FR2656883A1 - IMPROVEMENTS ON BRIDGE BRIDGES AND MORE ESPECIALLY THEIR BRIDGES, PYLONES AND APRON. - Google Patents

Abstract

In a cable-stayed bridge comprising a deck (1), at least one concrete pillar (2) and cables (3) in inverted V formation comprising multiple strands (4) each resting on a saddle (5), the strands extend individually from one foot to the other of the inverted V and there is provided, in order to maintain each strand under tension, on the one hand, two end anchoring devices (7,8), disposed at the two lower ends of the strand and each capable of anchoring one of these ends in the deck and, on the other hand, two intermediate anchoring devices (9, 10) traversed by the strand and respectively bearing on the two opposing vertical faces (F, G) of the pillar, these latter devices being arranged in such a way as to maintain the curved section of strand which rests on the saddle in its state of maximum tension.

Description

i

  Improvements to cable-stayed bridges and more

  linked to their stay cables Pylons and aprons.

  The invention relates to cable-stayed bridges comprising an apron, at least one pylon and guy lines composed of multiple strands and each stretched between a

  pylon and apron, and it concerns more particularly

  The pylons and decks of these bridges and their stay cables and the means of anchoring these stay cables

on these pylons and aprons.

  In general, in the known embodiments of said bridges, each guy is in the form of a large cable which extends from end to end in an oblique rectilinear segment, segment whose end

  lower is anchored in the deck and the end of which

  upper mite crosses a pylon and is anchored on the

  vertical face, of the pylon, furthest from the cable.

  Such a construction has both the first drawbacks at the level of the upper anchorage

  of each guy on its pylon and of the second inconveniences

  at the lower anchorage of each guy

on the apron.

  Among the first drawbacks, we can cite that of being unattractive, that of requiring numerous pylons to be drilled and that of exerting asymmetrical tensile or torsional forces on this pylon ", because it is then not possible to 'anchor on the pylon, at the same level thereof, two oblique guy lines symmetrical to each other and extending in

  the same longitudinal vertical plane.

  There is a formula which eliminates these first drawbacks: this formula uses a "saddle" or curved seat placed on the pylon and suitable for receiving an intermediate section of the shroud to be supported,

  which shroud then extends according to a V reversed in des-

  ascent obliquely towards the apron on either side of said saddle, the portions of strands constituting

  of said intermediate section being kept transversa-

  spaced apart from each other by mechanical spacers preferably made at least for the most part by a hardened grout.

  But the embodiments that have been pro-

  asked so far for this formula present

  still a number of drawbacks, and in particular

  the following: or the curved section of the multi-stranded cable resting on the saddle constitutes a connection

  autonomous intermediate precompressed between its two ends

  mites, which poses certain problems for the tensioning of this connection and for the connection between said connection and the oblique rectilinear sections of the shroud,

  or, using an indi- vidual coupling

  of the strands in the middle of the saddle, they are

  sensibly applicable to the exercise of symmetrical efforts

  triques on either side of the pylon carrying this saddle

  and do not lend themselves to application on this pylon of ef-

  strongly asymmetrical forts such as those developed during the total removal of one of the two oblique sections of the shroud arranged on one side of the pylon, in view

  including its replacement, with maintenance under tension

the other oblique section.

  Among the second drawbacks mentioned above

  above, we can cite the obligation to securely stow the lower anchor block of the stay in the deck, that of using means other than the concerned stay to reinforce this deck, and that of imposing on the anchor block above a location and an orientation which can make it difficult to access this

  block of tensioning devices.

  The invention aims, above all, to remove

  the first and / or second disadvantages above.

  For this purpose, the cable-stayed bridges of the kind in

  question according to the invention are essentially charac-

  terized in that each of the strands constituting at least one of their shrouds comprises, connected to one another in the mutual extension of one another, a first oblique rectilinear section extending freely from the deck to the pylon concerned and a second section not

  straight housed inside a solid concrete block

  titutive of the deck or pylon, and in that it is pre-

  seen an intermediate anchoring device traversed by said strand, device bearing on said block and arranged so as to be able to keep under tension the non-rectilinear strand section housed in this block after tensioning the entire length of said strand

  by exercising maximum traction between its two ex-

  hoppers and subsequent anchoring of these ends.

