EP0789110A1 - Suspension device for civil engineering structures and building method - Google Patents

Abstract

The suspension cable (1), for civil engineering, has an intermediate sheet (11) between the strands, which is corrugated alternately on both sides. The parallel corrugation peaks (12) are triangular with curved faces, to fit into the gaps (T) between the strands (7). Also claimed is production of the sheet, using extrusion. Preferably each strand (7) is covered (9) by a supple material of the same material as the intermediate sheet (11), preferably of high density polyethylene or a polyolefin. The sheet material, between the corrugations, has a thickness of ≤ 0.1 mm.

Description

The invention relates to civil engineering works comprising sub-assemblies suspended from carrying cables or guy wires themselves carried by pylons or the like, the suspension of each sub-assembly being effected by means of hangers hung by collars to said carrying cables or shrouds.

It relates more particularly to the case where the cables are formed by lateral juxtaposition of identical multiple strands distributed in superimposed layers, the word "strand" being adopted here, for the sake of simplification but in a nonlimiting manner, to designate strands as well individual or "strands" proper, as cables or bundles of such strands or even as bars.

It relates more particularly still to the suspension devices of works of the kind in question as well as the construction methods of these devices.

In the known embodiments of said works, each strand has a generally cylindrical shape and the mutual contacts of the strands with each other are made along narrow, even linear, longitudinal ranges of these strands.

The transverse load exerted on the cable by each hanger, and more precisely by the collar disposed at the upper end of this hanger, is then transmitted to the cable from strand to strand along said ranges according to non-homogeneous distribution laws, especially if these areas are made of a relatively flexible material such as that constituting a strand sheath of the self-protected type.

As a result, said strands are not all stressed equally by said load: some of said strands are therefore relatively overloaded, which requires a overall oversizing of the cable and increases the cost price of this cable and the structure it equips.

In German patent 759 490, it was proposed to interpose a trim sheet between the sections, located inside the collar, of the superimposed layers of strands. This trim sheet has the general shape of an inverted T, the transverse bar of which serves as a support stop to prevent the collar from descending along the carrying cable. The vertical bar of this T has the width of the strands of strands between which it is inserted. Its function is to provide an additional friction surface to strengthen the anchoring of the collar on the carrying cable: the overall friction which ensures this anchoring does not only result from the contact surface between the internal face of the collar and the periphery of the cable, but also additional surfaces thus created between the strand plies and the trim sheets. Consequently, this lining sheet is stressed in tension, and does not contribute to harmonizing the stresses exerted on the different strands inside the collar.

An object of the present invention is to better distribute between the strands the loads exerted at the level of the hanger collars.

The invention thus proposes a suspension device for a civil engineering structure, comprising a carrying cable itself constituted by lateral juxtaposition of multiple strands distributed in superimposed layers, and lines hung on this cable by collars and suitable for transmitting to said audit cable the load of the structure, an intermediate sheet being interposed between the sections, located inside each collar, of at least two superimposed plies of strands of the carrying cable, in which the intermediate sheet is ribbed alternately on its two faces by parallel bracing slats having a curvilinear triangle profile, slats suitable for filling the gaps in joint between said layers.

• dans un ouvrage pour lequel chaque toron est entouré par une gaine en un matériau souple, la feuille intercalaire est constituée en le même matériau que cette gaine ou en un matériau de dureté similaire,
• le matériau souple selon l'alinéa précédent est le polyéthylène haute densité où une polyéoléfine,
• les portions amincies, de la feuille intercalaire, qui sont comprises entre ses nervures, présentent une épaisseur très faible, de l'ordre de 0,1 mm ou même inférieure.

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

• in a structure for which each strand is surrounded by a sheath made of a flexible material, the intermediate sheet is made of the same material as this sheath or of a material of similar hardness,
• the flexible material according to the preceding paragraph is high density polyethylene where a polyolefin,
• the thinned portions of the interlayer sheet, which are included between its ribs, have a very small thickness, of the order of 0.1 mm or even less.

• soit par extrusion en un seul tenant,
• soit en formant par extrusion chacune des lattes présentant un profil de triangle curviligne et en collant celles-ci alternativement de part et d'autre d'une feuille mince ou d'un ensemble de bandes minces parallèles.

As regards the manufacturing process of the interlayer sheet, the latter is advantageously formed:

• either by extrusion in one piece,
• either by forming by extrusion each of the slats having a curvilinear triangle profile and by gluing them alternately on either side of a thin sheet or of a set of parallel thin strips.

