DE2904147A1 - Wire cable tensioner giving permanent rigidity - utilises gap filling between steel anchor head and cast metal cone - Google Patents

Abstract

The process is used for increasing oscillation rigidity of tensioners for suspension bridges, cable bridges, cable railways or other structures, made up from wire cables. The fine sheathing gap and cracks between the external steel anchor head and internal shrunken cast metal cone are pressed out with force-locking material after cooling. Atmospheric oxygen is prevented from entering places endangered by friction corrosion. The internal surface of the anchor head cone has annular corrugations producing serration between head and cast cone, permitting lengthways displacement only to the extent of the max. gap produced by shrinkage.

Description

Description: Process for improving the fatigue strength of rope,

Parallel wire and strand bundle anchorages.

The present invention relates to a method, the potting cone within steel anchor heads (also called anchor and rope sockets) for rope, To influence parallel wire and strand bundles so that their deformations after successful hardening as well as the mutual displacement and rubbing of the wires in the anchoring area and thus prevents the fretting corrosion phenomena leading to wire breaks or are at least greatly reduced and also on devices for performing this Procedure.

III, Invention To achieve an approximately good result with the metal casting To achieve this, the causes for the accumulating in the anchoring area must be found Endurance breaks are eliminated.

Since, as is well known, the zinc and zinc, which is mostly used for metal coating The zinc alloys shrink by up to 1.6% when they solidify, and are more three-dimensional Regarding detachments and a fine circumferential gap at the wide end of the potting cone.

To the entry of the tension member in the anchor cone are parallel to Longitudinal axis gap and detachment are hardly effective anymore, because this is where the casting compound is present is small at the cross-section.

The gap is indicated in an exaggerated manner in Fig. 2 under item 11 A large anchor body for about 295 # 7 mm wires will be a wide truncated cone end about 0.8 - 1.4 mm thick, depending on the extent to which there is have formed cavities within the potting material.

Small cracks can also solidify across the longitudinal axis of the anchor head Pull through potting material, especially where there are fei running parts as a result from sticking to the embedded steel wires no longer pull together sufficiently This will be the case especially in the narrow entry area, where it is known to be so far the fatigue fractures have been increasing. The edges of the cracked, rather brittle zinc alloy cause back and forth on the surfaces as a result of the dynamic stress rubbing wires where they have not yet been fixed by being pressed together are, damage and fretting corrosion when exposed to oxygen, as the tests recognize let.

If longitudinal tensile forces are now exerted on the potting cone via the tension member, so this is initially due to the lack of the transverse compression caused by the detachment from the perforated plate as well as the adhesion to the embedded wires are deformed until the material of the potting cone is compressed and largely crept against the cone wall of the anchor head.

Only then are the wires gradually cross-pressed and the increasing friction anchored. It was attached to the bodies of the Rhine bridge Mannheim a slip path of approx. 9 11 mm measured at the entry point, what, if not special precautions by the sleeve - Fig. 2 No. 4 - created would have been to tear off the corrosion protection skin of the tension member on this Would have led.

According to the invention, it is provided after the metal casting has cooled down In the example on Fig. 2 no. 9 and jQ the way shown the interior of the anchor head to be sealed pressure-proof and suitable material in a liquid state press in with high pressure so that it can be pushed in from below - item 12 - through the narrow cavities slowly ascend to a control port protruding from the top - item 13 must, with the aim of a. the gaps and voids caused by the shrinkage of the metal potting compound have arisen to close largely, so that subsequent after hardening Deformations under the action of the longitudinal train from the anchored wires in the Potting cones can no longer occur, rather the transverse pressure in the cone to fix the wires is built, b. especially at the entry end of the tension member, where in the area of gradually diverging wires from the opposite Side the potting material has penetrated in the form of a tongue and solidified, to subsequently fill up the piles existing here in order to remove any broken cast parts envelop, define and allow oxygen to reach this critical point to prevent.

That the breaks of pressure or friction points between the wires and the tongue-shaped ends of the zinc casting alloy run out and corrosion products which can be prevented by blocking the access of oxygen, was in the research and material testing institute for the building industry - Otto-Graf-Institut Stuttgart-Vaihingen made clear in 1976/77 x) and already existed Experiments in 1969/70 established that lead to the development of parallel wire bundle anchoring for the Mannheim Rhine Bridge.

x) Rehm, Patzak and Nuremberg cast metal anchoring for tension members & us high-strength wires; "Draht" 28 vol. (1977) issue 4.

