have an elongated rectangle shape, with a raised face 21 of very small width relative to its length.

Such a reduced spacing of the locks makes it possible to arrange three or four parallel locks over a strip length corresponding to its width whereas, in the old arrangement of the document FR-A-765,943, the locks were separated by a distance of the order of the width of the band.

This multiplication of the number of locks therefore allows, for equivalent support efforts, to significantly reduce the height of the locks and, therefore, the risk of fracturing of the concrete coating.

In practice, the height of the locks, that is to say the difference between the level of the raised faces 21 and that of the bottom 31 of the grooves 3, should not exceed one quarter of the thickness e of the strip and will preferably be between 0.08 e and 0.25 e.

In addition, since the locks have a length substantially equal to the width of the band, the connecting flanks 22, 23 also have the shape of elongated rectangles, of very small width relative to their length.

The bearing faces thus formed thus make it possible, on the one hand, to reduce the individual abutment forces applied by each latch on the coating concrete and, on the other hand, to distribute these forces over the entire width of the strip. .

In the embodiment illustrated in FIGS. 1 to 3, the elongate locks 2 are directed perpendicularly to the longitudinal axis x 'x of the band 1 and are regularly spaced from the pitch c, whereas the locks 2' of the opposite face 10 'are longitudinally offset by half a step. The bottom 31 'of each groove 3' of the lower face 10 'is thus substantially in register with the raised face 21 of a latch 2 of the upper face 10.

As indicated above, in the prior art described in document FR-A-765,943, a series of cavities is produced in the central part of one of the broad faces of the flat reinforcing bar, each one determining the formation of a protruding boss on the other side. The cavities and bosses having a height of the same order as the thickness of the bar, this results in a corrugated profile with a succession of points of least resistance.

In the invention, on the other hand, because the latches 2 '2' are formed on the two faces 10, 10 'of the strip and they have a very small height, the thickness of the active part resistant to the forces traction remains of the same order as the nominal thickness of the bar reinforcement and is practically preserved throughout its length, in the direction of application of the tensile force.

It should be noted that, for greater clarity, the locks shown in FIGS. 2 and 3 have been given a maximum height.

As shown diagrammatically in FIG. 2, when the grooved flat bar 1 embedded in the concrete is subjected to a tensile force T, the front inclined flank 22 of each lock 2 exerts on the concrete, in the longitudinal direction of traction, support forces F, distributed over the entire length of the inclined bearing face 22 and substantially perpendicular to it. Therefore, if the flanks 22 are inclined at an angle with respect to the plane of the upper face 10 of the strip, the bearing forces F are inclined, substantially, the complementary angle oc1.

It should be noted that, as shown in the two diagrams of FIG. 2, it is possible to vary the angle of inclination of flanks 22, 23 with respect to the mean plane of the strip and, consequently, complementary angle oc1, oc'1 of inclination of the support forces F, F '. However, this angle of inclination oc1, oc'1 must not exceed 45 ° to avoid a risk of splitting of the concrete by corner effect.

Since the latches 2 are rectilinear and extend substantially over the entire width I of the strip 1, each of said latches 2 exerts on the concrete, by its anterior face 22, support forces directed along an inclined plane P of the angle oc1 relative to the wide face 10 of the bar 1.

Similarly, each of the latches 2 'of the lower face 10' of the strip 1 exerts on the concrete, by its anterior face 22 ', support forces which are directed in an average plane P' inclined at an angle α ¹ relative to the lower face 10 'of the band 1.

Thus, when a strip-shaped reinforcing bar 1 is subjected to a tensile force T, the set of parallel grooves 2, 2 'formed respectively on its two wide faces 10, 10' of this strip 1, exerts on the concrete coating support efforts directed substantially in two series of parallel planes P, P 'inclined symmetrically with respect to the two faces 10, 10' of the strip 1.

In addition, because of the trapezoidal profile of the latches 2 and the grooves 3, the inclined flanks 22, 22 'of the grooves 2, 2' which extend substantially over the entire width of the strip, have a substantially constant height, such as so that the forces applied by each lock on the concrete, when the bar is subjected to traction, are evenly distributed over the entire length of the lock, that is to say over the entire width of the bar 1.

In addition, as each bar has, in cross section on its axis, a rectangular profile of small thickness relative to its width, the projection of the locks in the longitudinal direction of the tensile force, which corresponds to the stress transmitted by the concrete bar, may extend over at least 75% of the perimeter of the bar, calculated from the nominal section of the bar. This results in a lower risk of shearing the joint.

