EP2141300B1 - Method for manufacturing a concrete part and reinforcement cage for a part manufactured according to this method - Google Patents
Method for manufacturing a concrete part and reinforcement cage for a part manufactured according to this method Download PDFInfo
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- EP2141300B1 EP2141300B1 EP09173849.2A EP09173849A EP2141300B1 EP 2141300 B1 EP2141300 B1 EP 2141300B1 EP 09173849 A EP09173849 A EP 09173849A EP 2141300 B1 EP2141300 B1 EP 2141300B1
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- concrete
- reinforcement
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- stretched
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Images
Classifications
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/06—Reinforcing elements of metal, e.g. with non-structural coatings of high bending resistance, i.e. of essentially three-dimensional extent, e.g. lattice girders
- E04C5/0604—Prismatic or cylindrical reinforcement cages composed of longitudinal bars and open or closed stirrup rods
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C1/00—Building elements of block or other shape for the construction of parts of buildings
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/06—Reinforcing elements of metal, e.g. with non-structural coatings of high bending resistance, i.e. of essentially three-dimensional extent, e.g. lattice girders
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/06—Reinforcing elements of metal, e.g. with non-structural coatings of high bending resistance, i.e. of essentially three-dimensional extent, e.g. lattice girders
- E04C5/065—Light-weight girders, e.g. with precast parts
Definitions
- the invention relates to a method for producing a concrete part and relates more particularly to the use of a new type of reinforcement having multiple advantages and allowing, in particular, to considerably increase the level of stress to from which detrimental cracks may form.
- reinforced concrete is based on the combination of two materials with complementary properties, concrete which has a high compressive strength, but a very low tensile strength, and steel, which has excellent tensile strength and is protected from corrosion in the air when it is embedded in the concrete.
- the two materials having, in addition, adjacent expansion coefficients, their combination allows to achieve composite parts having the durability qualities of concrete and can, however, withstand moments or bending forces.
- Such a part comprises, under the effect of the applied stresses, two parts located on either side of a neutral axis, respectively a compressed part subjected to compression forces absorbed mainly by the concrete and a stretched part subjected to tensile stresses absorbed mainly by at least one stretched longitudinal reinforcement of the reinforcement cage embedded in the concrete.
- the reinforcing bars In order to be protected from the air and to avoid corrosion, the reinforcing bars must be located at a minimum distance from an external face of the room, called the "coating distance". However, under the effect of the stresses, one can not avoid deformation of the part with an elongation of the stretched part which causes the appearance of cracks in the concrete coating. These cracks, unavoidable in practice, may be admitted as long as their width is fairly small, for example less than 3/10 of a millimeter, to prevent the penetration of air and water until contact with the armature.
- a reinforced concrete part behaves like a composite part deforming in block with transfer of forces between the two components.
- it is usually sought to improve the transfer bond between the reinforcement and the concrete for example using so-called high-adhesion bars, which are notched along their entire length.
- the ends of these bars are usually bent to form anchoring butts that increase the reinforcement length embedded in the concrete and, therefore, the transfer length of the internal forces between the reinforcement and the concrete .
- the subject of the invention is a new method for producing concrete moldings that makes it possible to solve such problems by using a new type of reinforcement reinforcement, which makes it possible in particular to reduce the risk of cracking at equal solicitations.
- the method makes it possible to considerably improve the resistance to extreme stresses, the concrete parts thus produced being able to have a very high degree of flexibility and benefit from a high degree of safety between the appearance of the first cracks and the complete failure of the cracks. 'work.
- Such an advantage is particularly interesting for construction of structures or buildings in regions subject to seismic risk.
- the invention therefore applies, in a general manner, to the production of a concrete part provided with a reinforcement cage entirely embedded in the concrete during the casting thereof and comprising, when it is subjected to a bias, two parts located on either side of a neutral axis, respectively a compressed part subjected to compression forces absorbed mainly by the concrete and a tensioned part subjected to tensile forces absorbed mainly by at least a stretched longitudinal reinforcement of the reinforcement cage which extends at a short coating distance from a longitudinal stretched face of the workpiece and having a cross section determined according to the forces induced by the load and comprising a first level consisting of at least one flat strip with a rectangular section, with a wide face and a narrow face, and having a central portion between two blocking parts in the concrete, characterized in that each blocking portion in the concrete of the tensioned frame consists of an end of the curved flat strip shaped as a butt and supported on the concrete by its broad face in the opposite direction to the force absorbed traction, forming a locking
- At least each stretched longitudinal reinforcement consists of at least one rectangular section flat strip, with a wide face and a narrow face, and is shaped so as to provide, inside the room, at least two blocking zones spaced from each other, in which a portion of said tensioned frame bears on the concrete, in the opposite direction to the tensile force absorbed, and at least one slip zone between the locking zones, in which a corresponding portion of the tensioned frame is free to extend along its entire length, under the effect of absorbed forces.
- the idea of the invention is, on the contrary, to make separate locking zones, in which the reinforcement, because it consists of a flat strip, is supported in the concrete by a wide face without risk of exceeding the allowable limit of concrete compression and, from a certain level of stress, to leave the part of the frame between two compression zones, free to slide slightly with respect to the concrete which coats it, after detachment of it, so that the effect of elongation of the reinforcement resulting from the traction forces applied is always distributed over the entire length between two blocking zones, which avoids stress concentrations that can lead to a rupture of the armature in case of extreme stress.
- each blocking zone is made by deflecting the corresponding part of the band-shaped tensile reinforcement, with a gradual and continuous variation of the orientation of its wide face relative to the stretched longitudinal face of the room.
- each blocking zone is formed by bending the flat strip around a transverse axis, so as to form an anchor stock bearing on the concrete by a wide face.
- each locking zone is made by twisting the strip over a certain length, with a progressive rotation of its wide face about its longitudinal axis, over at least one quarter turn. But the twisted portion of the band can also rotate a full turn or more, so as to bear on the concrete over a longer length.
- This crossbar may consist of a distribution thread.
- the reinforcement cage usually comprises several longitudinal sectors interconnected by distribution threads consisting of bars perpendicular to the longitudinal main bars, the assembly constituting a reinforcement ply.
- These distribution threads can be welded to the longitudinal bars, whose flat strip shape allows for particularly strong welds.
- Each welded junction may constitute a blocking zone, the distribution thread being supported in the concrete on either side of the longitudinal bar.
- each sector of the reinforcement cage comprises at least two longitudinal bars respectively compressed and tensioned and interconnected by connecting stirrups.
- the compressed frames also consist of flat strips.
- the connecting stirrups may each consist of at least one flat strip secured to the reinforcements by welding beads or glued portions extending over a length equal to the width of the strip and therefore, particularly resistant.
- each band constituting a stirrup is inclined with respect to the direction of the tensioned bar and the whole of the welded joint between these two flat strips of different orientations, forms a kind of corner bearing on the concrete.
- each locking zone between the tensile reinforcement and the concrete may be constituted by a joining junction between the tensioned frame and a band-shaped connecting stirrup.
- the strip-shaped tensile reinforcement can be split axially over a certain length, the two band portions thus formed being spaced apart from one another to form a transverse passage opening of at least one rigid bar section likely to bear on the concrete on both sides of the longitudinal strip, in the opposite direction to the tensile force applied to the longitudinal reinforcement.
- This rigid bar may be a distribution wire passing through the longitudinal strip in the plane thereof, or a simple bar section passing through the longitudinal strip perpendicular to its plane.
- each longitudinal reinforcement may comprise at least two contiguous bands extending longitudinally, substantially in the extension of one another and subjected to traction forces in opposite directions, the two contiguous strips overlapping over a certain length and ending respectively, on both sides of the cover, by two sticks turned towards each other, which thus tend to come closer under the effect of the efforts of opposed traction applied to the two corresponding bands, inducing the compression of a concrete core between the two sticks, on said lap length.
- the reinforcement cage consists of parallel sectors connected by distribution threads
- the latter can pass inside the ends of two neighboring sectors, so as to transmit to the concrete part between said sectors, the compression efforts induced, in each sector, by the tendency towards the opposite ends.
- the two contiguous strips forming the longitudinal reinforcement of each sector of the cage may constitute two strands of a single band ending in opposite hooks and forming a loop between two separated levels, of way to surround a concrete core set in compression by clamping said loop under the effect of traction forces applied in opposite directions on the two strands of the longitudinal reinforcement.
- the longitudinal reinforcement in each sector, may consist of a series of consecutive strips each having two curved ends in the form of a butt, the adjacent butts of two consecutive strips being placed next to each other partially overlapping so as to limit a passage space, in the transverse direction, of at least one bar section forming a connecting key between the two consecutive strips.
- the longitudinal reinforcement then behaves like a tensioned chain consisting of a series of links each formed of a band and connected in pairs by pairs of adjacent sticks keyed together.
- the longitudinal reinforcement comprises a stack of flat strips, arranged on at least two superimposed levels, respectively a first level, the closest to a stretched longitudinal face of the workpiece. having a band, with two stick-shaped ends facing towards the inside of the piece and at least a second level comprising at least two substantially parallel flat strips arranged side by side with each two ends in the form of crosses, respectively internal and outer, and said strips of the second level overlap over a certain length, so that their inner ends in the form of crosses are facing each other.
- the part thus comprises at least one portion forming a core between the inner ends of the two strips and set in compression by the tendency towards the one towards the other of said internal butts under the effect of the tensile forces applied in the directions opposing on the corresponding bands, and two end parts each included between the outer hooks of the bands of the first and the second level and put in compression by the tendency to approach inwardly each outer stock of the band of the first level under the effect of the traction force supported by said band. It is thus possible to compress the entire concrete of the room.
- this concrete part 1 which constitutes, in the example shown in the drawings, a slab having two planar faces, respectively bottom and top 21, is a molded part made by casting a mass of concrete 2 in a formwork, after placing in it a reinforcement cage 3 comprising two reinforcement plies, respectively lower and upper 30 ', substantially parallel to the two faces 20, 21 of the slab 1.
- the reinforcement cage 3 normally consists of several sectors S1, S2, ... centered, respectively, in planes P1, P2 ... parallel to a longitudinal axis of the part 1, that is to say in terms of figure 1 and each comprising a lower longitudinal reinforcement 31 and an upper longitudinal reinforcement 31 'which are interconnected in the plane P1, P2 of the sector S1, S2 by transverse reinforcements called stirrups, which are not shown on the Figures 1 and 2 .
- the concrete part 1 can be divided into two parts located on either side of a neutral axis 10 , respectively a compressed portion 11 'between the neutral axis 10 and the face 21 on which the forces are applied and a tensioned portion 11 extending to the face 20 opposite the forces.
- the reinforcement cage 3 differs from the cages usually produced by the fact that, according to a provision described in the patent application FR-A-2,814,480 of the same inventor, at least the longitudinal reinforcements 31 situated in the stretched portion 11 of the part and extending at a short distance from the bottom face 20 are constituted by flat metal bars 4 with a rectangular section, with one face wide 41 and a narrow face 42, each flat bar thus consisting of a metal strip having a width I substantially greater than its thickness e.
- the compressed armatures 31 ' are also constituted by flat bars but, for economy, it would also be possible to use conventional round bars.
- the cross section (I xe) of the strip 4 is calculated, conventionally, as a function of the tensile forces to bear in view of the stresses applied to the piece 1. Indeed, under the effect of the load M, the part 1 tends to bend slightly, each longitudinal reinforcement 31 of the lower ply 30 being subjected to a tensile stress which tends to lengthen it.
- notched reinforcement bars are generally used in order to improve the transfer bond between the reinforcement and the concrete, thereby producing a composite part which is usually sought after. increase rigidity to avoid the appearance of harmful cracks.
- each blocking zone can be made simply by deflecting the corresponding part of the tensioned frame 31, the orientation of which is gradually and continuously changed. its wide face relative to the longitudinal stretched side 20 of the part so that, in this area, the band 4 forming the frame 31 is supported in the concrete by its wide side 41, in the opposite direction to the tensile force absorbed.