  In preferred embodiments, it has been shown

  in addition to one and / or the other of the following provisions: each intermediate anchoring device is

  arranged so that the strand running through it can

  have moved in the direction away from the solid, but it is automatically blocked in the opposite direction, means are provided to neutralize said blocking during the initial tensioning of the strand, each strand consists of at least at least two successive segments joined together by a coupler, namely a first segment which includes the non-rectilinear section and one end of which crosses the device

  intermediate anchor and a second segment which

  takes most of the rectilinear section, in a bridge according to the preceding paragraph, the first segment of the strand is of the type of greased sheathed strands, that is to say stripped and arranged in a sheath with interposition of grease and the second segment is of the type of strands individually protected by an extruded sheath, the cable-stayed bridge considered comprising at least one saddle as defined above, each strand constituting at least one of the shrouds of this bridge and cooperating with such a saddle extends individually from one foot to the other of the inverted V defining this stay, the non-rectilinear section of said strand is its curved section resting on the saddle and it is intended to keep this strand taut, on the one hand, two devices

  anchor terminals arranged at the two lower ends

  strands of the strand and suitable for anchoring each of these ends in the bridge deck or in a solid block

  analogous and, on the other hand, in addition to the an-

  intermediate crating crossed by the strand in question and

  leaning on one of the two vertical faces oppo-

  of the pylon comprising the saddle, a second intermediate anchoring device also crossed by the strand and bearing on the other vertical face of the pylon, in the opposite direction to the first, the non-rectilinear section comprised by each

  cable strand is housed in a solid concrete block

  titutive of the bridge deck and this section is stretched between the intermediate anchoring device it crosses and a terminal anchoring device supported on said

  massive in the opposite direction to the previous one.

  The invention comprises, apart from these arrangements

  main provisions, certain other provisions which are preferably used at the same time and which will be

  more explicitly question below.

  In the following, preferred embodiments of the invention will be described with reference to

  drawings appended hereto in a manner of course not limited to

tative.

  Figure 1, of these drawings, shows schematically-

  a portion of a cable-stayed bridge established according to the invention

  tion. Figure 2 shows again schematically, but in more detail than Figure 1, the portions of the bridge above, which relate to the anchoring according to

the invention of one of its shrouds.

  Figure 3 shows on an enlarged scale, in vertical section, a portion of said stay cable and of the pylon

who wears it.

  Figure 4 shows schematically and again in

  part of a cable-stayed bridge variant in accordance with the invention

tion.

  In a manner known per se, the bridge to be equipped comprises an apron 1 suspended from at least one concrete pylon or pillar 2 using guy wires 3 anchored on this

pylon and on this apron.

  In the first embodiments illustrated in Figures 1 to 3, the shrouds 3 are distributed on either side of the pylon 2, symmetrically with respect to

  to its median transverse plane T by forming inverted V-

his.

  They are arranged in a single layer

  held in a median longitudinal vertical plane of the bridge or in several such parallel plies, in particular two in number, in which case they border the

apron 1.

  Each guy 3 is constituted by a plurality of independent strands 4, that is to say which can be mounted and tensioned independently of each

  others and even, in some cases, replaced in isolation.

  Each strand may consist of a large wire, but is preferably composed of a central core

  surrounded by a plurality of adjoining wires, generally-

  six in number, helically wrapped around

said soul.

  The possibility of individual replacement of

  strands can be very advantageous in practice.

  that, because it ensures such replacements without interrupting traffic on the bridge: in fact, if each layer of guy lines extending on one side of a pylon includes twenty guy lines and each guy line is made up of twenty strands , the load supported by each strand is only 1/400 th of the total, a proportion which is considerably lower than the tolerances or safety margins

  retained for the construction of bridges.

  Each stay 3 forms an inverted V covering a pylon or at least a portion of this pylon and its upper portion, forming the top of the inverted V is rounded and rests on a curved surface 5 of the pylon

forming 'saddle'.

  This saddle is here constituted by the base of a curved tunnel 6 hollowed out in the pylon 2 and extending

  in a downward curved arc, a tunnel whose ends

  lower mites emerge respectively in the two transverse faces F and G of the pylon and are

oriented obliquely downwards.

  The two feet of the shroud 3 are anchored on two blocks 7,8 which form part of the framework of the deck 1 or of suitable solid masses linked to the soil constituting the banks.

connected by the bridge.

  Each of the strands 4 constituting a stay 3

  extends from one block 7 to the other 8 and crosses successively

  two intermediate anchor blocks 9, 10 located respectively near the two ends of the tunnel 6.

  Inside tunnel 6, whose inner wall

  preferably is upholstered with a shirt

  formwork 11, the strands 4 are guided so as to

  rer parallel to each other and able to slide

  slightly relative to each other.

  For this purpose, they are advantageously housed with the interposition of grease in sheaths 12, for example of polyethylene, kept apart from one another by a hardened cement grout 13 and possibly by

  additional special parts.