Furthermore, the longitudinal spacing of the average planes Ρ, Ρ 'of the support forces on the concrete corresponds, on each face 10, 10' of the strip, to the reduced pitch c of spacing of the elongate locks 2,2 'which , as indicated above, is less than half the width of the band 1. As a result, the abutment stresses which are exerted along two directions inclined symmetrically on either side of the mean plane of the strip, along the two series of parallel planes Ρ, Ρ ', little spaced from each other, are therefore distributed substantially uniformly over the entire width and the entire length of the bar 1.

This uniform distribution of the abutment stresses in the entire concrete sheath surrounding the bar promotes, from a tensile stress limit, the gradual formation of a set of microcracks whose opening remains acceptable and, in case Increasing the tensile force, the number of these microcracks increases, which avoids their location in macrofissures opening damaging.

This standardization, along a tensioned reinforcing bar, of the distribution of the support forces on the concrete thus makes it possible to distribute, also over a greater length, the stressing of the concrete and, consequently, the risk cracking. Therefore, when the traction force transmitted to the concrete exceeds the resistance thereof, this effort can be spread over a certain length of the bar gradually forming multiple cracks of small width, to prevent excessive expansion of a localized crack.

Furthermore, as indicated above, the latches 2 'of the lower face 10' of the bar, are offset by a half-step relative to the latches 2 of the upper face 10 and are therefore placed substantially in line with the grooves 3 between them. As a result, the metal cross-section on which the tensile force T is applied remains substantially constant over the entire length of the strip, which thus fully participates in the resistance, whereas the strength of a conventional reinforcing bar Circular section should be calculated only according to its nominal diameter, without taking into account the volume of metal corresponding to the anchoring parts.

It should be noted, moreover, that the realization of elongated locks and grooves extending over the entire width of the strip makes it possible to retain all the advantages provided by the use of a flat strip as a reinforcing bar.

In particular, because the perimeter of a flat bar with a rectangular section corresponds to about 1.5 times the circumference of a round bar of the same cross-section, the use, as reinforcements, of flat bars provided, according to the In the invention, elongate locks brought closer to each other makes it possible to increase the adhesion bond on the raised faces 21 of the latches 2 and the bottoms 31 of the grooves 3.

On the other hand, it is known that, in a round bar provided with protruding circular locks, abrupt section variations of the material can cause a certain fragility when folding the bar. On the other hand, the use of reinforcing bars according to the invention, comprising a large number of loosely spaced and low height locks, makes it possible to reduce this risk of embrittlement when the bar is bent, for example to form sticks. anchoring at the ends or to adapt the profile of the bar to the shape of the part or the distribution of the stresses in the concrete part.

However, since the latches 2 and the grooves 3 extend substantially over the entire width I of the strip, their ends may form dangerous sharp angles for the handling of the bar and may facilitate cracking of the concrete during the tensioning of the bar.

This is why, as shown in the drawings, the latches 2 and the grooves 3 extend transversely only over a width a little smaller than that of the flat strip 1, so as to leave along each of the two edges side of the latter, a flat surface 12 having a small width, for example of the order of 0.2 e, e being the thickness of the strip at each of its sides 1 1.

In the embodiment of FIGS. 1 and 2, the elongated latches 2.2 'formed respectively on the two faces 10, 10' of the strip and separated from each other by the grooves 3,3 'are directed perpendicular to the longitudinal axis χ ', χ of the bar. It is, however, more advantageous in another embodiment of the invention, shown in perspective in FIG. 3, that the elongated latches 2,2 ', of the two faces 10, 10' of the strip, are inclined by a certain angle β with respect to the longitudinal axis χ ', χ of the strip 1.

It is therefore the same plans Ρ, Ρ 'in which are located, as before, the support forces exerted by the set of locks 2,2' on the concrete coating.

In this way, as shown in FIGS. 3 and 4, each of the two faces 10, 10 'of the bar 1 has, in a direction perpendicular to the longitudinal tensile force T, an alternation of protruding parts and hollow corresponding to several inclined locks 2a, 2b, 2c whose bearing faces 22 intersect the cross sectional plane. This results in a better uniformity, along the longitudinal axis x 'x, of the bearing forces exerted on the concrete by the two grooved faces 10, 10' of the bar 1, when this is subjected to an effort longitudinal traction.

The angle of inclination β of the locks may be the same on the two faces 10, 10 'which are then provided with parallel locks 2, 2'which, as previously, can be offset by half a step, so that each latch on one side corresponds to a groove on the other side.