Whether instead of the one in Fi. 2 shown press-fit better from wide cone end to the narrow cone part to press the grout is to be determined on a trial basis.

It is also known that one wants to try on the hardened potting compound exert pressure from the wide end of the cone and move it up this way to press together to rest against the Miker sleeve. However, the embedded Wires compressed. The adhesion between the potting metal and the embedded wires is disturbed and thus goal a.) is only partially achieved and goal b.) is not achieved at all.

The material pressed into the joints according to the invention is later included on all sides. It is sufficient if there are pressures of almost 100 - 120 N / mm² can accommodate.

A metal alloy with a low solidification range, e.g. cadmium or a similar metal, if possible with a higher compressive strength, compared to that Steel is not allowed to enter an electrochemical potential, for example.

But since the injection of liquid metal with high pressure certain As an alternative, a casting resin with low viscosity is also a problem and particularly good flowability, preferably epoxy resin with hardener, for these Purpose usable that to raise the pressure resistance fillers with large Hardness e.g. steel grit, steel balls of small diameter, steel filings or selected solid quartz grains and similar microballoons are to be mixed with. The intrusion The potting material into the fine cavities is attached to the outside of the anchor body Vibrators supported. It is sufficient if in the narrow cavities of the narrow cone part only the epoxy resin penetrates to shut off the oxygen in the air.

There where the contact pressure in the gap between the outer and inner The additions mentioned are used to increase the strength values important. In the area where the gap is gradually opening, the epoxy is in able to let the fillers flow in and immediately after hardening With the occurrence of the tensile forces, the necessary transverse compression without further deformations produce.

At this point it should be pointed out that also from within of the tension member is pressed out of the directly adjoining the anchor head Tension member area with a corrosion-preventing plastic, preferably polyurethane with Zinkchrc.mat, is provided - see O.L.S.P 27 36 355.9 -. According to the employees Experience penetrates this inside the tension member from the outside into the anchor head a. Through the interaction of these penetrating from different directions Plastic impressions will shut off the atmospheric oxygen from the critical one Anchoring zone soaked through. The advantage of metal cast anchoring remains get it.

As is well known, nan tried to find the cone shape according to an exponential function : y = q. e c. x in such a way that the inner grouting cone with the over the entire length different amounts of shrinkage after cooling, slightly to the narrow The end of the cone is displaced, fits back into the outer shell and has a firm connection. Tests have shown, however, that in this way the slip and the concentration of the Cross pressures in the entry area cannot be sufficiently reduced.

According to the invention is desahlb provided by circumferential ribs a to establish a certain interlocking of the two parts over the entire length of the anchor cone and preferably in the wider cone blunt part. A hike to the narrow anchor head area even if no squeezing has taken place, it is only at the maximum in the maximum Gap thickness sizes of the cross section are possible. Through the intended training of the surrounding wave crests can after this slight longitudinal displacement also in wider cone part, annular contact pressures and pressure arches are generated, see Fig. 3, no.

16, even if the crevices have not been filled in beforehand. on In this way you can prevent the long-term creeping of the forgetting material by simply focusing on the previous concentration of power transmission the limited short sticks of the entry area and the resulting Increase in the transmitted contact pressure, which increases the fatigue strength of the zinc alloy exceed, avoid. The result of these measures are: one huber a larger one Distance distributed force transfer and thus lower local pressures.

On the basis of the tests carried out in the Otto-Graf-Instittt the transverse pressures do not adversely affect the fatigue strengths. But wherever strong cross pressures and relative displacements of the wires come together, a considerable decrease in fatigue strength was found. It is inevitable that especially in the entry area, the voltage changes under the acting traffic load exposed wires are subject to corresponding elongations up to the point where the Frictional forces force the rest position. There are therefore pressure concentrations in to reduce this area by the design according to the invention and also the damage due to fretting corrosion due to the exclusion of atmospheric oxygen in the intended way to prevent. You should just refer to the suggested one Restrict meaningful design of the conical surfaces causing a toothing wanted, so is the closure of atmospheric oxygen by the invention - O.L.S.S. 27 36 355.9 - to be carried out by pressing out from the inside of the tension members.

