EP0465303B1 - Improvements in cable-stayed bridges, especially in their cables and pillars - Google Patents

Description

The invention relates to cable-stayed bridges comprising an apron, at least one concrete pylon and guy lines stretched obliquely between the pylon and the deck to support the latter, and it relates more particularly to the pylons and guy lines of these bridges as well as the anchoring devices for the shrouds on the pylons.

It relates more particularly to the case where each guy is formed by a bundle of strands or strands juxtaposed side by side over the greater part of their length and where the upper portion of each guy passes right through the pylon which supports it, the free end of this upper portion being anchored on a block bearing on the face of the pylon, located on the side opposite to that where the stay is located.

In such assemblies, it is appropriate, for reasons of mechanical strength of the pylon, simplicity of manufacture and even aesthetics, that the shrouds are grouped in pairs of shrouds extending obliquely downward from the same section vertical of the pylon, on either side thereof in the longitudinal direction of the bridge.

But as the shrouds in question have a non-negligible overall diameter, especially in their upper portion which is gradually opened out towards the end to allow the individual anchors of the different strands on the corresponding block, it is not possible to locate the lines means of the two shrouds of each pair in the same vertical plane extending in the longitudinal direction of the bridge.

This is why, in the known embodiments of the assemblies defined above, the middle lines of the two shrouds of each pair are arranged according to two distinct parallel vertical planes.

The areas of application of their tension forces on the pylon are then offset transversely with respect to the longitudinal direction of the bridge, which leads to the application of torques on the pylons as well as to questionable aesthetics.

The object of the invention is, above all, to remedy these drawbacks.

For this purpose the guyed bridges of the type in question according to the invention are essentially characterized in that the different sections of strands respectively constituting the slightly flared upper portions of two guy wires anchored on the same vertical section of pylon and extending from other of this pylon are crossed with mutual nesting so that the middle lines of these two portions are both located in the same vertical plane of the pylon parallel to the longitudinal direction of the bridge.

• il est prévu pour chaque paire de haubans ancrés sur le pylône une pièce rigide préfabriquée de guidage et de croisement comprenant une pluralité de guides tubulaires affectés respectivement aux différents tronçons croisés de torons,
• la pièce de guidage comprend un noyau de ciment durci percé par des canaux constituant les guides tubulaires,
• chacun des canaux est tapissé intérieurement par un tube en matière plastique,
• le noyau est enveloppé dans un boîtier de coffrage,
• le noyau est solidarisé avec deux plaques rigides perforées servant à l'ancrage des extrémités libres des torons qui traversent ce noyau ou servant d'assises à des blocs d'ancrage desdites extrémités,
• la pièce de guidage présente la forme générale d'un pont avec deux jambes divergentes correspondant au départ des deux haubans et un plateau supérieur horizontal bordé par deux flancs terminaux verticaux délimités par les deux plaques perforées,
• la pièce de guidage présente la forme générale d'un boudin recourbé selon un arc de cercle ouvert vers le bas et terminé par les deux plaques perforées, lesquelles sont orientées perpendiculairement à sa ligne moyenne,
• à chaque extrémité du boudin, les extrémités des torons correspondant au hauban situé de l'autre côté du pylône, extrémités relativement écartées les unes des autres pour leurs ancrages individuels, entourent les portions courantes, quasiment jointives, des torons constitutifs du hauban qui sort obliquement vers le bas de ladite extrémité de boudin.

In preferred embodiments, use is also made of one and / or the other of the following arrangements:

• there is provided for each pair of guy wires anchored on the pylon a rigid prefabricated guide and crossing piece comprising a plurality of tubular guides assigned respectively to the different crossed sections of strands,
• the guide part comprises a hardened cement core pierced by channels constituting the tubular guides,
• each channel is lined internally with a plastic tube,
• the core is wrapped in a formwork box,
• the core is secured with two plates rigid perforated bars used for anchoring the free ends of the strands which pass through this core or serving as seats for anchoring blocks of said ends,
• the guide piece has the general shape of a bridge with two divergent legs corresponding to the start of the two shrouds and a horizontal upper plate bordered by two vertical end flanks delimited by the two perforated plates,
• the guide part has the general shape of a rod curved in an arc of a circle open downwards and terminated by the two perforated plates, which are oriented perpendicular to its mean line,
• at each end of the strand, the ends of the strands corresponding to the strut located on the other side of the pylon, ends relatively spaced apart from one another for their individual anchorages, surround the common portions, almost contiguous, of the strands constituting the stay which comes out obliquely down from said end of the rod.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, preferred embodiments of the invention will be described with reference to the accompanying drawings in a manner which is of course not limiting.