However, in another embodiment that is even more advantageous and is shown in plan view in FIG. 5, the two series of locks formed respectively on the two wide faces 10, 10 'of the strip are inclined symmetrically, by an angle β on the upper face 10 and the opposite angle β 'on the lower face 10'. As a result, any lateral offset effects compensate each other and the bar 1 remains better centered on the longitudinal axis χ ', χ of application of the tensile force T. Moreover, since each of the two faces 10, 10 'has, in cross-section, an alternation of protruding parts 2 and recessed portions 2' offset by a small height with respect to the thickness of the strip, the overall cross section thereof remains substantially constant over any its length.

As before, the inclined latches 2,2 'and the grooves 3,3' are stopped at a small distance from the lateral edges of the strip 1, in order to provide, along each of the sides and on each face 10, 10 'of the band 1, a smooth flat 12,12 'having a small width, of the order of 0.2 e. Moreover, as shown in FIG. 4, on each of the wide faces 10, 10 ', the raised faces 21, 21' of the locks 2,2 'and the bottoms 31, 31' of the grooves 3,3 'are located, respectively, in parallel planes extending on either side of an average plane of the strip and in which the flat flats 12, 12 'are placed.

The invention also covers an original method for producing such flat bar bars, from a commercial wire rod or, more generally, a smooth bar with a circular section.

In this process, as shown schematically in FIG. 10, such a round bar 4 may first be subjected to a first rolling pass between two rollers 41 rotating about horizontal axes 40, in order to give it the desired thickness. e, then to a second rolling pass between two rollers 42 rotating about vertical axes, in order to adjust its width I. A rectangular flat strip 1 is thus obtained, which is then subjected to a third rolling pass between two rollers opposed 5, 5 'rotating about horizontal axes 50, 50' parallel to the wide faces 10, 10 'and each provided on its periphery with an alternation of indentations 51, 51' intended to form the latches 2, 2 'and teeth 52, 52' intended to form the grooves 3,3 ', as shown diagrammatically in FIG. 11, which is a detailed sectional view through a plane L, passing through the axes 50, 50 rollers 5, 5 '.

Preferably, the cavities 51 and the teeth 52 formed on the periphery of each of the rollers 5, 5 'do not extend over the entire width of the latter, in order to leave at their ends smooth portions 53 , 53 'for the formation of the flats 12, 12' along the lateral edges of each of the two faces 10, 10 'of the strip 1.

Furthermore, to facilitate the placement of the concrete in the grooves 3 and avoid sharp angles to the ends of the locks 2, the indentations 51 and the teeth 52 formed on the periphery of the rolling rollers 5, 5 'have a trapezoidal section. , both lengthwise and crosswise, so that on each of the faces 10, 10 'of the band 1, the bolts 2 are connected, at each end, to the corresponding flat section 12, by an inclined face 24, as are the grooves 3 which terminate at each end by an inclined face 34 (Fig.3).

Such notched reinforcement bars, provided on their wide faces with latches and parallel grooves with trapezoidal cross-section, make it possible to retain all the advantages provided by the use of flat reinforcing bars for making a cage. reinforcement, for example as described in document FR-A-2,814,480.

FIG. 8, for example, is a schematic detail view, in longitudinal section, of a concrete part 6 such as a beam or slab subjected to bending stresses, having two parallel facing faces, one face respectively. tensioned 61 under the effect of the applied forces and a compressed face 62, and in which is embedded a reinforcement cage 7 comprising two layers of longitudinal bars 71, 72 intersecting with transverse bars 71 ', 72', which extend at a short coating distance, respectively, from the two facing faces 61, 62 and are connected by stirrups 73. As described in document FR-A-2 814 480, the longitudinal and transverse bars are advantageously consisting of flat strips, as well as the transverse stirrups which may consist of a corrugated strip alternately welded, by its vertices, on the two layers of bars or a series of flat tongues shaped so as to provide, at their ends , two flat welding faces, respectively, on the bars of the two layers.

According to the invention, the longitudinal bars 71 extending along the stretched face 61, consist of notched flat strips of the type described above, comprising, on each broad face, a series of parallel anchor bolts separated by grooves . However, the transverse flat irons 71 'and the corrugated band stirrups 73 can still be easily welded to the planar raised faces 21 of the elongated latches 2 due to the trapezoidal profile and the small width thereof.