  Each of the two intermediate anchor blocks

  9,10 is arranged so as to ensure a unidirectional anchoring

  tional in the sense that the strands 4 which pass through it can move away from the pylon 2, but not

reverse.

  For this purpose, for example, each crossing of a block 9.10 by a strand 4 is carried out in line with a frustoconical housing hollowed out in this block, converging in

direction of the pylon.

  This housing cooperates with a split frustoconical jaw 14 (FIG. 2) surrounding the strand concerned on the side, of the block, furthest from the pylon, said jaw preferably being urged into its housing by a spring 15 interposed between it and a retaining plate 16 itself crossed by the strands 4 and secured to the block concerned, at a small distance from this block, for example of the order of a centimeter, by

balusters 17.

  However, to energize such a

  guy, we set up each of its strands 4 consti-

  tutifs by making it successively cross the two blocks 9 and 10, at least one of which is not yet made unidirectional: it suffices for this purpose, for the

  embodiment described by way of example, now

  attach the jaw 14 concerned slightly apart from its housing-

  ment in the corresponding block, compressing the res-

  sort 15 associated with it if such a spring exists.

  Then the different strands 4 are successively energized from their two ends passing through the two blocks 7 and 8 respectively,

  any suitable way, until the tension is reached

  normal service in each strand.

  The crossings of the two blocks 9 and 10 are then made unidirectional by the stretched strands, in particular

  by releasing the springs 15 in the above example.

  Consequently, the curved section, of each strand 4, which is disposed between the two blocks 9 and 10 remains stretched to a value which is at least its initial value

  and which can be gradually increased, irreversibly

  clearly, up to a maximum value. This tension persists even when, during

  the putting into service of the shroud comprising the strand

  déré, the tension is reduced in one of the two oblique rectilinear sections of this stay, sections arranged respectively between blocks 7 and 9 and between blocks

8 and 10.

  Such transient voltage reductions are

  common and are one of the main sources of fati-

gue and therefore wear of the shrouds.

  They are due for example to the passage of heavy vehicles on the cable-stayed bridge at the foot of the shrouds considered, or to the thrusts of the wind on these shrouds, which often result in oscillations and therefore in alternation of states

stretched and relaxed guy lines.

  In the present case, the curved section of the shroud which rests on the saddle 5 is sheltered from these alternations which generate fatigue due to the maintenance

permanent tension.

  However, the curved portion of each strand is its most fragile portion because it is stressed not only in traction, but also in bending and possibly in friction against its support: the shelter from the fatigue of this curved portion therefore results in a greatly increased longevity for the stay. In the preferred embodiments, each strand 4 is composed of at least two segments connected to each other, namely:

  a first segment A comprising the entire range

  curved tion which rests on saddle 5, segment of which

  the two ends, rectilinear, cross respectively

  the two blocks 9 and 10 with their retaining plates, and at least one other straight segment B extending from one of the ends, of the first segment A, coming out of block 9 or 10 on its most

  away from the pylon, to one of the two blocks 7 and 8.

  The connection between these two segments A and B is carried out using an individual coupler 18 at

  immediate vicinity of the corresponding block 9 or 10.

  This fitting, like the one-way lock

  nel performed at block 9 or 10 concerned, block which will be assumed to be block 9 for the present example, is

  performed on bare portions of strands.

  To protect them and in particular prevent their corrosion, these stripped portions are enclosed in a box 19 filled with grease 20 and directly mounted on

block 9.

  On its side opposite to the box 19, the block 9 is extended by a short sleeve 21 and the two axial ends of the tubular assembly composed of the box 19 and the sleeve 21 are constituted by cable glands

  22.23 tightly crossed by cheerful portions

born from strands.

  In the present example, the sheath enveloping the strand segment A is that previously designated by the reference 12, in which the strand concerned is

  housed with interposition of grease, and the sheath 24 rela-

  tive to the strand segment B is directly extruded con-

  be this, with possibly the interposition of a layer of wax or the like, said sheath being in particular

  made of a plastic material such as poly-

ethylene or a polyamide.

  To reduce the transverse size of the

  seems to be formed by the different couplers 18, we repair-

  preferably tit these according to a triangulated mesh

  equilateral spanning several floors and pre-

ference on three floors.

  With such a distribution, each individual coupler 18 is surrounded by a plurality of common portions of strands which are housed in external grooves of said coupler, the number of these grooves being

usually six.

  The individual couplers 18, which are known in

  themselves, can be of an easily disassembled type

  ble the proposed construction therefore lends itself to demon-

  tage of the different constituent strands of strands A

  oblique straight sections of the shroud.

  One can thus replace at least partially one of these oblique sections while maintaining the other in

  place and without in any way reducing the tension applied

  the curved section B: this is an important advantage

both of the present invention.