- the width I of the band 4 can be determined according to the stresses applied, so that the compressive stress applied to the concrete remains below a permissible limit.
- the stretched longitudinal bars must be curved in the shape of a butt at their ends in order to increase the transfer length between the reinforcement and the concrete.
- the curvature that can be given to a bar is necessarily limited and the regulation requires, moreover, to give the stick a diameter of at least 10 times the diameter of the bar.
- a concrete part must have a minimum thickness of twelve times the diameter of the tension bars, to which must be added twice the minimum thickness of the coating.
- each butt 5 constitutes a blocking zone B1 in the concrete 2.
- the reinforcing strip 4 thus secured to the concrete by two locking zones B 1 and B 1 'can, on the other hand, lie freely in its central part.
- each band 4 constituting a longitudinal reinforcement 31 is secured to the concrete only in the two locking zones which are spaced from each other and the tendency to elongation of the reinforcement under the effect of the applied voltage can be evenly distributed over the entire length of the central portion, the latter can peel off the concrete from a certain level of stress.
- concrete 2 can not be deformed in the same way as the reinforcement and we can not avoid the appearance of cracks but this risk of cracking is evenly distributed over the entire length of the central part and cracks more numerous may have a small enough width to not be detrimental.
- the piece behaves, as usual, as a composite part, the concrete deforming in the same way as the reinforcement.
- the reinforcement remains secured to the concrete only in its blocking parts and its central part can, on the contrary, peel off the concrete that coats it and slide slightly with respect to it. This.
- the tension and, therefore, the tendency to elongation of the armature is therefore distributed substantially uniformly over the entire length of the central portion. This avoids a concentration of the tensile stress over a short length of the armature and, therefore, the risk of rupture of the armature at a crack under the effect of excessive stresses is reduced.
- slabs produced according to the invention have been subjected to bending tests with progressive increase of the applied load and it has been found that slab thus realized could, surprisingly, admit a very important arrow before the breaking of the slab and with cracks of relatively small width.
- the longitudinal reinforcement is, in a way, attached to the concrete in the blocking zones 5 while the central part is free to stretch, the stresses applied by the reinforcement on the concrete are stronger than in the case of a conventional reinforcement where one seeks to achieve a solid connection over the entire length of the frame. Of course, this is reflected in the locking zones by a greater compressive force in the concrete but, precisely, the concrete has excellent compressive strength.
- the band 4 is subjected to a large tensile force T which is concealed by the blocking zone B1 located inside the butt 5, it may tend to unfold if the adhesion between the bar 4 is the concrete is not enough.
- each tension bar 31 consisting of a flat strip 4 is oriented so that its wide face 41 is substantially parallel to the taut face 20 of the workpiece.
- Such an arrangement increases the flexibility of the slab because the bar 4 thus oriented has a low resistance to bending and the bending of the piece simply results in an elongation of the frame.
- each reinforcing strip 4 is twisted in two parts 43, 43 'spaced apart from each other, but only over a quarter of a turn so that in the central portion 44' and along the entire length thereof the wide side 41 of the strip 4 is located in a plane orthogonal to the stretched face 20 of the part.
- the blocking of the band 4 in the concrete is essentially achieved at the level of the zones B1, B'1, inside the butts 5, 5 ', formed at the ends of the band 4.
- the longitudinal bars 31, 31 'of the two plies, respectively lower and upper 30' can be connected by stirrups which, as described in the document FR-A-2,814,480 , advantageously consist of corrugated flat strips 13 secured to the longitudinal reinforcements, at the top of the corrugations, by welding or gluing.
- the welds between the corrugated strips 13 and the strips 4 constituting the tensioned frames 31, are made only near the two ends of the part 1 so that the central portion 44 of each band 4 can lie freely.
- stirrups may be welded or glued to the compressed bars 31 'at the top of each corrugation.
- each compressed bar 31 ' also consists of at least one flat strip, in order to produce a weld bead over the entire width of the corrugated strip 13.
- each welded or glued junction 14 between a bar 4 and the corresponding part of the stirrup 13 which forms an angle with this bar 4 constitutes, by wedge effect, a blocking zone B.
- the ends curved rods 5 allow to provide, as previously, blocking areas B1, B'1 at both ends of the frame 31.
- two other locking zones B, B ' are produced by twisting the band 4 over a certain length L1, with a progressive rotation of its wide face 41 about its longitudinal axis 40.
- each sector of the reinforcement cage 3 comprises a longitudinal reinforcement 31 consisting of a flat band which extends over the entire length of the workpiece 1 and whose ends 5, 5 'are curved in the shape of a stick as indicated above.
- longitudinal bars 31 are associated with a second level of longitudinal bars offset upwards and comprising, in each sector of the cage, two bars 33, 34 each formed of a flat strip and placed side by side, each of these bars. 33, 34 being provided with curved ends in the form of hooks 51, 51 ', 52, 52'.
- the two contiguous strips 33, 34 of the same sector are offset longitudinally relative to each other so that the two brackets 51, 51 '(52, 52') formed at the ends of each strip 33 (34) are placed at different distances from the transverse median plane Q of the part 1, on both sides of it.
- the outer stock 51 of the bar 33 placed on the left on the figure 10 is farther from the median plane Q than the outer stock 51 'of the same band 31, placed on the right and the disposition is reversed for the second longitudinal band 34.
- the lengths of the longitudinal bars 33, 34 are determined from so that the different brackets 5, 51, 52 placed on the same side of the transverse median plane Q are distributed over a certain length of the piece 1 from its end 11.
- the longitudinal reinforcements are subjected to tensile forces and are supported in the concrete by their ends in the form of sticks which are therefore urged inwards .
- the longitudinal reinforcements 33, 34 which overlap in the central part of the part, are stretched in different directions and the central blocking area B3 is therefore compressed by the tendency towards the one towards the other of the internal butts 51 ' , 52 of the two frames 33, 34.
- end zones B1, B'1 are also put in compression by the butts 5, 5 'which oppose the tensile forces applied to the frame 31.
- the piece 1 is put into compression practically over its entire length by the tendency towards the inside of the butts of the various reinforcements and this compression effect is exerted over the entire thickness of the concrete limited by the butts and not only, as usual, above the neutral axis 10.
- the tensile reinforcement of the cage 3 may also consist of a simple stack of longitudinal strips of different lengths, respectively a first band 35 extending over a length I 1 slightly less than that of the piece and a second band 36 extending over a length I 2 less than I 1 , each band being provided with ends in the form of brackets turned towards the interior of the room.
- the metal strips having different mechanical characteristics so as to modulate the compression forces applied by the butts according to the distribution of forces applied to the workpiece.
- FIGS. 12 and 13 show a variant of the embodiment of the figure 10 wherein the two adjacent strips 33, 34 constitute two strands of a single band forming a closed loop, the two opposite brackets 51 ', 52 being connected by a portion 37 of the band located at the upper level 30' of the cage 3.
- Each longitudinal reinforcement thus consists of a single band 33, 37, 34 surrounding a concrete core B3 which is compressed by clamping of the loop thus formed under the effect of traction forces applied in opposite directions on both strands 33, 34 of the longitudinal reinforcement when the part 1 is subjected to a vertical load.
- each longitudinal reinforcement in the form of a loop may form part of the upper ply 30 'of the reinforcement cage 3.
- the opposing brackets 51 ', 52 which tend to compress a concrete core B3, are not necessarily spaced symmetrically on either side of the transverse median plane Q of the piece 1. Indeed, depending on the loading mode of the part, it is possible to determine certain parts of the part 1 in which the tensile forces induced in the concrete by the applied stresses are maximum and to arrange the reinforcements and their butts so that the tensile forces resulting from the stresses at least partially compensated by compressing, in the same areas, a concrete core between two brackets biased towards each other by the tensile forces applied to the armature.
- each of the figures described above shows a sector of the reinforcement cage centered in a vertical plane parallel to the longitudinal axis and the butts formed on the reinforcements of two adjacent sectors are placed substantially at the same level so as to passing, in the aligned locking zones of sectors S 1 , S 2 , S 3 , transverse threads 32 which are also biased inward and thus distribute on the concrete between two adjacent sectors, the compression forces applied by the crossheads 5, 51, 52.
- These distribution threads may have a round or rectangular section, as shown in the figures.
- the use of flat bars makes it easier to produce a weld bead between the longitudinal and transverse bars.
- each stretched longitudinal reinforcement 6 of the cage 3 is constituted by a series of consecutive strips 6a, 6b .... each having two ends curved in the form of hooks 5a, 5'a, 5b, 5'b ... and these bars are arranged so that the pairs of adjacent sticks 5'a, 5b of two successive bands 6a, 6b are located substantially at the same level, overlapping slightly so as to surround a space E in which is passed a bar 38 which can constitute a transversal thread of distribution.
- Each bar 38 passing through a space E placed in compression by the two opposite brackets 5'a, 5b constitutes a connecting key between the two consecutive strips 6a, 6b.
- Each longitudinal reinforcement 6 consisting of a series of strips 6a, 6b, 6c .... thus behaves like a chain of which the links 6a, 6b, 6c ... are stretched under the effect of the charges applied to the part 1.
- each blocking zone could be obtained simply by means of a transverse bar passing through an orifice formed on the longitudinal reinforcing bar.
- a flat strip 4 as a longitudinal reinforcing bar makes it possible to fit therein a median slot 45 extending over a certain length and limiting two lateral parts 46, 47 which can be spaced apart from each other. the other so as to open a hole 45 'for passage of a transverse bar 48.
- a tensile force for example in the direction of the arrow indicated on the figure 16 , it is supported on the crossbar 48 which itself is supported in the concrete, thus realizing the blocking of the band 4.
- transverse bar 48 which, in this case, is parallel to the plane of the strip.
- This bar could therefore constitute a transverse thread 32 of distribution between several sectors of the reinforcement cage.
- this twisted part 43 could also be provided with a median slot allowing the two parts of the band to be separated from one another to provide an opening 45 ' passage of a distribution thread 32, as shown in FIG. figure 18 .
- the use of flat strips 4 to form the longitudinal reinforcing bars makes it possible to vary the orientation of the butt formed at the end of such a bar.
- the flat strip 4 can be easily bent around an axis parallel to its plane. It would therefore be possible, as shown in figure 20 twist a quarter turn the end of a strip 4 so that the butt 5 rotates about a vertical axis 50 '. This would give the same locking effect by giving the stock a height limited to the width e of the strip 4.
- Such an arrangement could be advantageous for making particularly thin pieces or, for example, for thinning the ends of a slab.
- the use of a flat strip 4 allows, if necessary, to vary the orientation thereof, as shown in FIG. figure 20 for example, to thin some parts of the room.
- the flat strips constituting the longitudinal and transverse reinforcements could even be curved in opposite directions so as to adapt to a left profile in the transverse direction, such as a regulated surface having non parallel parallel generatrices. This is the case, for example, the decking of a laterally inclined bridge of variable angle from one end to the other and whose reinforcement is difficult to achieve by conventional methods.
- the invention is especially adapted to the realization of crossing structures buried under an embankment and having a curved profile allowing them to slightly deform under the load applied to support the side embankments by their sides.
- the blocking zones between which the concrete is placed in compression can be placed at locations, determined by calculation, in which the concrete is subjected to a tensile stress maximum and where the risk of cracking is greatest.
- the invention therefore makes it possible, from a standard model, to adapt the reinforcement of each part to the predictable distribution of the stresses, taking into account the loads applied.
- the arrangement of the compression zones is not necessarily symmetrical with respect to the median plane of the part.
- the arrangements according to the invention therefore make it possible to vary the shape of the reinforcement cage so as to modulate the action of the reinforcements as a function of the stresses applied in service on the part.
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Abstract
Description
L'invention a pour objet un procédé de réalisation d'une pièce en béton et porte plus spécialement sur l'utilisation d'un ferraillage de type nouveau présentant de multiples avantages et permettant, en particulier, d'augmenter considérablement le niveau de sollicitation à partir duquel des fissures préjudiciables risquent de se former.The invention relates to a method for producing a concrete part and relates more particularly to the use of a new type of reinforcement having multiple advantages and allowing, in particular, to considerably increase the level of stress to from which detrimental cracks may form.