Figure 1 of these drawings shows schematically from the side the top of a guyed pylon.

Figure 2 shows schematically in plan the same vertex established in a manner known per se.

FIG. 3 schematically shows in plan said vertex established in accordance with the invention.

Figure 4 shows in more detail in vertical section a device for guiding and crossing guy ropes established and placed in a pylon in accordance with the invention.

Figures 5 and 6 show respectively in vertical section and in end view along arrow VI of Figure 5 a variant of such a guide and crossing device also established and implemented in accordance with the invention.

FIG. 7 schematically shows another device for guiding and crossing the shrouds.

FIGS. 8 and 9 respectively show an end view and a longitudinal section of one end of the device according to FIG. 7.

FIG. 10 schematically shows yet another guide and crossing device established in accordance with the invention.

Figure 11 shows an end view of one end of the latter device.

Generally, it is to anchor on a concrete pylon 1 constituting a guyed bridge the high ends of two guy wires 2 each composed by a bundle of strands or strands extending obliquely downward and on the other side of this pylon so as to connect thereto the deck of said bridge.

The upper section of each guy 2 crosses for this purpose the pylon 1 right through so that its free end is anchored on a block 3 horizontally bearing against the pylon.

The bundle of strand sections making up each free end of the stay cable is then spread towards this end so that each of these sections can pass through a bore in the associated block 3 as well as an individual anchoring jaw 4 (FIG. 4) bearing on this block.

The transverse dimensions of each open end of the stay cable not being zero, it is hardly possible to place the two upper ends blooming guy lines on the same level of the pylon, with their average lines combined.

• ou bien à des niveaux différents du pylône,
• ou bien au même niveau, mais alors décalées transversalement par rapport à la direction longitudinale du pont, ainsi que visible sur la figure 2.

In the known embodiments, there are therefore these two ends,

• or at different levels of the pylon,
• or else at the same level, but then offset transversely with respect to the longitudinal direction of the bridge, as can be seen in FIG. 2.

In each case, this results in the application of asymmetrical forces on the pylon: in particular, if the shrouds are anchored in locations offset transversely as visible in FIG. 2, the pylon is subjected to torsional forces symbolized by the arrows F.

In addition, the reported offsets are not favorable to the general aesthetics of the bridge.

To remedy these drawbacks, according to the invention, the open upper ends of the two shrouds are crossed mutually by mutually nesting their strands in each other.

To guide these mutual crossings of the strands, use is made of a prefabricated guide and crossing piece 5 comprising a plurality of channels 6 each assigned to a strand or strand 7 constituting a stay 2.

This guide and crossing piece 5 is preferably constituted by a body or core 8 of hardened cement in which are embedded plastic tubes 9 open right through and delimiting the channels 6.

The body or core 5 has the very general shape of an X which can be more or less deformed while having symmetry with respect to a transverse median vertical plane.

Two of the branches of this X, symmetrical to each other with respect to the said plane, are capped by perforated plates 10.

The perforations 11 of these plates are arranged opposite the mutually spaced ends of the channels 6 so that they can be crossed by the corresponding ends of the strands or strands 7.

As can be seen in FIG. 4, these strands or strands 7 are generally "self-protected", that is to say constituted by a metallic core 7 une surrounded by a protective sheath 7₂, generally made of plastic, with the interposition of a protective material such as grease, wax, or epoxy pitch.

As can be seen in FIG. 9, each sheath 7₂ is advantageously interrupted at the level of the entry of the corresponding strand into the "guide piece" 5, this sheath being extended, inside said piece, by a tube 9 presenting the same diameters and thickness as it.

In the embodiment shown diagrammatically in FIG. 4, each plate 10 itself constitutes the anchoring block 3, each perforation 11 is extended externally by a frustoconical bore 12 flared outwards and capable of serving as a housing for a jaw frustoconical anchor 4 and each upper end of strand or strand 7 is stripped so that only the metal core end 7₁ passes through the jaw 4 and the end of the sheath 7₂ (or of the tube 9 which is there substituted) is introduced contiguously in the associated perforation 11.