As regards the positioning of the interlayer sheet on the cable, the procedure is advantageously as follows: before mounting a collar on the section of cable intended to receive it, the layers of superimposed strands are removed two by two constituting said section, then horizontally introduced into each of the spaces thus cleared successively between two layers a section of sufficient area of the bracing sheet, then the two said layers are brought together vertically, which makes it fill by the ribs of the sheet the interstices between these layers, and after having thus filled all the interstices between the layers, the suspension collar is mounted on the section of cable thus equipped.

Embodiments of the invention will now be described by way of examples in no way limiting, with reference to the attached drawing.

Figure 1 of this drawing very schematically shows a suspension bridge to which the invention is applicable.

Figure 2 shows the partial cross section of a suspension device according to the invention included by such a bridge.

Figure 3 shows on a larger scale a detail of this section.

Figures 4 and 5 show two alternative embodiments of a ribbed bracing sheet according to the invention fitted to the above device.

Figure 6 shows in perspective view a piece of the first of these two sheets.

Figure 7 shows very schematically a phase of the manufacturing process according to the invention of the above suspension device.

The bridge shown diagrammatically in FIG. 1 comprises, on the one hand, a carrying cable 1 which rests on two pylons 2 and which is stretched between two anchoring blocks 3 and, on the other hand, an apron 4 which is suspended from said cable carrier 1 via lines 5.

These lines 5 are hung on the cable by collars 6 and can extend both vertically, as visible on the left portion of Figure 1, as perpendicular to the cable, as visible on the right portion of said figure.

The cable 1 is composed of a plurality of individual strands 7 distributed in a plurality of plies vertically superimposed, each ply comprising a variable number of strands juxtaposed horizontally, this number varying for example from three for the two extreme plies to ten or fifteen or even more for the central ply: if the general section of the cable is circular, which is the most frequent case, the number of said plies is of the same order of magnitude as the number of strands constituting the central ply.

During their natural contiguous superposition, the strands 7 are automatically placed in staggered rows, as clearly visible in FIGS. 2 and 3, the base of each strand coming automatically to be housed in the upper groove formed between two strands horizontally juxtaposed with the immediately lower ply .

The interstice T thus formed between the three strands considered - and more generally between any three strands mutually contiguous to the assembly - has the general shape of a prism whose cross section is delimited by a curvilinear triangle: more precisely, said section triangular is delimited by three arcs of circle of identical rays tangent two by two and curved towards the inside of the triangle.

Each strand 7 is advantageously of a self-protected type, that is to say constituted by a plurality of twisted wires 8 (FIG. 3) housed inside a sheath 9 with the interposition of a protective product 10 such than an epoxy resin, wax or grease.

The sheath 9 is generally formed by an incompressible product, but having a certain flexibility, such as high density polyethylene (HDPE) or a polyolefin.

The contacts between the various strands 7 are then established according to very narrow, and even theoretically linear, ranges P which extend longitudinally along said strands.

Each gap T is then delimited by three portions of sheath 9 each extending transversely between two successive areas P.

In the currently known embodiments, the interstices T are empty and the load C applied by the lines 5 to the cable 1 by means of the collars 6 is transmitted to the various strands 7 constituting said cable at the level of only areas P.

Given the relative flexibility of the sheath portions 9 delimiting the said ranges P, the transmission in question may give rise to poorly controlled local crushing, resulting in an irregular distribution of the stresses in the different strands 7.

The invention overcomes this drawback by filling the gaps T in each section of the cable 1, intended to be surrounded by a collar 6.

This filling is carried out using filling elements whose volume is practically complementary to that of the interstices to be filled.

However, these elements are not made up solely of rods corresponding individually to each gap: it would be too difficult to install such rods.

Said element is here constituted by sheets 11 ribbed by parallel slats 12 projecting alternately on their two faces, each slat having the shape of one of the interstices T, that is to say that of a prism whose base is delimited by a curvilinear triangle.

The bridges 13, of each sheet 11, which interconnect two successive ribs or slats 12 have a width corresponding to the mutual spacing of two interstices T in the cable 1.

The thickness of each trigger guard can be very small, and for example of the order of 0.1 mm or even less: experience has shown that the tensile strength of such thin plastic sheets is largely sufficient to ensure the consistency required for such a sheet during handling.

The sheets in question are advantageously made of the same material as the sheaths 9, but this material could be different while of course being compatible with that constituting said sheaths.

• par extrusion en un seul tenant (figure 4),
• ou par formage préalable de lattes prismatiques 12, puis fixation alternée de ces lattes sur les deux faces d'une feuille indépendante 11 (voir figure 5) -feuille qui peut être constituée par une pluralité de bandes minces parallèles- notamment par collage desdites lattes sur ces deux faces, prévues auto-collantes.