On sait que le principe du béton armé repose sur l'association de deux matériaux ayant des propriétés complémentaires, le béton qui présente une résistance à la compression importante, mais une résistance à la traction très faible, et l'acier, qui présente une excellente résistance à la traction et se trouve protégé de la corrosion à l'air lorsqu'il est noyé dans le béton. Les deux matériaux ayant, en outre, des coefficients de dilatation voisins, leur association permet de réaliser des pièces composites ayant les qualités de durabilité du béton et pouvant, cependant, résister à des moments ou des efforts de flexion. Une telle pièce comporte, en effet, sous l'effet des sollicitations appliquées, deux parties situées de part et d'autre d'un axe neutre, respectivement une partie comprimée soumise à des efforts de compression absorbés principalement par le béton et une partie tendue soumise à des efforts de traction absorbés principalement par au moins une armature longitudinale tendue de la cage de ferraillage noyée dans le béton.It is known that the principle of reinforced concrete is based on the combination of two materials with complementary properties, concrete which has a high compressive strength, but a very low tensile strength, and steel, which has excellent tensile strength and is protected from corrosion in the air when it is embedded in the concrete. The two materials having, in addition, adjacent expansion coefficients, their combination allows to achieve composite parts having the durability qualities of concrete and can, however, withstand moments or bending forces. Such a part comprises, under the effect of the applied stresses, two parts located on either side of a neutral axis, respectively a compressed part subjected to compression forces absorbed mainly by the concrete and a stretched part subjected to tensile stresses absorbed mainly by at least one stretched longitudinal reinforcement of the reinforcement cage embedded in the concrete.
Pour rester à l'abri de l'air et éviter la corrosion, les armatures doivent être situées à une distance minimale d'une face externe de la pièce, appelée "distance d'enrobage". Cependant, sous l'effet des sollicitations, on ne peut éviter une déformation de la pièce avec un allongement de la partie tendue qui provoque l'apparition de fissures dans le béton d'enrobage. Ces fissures, inévitables en pratique, peuvent être admises tant que leur largeur est assez faible, par exemple inférieure à 3/10 de millimètre, pour interdire la pénétration de l'air et de l'eau jusqu'au contact de l'armature.In order to be protected from the air and to avoid corrosion, the reinforcing bars must be located at a minimum distance from an external face of the room, called the "coating distance". However, under the effect of the stresses, one can not avoid deformation of the part with an elongation of the stretched part which causes the appearance of cracks in the concrete coating. These cracks, unavoidable in practice, may be admitted as long as their width is fairly small, for example less than 3/10 of a millimeter, to prevent the penetration of air and water until contact with the armature.
Tant que les sollicitations appliquées ne dépassent pas une certaine limite, une pièce en béton armé se comporte donc comme une pièce composite se déformant en bloc avec transfert des efforts entre les deux composants. Pour cela, on cherche, habituellement, à améliorer la liaison de transfert entre l'armature et le béton, par exemple en utilisant des barres dites à haute adhérence, qui sont crantées sur toute leur longueur. D'autre part, les extrémités de ces barres sont habituellement recourbées pour former des crosses d'ancrage qui augmentent la longueur d'armature noyée dans le béton et, par conséquent, la longueur de transfert des efforts internes entre l'armature et le béton.As long as the applied stresses do not exceed a certain limit, a reinforced concrete part behaves like a composite part deforming in block with transfer of forces between the two components. For this, it is usually sought to improve the transfer bond between the reinforcement and the concrete, for example using so-called high-adhesion bars, which are notched along their entire length. On the other hand, the ends of these bars are usually bent to form anchoring butts that increase the reinforcement length embedded in the concrete and, therefore, the transfer length of the internal forces between the reinforcement and the concrete .
Cependant, si la charge dépasse une certaine limite, les fissures s'élargissent et la partie libre, de faible longueur, de l'armature tendue qui s'étend entre les faces opposées d'une fissure, supporte seule l'allongement correspondant à l'épaisseur de cette fissure, alors que les parties voisines sont bloquées dans le béton. La tendance à l'allongement de la face tendue sous l'effet des sollicitations appliquées se concentre donc sur les parties libres de l'armature et, en raison de leur faible longueur, l'allongement appliqué peut faire dépasser la limite élastique du métal, ce qui provoque la striction de l'armature et la ruine de l'ouvrage.However, if the load exceeds a certain limit, the cracks widen and the free part, of short length, of the stretched reinforcement which extends between the opposite faces of a crack, only supports the elongation corresponding to the The thickness of this crack, while the neighboring parts are blocked in the concrete. The tendency of the stretched face to stretch under the effect of the stresses applied is therefore concentrated on the free parts of the reinforcement and, because of their short length, the elongation applied may cause the elastic limit of the metal to exceed which causes the narrowing of the frame and the ruin of the work.
L'invention a pour objet un nouveau procédé de réalisation de pièces moulées en béton permettant de résoudre de tels problèmes grâce à l'utilisation d'un nouveau type d'armature de ferraillage, permettant, en particulier, de diminuer le risque de fissuration à sollicitations égales. En outre, le procédé permet d'améliorer considérablement la résistance aux sollicitations extrêmes, les pièces en béton ainsi réalisées pouvant avoir une très grande souplesse et bénéficier d'un grand coefficient de sécurité entre l'apparition des premières fissures et la ruine complète de l'ouvrage. Un tel avantage est particulièrement intéressant pour la construction d'ouvrages d'art ou de bâtiments dans les régions soumises à un risque sismique.The subject of the invention is a new method for producing concrete moldings that makes it possible to solve such problems by using a new type of reinforcement reinforcement, which makes it possible in particular to reduce the risk of cracking at equal solicitations. In addition, the method makes it possible to considerably improve the resistance to extreme stresses, the concrete parts thus produced being able to have a very high degree of flexibility and benefit from a high degree of safety between the appearance of the first cracks and the complete failure of the cracks. 'work. Such an advantage is particularly interesting for construction of structures or buildings in regions subject to seismic risk.
L'invention s'applique donc, d'une façon générale, à la réalisation d'une pièce en béton munie d'une cage de ferraillage entièrement noyée dans le béton lors de la coulée de celui-ci et comportant, lorsqu'elle est soumise à une sollicitation, deux parties situées de part et d'autre d'un axe neutre, respectivement une partie comprimée soumise à des efforts de compression absorbés principalement par le béton et une partie tendue soumise à des efforts de traction absorbés principalement par au moins une armature longitudinale tendue de la cage de ferraillage qui s'étend à une faible distance d'enrobage d'une face longitudinale tendue de la pièce et ayant une section transversale déterminée en fonction des efforts induits par la sollicitation et comportant un premier niveau constitué d'au moins une bande plate à section rectangulaire, avec une face large et une face étroite, et comportant une partie centrale comprise entre deux parties de blocage dans le béton, caractérisé par le fait que chaque partie de blocage dans le béton de l'armature tendue est constituée d'une extrémité de la bande plate recourbée en forme de crosse et prenant appui sur le béton par sa face large dans le sens opposé à l'effort de traction absorbé, en formant une zone de blocage et que la partie centrale de la bande comprise entre lesdites zones de blocage est laissée libre de se décoller du béton qui l'enrobe, en glissant légèrement par rapport à celui-ci, à partir d'un certain niveau de sollicitation, de telle sorte que l'armature tendue ne reste solidarisée avec le béton que dans ses parties de blocage, alors que ladite partie centrale est libre de s'allonger sous l'effet des efforts absorbés, avec une répartition uniforme de la tension sur toute sa longueur, et un second niveau de barres longitudinales décalées vers le haut et constitué d'au moins deux barres longitudinales formées chacune d'une bande plate et munies d'extrémités recourbées en forme de crosses, lesdites barres étant posées côte à côte et décalées longitudinalement l'une par rapport à l'autre de façon que les crosses ménagées à leurs extrémités soient placées à des distances différentes du plan médian transversal de la pièce, lesdites barres se recouvrant sur une certaine longueur et se terminant vers l'intérieur, par deux crosses opposées sollicitées l'une vers l'autre sous l'effet des efforts de traction opposés appliqués respectivement sur les deux bandes correspondantes, en induisant la mise en compression d'un noyau de béton compris entre lesdites crosses internes, sur ladite longueur de recouvrement.The invention therefore applies, in a general manner, to the production of a concrete part provided with a reinforcement cage entirely embedded in the concrete during the casting thereof and comprising, when it is subjected to a bias, two parts located on either side of a neutral axis, respectively a compressed part subjected to compression forces absorbed mainly by the concrete and a tensioned part subjected to tensile forces absorbed mainly by at least a stretched longitudinal reinforcement of the reinforcement cage which extends at a short coating distance from a longitudinal stretched face of the workpiece and having a cross section determined according to the forces induced by the load and comprising a first level consisting of at least one flat strip with a rectangular section, with a wide face and a narrow face, and having a central portion between two blocking parts in the concrete, characterized in that each blocking portion in the concrete of the tensioned frame consists of an end of the curved flat strip shaped as a butt and supported on the concrete by its broad face in the opposite direction to the force absorbed traction, forming a locking zone and that the central portion of the strip between said blocking zones is left free to peel off the concrete which coats it, sliding slightly with respect to it, from a certain level of stress, so that the tensioned reinforcement remains secured to the concrete only in its blocking parts, while said central portion is free to stretch under the effect of absorbed forces, with a distribution uniformity of the tension over its entire length, and a second level of longitudinal bars offset upwards and consisting of at least two longitudinal bars each formed of a flat strip and provided with curved ends in the form of butts, said bars being laid side by side and staggered longitudinally with respect to each other so that the butts at their ends are placed at different distances from the transverse medial plane of the workpiece, said bars overlapping for a certain length and ending inwardly by two opposing butts pressed against each other under the effect of the opposing tensile forces applied respectively to the two corresponding bands, inducing the compression of a concrete core between said internal butts, on said overlap length.
Conformément à l'invention, au moins chaque armature longitudinale tendue est constituée d'au moins une bande plate à section rectangulaire, avec une face large et une face étroite, et est conformée de façon à ménager, à l'intérieur de la pièce, au moins deux zones de blocage écartées l'une de l'autre, dans lesquelles une partie de ladite armature tendue prend appui sur le béton, dans le sens opposé à l'effort de traction absorbé, et au moins une zone de glissement comprise entre les zones de blocage, dans laquelle une partie correspondante de l'armature tendue est libre de s'allonger sur toute sa longueur, sous l'effet des efforts absorbés.According to the invention, at least each stretched longitudinal reinforcement consists of at least one rectangular section flat strip, with a wide face and a narrow face, and is shaped so as to provide, inside the room, at least two blocking zones spaced from each other, in which a portion of said tensioned frame bears on the concrete, in the opposite direction to the tensile force absorbed, and at least one slip zone between the locking zones, in which a corresponding portion of the tensioned frame is free to extend along its entire length, under the effect of absorbed forces.
Comme on le verra plus en détail par la suite, alors que la technique du béton armé a pour objet, d'une façon générale, de solidariser sur toute sa longueur chaque armature avec le béton qui l'enrobe, afin de réaliser une pièce composite se déformant en bloc sous l'effet des sollicitations, l'idée de l'invention est, au contraire, de réaliser des zones de blocage écartées, dans lesquelles l'armature, du fait qu'elle est constituée d'une bande plate, prend appui dans le béton par une face large sans risque de dépasser la limite admissible de compression du béton et, à partir d'un certain niveau de sollicitation, de laisser la partie de l'armature comprise entre deux zones de compression, libre de glisser légèrement par rapport au béton qui l'enrobe, après décollement de celui-ci, afin que l'effet d'allongement de l'armature résultant des efforts de traction appliqués soit toujours réparti sur toute la longueur comprise entre deux zones de blocage, ce qui permet d'éviter les concentrations de contraintes pouvant conduire à une rupture de l'armature en cas de sollicitations extrêmes.As will be seen in more detail later, while the purpose of the reinforced concrete technique is, in general, to secure along its entire length each reinforcement with the concrete that surrounds it, in order to produce a composite part. being deformed as a block under the effect of the stresses, the idea of the invention is, on the contrary, to make separate locking zones, in which the reinforcement, because it consists of a flat strip, is supported in the concrete by a wide face without risk of exceeding the allowable limit of concrete compression and, from a certain level of stress, to leave the part of the frame between two compression zones, free to slide slightly with respect to the concrete which coats it, after detachment of it, so that the effect of elongation of the reinforcement resulting from the traction forces applied is always distributed over the entire length between two blocking zones, which avoids stress concentrations that can lead to a rupture of the armature in case of extreme stress.