According to a variant, the plate 10 does not itself constitute the anchoring block, which is applied against the plate 10, outside of this plate.

Protective covers 13 are attached externally to the blocks or anchoring plates in a manner known per se.

The outer face of the core 8 can be itself constituted by a hard and smooth cement skin forming a block with this core, of the kind which forms just inside the molds or formwork of concrete parts, when they are cast.

Said external face can also be delimited by an independent envelope, in particular of plastic or sheet metal, as visible at 14 in FIGS. 5 and 9.

In the first embodiment illustrated in FIG. 4, the X defining the general shape of the core 8 is not deformed: it is composed of two rectilinear sections crossed substantially in their middle.

As can be seen in this FIG. 4, the whole of part 5 is embedded in the concrete constituting the pylon 1 and the mounting of the different strands, followed by their individual anchors, is carried out after the pylon has been manufactured.

In the second embodiment illustrated in Figures 5 and 6, each of the two upper branches of the X defining the general shape of the core 8 is lowered outward so that its end extends horizontally and that the perforated plates 10 which end these ends extend vertically.

The assembly of the guide and crossing piece 5 then has the general shape of a bridge whose two feet diverge downwards and whose horizontal plate is terminated at its two ends by the vertical plates 10.

• l'encombrement vertical global de la pièce 5 et des entailles de raccordement 15 évidées dans les faces transversales du pylône 1 est relativement petit, ce qui permet de disposer dans le pylône plusieurs telles pièces verticalement rapprochées les une des autres : un morceau d'une telle seconde pièce a été représenté en traits interrompus en 5′ sur la figure 5,
• les extrémités de torons à tirer pour leurs ancrages respectifs se présentent horizontalement à leur sorties des plaques 10, ce qui facilite la mise en oeuvre des vérins de traction.

This construction has the following two advantages:

• the overall vertical size of the part 5 and the connecting notches 15 hollowed out in the transverse faces of the pylon 1 is relatively small, which makes it possible to have in the pylon several such parts vertically close to one another: a piece of such a second piece has been shown in broken lines at 5 ′ in FIG. 5,
• the ends of strands to be pulled for their respective anchors are presented horizontally at their exits from the plates 10, which facilitates the implementation of the traction cylinders.

In the third embodiment illustrated in Figures 7 to 9, the X defining the general shape of the core 8 is completely flattened on itself and curved according to an arc of a circle open downwards.

In other words, the core 8 is in the form of a cylindrical rod extending in an arc, the extent of which is for example 90 °.

In this case, each of the perforated plates 10 which extend transversely at one end of the tube is crossed by each of the two stay cables, the central portion being reserved for crossing the current portion of the stay cable which exits on the same side as the plate concerned. and the periphery being assigned to the anchoring of the ends of the other shroud: as visible in FIGS. 8 and 9, the strands corresponding to the current portion of the shroud are contiguous or practically such while the anchored ends are slightly apart others.

In the fourth embodiment illustrated in FIGS. 10 and 11, the guide and crossing device 5 has the same general shape of a rod in an arc of a circle as that of FIGS. 7 to 9, with its end perforated plates 10.

This fourth embodiment differs from the previous one in that the current portion of guy wire which passes through each plate 10 is no longer located in the center of this plate, but in its lower part.

• chacune des deux extrémités de hauban considérées est épanouie en vue de son ancrage en bout à partir de sa portion courante d'introduction dans le pylône à travers une plaque 10, portion courante dont les brins constitutifs sont jointifs,
• et la construction est symétrique par rapport à un plan vertical transversal médian.

Here again,

• each of the two guy ends considered is opened out for anchoring at the end from its current portion of introduction into the pylon through a plate 10, a current portion whose constituent strands are joined,
• and the construction is symmetrical with respect to a median transverse vertical plane.

The face externally delimiting the core 8, face possibly materialized by an envelope 14, has been shown as smooth in the various drawings.

In some cases it may be advantageous to provide externally on this face or envelope special reliefs such as ribs, ridges, bosses, keys, etc. to improve the adhesion between the guide part 5 and the concrete constituting the pylon 1 .