The sheets 11 can be produced in any desirable way, for example:

• by one-piece extrusion (Figure 4),
• or by prior forming of prismatic slats 12, then alternating fixing of these slats on the two faces of an independent sheet 11 (see FIG. 5) -sheet which can be constituted by a plurality of thin parallel strips- in particular by gluing said slats on these two faces, provided self-adhesive.

The sheets obtained are in the general form of blinds or rolling shutters with parallel slats (see Figure 6) and can be delivered, like these, in rolls which can be delivered to the site on request.

To simplify the manufacture of the slats 12 and reinforce them, whether these form a body with the sheet 11 or are attached to it, their edges A can be truncated, which gives them a small thickness, for example of the order of mm as visible at A 'in Figure 5, while theoretically this thickness should be zero.

To ensure good continuity between the inner face of each collar 6 and the periphery of the cable section 1 surrounded by this collar, there is advantageously provided between this face and this section a jacket 14, for example made of HDPE, and, against the inner face of this shirt, a layer 15 made of a material more deformable than that constituting the shirt and offering good resistance to compression, such as neoprene.

The establishment of a spacer sheet of the kind described above between the strands of a cable is relatively easy.

For this purpose, it suffices to separate successively two by two, before fitting each collar 6, the sections, strands of strands, which are intended to be surrounded by this collar, for example using metal rods, the end is rounded to avoid any risk of damage to the sheaths 9.

We then thread transversely, according to arrow F of FIG. 7, in each space E thus cleared between two layers of strands 7 superimposed, a sufficient section of ribbed bracing sheet 11 taking care to have, at the end of this operation, the edges A of the slats 12 vertically in look of the hollows they are intended to fill.

The projecting portion of the sheet 11 is then sectioned at S.

Then the strands of strands thus filled are brought together vertically: the ribbed sheets then blocked between these plies fill the interstices T.

When all the interstices T are filled, the collar 6 is placed around the cable section thus trimmed and the corresponding hanger 5 is hitched to this collar 6: because of said filling, the transfer of the transverse stresses generated by the load C is then performed in an excellent and very homogeneous manner between the different strands 7.

As goes without saying, and as it already follows from the above, 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 of its variants, in particular those in which the supporting cables are constituted by oblique shrouds.

Claims (8)

Suspension device for civil engineering works, comprising a carrying cable (1) itself constituted by lateral juxtaposition of multiple strands (7) distributed in superimposed layers, and hangers (5) attached to this cable by collars (6 ) and suitable for transmitting to said cable the load (C) of the structure, an intermediate sheet (11) being interposed between the sections, located inside each collar (6), of at least two of the layers of strands superimposed (7) of the carrying cable, characterized in that the intermediate sheet (11) is ribbed alternately on its two faces by parallel bracing slats (12) having a curvilinear triangle profile, slats capable of filling the gaps intimately (T ) included between said layers. Suspension device according to claim 1, relating to a structure for which each strand (7) is surrounded by a sheath (9) made of a flexible material, characterized in that the intermediate sheet (11) is made of the same material as this sheath . Suspension device according to claim 2, characterized in that the flexible material is high density polyethylene or a polyolefin. Suspension device according to any one of the preceding claims, characterized in that the thinned portions (13) of the interlayer sheet (11), which are included between its ribs (12), have a very small thickness, from the order of 0.1 mm or even less. Ribbed spacer sheet (11) for a suspension device according to any one of the preceding claims, characterized in that it alternately comprises on its two faces parallel ribs or slats (12) having the general shape of prisms based on delimited by a curvilinear triangle, said slats being suitable for filling the interstices (T) between the multiple juxtaposed strands (7) constituting the carrying cable (1) of the device. Method for manufacturing a ribbed spacer sheet according to claim 5, characterized in that this sheet is manufactured by extrusion in one piece. Method for manufacturing a ribbed spacer sheet according to claim 5, characterized in that each of the slats (12) having a curvilinear triangle profile is formed by extrusion and in that these slats are glued alternately from side to side and on the other side of a thin sheet. Method for placing a ribbed spacer sheet according to claim 5, characterized by the following operations: before mounting a collar (6) on the cable section (1) intended to receive it, two successively are discarded two layers of strands (7) superimposed constituting said section, then is introduced horizontally into each of the spaces (E) thus cleared successively between two layers a section of sufficient surface of the bracing sheet (11), then we bring vertically the two said plies from one another, which makes the gaps (T) between the plies fill between the ribs (12) of the sheet, and after having thus filled all the interstices between the plies, we mount the suspension collar (6) on the cable section (1) thus equipped.

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