De façon particulièrement avantageuse, chaque zone de blocage est réalisée par déviation de la partie correspondante de l'armature tendue en forme de bande, avec une variation progressive et continue de l'orientation de sa face large par rapport à la face longitudinale tendue de la pièce.Particularly advantageously, each blocking zone is made by deflecting the corresponding part of the band-shaped tensile reinforcement, with a gradual and continuous variation of the orientation of its wide face relative to the stretched longitudinal face of the room.
Dans un premier mode de réalisation, chaque zone de blocage est réalisée par courbure de la bande plate autour d'un axe transversal, de façon à former une crosse d'ancrage prenant appui sur le béton par une face large.In a first embodiment, each blocking zone is formed by bending the flat strip around a transverse axis, so as to form an anchor stock bearing on the concrete by a wide face.
Dans un autre mode de réalisation qui ne fait pas partie de l'invention, chaque zone de blocage est réalisée par vrillage de la bande sur une certaine longueur, avec une rotation progressive de sa face large autour de son axe longitudinal, sur au moins un quart de tour. Mais la partie vrillée de la bande peut aussi tourner d'un tour complet ou plus, de façon à prendre appui sur le béton sur une plus grande longueur.In another embodiment which does not form part of the invention, each locking zone is made by twisting the strip over a certain length, with a progressive rotation of its wide face about its longitudinal axis, over at least one quarter turn. But the twisted portion of the band can also rotate a full turn or more, so as to bear on the concrete over a longer length.
Dans encore un autre mode de réalisation qui ne fait pas partie de l'invention, il est possible également de réaliser une zone de blocage en fixant sur la bande plate, à l'endroit voulu, au moins un tronçon de barre rigide s'étendant transversalement de façon à prendre appui dans le béton de part et d'autre de la bande plate.In yet another embodiment which does not form part of the invention, it is also possible to realize a locking zone by fixing on the flat strip, at the desired place, at least one rigid bar section extending transversely so as to bear in the concrete on both sides of the flat strip.
Cette barre transversale peut être constituée d'un filant de répartition.This crossbar may consist of a distribution thread.
En effet, de façon classique, la cage de ferraillage comporte, habituellement, plusieurs secteurs longitudinaux reliés entre eux par des filants de répartition constitués de barres perpendiculaires aux barres principales longitudinales, l'ensemble constituant une nappe de ferraillage.In fact, conventionally, the reinforcement cage usually comprises several longitudinal sectors interconnected by distribution threads consisting of bars perpendicular to the longitudinal main bars, the assembly constituting a reinforcement ply.
Ces filants de répartition peuvent être soudés sur les barres longitudinales, dont la forme de bande plate permet de réaliser des soudures particulièrement résistantes.These distribution threads can be welded to the longitudinal bars, whose flat strip shape allows for particularly strong welds.
Chaque jonction soudée peut constituer une zone de blocage, le filant de répartition prenant appui dans le béton de part et d'autre de la barre longitudinale.Each welded junction may constitute a blocking zone, the distribution thread being supported in the concrete on either side of the longitudinal bar.
Par ailleurs, habituellement, chaque secteur de la cage de ferraillage comporte au moins deux barres longitudinales respectivement comprimée et tendue et reliées entre elles par des étriers de liaison.Furthermore, usually, each sector of the reinforcement cage comprises at least two longitudinal bars respectively compressed and tensioned and interconnected by connecting stirrups.
De préférence, les armatures comprimées sont également constituées de bandes plates.Preferably, the compressed frames also consist of flat strips.
De même, selon une autre disposition avantageuse, les étriers de liaison peuvent être constitués chacun d'au moins une bande plate solidarisée avec les armatures par des cordons de soudure ou des parties collées s'étendant sur une longueur égale à la largeur de la bande, et donc, particulièrement résistants.Similarly, according to another advantageous arrangement, the connecting stirrups may each consist of at least one flat strip secured to the reinforcements by welding beads or glued portions extending over a length equal to the width of the strip and therefore, particularly resistant.
En outre, chaque bande constituant un étrier est inclinée par rapport à la direction de la barre tendue et l'ensemble de la jonction soudée entre ces deux bandes plates d'orientations différentes, forme une sorte de coin prenant appui sur le béton.In addition, each band constituting a stirrup is inclined with respect to the direction of the tensioned bar and the whole of the welded joint between these two flat strips of different orientations, forms a kind of corner bearing on the concrete.
De ce fait, bien que cela ne fasse pas partie de l'invention, chaque zone de blocage entre l'armature tendue et le béton peut être constituée par une jonction de solidarisation entre cette armature tendue et un étrier de liaison en forme de bande.Therefore, although this is not part of the invention, each locking zone between the tensile reinforcement and the concrete may be constituted by a joining junction between the tensioned frame and a band-shaped connecting stirrup.
Mais l'utilisation de bandes plates pour réaliser au moins les armatures tendues donne encore d'autres possibilités, en dehors de la présente invention.But the use of flat strips to achieve at least tensioned frames gives further possibilities, apart from the present invention.
Ainsi, pour former une zone de blocage, l'armature tendue en forme de bande peut être fendue axialement sur une certaine longueur, les deux parties de bande ainsi constituées étant écartées l'une de l'autre pour former une ouverture de passage transversal d'au moins un tronçon de barre rigide susceptible de prendre appui sur le béton de part et d'autre de la bande longitudinale, dans le sens opposé à l'effort de traction appliqué sur l'armature longitudinale.Thus, to form a locking zone, the strip-shaped tensile reinforcement can be split axially over a certain length, the two band portions thus formed being spaced apart from one another to form a transverse passage opening of at least one rigid bar section likely to bear on the concrete on both sides of the longitudinal strip, in the opposite direction to the tensile force applied to the longitudinal reinforcement.
Cette barre rigide peut être un filant de répartition traversant la bande longitudinale dans le plan de celle-ci, ou bien un simple tronçon de barre traversant la bande longitudinale perpendiculairement à son plan.This rigid bar may be a distribution wire passing through the longitudinal strip in the plane thereof, or a simple bar section passing through the longitudinal strip perpendicular to its plane.
Par ailleurs, l'utilisation de bandes plates permet de multiples possibilités pour la mise en oeuvre du procédé selon l'invention.Furthermore, the use of flat strips allows multiple possibilities for the implementation of the method according to the invention.
En particulier, comme indiqué précédemment, selon l'invention, chaque armature longitudinale peut comporter au moins deux bandes accolées s'étendant longitudinalement, sensiblement dans le prolongement l'une de l'autre et soumises à des efforts de traction en des sens opposés, les deux bandes accolées se recouvrant sur une certaine longueur et se terminant respectivement, de part et d'autre du recouvrement, par deux crosses tournées l'une vers l'autre, qui ont ainsi tendance à se rapprocher sous l'effet des efforts de traction opposés appliqués sur les deux bandes correspondantes, en induisant la mise en compression d'un noyau de béton compris entre les deux crosses, sur ladite longueur de recouvrement.In particular, as indicated above, according to the invention, each longitudinal reinforcement may comprise at least two contiguous bands extending longitudinally, substantially in the extension of one another and subjected to traction forces in opposite directions, the two contiguous strips overlapping over a certain length and ending respectively, on both sides of the cover, by two sticks turned towards each other, which thus tend to come closer under the effect of the efforts of opposed traction applied to the two corresponding bands, inducing the compression of a concrete core between the two sticks, on said lap length.
Dans le cas habituel où la cage de ferraillage est constituée de secteurs parallèles reliés par des filants de répartition, ces derniers peuvent passer à l'intérieur des crosses de deux secteurs voisins, de façon à transmettre à la partie du béton comprise entre lesdits secteurs, les efforts de compression induits, dans chaque secteur, par la tendance au rapprochement des crosses opposées.In the usual case where the reinforcement cage consists of parallel sectors connected by distribution threads, the latter can pass inside the ends of two neighboring sectors, so as to transmit to the concrete part between said sectors, the compression efforts induced, in each sector, by the tendency towards the opposite ends.
Selon une disposition particulière de l'invention, les deux bandes accolées formant l'armature longitudinale de chaque secteur de la cage, peuvent constituer deux brins d'une bande unique se terminant par des crosses opposées et formant une boucle entre deux niveaux écartés, de façon à entourer un noyau de béton mis en compression par serrage de ladite boucle sous l'effet des efforts de traction appliqués en des sens opposés sur les deux brins de l'armature longitudinale.According to a particular embodiment of the invention, the two contiguous strips forming the longitudinal reinforcement of each sector of the cage, may constitute two strands of a single band ending in opposite hooks and forming a loop between two separated levels, of way to surround a concrete core set in compression by clamping said loop under the effect of traction forces applied in opposite directions on the two strands of the longitudinal reinforcement.
De façon particulièrement avantageuse, dans une réalisation ne faisant pas partie de l'invention, dans chaque secteur, l'armature longitudinale peut être constituée d'une série de bandes consécutives ayant chacune deux extrémités courbées en forme de crosse, les crosses adjacentes de deux bandes consécutives étant placées l'une à côté de l'autre en se chevauchant partiellement de façon à limiter un espace de passage, dans le sens transversal, d'au moins un tronçon de barre formant une clavette de liaison entre les deux bandes consécutives. L'armature longitudinale se comporte alors comme une chaîne tendue constituée d'une série de maillons formés chacun d'une bande et reliés deux à deux par des paires de crosses adjacentes clavetées entre elles.Particularly advantageously, in an embodiment not forming part of the invention, in each sector, the longitudinal reinforcement may consist of a series of consecutive strips each having two curved ends in the form of a butt, the adjacent butts of two consecutive strips being placed next to each other partially overlapping so as to limit a passage space, in the transverse direction, of at least one bar section forming a connecting key between the two consecutive strips. The longitudinal reinforcement then behaves like a tensioned chain consisting of a series of links each formed of a band and connected in pairs by pairs of adjacent sticks keyed together.
Dans le mode de réalisation de l'invention, dans chaque secteur, l'armature longitudinale comprend un empilement de bandes plates, disposées sur au moins deux niveaux superposés, respectivement un premier niveau, le plus proche d'une face longitudinale tendue de la pièce comportant une bande, avec deux extrémités en forme de crosses tournées vers l'intérieur de la pièce et au moins un second niveau comportant au moins deux bandes plates sensiblement parallèles disposées côte à côte avec, chacune, deux extrémités en forme de crosses, respectivement interne et externe, et lesdites bandes du second niveau se chevauchent sur une certaine longueur, de façon que leurs extrémités internes en forme de crosses soient tournées l'une vers l'autre. La pièce comporte ainsi au moins une partie formant un noyau compris entre les crosses internes des deux bandes et mis en compression par la tendance au rapprochement l'une vers l'autre desdites crosses internes sous l'effet des efforts de traction appliqués en des sens opposés sur les bandes correspondantes, et deux parties extrêmes comprises chacune entre les crosses externes des bandes du premier et du second niveau et mises en compression par la tendance au rapprochement vers l'intérieur de chaque crosse externe de la bande du premier niveau sous l'effet de l'effort de traction supporté par ladite bande. Il est ainsi possible de mettre en compression l'ensemble du béton de la pièce.In the embodiment of the invention, in each sector, the longitudinal reinforcement comprises a stack of flat strips, arranged on at least two superimposed levels, respectively a first level, the closest to a stretched longitudinal face of the workpiece. having a band, with two stick-shaped ends facing towards the inside of the piece and at least a second level comprising at least two substantially parallel flat strips arranged side by side with each two ends in the form of crosses, respectively internal and outer, and said strips of the second level overlap over a certain length, so that their inner ends in the form of crosses are facing each other. The part thus comprises at least one portion forming a core between the inner ends of the two strips and set in compression by the tendency towards the one towards the other of said internal butts under the effect of the tensile forces applied in the directions opposing on the corresponding bands, and two end parts each included between the outer hooks of the bands of the first and the second level and put in compression by the tendency to approach inwardly each outer stock of the band of the first level under the effect of the traction force supported by said band. It is thus possible to compress the entire concrete of the room.