As a result of which, and whatever the embodiment adopted, there is finally a cable-stayed bridge whose constitution results sufficiently from the above.

• chacune des extrémités supérieures de hauban ancrée sur le pylône prend appui sur une plaque elle-même appliquée horizontalement contre l'une des faces transversales du pylône, ce qui assure un ancrage extrêmement sûr ainsi qu'une précontrainte longitudinale du pylône,
• malgré ce type d'ancrage, les haubans sont disposés par paires, les deux haubans de chaque paire étant disposés en général symétriquement par rapport au plan transversal médian du pylône de sorte que les efforts exercés par ces deux haubans sur ce pylône ont pour résultante une simple force verticale orientée vers le bas,
• cette symétrie ou quasi symétrie des haubans deux à deux est un facteur déterminant de l'esthétique générale du pont.

This bridge has many advantages over those previously known and in particular the following:

• each of the upper ends of the stay anchored on the pylon rests on a plate itself applied horizontally against one of the transverse faces of the pylon, which ensures extremely secure anchoring as well as longitudinal prestressing of the pylon,
• despite this type of anchoring, the shrouds are arranged in pairs, the two shrouds of each pair being generally arranged symmetrically with respect to the median transverse plane of the pylon so that the forces exerted by these two shrouds on this pylon result in a simple vertical force pointing downwards,
• this symmetry or almost symmetry of the guys two by two is a determining factor in the general aesthetics of the bridge.

As is obvious, and as already follows from the foregoing, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular those where the two shrouds of the same pair, although having their upper ends still anchored on the pylon at the same level thereof and still crossed so that their lines are in the same longitudinal vertical plane of the bridge, would not be completely symmetrical to each other with respect to the median transverse plane of the pylon, the inclinations of the two shrouds considered on the horizontal being then not identical and the tensions exerted on each of them are not equal between them either.

Claims (9)

1. Cable-stayed bridge comprising at least one pylon (1) and stay cables (2) anchored on this pylon, each stay cable being formed by a bundle of strands or twisted strands (7), the upper portion of each stay cable passing through the pylon from one side to the other and its free end being anchored on a block (3) which bears on the face of the pylon located on the side opposite that where the stay cable is situated, characterized in that the slightly flared upper portions of two stay cables (2) anchored on the same vertical pylon section (1) and extending on each side of this pylon are crossed with mutual imbrication so that the mean lines of these two portions are both situated in the same vertical plane of the pylon parallel to the longitudinal direction of the bridge.
2. Cable-stayed bridge according to claim 1, characterized in that it comprises, for each pair of stay cables (2) anchored on the same vertical pylon section, a rigid prefabricated guide and crossing piece (5) comprising a plurality of tubular guides (6) assigned respectively to the different crossed strand sections (7).
3. Cable-stayed bridge according to claim 2, characterized in that the guide piece (5) comprises a hardened cement core (8) having channels forming the tubular guides (6).
4. Cable-stayed bridge according to claim 3, characterized in that each of the channels is lined on the inside with a plastic material tube (9).
5. Cable-stayed bridge according to any one of claims 3 and 4, characterized in that the core (8) is sheathed in a shuttering casing (14).
6. Cable-stayed bridge according to any one of claims 3 to 5, characterized in that the core (8) is made fast with two rigid perforated plates (10) serving for anchoring the free ends of the strands (7) which pass through this core or serving as base plates for the blocks anchoring said ends.
7. Cable-stayed bridge according to claim 6, characterized in that the guide piece (5) has the general shape of a bridge with two divergent legs corresponding to the start of the two stay cables (2) and an upper horizontal platen bordered by two vertical end sides defined by the two perforated plates (10)
8. Cable-stayed bridge according to claim 6, characterized in that the guide piece has the general form of a "sausage" curved in an arc of a circle which is open downwards and ends in the two perforated plates (10), which are oriented perpendicularly to the mean line of the "sausage".
9. Cable-stayed bridge according to claim 8, characterized in that, at each end of the "sausage", the ends of the strands (7) corresponding to the stay cable (2) situated on the other side of the pylon (1), which ends are spaced relatively apart from each other for individual anchoring thereof, surround the substantially jointing current portions of the strands forming the stay cable which leaves obliquely downwards from said "sausage" end.

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