Moreover, the arrangement of FIGS. 3 and 4, comprising, on each wide face, a series of parallel latches, inclined at the same angle with respect to the longitudinal axis x 'x of the bar 1, makes it possible to apply and solder each transverse iron 71 'on the raised faces 21 of several neighboring bolts, and it is the same for the stirrups 73, the top of the corrugations.

Of course, the invention is not limited to the embodiments described above as simple examples but also covers all variants using equivalent means and remaining in the same protective frame.

In particular, if it is advantageous that the locks 2,2 'are spaced from a constant pitch c along each face 10, 10' of a bar 1, it would be possible in certain cases to adjust the distribution of the cavities 51 and teeth 52 on the periphery of the rollers 5,5 'to periodically vary the spacings of the anchor locks. For example, it would thus be possible, on each face 10, 10 'of the band 1, alternating locking zones provided with locks and areas left smooth, as described in detail in the document WO 2010/067023 A1, in order to spread the risk of cracking over the length of the part, by decreasing the opening of the cracks under a certain load.

On the other hand, the elongate latches 2.2 'formed on both sides of the strip, do not necessarily extend in a straight line between the two sides 1 1 a, 1 1 b of the strip 1.

Figure 9, for example, shows two variants of the invention. The upper part shows, in plan view, a flat bar 1 provided, on its upper face 10, anchoring latches 2 in the form of interlocking chevrons, centered on the longitudinal axis χ ', χ of the strip. The opposite face 10 'is also provided with interlocking herringbone latches which can be rotated in the same direction or in the opposite direction to better withstand alternating pulling forces.

The lower part of FIG. 9 shows another variant in which the latches 2a, 2b are arranged in two rows extending only over half the width of the strip 1 and are inclined alternately to the right and to the left of the longitudinal axis χ ', χ.

Furthermore, it is more advantageous for the flanks of the bolts to be rectilinear, so that the support forces are exerted in a succession of parallel planes, but it would also be possible to make wavy locks. Furthermore, if it is preferable to subject a round iron to two successive rolling passes, as shown in FIG. 10, in order to precisely adjust the thickness and the width of the flat strip, it is not not essential that it has a strictly rectangular section. Indeed, in a simpler embodiment, it would be possible to subject the round bar to a single rolling pass to obtain an oblong section strip, as shown in FIG. 12, such a strip that can still be provided with locks lying on each of its wide faces.

Finally, the grooving of the broad faces of the strip could be removed in some places and on a short length, for example for marking the bar.

Claims

Reinforced reinforcing bar for a reinforced concrete part, consisting of a metal profile (1) extending in a longitudinal direction, in the form of a flattened strip of substantially rectangular cross-section, with two opposite broad faces (10, 10 ') extending between two lateral sides (1 1, 1 1') and comprising a plurality of projecting anchoring parts spaced longitudinally from each other and resting on the concrete in a direction opposite to a tensile force applied to the bar (1), characterized in that each of the two broad faces (10, 10 ') of the strip (1) is provided with a series of anchoring portions in the form of elongated locks ( 2,2 ') separated from each other by groove-shaped hollow portions (3,3') and extending transversely across the width of the strip (1), substantially to the lateral sides (1 1, 1 1 ') thereof, that each of said elongated latches (2) extends protruding over a small height, not exceeding one quarter of the thickness of the strip (1) and having, in cross section, a substantially trapezoidal profile, with a raised face (21) of small width compared to its length and two inclined flanks (22, 23) for connection with the elongated bottom (31, 31 ') of the adjacent grooves (3, 3'), which constitute, for each latch (2), two inclined faces (22, 23) d support, each in one direction, on the encasement concrete, said inclined faces (22, 23) each having an elongate shape extending between the two sides of the strip (1), so as to distribute the forces of support the entire width of it.

Reinforcing bar according to Claim 1, characterized in that on each face

(10,10 ') of the strip (1), the elongated locks (2,2') are spaced from each other by a constant pitch (c) not exceeding half the width (I) of the band (1).

Reinforcing bar according to one of Claims 1 and 2, characterized in that, on each face (10, 10 ') of the strip (1), the raised faces (21, 21') of the elongate bolts ( 2.2 ') have a width less than half the width (I) of the strip (1).

Reinforcing bar according to one of the preceding claims, characterized in that the elongated latches (2, 2 ') extend transversely in directions inclined at a non-zero angle with respect to a longitudinal axis of each face ( 10,10 ') of the band

(1) -

Reinforcing bar according to Claim 4, characterized in that the elongated latches (2, 2 ') formed on the two faces (10, 10') of the strip (1) are symmetrically inclined, respectively. opposite, with respect to the longitudinal axis X ', X, of the strip (1) -

Reinforcing bar according to one of claims 4 and 5, characterized in that, on each face (10, 10 ') of the strip (1), the elongate locks (2, 2') are parallel and inclined to an angle β between 35 ° and 75 °.