Mais l'invention permet encore d'autres dispositions et couvre de nombreuses caractéristiques avantageuses qui apparaîtront dans la description qui va suivre de certains modes de réalisation donnés à titre d'exemples non limitatifs illustrés par les dessins annexés.
- La
figure 1 est une vue schématique, en coupe longitudinale, d'une pièce en béton en dehors del'invention. - La
figure 2 est une vue partielle en coupe transversale selon II-II de lafigure 1 . - La
figure 3 est une vue en perspective d'une partie vrillée de l'armature de la réalisation de lafigure 1 . - La
figure 4 est une vue en coupe, selon un plan médian transversal, de la partie vrillée de la réalisation de lafigure 1 . - La
figure 5 est une vue partielle, en perspective, d'une partie en forme de crosse selon l'invention. - La
figure 6 est une vue partielle de côté, d'une crosse double. - La
figure 7 est une vue en coupe longitudinale d'une pièce réalisée selon une variante ne faisant pas partie de l'invention. - La
figure 8 montre, en perspective, une partie vrillée appliquée au mode de réalisation de lafigure 7 . - La
figure 9 montre, en coupe longitudinale, une pièce réalisée selon une autre variante ne faisant pas partie de l'invention. - Les
figures 10 (selon l'invention) et 11 (en dehors de l'invention) montrent, en coupe longitudinale, des réalisations avec plusieurs nappes d'armatures. - La
figure 12 montre, en coupe longitudinale, une pièce du type représenté sur lafigure 10 , avec une armature en boucle fermée. - La
figure 13 est une vue en perspective d'une armature en boucle fermée. - La
figure 14 montre, en coupe longitudinale, une autre variante en dehors de l'invention, avec une armature en forme de chaîne. - La
figure 15 montre, en perspective, la jonction entre deux éléments de l'armature du type représenté sur lafigure 14 . - Les
figures 16, 17, 18 montrent, en perspective, d'autres modes de réalisation d'une zone de blocage ne faisant pas partie de l'invention. - La
figure 19 montre, en perspective, une zone de blocage en forme de crosse. - La
figure 20 montre, en perspective, un autre mode de réalisation d'une extrémité d'armature en forme de crosse.
- The
figure 1 is a schematic view, in longitudinal section, of a concrete part outside 1'invention. - The
figure 2 is a partial cross sectional view along II-II of thefigure 1 . - The
figure 3 is a perspective view of a twisted part of the frame of the realization of thefigure 1 . - The
figure 4 is a sectional view, along a transverse median plane, of the twisted portion of the embodiment of thefigure 1 . - The
figure 5 is a partial view, in perspective, of a butt-shaped portion according to the invention. - The
figure 6 is a partial side view of a double butt. - The
figure 7 is a longitudinal sectional view of a part made according to a variant not forming part of the invention. - The
figure 8 shows, in perspective, a twisted part applied to the embodiment of thefigure 7 . - The
figure 9 shows, in longitudinal section, a part made according to another variant not forming part of the invention. - The
figures 10 (according to the invention) and 11 (outside the invention) show, in longitudinal section, embodiments with several reinforcing plies. - The
figure 12 shows, in longitudinal section, a part of the type shown on thefigure 10 , with a closed loop frame. - The
figure 13 is a perspective view of a closed-loop frame. - The
figure 14 shows, in longitudinal section, another variant outside the invention, with a chain-like reinforcement. - The
figure 15 shows, in perspective, the junction between two elements of the armature of the type represented on thefigure 14 . - The
Figures 16, 17, 18 show, in perspective, other embodiments of a blocking zone not forming part of the invention. - The
figure 19 shows, in perspective, a locking zone in the shape of a stick. - The
figure 20 shows, in perspective, another embodiment of a butt-shaped frame end.
Sur les
Comme habituellement, cette pièce en béton 1 qui constitue, dans l'exemple représenté sur les dessins, une dalle ayant deux faces planes, respectivement inférieure 20 et supérieure 21, est une pièce moulée réalisée par coulée d'une masse de béton 2 dans un coffrage, après mise en place, dans celui-ci d'une cage de ferraillage 3 comportant deux nappes d'armature, respectivement inférieure 30 et supérieure 30', sensiblement parallèles aux deux faces 20, 21 de la dalle 1.As usual, this
La cage de ferraillage 3 est constituée, normalement, de plusieurs secteurs S1, S2,... centrés, respectivement, dans des plans P1, P2... parallèles à un axe longitudinal de la pièce 1, c'est-à-dire au plan de la
De plus, les différents secteurs S1, S2... de la cage sont reliés entre eux par des filants transversaux 32, 32' perpendiculaires au plan de la
Comme on le sait, sous l'effet, par exemple, d'une charge verticale M appliquée sur sa face supérieure 21, la pièce en béton 1 peut être divisée en deux parties situées de part et d'autre d'un axe neutre 10, respectivement une partie comprimée 11' comprise entre l'axe neutre 10 et la face 21 sur laquelle sont appliqués les efforts et une partie tendue 11 s'étendant jusqu'à la face 20 opposée aux efforts.As is known, under the effect, for example, of a vertical load M applied on its
Toutes ces dispositions sont classiques et ne nécessitent pas une description détaillée.All these arrangements are conventional and do not require a detailed description.
Cependant, la cage de ferraillage 3 se distingue des cages réalisées habituellement par le fait que, selon une disposition décrite dans la demande de brevet
De préférence, les armatures comprimées 31' sont également constituées de barres plates mais, par économie, on pourrait aussi utiliser des barres rondes classiques.Preferably, the compressed armatures 31 'are also constituted by flat bars but, for economy, it would also be possible to use conventional round bars.
Comme l'indique le brevet précédent
Dans la technique classique du béton armé, on utilise, généralement, des barres d'armature crantées afin d'améliorer la liaison de transfert entre l'armature et le béton et l'on réalise ainsi une pièce composite dont on cherche, habituellement, à augmenter la rigidité afin d'éviter l'apparition de fissures préjudiciables. Cependant, on ne peut éviter une déformation même minime de la pièce avec un allongement des armatures tendues ainsi que du béton qui les enrobe, dont la résistance à la traction est minime. Il en résulte donc l'apparition de fissures à partir d'une certaine charge.In the conventional reinforced concrete technique, notched reinforcement bars are generally used in order to improve the transfer bond between the reinforcement and the concrete, thereby producing a composite part which is usually sought after. increase rigidity to avoid the appearance of harmful cracks. However, one can not avoid even minimal deformation of the workpiece with an elongation of tensile reinforcement and the concrete that enrobe, whose tensile strength is minimal. This results in the appearance of cracks from a certain load.
Dans l'invention, au contraire, on ne cherche pas, comme habituellement, à solidariser l'armature avec le béton sur toute sa longueur mais, au contraire, on ménage dans le béton 2, le long de chaque armature longitudinale tendue 31, deux zones de blocage écartées de part et d'autre du plan médian transversal Q de la pièce, entre lesquelles s'étend une zone centrale C dans laquelle l'armature 31 est libre de s'allonger sous l'effet des efforts appliqués, en glissant par rapport au béton qui l'enrobe.In the invention, on the contrary, it is not sought, as usually, to secure the reinforcement with the concrete over its entire length but, on the contrary, it is cleaned in the concrete 2, along each stretched longitudinal reinforcement 31, two blocking zones spaced apart on either side of the transverse median plane Q of the part, between which extends a central zone C in which the armature 31 is free to stretch under the effect of the forces applied, by sliding compared to the concrete that surrounds it.
Du fait que l'on utilise, comme armature longitudinale, des bandes plates, chaque zone de blocage peut être réalisée simplement par déviation de la partie correspondante de l'armature tendue 31, dont on fait varier progressivement et de façon continue l'orientation de sa face large par rapport à la face longitudinale tendue 20 de la pièce afin que, dans cette zone, la bande 4 formant l'armature 31 prenne appui dans le béton par son côté large 41, dans le sens opposé à l'effort de traction absorbé.Because flat belts are used as longitudinal reinforcement, each blocking zone can be made simply by deflecting the corresponding part of the tensioned frame 31, the orientation of which is gradually and continuously changed. its wide face relative to the longitudinal stretched side 20 of the part so that, in this area, the band 4 forming the frame 31 is supported in the concrete by its wide side 41, in the opposite direction to the tensile force absorbed.
Du fait que la bande est plate et prend appui dans le béton par deux faces larges, le béton ne risque pas de se cisailler, la contrainte de compression étant faible. D'ailleurs, la largeur I de la bande 4 peut être déterminée en fonction des sollicitations appliquées, de façon à ce que la contrainte de compression appliquée sur le béton reste inférieure à une limite admissible.Because the strip is flat and supported in the concrete by two large faces, the concrete is not likely to shear, the compression stress is low. Moreover, the width I of the band 4 can be determined according to the stresses applied, so that the compressive stress applied to the concrete remains below a permissible limit.
En outre, dans une pièce en béton armé réalisée de façon classique, les barres longitudinales tendues doivent être recourbées en forme de crosse à leurs extrémités afin d'augmenter la longueur de transfert entre l'armature et le béton. Or, compte tenu de la dureté de l'acier employé, la courbure que l'on peut donner à une barre est nécessairement limitée et la réglementation impose, d'ailleurs, de donner à la crosse un diamètre d'au moins 10 fois le diamètre de la barre. Pour cette seule raison, une pièce en béton doit avoir une épaisseur minimale de douze fois le diamètre des barres tendues à laquelle il faut ajouter deux fois l'épaisseur minimale d'enrobage.In addition, in a conventionally made reinforced concrete part, the stretched longitudinal bars must be curved in the shape of a butt at their ends in order to increase the transfer length between the reinforcement and the concrete. However, given the hardness of the steel used, the curvature that can be given to a bar is necessarily limited and the regulation requires, moreover, to give the stick a diameter of at least 10 times the diameter of the bar. For this reason alone, a concrete part must have a minimum thickness of twelve times the diameter of the tension bars, to which must be added twice the minimum thickness of the coating.
Si l'on utilise, comme dans l'invention, des barres plates, celles-ci sont munies à leurs extrémités, de crosses 5, de la façon représentée en perspective sur la
En outre, même si l'on utilise des aciers à limite élastique élevée, l'utilisation de bandes plates permet de réduire encore le diamètre D de la partie recourbée car celle-ci peut être plus facilement pliée autour d'un axe 50 parallèle au plan de la face large de la bande.In addition, even if high yielding steels are used, the use of flat belts makes it possible to further reduce the diameter D of the curved portion since it can be more easily folded around an
Par ailleurs, chaque crosse 5 constitue une zone B1 de blocage dans le béton 2.Moreover, each butt 5 constitutes a blocking zone B1 in the concrete 2.
La bande d'armature 4 ainsi solidarisée avec le béton par deux zones de blocage B1 et B1' peut, en revanche, s'allonger librement dans sa partie centrale.The reinforcing strip 4 thus secured to the concrete by two locking zones B 1 and B 1 'can, on the other hand, lie freely in its central part.
Certes, après le bétonnage, il existe une liaison d'adhérence entre le béton et l'armature sur toute la longueur de celle-ci. Cependant, on évite, contrairement à la technique habituelle d'améliorer cette adhérence, par exemple au moyen de crans.Admittedly, after concreting, there is a bond of adhesion between the concrete and the reinforcement over the entire length of the latter. However, it is avoided, contrary to the usual technique to improve this adhesion, for example by means of notches.