  In the embodiment illustrated in FIG. 3, the block 9 is not directly applied against the corresponding transverse face F of the pylon 2. This block 9 is here applied axially against one end of the jacket It internally lining the hollowed-out tunnel 6 in the concrete of the pylon 2 This jacket 11 must therefore be designed so as to be able to transmit

  some axial force at pylon 2.

  This transmission is favored by making

  rough outer surface, jacket 11, interior

  superior to the pylon, even by reporting externally on

  this suitable reliefs such as a wire 25

helical.

  It should be noted that the maximum value of the axial force that the jacket 11 must be able to transmit

  at tower 2 can be relatively small.

  Indeed, when switching on the diff-

  strands up to their maximum value in the manner 1 1 described above, this effort is practically zero if we consider that the tensions then exerted on the

  different strands on either side of block 9 towards

  tion respectively of the two blocks 7 and 8 are identi-

  ques. The maximum value in question would correspond to the case where the entire oblique section of the shroud connected to block 9 is dismantled: or in such a case,

  the maximum voltage then applied to block 9 in the direction

  tion of the pylon would be applied not only to the jacket 11, but also to the entire hardened core of grout 13 filling the portions, of the volume inside said jacket, which are not occupied by the greased sheathed strands 12, which core is itself - even strongly adhered against the inner wall of the

shirt 11.

  The version illustrated in FIG. 3, for which the block 9 is not directly applied against the pylon, therefore has the disadvantage of a slightly more rigorous requirement as regards resistance.

of shirt 11 to compression.

  But it avoids having to plan at the level of

  the transverse face of the pylon, i.e. a general boss

  not very aesthetic, or a complicated recess

  slightly the problems of concrete reinforcement.

  It should also be noted that, in the embodiment according to FIG. 3, the sleeve 21 described above is formed directly by one end of the jacket 11 itself, the end which is welded to an end ring 26 The periphery of this ring 26 is fitted onto the block 9, crossed by the columns 17 above and extended by gussets 27 along the

shirt 21.

  In the variant shown diagrammatically in FIG. 4, the elements identical to those previously described are

  designated by the same references as above.

  To simplify, a single strand 4 constituting the shroud 3 has been shown in this figure 4, but it

  It is understood that this strand is associated with a plura-

  bed of other parallel strands to constitute the upper

ban 3.

  Said strand 4 also comprises a straight section.

  oblique line 41 stretched between the deck 1 of the bridge

  flabbergasted and the top of the pylon 2 and a second non-rectilinear section 42 embedded in the concrete, these two sections being connected end to end at an intermediate anchoring device 28 bearing on the concrete structure portion in which is drowned said section 42 'But instead of being drowned in the pylon 2 as before, along a saddle, this second section 42

  is here embedded in a portion of deck 1.

  More specifically, this section 42 includes a segment

  curved in an arc arranged in the extension

  ment of the oblique rectilinear section 41 and itself pro-

  bordered by a straight horizontal segment extending

  in the longitudinal direction of the bridge.

  This horizontal segment is itself terminated by an anchoring device 29 of the usual type taking

  support horizontally against the apron 1.

  The other end of the strand 4 considered, namely the ex-

  upper end of the section 41 ^ after crossing a straight channel 30 hollowed out in the pylon 2, is supported, by an anchoring device 31 of the usual type, against the vertical transverse face G, of the pylon, the most

distant from the rest of the stay cable 3.

  As for the intermediate anchoring device 28, it bears against the bulkhead 1 in the opposite direction to the support of the anchoring device 29 so that these two supports make it possible to keep the section under tension.

  4 after initial initial power up.

  In a preferred embodiment, the provision

  intermediate anchor sitive 28 is also designed so as to be able to block the strand 4 which passes through it in one direction, namely that directed towards the deck 1. Of course, if the tensioning of the strand 4 is carried out from the lower anchoring device 29, the blocking should be temporarily neutralized

  generated on this strand by the unidi-

rectionnel 28.

  But from the moment this neutralization is removed, the section 42 remains under its tension

  maximum, as was the case previously with the

  strand resting on the stool.

  Therefore, and just as before, the

  only portion of the strands 4 which is subject to the varia-

  voltage conditions during the commissioning of the bridge

  is its oblique section 411 which is only a drawback

  deny reduced by the fact that this section is rectilinear and that it is therefore less subject to fatigue than the non-rectilinear section 42 We still see in FIG. 4 at 32 a coupler of the kind of that designated by the references 18 to 23 below above and arranged in the immediate vicinity of the intermediate anchoring device 28: this coupler 32 is also intended, like the previous one, to be connected together

  constituent portions of the same strand 4, namely a por-

* greased sheathed section comprising section 42 and housed

  in a channel 33 hollowed out in the deck 1 with interpolation

  sition of a grout 34 and a portion essentially corresponding to the section 41 and formed of a strand element protected by a plastic sheath or

  analog directly adhered around it.