Reinforcing bar according to Claim 3, characterized in that the anchoring bolts (2, 2 ') provided on each wide face (10, 10') of the strip (1) have the shape of chevrons in V nested, with two rectilinear parts inclined symmetrically on either side of a longitudinal axis (Χ ', X) of the strip (1).

Reinforcing bar according to one of Claims 4 to 6, characterized in that the anchoring bolts (2, 2 ') provided on each wide face (10, 10') of the strip (1) have a corrugated shape, symmetrical with respect to the longitudinal axis (Χ ', X) of the strip (1).

Reinforcing bar according to Claim 1, characterized in that, on each wide face (10, 10 ') of the strip (1), the elongated anchoring locks (2, 2') extend up to at a short distance from each of the lateral edges (1 1 a, 1 1 b) of the strip (1), so as to leave a smooth flat (12) of small width along each of said edges (1 1, 1 1 ').

10. Reinforcing bar according to claim 9, characterized in that the flats (12) formed, respectively, along the two side edges (1 1, 1 1 ') of the strip (1), on each of its faces. wide (10, 10 '), have a width of the order of 0.2 e, e being the average thickness of the strip.

1 1. Reinforcing bar according to one of Claims 9 and 10, characterized in that, on each wide face (10, 10 ') of the strip (1), the raised faces (21) of the locks (2) and the the bottoms (31) of the grooves (3) are located, respectively, in two parallel planes extending on either side of an average plane Q of the wide face (10), in which the two flats (12a) are placed. , 12b) extending respectively along the two side edges (11a, 11b) of the strip (1).

Reinforcing bar according to Claim 1 1, characterized in that the two planes in which the raised faces (21) of the latches (2) and the bottoms (31) of the ribs (3) are located, respectively, are spaced from a height h which can range from 0.08 e to 0.24 e, where e is the average thickness of the strip (1).

Reinforcing bar according to one of the preceding claims, characterized in that the connecting flanks (22, 23) between the raised faces (21) of the bolts and the bottom (31) of the corresponding grooves (3), are inclined at an angle α of at least 45 ° with respect to a plane in which said raised faces (21) are placed.

Reinforcing bar according to one of the preceding claims, characterized in that the anchoring bolts (2) are spaced longitudinally by a pitch (c) of between one and three times the average thickness e of the strip. (1).

Reinforcing cage (7) for a reinforced concrete part (6) comprising two webs of reinforcing bars connected by stirrups and extending at a short coating distance, respectively, from two faces (61, 62 ) facing away from the workpiece (6), characterized in that at least one of the two plies of the cage is constituted by bars (71) with improved adhesion according to one of the preceding claims, and that the stirrups are formed of metal flat strips (73), alternately welded to the raised faces (21) of the anchoring locks (2) of said bars (71) with improved adhesion.

16. A method of producing a reinforcing bar according to one of claims 1 to 14, characterized in that it is first realized a metal bar (1) shaped flattened strip having two opposite broad faces (10, 10 ') and centered on a longitudinal axis (x' x) and that said strip (1) is subjected to a rolling pass between two rollers (5, 5 ') rotating about parallel axes (50, 50') and orthogonal to the longitudinal axis (x 'x) of the strip (1), said rollers (5, 5 ') being provided on their periphery with spaced-apart impressions

(51), for forming, by rolling, elongated latches (2) separated by parallel grooves (3), on each of the two wide faces (10, 10 ') of the strip (1).

17. The method according to claim 16, characterized in that the two rolling rolls (5, 5 ') are each provided on their periphery with an alternation of impressions (51) and teeth.

(52) for forming, respectively, the latches (2) and the grooves (3) on each of the wide faces (10, 10 ') of the strip (1) and extending between two smooth portions (53) for the forming two flats (12) along the two lateral sides (11a, 11b) of the strip (1).

18. Method according to one of claims 16 and 17, characterized in that the fingerprints (51) for forming the latches (2) are regularly spaced along the periphery of each of the rolling rollers (5, 5 ').

19. according to one of claims 16 and 17, characterized in that the cavities (51) are distributed along the periphery of each of the rolling rollers (5, 5 ') so as to periodically vary the spacings of the locks. (2) obtained on each wide face (10, 10 ') of the strip (1).