Dans l'invention, en effet, chaque bande 4 constituant une armature longitudinale 31 n'est solidarisée avec le béton que dans les deux zones de blocage qui sont écartées l'une de l'autre et la tendance à l'allongement de l'armature sous l'effet de la tension appliquée peut se répartir uniformément sur toute la longueur de la partie centrale, celle-ci pouvant se décoller du béton à partir d'un certain niveau de sollicitation.In the invention, in fact, each band 4 constituting a longitudinal reinforcement 31 is secured to the concrete only in the two locking zones which are spaced from each other and the tendency to elongation of the reinforcement under the effect of the applied voltage can be evenly distributed over the entire length of the central portion, the latter can peel off the concrete from a certain level of stress.
Certes, le béton 2 ne peut pas se déformer de la même façon que l'armature et l'on ne peut donc éviter l'apparition de fissures mais ce risque de fissuration se répartit uniformément sur toute la longueur de la partie centrale et les fissures plus nombreuses peuvent avoir une largeur assez réduite pour ne pas être préjudiciable.Admittedly, concrete 2 can not be deformed in the same way as the reinforcement and we can not avoid the appearance of cracks but this risk of cracking is evenly distributed over the entire length of the central part and cracks more numerous may have a small enough width to not be detrimental.
De la sorte, il n'est plus nécessaire, comme auparavant, d'augmenter la rigidité de la pièce en béton pour diminuer sa déformation et, au contraire, on peut réaliser des pièces en béton relativement souples.In this way, it is no longer necessary, as before, to increase the rigidity of the concrete part to reduce its deformation and, on the contrary, it is possible to make relatively flexible concrete parts.
Lorsque les sollicitations appliquées restent faibles, la pièce se comporte, comme habituellement, comme une pièce composite, le béton se déformant de la même façon que l'armature.When the applied stresses remain low, the piece behaves, as usual, as a composite part, the concrete deforming in the same way as the reinforcement.
A partir d'un certain niveau de sollicitation, l'armature ne reste solidarisée avec le béton que dans ses parties de blocage et sa partie centrale peut, au contraire, se décoller du béton qui l'enrobe et glisser légèrement par rapport à celui-ci. La tension et, par conséquent, la tendance à l'allongement de l'armature, se répartit donc de façon sensiblement uniforme sur toute la longueur de la partie centrale. On évite ainsi une concentration de la contrainte de traction sur une faible longueur de l'armature et, par conséquent, on diminue le risque de rupture de l'armature au niveau d'une fissure, sous l'effet de sollicitations excessives.From a certain level of stress, the reinforcement remains secured to the concrete only in its blocking parts and its central part can, on the contrary, peel off the concrete that coats it and slide slightly with respect to it. this. The tension and, therefore, the tendency to elongation of the armature, is therefore distributed substantially uniformly over the entire length of the central portion. This avoids a concentration of the tensile stress over a short length of the armature and, therefore, the risk of rupture of the armature at a crack under the effect of excessive stresses is reduced.
A titre d'exemple on a soumis des dalles réalisées selon l'invention à des essais de flexion avec augmentation progressive de la charge appliquée et l'on a constaté qu'une dalle ainsi réalisée pouvait, de façon surprenante, admettre une flèche très importante avant la rupture de la dalle et avec des fissures de largeur relativement faibles.By way of example, slabs produced according to the invention have been subjected to bending tests with progressive increase of the applied load and it has been found that slab thus realized could, surprisingly, admit a very important arrow before the breaking of the slab and with cracks of relatively small width.
Il est à noter, en outre, que comme on l'avait indiqué dans la demande de brevet
Etant donné que, selon l'invention, l'armature longitudinale est, en quelque sorte, accrochée au béton dans les zones de blocage 5 alors que la partie centrale est libre de s'allonger, les sollicitations appliquées par l'armature sur le béton sont plus fortes que dans le cas d'un ferraillage classique où l'on cherche à réaliser une solidarisation sur toute la longueur de l'armature. Bien entendu, ceci se traduit, dans les zones de blocage par un effort de compression plus important dans le béton mais, précisément, le béton présente une excellente résistance à la compression.Since, according to the invention, the longitudinal reinforcement is, in a way, attached to the concrete in the blocking zones 5 while the central part is free to stretch, the stresses applied by the reinforcement on the concrete are stronger than in the case of a conventional reinforcement where one seeks to achieve a solid connection over the entire length of the frame. Of course, this is reflected in the locking zones by a greater compressive force in the concrete but, precisely, the concrete has excellent compressive strength.
De plus, il n'y a pas à craindre comme dans le cas d'une barre ronde, un effet de cisaillement du béton, car la largeur I de chaque barre plate peut être déterminée en fonction des efforts appliqués de façon que la contrainte de compression du béton ne dépasse pas une limite donnée.In addition, there is no need to fear, as in the case of a round bar, a shearing effect of the concrete, since the width I of each flat bar can be determined according to the forces applied so that the stress of concrete compression does not exceed a given limit.
Du fait que la bande 4 est soumise à un effort important de traction T qui est encaissé par la zone de blocage B1 située à l'intérieur de la crosse 5, celle-ci peut avoir tendance à se dérouler si l'adhérence entre la barre 4 est le béton n'est pas suffisante.Because the band 4 is subjected to a large tensile force T which is concealed by the blocking zone B1 located inside the butt 5, it may tend to unfold if the adhesion between the bar 4 is the concrete is not enough.
Pour éviter un tel effet, il est possible d'adjoindre à la crosse 5 une crosse auxiliaire 51 tournée dans le sens opposé et ayant un diamètre un peu plus faible, afin d'éviter cet effet de déroulement.To avoid such an effect, it is possible to add to the stock 5 an
De plus, comme le montre la
Pour cette raison, il est possible à poids de ferraillage égal, de réaliser des pièces plus minces que les pièces réalisées de façon classique en béton armé.For this reason, it is possible for even reinforcement weight to produce thinner parts than those made in conventional reinforced concrete.
Il est à noter, par ailleurs, que dans le mode de réalisation préférentiel comme représenté notamment sur la
Cependant, en sortant du cadre de la présente invention, il est possible, si l'on souhaite augmenter la résistance au fléchissement, d'utiliser des bandes 4 orientées de la façon indiquée sur la
Dans ce cas, le blocage de la bande 4 dans le béton est réalisé essentiellement au niveau des zones B1, B'1, à l'intérieur des crosses 5, 5', ménagées aux extrémités de la bande 4.In this case, the blocking of the band 4 in the concrete is essentially achieved at the level of the zones B1, B'1, inside the butts 5, 5 ', formed at the ends of the band 4.
En revanche, chaque bande d'armature 4 orientée, dans sa partie centrale 44', perpendiculairement à la face tendue 20, apporte par elle-même une certaine résistance à la flexion qui permet d'augmenter la rigidité de la pièce et de diminuer la flèche résultant des efforts appliqués.On the other hand, each reinforcing strip 4 oriented, in its central part 44 ', perpendicular to the stretched face 20, itself provides a certain resistance to bending which makes it possible to increase the rigidity of the part and to reduce the arrow resulting from the efforts applied.
Comme habituellement, les barres longitudinales 31, 31' des deux nappes, respectivement inférieures 30 et supérieures 30' peuvent être reliées par des étriers qui, de la façon décrite dans le document
Cependant, comme le montre la
En revanche, les étriers peuvent être soudés ou collés sur les barres comprimées 31' à la partie supérieure de chaque ondulation. Pour cela, il est préférable que chaque barre comprimée 31' soit également constituée d'au moins une bande plate, afin de réaliser un cordon de soudure sur toute la largeur de la bande ondulée 13.In contrast, the stirrups may be welded or glued to the compressed bars 31 'at the top of each corrugation. For this, it is preferable that each compressed bar 31 'also consists of at least one flat strip, in order to produce a weld bead over the entire width of the
Il est à noter que chaque jonction soudée ou collée 14 entre une barre 4 et la partie correspondante de l'étrier 13 qui forme un angle avec cette barre 4 constitue, par effet de coin, une zone de blocage B. Par ailleurs, les extrémités recourbées en forme de crosses 5 permettent de ménager, comme précédemment, des zones de blocage B1, B'1 aux deux extrémités de l'armature 31.It should be noted that each welded or glued junction 14 between a bar 4 and the corresponding part of the
Dans l'exemple de réalisation en dehors de la présente invention représenté sur les
Mais l'invention qui est illustrée en particulier aux
Dans la réalisation selon l'invention représentée sur la
Cependant ces barres longitudinales 31 sont associées à un second niveau de barres longitudinales décalées vers le haut et comprenant, dans chaque secteur de la cage, deux barres 33, 34 formées chacune d'une bande plate et posées côte à côte, chacune de ces barres 33, 34 étant munie d'extrémités recourbées en forme de crosses 51, 51', 52, 52'.However, these longitudinal bars 31 are associated with a second level of longitudinal bars offset upwards and comprising, in each sector of the cage, two
En outre, les deux bandes accolées 33, 34 d'un même secteur sont décalées longitudinalement l'une par rapport à l'autre de façon que les deux crosses 51, 51' (52, 52') ménagées aux extrémités de chaque bande 33 (34) soient placées à des distances différentes du plan médian transversal Q de la pièce 1, de part et d'autre de celui-ci.In addition, the two
Ainsi, la crosse externe 51 de la barre 33 placée à gauche sur la
La pièce 1 est ainsi divisée en plusieurs zones adjacentes :
- une zone centrale B3 comprise entre la crosse interne 51' de l'armature longitudinale 33 placée à droite du plan médian transversal Q et la
crosse interne 52 de l'armature 34 placée à gauche de ce plan; - deux zones latérales B2, B'2 placées respectivement, à gauche et à droite du plan Q la zone de gauche B2 étant comprise entre la crosse externe 51 de la bande 33 et la crosse interne de la
barre 34 et la zone de droite B'2 entre la crosse externe 52' de la bande 34 et la crosse interne 51' de la bande 33; - deux zones extrêmes B1 et B'1 comprises, respectivement à gauche et à droite, entre les crosses 5, 5' de la bande inférieure 31, et les crosses
externes 51, 52' des bandes supérieures 33, 34.
- a central zone B3 between the internal butt 51 'of the longitudinal reinforcement 33 placed to the right of the transverse median plane Q and the
internal butt 52 of thearmature 34 placed to the left of this plane; - two lateral zones B2, B'2 placed respectively to the left and to the right of the plane Q the left zone B2 being between the
outer stick 51 of the band 33 and the inner butt of thebar 34 and the right zone B ' 2 between the external stick 52 'of theband 34 and the internal stock 51' of the band 33; - two extreme zones B1 and B'1 included, respectively on the left and on the right, between the butts 5, 5 'of the lower band 31, and the
external butts 51, 52' of theupper bands 33, 34.
Lorsque la pièce 1 est soumise à une sollicitation ayant tendance à la faire fléchir vers le bas, les armatures longitudinales sont soumises à des efforts de traction et prennent appui dans le béton par leurs extrémités en forme de crosses qui sont donc sollicitées vers l'intérieur.When the
Les armatures longitudinales 33, 34 qui se chevauchent dans la partie centrale de la pièce, sont tendues dans des sens différents et la zone centrale de blocage B3 est donc comprimée par la tendance au rapprochement l'une vers l'autre des crosses internes 51', 52 des deux armatures 33, 34.The
De même, les crosses externes 51, 52' ont tendance à se rapprocher du plan Q sous l'effet des efforts de traction appliqués sur les barres 33, 34 et les zones latérales B2, B'2 sont ainsi mises en compression.Similarly, the
Pour les mêmes raisons, les zones extrêmes B1, B'1 sont également mises en compression par les crosses 5, 5' qui s'opposent aux efforts de traction appliqués sur l'armature 31.For the same reasons, the end zones B1, B'1 are also put in compression by the butts 5, 5 'which oppose the tensile forces applied to the frame 31.