  This variant of FIG. 4 presents by

  compared to those of FIGS. 1 to 3, the advantages

  wings: easy realization of the terminal anchor 29 since it rests against a concrete block instead of being at the exit of this block, possibility of giving said anchor 29 a position and an orientation facilitating tensioning strands making up the corresponding shroud, use of the tension of the shroud for

  prestress a portion of the solid concrete block

apron 1.

  Following what and whatever the embodiment adopted, there is finally a bridge to

  guy wires whose constitution and implementation result

  try enough of the above.

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

  virtual absence of fatigue in the incur-

  length of each shroud due to the fact that this portion is under tension and its blockage, which prohibits its deformations and / or chronic displacements, and consequently increased longevity of the shrouds, possibility of using shrouds with multiple strands and of replacing less partially these shrouds without requiring an interruption of traffic on the

bridge.

  As it goes without saying, and as it results from

  their already from the above, the invention is not limited

  in no way to those of its modes of application and implementation

  which have been more specifically contemplated; she in

  embraces, on the contrary, all variants and in particular

  ment those where the construction described with reference to

  FIG. 4, for which each strand 4 comprises a door

  constantly stretched non-rectilinear

  bridge deck, would be adopted in combination with this

  the described with reference to Figures 1 to 3, for-

  which each strand 4 comprises a curved portion

  constantly taut resting on a saddle of a pylon.

Claims (6)

  1 Cable-stayed bridge including an apron (1), at   minus a pylon (2) and shrouds (3) composed of to-   multiple lines (4) and each stretched between a pylon and the deck, characterized in that each of the strands constituting at least one of its shrouds comprises, connected to each other in the mutual extension of one the other, a first oblique rectilinear section extending freely from the deck to the pylon concerned and a second non-rectilinear section housed inside a   massive concrete (1,2) constituting the deck or pylô-   not, and in that there is provided an anchoring device   intermediate (9,10,28) crossed by said strand, available   sitive bearing on said massif and arranged so as to be able to keep under tension the non-rectilinear strand section housed in this massif after tensioning of   the entire length of said strand by exercising a trac-   maximum tion between its two ends and sub-anchoring follow from these ends.   2 cable-stayed bridge according to claim 1,   characterized in that each anchoring device inter-   medial (9,10,28) is arranged so that the strand (4) which passes through it can be moved in the direction away from the solid (1,2), but that it is   automatically blocked in reverse.   3 cable-stayed bridge according to claim 2,   characterized in that means are provided for neu-   identify the said blockage during power-up initial of the strand.   4 Cable-stayed bridge according to any one of   previous claims, characterized in that each   strand consists of at least two successive segments joined together by a coupler (18-23,32), namely a first segment which comprises the non-rectilinear section and one end of which crosses the intermediate anchoring device and a second segment which understands most   large part of the straight section.   Bridge according to claim 4, characterized in   that the first segment of the strand is of the to- type   sheathed greased, that is to say stripped and arranged in a sheath with interposition of grease and in this   that the second segment is of the individual strand type-   Lely protected by an extruded sheath.   6 Cable-stayed bridge according to any one of   previous claims, comprising at least one   saddle (5) or curved portion placed on a pylon to support an intermediate curved portion of a stay (3), characterized in that each strand constituting at least one of the stays of this bridge and cooperating with such a saddle 'extends individually from one foot to the other of the inverted V defining this stay, in that the non-rectilinear section of said strand is its curved section resting on the saddle and in that it is provided   to keep this strand taut, on the one hand, two available   end anchoring devices (7,8) arranged at the two lower ends of the strand and suitable for anchoring each one of these ends in the deck (1) of the bridge or in a similar block and, in addition, in addition of the intermediate anchoring device (9) crossed by the strand considered and bearing on one (F) of the two opposite vertical faces of the pylon comprising the saddle, a second intermediate anchoring device (10) also crossed by the strand and resting on the other vertical face (G) of the pylon, in the direction inverse of the first.   7 Cable-stayed bridge according to any one of   Claims 1 to 5, characterized in that the section   non-rectilinear (42) comprised by each strand of the stay cable is housed in a concrete block constituting the deck (1) of the bridge and in that this section is stretched between the intermediate anchoring device (28) which it crosses and a terminal anchoring device (29) supported   on said massif in the opposite direction to the previous one.