Ainsi, la pièce 1 est mise en compression pratiquement sur toute sa longueur par la tendance au rapprochement vers l'intérieur des crosses des différentes armatures et cet effet de compression s'exerce sur toute l'épaisseur du béton limitée par les crosses et non pas seulement, comme habituellement, au-dessus de l'axe neutre 10.Thus, the
Le risque de fissuration de la pièce, même au voisinage de la face tendue 20 est donc considérablement diminué et des essais de chargement effectués sur une pièce ainsi réalisée ont montré qu'une telle pièce pouvait supporter, avant rupture, une flèche très importante et tout à fait inhabituelle pour une pièce en béton armé.The risk of cracking of the part, even in the vicinity of the tensioned face 20 is therefore considerably reduced and loading tests carried out on a part thus produced have shown that such a part could withstand, before rupture, a very large deflection and all unusual for a reinforced concrete part.
Dans le mode de réalisation qui vient d'être décrit, la mise en compression de la zone centrale B3 de la pièce entre les crosses internes 52, 51' des deux bandes accolées 33, 34 résulte du chevauchement de celles-ci qui sont tendues en des sens opposés de part et d'autre du plan médian transversal Q.In the embodiment which has just been described, the compression of the central zone B3 of the part between the
Cependant, en dehors du cadre de la présente invention, comme le montre la
Dans ce cas, également, le béton est mis en compression par les crosses 5, 5', 51, 51' qui absorbent les efforts de traction appliqués sur les bandes 35, 36 en raison du fléchissement de la pièce.In this case, too, the concrete is put in compression by the
A cet égard, il peut être avantageux de réaliser les bandes en métaux ayant des caractéristiques mécaniques différentes de façon à moduler les efforts de compression appliqués par les crosses en fonction de la répartition des efforts appliqués sur la pièce.In this regard, it may be advantageous to make the metal strips having different mechanical characteristics so as to modulate the compression forces applied by the butts according to the distribution of forces applied to the workpiece.
Il est à noter que l'utilisation de bandes plates comme barres d'armatures, permet assez facilement de faire varier leur module d'élasticité car les bandes plates peuvent être réalisées par refendage de tôles et l'on peut trouver sur le marché des tôles de caractéristiques différentes alors que les possibilités de choix sont plus réduites pour les ronds à béton.It should be noted that the use of flat bands as rebars, allows quite easily to vary their modulus of elasticity because the flat strips can be made by slitting sheet metal and one can find on the market sheet metal of different characteristics while the possibilities of choice are more reduced for concrete reinforcing bars.
Par ailleurs, du fait que, contrairement à la technique classique, on ne cherche pas à solidariser l'armature avec le béton qui l'enrobe, il est possible de placer l'une contre l'autre les deux bandes superposées 31, 35 qui se comportent alors comme une sorte de ressort à lames.Moreover, because, contrary to the conventional technique, it is not sought to join the reinforcement with the concrete that surrounds it, it is possible to place against one another the two
Les
Chaque armature longitudinale est ainsi constituée d'une bande unique 33, 37, 34 entourant un noyau de béton B3 qui est mis en compression par serrage de la boucle ainsi formée sous l'effet des efforts de traction appliqués en des sens opposés sur les deux brins 33, 34 de l'armature longitudinale lorsque la pièce 1 est soumise à une charge verticale.Each longitudinal reinforcement thus consists of a
Il est à noter que dans ce cas, la partie supérieure 37 de chaque armature longitudinale en forme de boucle peut constituer une partie de la nappe supérieure 30' de la cage de ferraillage 3.It should be noted that in this case, the
D'autre part dans le cas de la
D'une façon générale, chacune des figures décrites précédemment montre un secteur de la cage de ferraillage centré dans un plan vertical parallèle à l'axe longitudinal et les crosses ménagées sur les armatures de deux secteurs voisins sont placées sensiblement au même niveau de façon à faire passer, dans les zones de blocage alignées des secteurs S1, S2, S3, des filants transversaux 32 qui sont également sollicités vers l'intérieur et répartissent donc sur le béton compris entre deux secteurs voisins, les efforts de compression appliqués par les crosses 5, 51, 52. Ces filants de répartitions peuvent avoir une section ronde ou rectangulaire, comme le montrent les figures. Cependant, l'utilisation de barres plates permet de faciliter la réalisation d'un cordon de soudure entre les barres longitudinales et transversales.In general, each of the figures described above shows a sector of the reinforcement cage centered in a vertical plane parallel to the longitudinal axis and the butts formed on the reinforcements of two adjacent sectors are placed substantially at the same level so as to passing, in the aligned locking zones of sectors S 1 , S 2 , S 3 ,
Dans un autre mode de réalisation, ne faisant pas partie de la présente invention, représenté schématiquement sur la
Chaque barre 38 passant dans un espace E mis en compression par les deux crosses opposées 5'a, 5b constitue une clavette de liaison entre les deux bandes consécutives 6a, 6b. Chaque armature longitudinale 6 constituée d'une série de bandes 6a, 6b, 6c.... se comporte ainsi comme une chaîne dont les maillons 6a, 6b, 6c... sont tendus sous l'effet des charges appliquées sur la pièce 1.Each
Mais l'invention ne se limite pas aux détails des divers modes de réalisation qui viennent d'être décrits, et pourrait encore faire l'objet d'autres variantesqui ne font pas partie de la présente invention.But the invention is not limited to the details of the various embodiments which have just been described, and could still be the subject of other variants that are not part of the present invention.
Par exemple, chaque zone de blocage pourrait être obtenue simplement au moyen d'une barre transversale passant dans un orifice ménagé sur la barre d'armature longitudinale.For example, each blocking zone could be obtained simply by means of a transverse bar passing through an orifice formed on the longitudinal reinforcing bar.
En effet, comme on l'a représenté sur la
Dans le cas de la
Mais il est possible également, comme on l'a représenté sur la
Dans le cas où la bande est vrillée pour constituer une zone de blocage, cette partie vrillée 43 pourrait également être munie d'une fente médiane permettant d'écarter l'une de l'autre les deux parties de la bande afin de ménager une ouverture 45' de passage d'un filant de répartition 32, de la façon représentée sur la
Par ailleurs, comme on l'a représenté sur la
Il est à noter, par ailleurs, que l'utilisation de bandes plates 4 pour constituer les barres d'armature longitudinales permet de faire varier l'orientation de la crosse ménagée à l'extrémité d'une telle barre. En effet, d'une façon générale, la bande plate 4 peut être facilement courbée autour d'un axe parallèle à son plan. Il serait donc possible, comme le montre la
D'autre part, comme on l'a déjà indiqué, il est avantageux de réaliser également les armatures comprimées 31' sous forme de bandes plates mais, par économie, on pourrait aussi utiliser des barres classiques.On the other hand, as already indicated, it is advantageous to also realize the compressed armatures 31 'in the form of flat strips but, for economy, one could also use conventional bars.
Il faut noter, cependant, que les avantages apportés par l'utilisation de barres plates compensent largement un surcoût éventuel sur les armatures.It should be noted, however, that the advantages provided by the use of flat bars largely offset any additional cost on the reinforcements.
A cet égard, il pourrait même être avantageux de réaliser des barres en acier inoxydable en raison, non seulement, de la résistance à la corrosion qui permettrait de diminuer l'épaisseur d'enrobage mais également d'une plus grande ductilité, ce qui augmente la résistance à la fatigue et la capacité d'absorption d'énergie. De tels avantages sont particulièrement intéressant pour la réalisation d'ouvrages d'art car ils améliorent la résistance aux tassements différentiels et, dans certains cas, aux secousses sismiques.In this respect, it could even be advantageous to produce stainless steel bars because of not only the corrosion resistance which would make it possible to reduce the thickness of the coating but also of greater ductility. increases fatigue resistance and energy absorption capacity. Such advantages are particularly advantageous for the construction of structures because they improve the resistance to differential settlements and, in some cases, to earthquakes.
Par ailleurs, pour simplifier les figures, celles-ci représentent des dalles ou poutres planes mais il faut remarquer que l'utilisation de bandes plates comme barres d'armatures présente de nombreux avantages pour la réalisation de pièces courbes ou mêmes gauches. En effet, une bande plate ayant un côté large parallèle à la face de parement de la pièce peut suivre facilement le profil incurvé de celle-ci.Furthermore, to simplify the figures, they represent slabs or flat beams but it should be noted that the use of flat strips as reinforcement bars has many advantages for producing curved or even left pieces. Indeed, a flat strip having a broad side parallel to the facing face of the workpiece can easily follow the curved profile thereof.
En particulier, il est ainsi possible de réaliser à plat une cage de ferraillage adaptée à une pièce incurvée, une telle cage pouvant ensuite prendre naturellement le profil du fond du moule lorsqu'elle est posée dans celui-ci.In particular, it is thus possible to form a flat reinforcement cage adapted to a curved piece, such a cage can then naturally take the profile of the bottom of the mold when it is placed therein.
Les bandes plates constituant les armatures longitudinales et transversales pourraient même être incurvées dans des sens opposés de façon à s'adapter à un profil gauche dans le sens transversal, tel qu'une surface réglée ayant des génératrices transversales non parallèles. C'est le cas, par exemple, du platelage d'un pont incliné latéralement d'un angle variable d'une extrémité à l'autre et dont le ferraillage est difficile à réaliser par les méthodes classiques.The flat strips constituting the longitudinal and transverse reinforcements could even be curved in opposite directions so as to adapt to a left profile in the transverse direction, such as a regulated surface having non parallel parallel generatrices. This is the case, for example, the decking of a laterally inclined bridge of variable angle from one end to the other and whose reinforcement is difficult to achieve by conventional methods.
D'autre part, comme elle permet de réaliser des pièces en béton particulièrement souples pouvant admettre une flèche assez importante, l'invention est spécialement adaptée à la réalisation d'ouvrages de franchissement enterrés sous un remblai et ayant un profil incurvé leur permettant de se déformer légèrement sous la charge appliquée pour prendre appui par leurs côtés sur les remblais latéraux.On the other hand, since it makes it possible to produce particularly flexible concrete parts that can accommodate a large enough spire, the invention is especially adapted to the realization of crossing structures buried under an embankment and having a curved profile allowing them to slightly deform under the load applied to support the side embankments by their sides.
En outre, comme indiqué plus haut, les zones de blocage entre lesquelles le béton est mis en compression peuvent être placées à des endroits, déterminés par le calcul, dans lesquelles le béton est soumis une contrainte de traction maximale et où le risque de fissuration est le plus grand. L'invention permet donc, à partir d'un modèle type, d'adapter le ferraillage de chaque pièce à la répartition prévisible des contraintes, compte tenu des charges appliquées.In addition, as indicated above, the blocking zones between which the concrete is placed in compression can be placed at locations, determined by calculation, in which the concrete is subjected to a tensile stress maximum and where the risk of cracking is greatest. The invention therefore makes it possible, from a standard model, to adapt the reinforcement of each part to the predictable distribution of the stresses, taking into account the loads applied.
Par exemple, on sait que l'on peut distinguer, dans une dalle ou poutre chargée verticalement de façon uniforme, une zone centrale dans laquelle l'effort de traction appliqué sur la face inférieure est maximal, deux zones latérales dans lesquelles la dalle est soumise à un effet de cisaillement, et deux extrémités d'appui. Cependant, comme indiqué précédemment, la disposition des zones de compression n'est pas nécessairement symétrique par rapport au plan médian de la pièce.For example, it is known that it is possible to distinguish, in a slab or beam loaded vertically in a uniform manner, a central zone in which the tensile force applied to the lower face is maximum, two lateral zones in which the slab is subjected to a shearing effect, and two support ends. However, as indicated above, the arrangement of the compression zones is not necessarily symmetrical with respect to the median plane of the part.
Grâce à l'invention il sera possible, sans complication du ferraillage d'adapter celui-ci, dans chaque partie de la pièce, aux efforts principaux à encaisser, en faisant judicieusement varier l'orientation des bandes plates constituant les armatures de façon à réaliser des zones de blocage dans les parties les plus tendues, afin de compenser cette tension par un effet de compression du béton.Thanks to the invention it will be possible, without complication of the reinforcement to adapt it, in each part of the room, the main efforts to cash, by judiciously vary the orientation of the flat strips constituting the frames so as to achieve blocking zones in the most tensioned parts, in order to compensate for this tension by a compression effect of the concrete.
De plus, comme indiqué plus haut, et bien que cela ne fasse pas partie de la présente invention, il est possible d'orienter verticalement les bandes tendues de la façon représentée sur la
En outre, comme indiqué précédemment, la disposition des zones de compression n'est pas nécessairement symétrique par rapport au plan médian de la pièce.In addition, as indicated above, the arrangement of the compression zones is not necessarily symmetrical with respect to the median plane of the part.
Les dispositions selon l'invention permettent donc de faire varier la forme de la cage de ferraillage de façon à moduler l'action des armatures en fonction des sollicitations appliquées en service sur la pièce.The arrangements according to the invention therefore make it possible to vary the shape of the reinforcement cage so as to modulate the action of the reinforcements as a function of the stresses applied in service on the part.
Claims (11)
- A manufacturing method of a concrete piece (1) provided with a reinforcing cage (3) bedded in concrete (2) during the casting thereof, so that, when said piece is subjected to a load, it includes, under the effect thereof, two sections on both sides of a neutral axis, respectively a compressed section subjected to compressive stress absorbed mainly by the concrete (2) and a stretched section subjected to tensile stress absorbed mainly by at least one stretched longitudinal reinforcement (31) of the reinforcing cage (3) extending along a longitudinal direction of application of the tensile stress, at a short covering distance of a stretched longitudinal face (20) of the piece (1) and having a cross-section determined relative to the stresses induced by the load, said longitudinal reinforcement (31) comprising at least one flat band (4) with a rectangular section, having a wide face (41) and a narrow face (41'), and including a central part (C) comprised between two parts clamping in the concrete, each clamping part in the concrete of the stretched reinforcement (31) consists of an end (5, 5') of the flat band (4) which is curved in a crosshead shape and taking rest in the concrete through its wide face (41) in a direction opposite to the absorbed tensile stress, by forming a clamping zone (B1, B'1), and that the central part (C) of the band (4) comprised between said clamping zones (B1, B'1) is let free to separate from the concrete with which it is covered, by sliding slightly relative thereto, from a certain level of load, so that the stretched reinforcement (31) remains unified with the concrete only within the clamping parts (5, 5'), whereas said central part (C) is free to be elongated under the effect of the absorbed stresses, with a uniform distribution of tension over the whole length of said central part (44),
characterized in that said stretched longitudinal reinforcement (31) comprises a second level of longitudinal bars shifted upward and consisting of at least two longitudinal bars (33, 34), each formed of a flat band and with ends curved in the shape of crossheads (51, 51' ; 52, 52'), said longitudinal bars (33, 34) lying side-by-side and being longitudinally staggered relative to each other, so that the crossheads (51, 51') (52, 52') provided at their ends are placed at different distances from the median transversal plane (Q) of piece (1), said bars (33, 34) overlapping each other on a certain length (I2) and ending towards the interior, with two opposed crossheads (51', 52) sollicitated towards each other under the opposed tensile stresses applied respectively on two corresponding bands (33, 34), inducing the compression of a concrete core included within said internal crossheads (51', 52), over said overlapping length (I2). - A method according to claim 1, characterised by the fact that the width (I) and the thickness (e) of a stretched longitudinal reinforcement in the form of band (4) are determined relative to a maximum tensile stress to be absorbed, on the one hand in order to provide a sufficient cross-section for the absorption of said maximum stress while remaining in the resilient domain and, on the other hand, so that, in each clamping zone (B1, B'1), the part of the concrete where the wide face (41) of the band (4) rests is subjected to a compressive stress not exceeding an admissible threshold.
- A method according to any of the previous claims, characterised by the fact that each crosshead is realized by curving the end of the band (4) parallel to the plane of its wide face (41).
- A method according to claim 3, characterised by the fact that the crosshead (5) turns around a vertical axis (50') to reduce the thickness of piece (1).
- A method according to any of the previous claims, characterised by the fact that each stretched bar (31) consists of a flat band (4) oriented such that its wide face (41) is almost parallel to the stretched face (20) of piece (1).
- A method according to any of the previous claims, in which the reinforcing cage comprises two sheets of longitudinal reinforcements, respectively (31) in the stretched section and (31') in the compressed section, characterized by the fact that the compressed longitudinal reinforcements (31') also consist of flat bars.
- A method according to any of claims 1 to 6, characterised by the fact that two coupled bands (33, 34) forming a longitudinal reinforcement consist of two strands of a single band, forming a loop between two separated levels (30, 30'), in order to surround a concrete core (B3) placed under compression by tightening said loop under the effect of the tensile stresses applied in opposite directions on the two strands (33, 34) of the longitudinal reinforcement.
- A method according to any of claims 1 to 7, characterised by the fact that the opposed crossheads (51', 52) for placing under compression the concrete core (B3) are placed according to the mode of loading piece (1), so that the tensile stresses induced in the concrete by the applied loads are balanced, at least partially by compression of said core (B3) between the opposed crossheads (51', 52).
- A method according to any of claims 1 to 8, characterised by the fact that piece (1) is placed under compression practically over its entire length by the tendency of the crossheads (5, 51, 52, 51', 52`, 5') of the different reinforcements to internally bring closer, in order to diminish the cracking risk of the piece, even in the vicinity of the stretched face (20).
- A method according to any of the previous claims, for the realization of a concrete piece (1) provided with a reinforcement cage (3) comprising at least two longitudinal sectors (51, 52) linked together by transversally disposed tie rods and including each at least two longitudinal reinforcements, respectively a compressed reinforcement (31') and a stretched reinforcement (31) in form of flat band (4), said compressed (31') and stretched (31) reinforcements being linked to each other by at least two binding straps (13), characterized by the fact that the binding straps (13) are in the shape of bands and are unified with the stretched reinforcement through at least one junction (14) managed close to each longitudinal end of the reinforcement (31) in order to form a blocking zone (B) at the level of each junction (14), the central part (44) of the stretched reinforcement being left free of stretching.
- A manufacturing method of a concrete piece (1) provided with a reinforcing cage (3) according to any of the claims 1 to 10, characterised by the fact that the concrete piece (1) is curved and obtained by casting concrete into a mould or casing with a curved bottom, after laying into the mould the reinforcing cage (3) and that the reinforcing cage is manufactured down flat and exhibits, by reason of the use of flat bands, sufficient flexibility to adopt, by its own weight, the curved shape of the bottom of the mould after laying the cage (3) therein.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0350857A FR2862323B1 (en) | 2003-11-18 | 2003-11-18 | METHOD FOR PRODUCING A CONCRETE PIECE AND PIECE PRODUCED THEREBY |
EP04805843A EP1689951B1 (en) | 2003-11-18 | 2004-11-18 | Method for production of a block of concrete and a block of concrete |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04805843A Division EP1689951B1 (en) | 2003-11-18 | 2004-11-18 | Method for production of a block of concrete and a block of concrete |
Publications (3)
Publication Number | Publication Date |
---|---|
EP2141300A2 EP2141300A2 (en) | 2010-01-06 |
EP2141300A3 EP2141300A3 (en) | 2010-01-20 |
EP2141300B1 true EP2141300B1 (en) | 2014-03-05 |
Family
ID=34508768
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04805843A Active EP1689951B1 (en) | 2003-11-18 | 2004-11-18 | Method for production of a block of concrete and a block of concrete |
EP09173849.2A Active EP2141300B1 (en) | 2003-11-18 | 2004-11-18 | Method for manufacturing a concrete part and reinforcement cage for a part manufactured according to this method |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
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EP04805843A Active EP1689951B1 (en) | 2003-11-18 | 2004-11-18 | Method for production of a block of concrete and a block of concrete |
Country Status (13)
Country | Link |
---|---|
EP (2) | EP1689951B1 (en) |
JP (1) | JP4709767B2 (en) |
KR (1) | KR20060129218A (en) |
AT (1) | ATE452255T1 (en) |
AU (1) | AU2004291708B2 (en) |
DE (1) | DE602004024707D1 (en) |
DK (1) | DK1689951T3 (en) |
ES (1) | ES2338235T3 (en) |
FR (1) | FR2862323B1 (en) |
MA (1) | MA28165A1 (en) |
PT (1) | PT1689951E (en) |
TN (1) | TNSN06144A1 (en) |
WO (1) | WO2005049934A1 (en) |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US887863A (en) * | 1907-07-26 | 1908-05-19 | Edgar N Spaulding | Steel girder-frame for reinforced-concrete girders. |
GB410866A (en) * | 1933-10-11 | 1934-05-31 | Robert Hopewell | Improvements in reinforced concrete |
US2167029A (en) * | 1936-11-19 | 1939-07-25 | Joel E Mclafferty | Reinforcing member for heterogeneous beams |
US3825465A (en) * | 1972-03-24 | 1974-07-23 | R Stock | Three dimensional reticulated structure |
JPS5976348A (en) * | 1982-10-21 | 1984-05-01 | 鹿島建設株式会社 | Beam with wall of reinforced concrete structure |
JPS5963127U (en) * | 1982-10-21 | 1984-04-25 | 鹿島建設株式会社 | Joint structure of major and minor beams |
DE3541875A1 (en) * | 1985-11-27 | 1987-06-04 | Ostertag Werke Gmbh | Security reinforcement means for a strongroom, safe, banking area or the like |
FR2814480B1 (en) * | 2000-09-26 | 2008-10-17 | Soc Civ D Brevets Matiere | REINFORCING CAGE FOR AN ARMED CONCRETE ELEMENT |
-
2003
- 2003-11-18 FR FR0350857A patent/FR2862323B1/en not_active Expired - Lifetime
-
2004
- 2004-11-18 WO PCT/FR2004/050600 patent/WO2005049934A1/en active Application Filing
- 2004-11-18 DK DK04805843.2T patent/DK1689951T3/en active
- 2004-11-18 AU AU2004291708A patent/AU2004291708B2/en not_active Ceased
- 2004-11-18 PT PT04805843T patent/PT1689951E/en unknown
- 2004-11-18 KR KR1020067011917A patent/KR20060129218A/en not_active Application Discontinuation
- 2004-11-18 EP EP04805843A patent/EP1689951B1/en active Active
- 2004-11-18 JP JP2006540557A patent/JP4709767B2/en not_active Expired - Fee Related
- 2004-11-18 EP EP09173849.2A patent/EP2141300B1/en active Active
- 2004-11-18 DE DE602004024707T patent/DE602004024707D1/en active Active
- 2004-11-18 AT AT04805843T patent/ATE452255T1/en not_active IP Right Cessation
- 2004-11-18 ES ES04805843T patent/ES2338235T3/en active Active
-
2006
- 2006-05-17 MA MA29036A patent/MA28165A1/en unknown
- 2006-05-17 TN TNP2006000144A patent/TNSN06144A1/en unknown
Also Published As
Publication number | Publication date |
---|---|
PT1689951E (en) | 2010-03-16 |
DK1689951T3 (en) | 2010-04-26 |
EP1689951A1 (en) | 2006-08-16 |
KR20060129218A (en) | 2006-12-15 |
AU2004291708A1 (en) | 2005-06-02 |
EP2141300A2 (en) | 2010-01-06 |
EP2141300A3 (en) | 2010-01-20 |
TNSN06144A1 (en) | 2007-11-15 |
FR2862323B1 (en) | 2006-03-10 |
JP2007511689A (en) | 2007-05-10 |
MA28165A1 (en) | 2006-09-01 |
FR2862323A1 (en) | 2005-05-20 |
ES2338235T3 (en) | 2010-05-05 |
EP1689951B1 (en) | 2009-12-16 |
ATE452255T1 (en) | 2010-01-15 |
AU2004291708B2 (en) | 2010-05-27 |
WO2005049934A1 (en) | 2005-06-02 |
DE602004024707D1 (en) | 2010-01-28 |
JP4709767B2 (en) | 2011-06-22 |
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