IV. Drawings The details are illustrated by figures: Fig. No. Number Designation 1 - isometric representation of the essential parts of anchoring 1 anchor head - anchor sleeve = rope sleeve 3 tension member 4 perforated plate 5 casting metal 6 sleeve 8 corrosion protection layers on the tension member 2 - schematic section 2 support ring with counter ring for transferring the tensile forces through anchor head fig. No. Number Designation 7 Two-part plastic socket to prevent an electrical connection Potential between the metals of the anchor head and the sleeve 9 to be screwed in temporary cover 10 to be screwed two-part ring to secure the Temporary pressure lock 11 by shrinkage formed gap around the interior Cast metal cone inside the anchor head 12 temporary press-in socket 13 control socket (12 and 13 can be placed in reverse position on the truncated cone ends) 14 Asbestos seal between anchor head and projection 15 Press-in opening for material to close the gap between the anchor head and sleeve after assembly.

3 and 4 (Fig. 4 is 5 times against the correspondingly marked point 3 shown larger).

schematic representation of the perpendicular to the direction of pull, ring-shaped shafts for the purpose of interlocking the anchor head and casting cone for reduction the contact pressure peaks and the longitudinal displacement (slip).

16 inclined partial surfaces of the arranged inside the anchor head Waves against which the longitudinal direction after a slight slip occurs the inner potting cone lays and in this way in the broad cone part in annular Distribution of forces takes over, so that pressure arches built up inside the potting material by which the adhesion to the covered wires is increased and equally the transfer of forces is distributed over a larger stretch of the anchor head. the Load distribution to a larger number of such ring- Fig. No. Digit designation shaped pressing surfaces is regulated by the fact that in places where there is an overload, the potting material filling the adjoining crevices that are almost inclined in the direction of pull, creeps until a sufficiently large number of support ring surfaces to be carried along are used.

At least all surfaces are claimed when the longitudinal displacement has reached the largest gap caused by shrinkage. The wandering in of the inner cone in the area of the tension member entry into the anchor head, for which earlier Paths of 9-11 mm have been determined at the Mannheim Bridge this rd is considerably reduced in this way and with it the concentration of the load transfer considerably reduced in this critical area.

17 the remaining distances between the anchor head and in the direction of pull Press taper ring surfaces after toothing and transfer of forces to the surfaces No. 16.

Claims (6)

I. Claims 1. Method by which the fatigue strength the tension members made of high-strength steel wires for suspension bridges, cable-stayed bridges, Wire ropes or for similar technical purposes at the generally critical Anchoring point, which is the case with the usual grouting of the anchor heads (also rope or Called anchor sleeves) by the shrinkage of the wire ends surrounding and through Transverse compression of the truncated cone made of casting metal within the anchor head is adversely affected, can be increased considerably, characterized in that that the fine enveloping gap that forms and the other separations between the steel anchor head on the outside and the one on the inside that shrinks when it hardens Cone made of forgotten metal with a strong material after it has cooled down pressed out - Fig. 2. Numbers 9, 10, 12 and 13 -, shifting and deforming the Potting material due to the applied ZuO forces until it is gradually applied the cone of the outer anchor head avoided and the access of atmospheric oxygen to the areas at risk from fretting corrosion are prevented and / or as a result, that the hitherto unavoidable excessive pulling of the potting cone into the narrow Cone part and the resulting concentration and increase in the contact pressure than the wires embedded in the inner potting cone as a result of the agglomeration of the power transmission essentially to the area of the relatively short entry sections Constructive measures and measures shaping the conical surfaces in detail are prevented, preferably in that the inner surface of the anchor head cone in a suitable manner shaped annular circumferential waves - Fig. 3 and 4 numbers 16 and 17 - receives and thereby a toothing between anchor head and potting cone is created, which a longitudinal displacement at most as large as that caused by the shrinkage largest gap. 2. The method according to claim 1, characterized in that a metal with a low melting temperature at a location close to the narrow cone area in the liquid state from below after heating the anchor head in the surrounding area Gap is pressed in until it is at the control port that is at the other end of the cone is located, rises, with the opposite press-in direction from wide to narrow Cone end is possible. 3. The method according to claim 1, characterized in that a modified Cast resin, preferably for these purposes epoxy resin and hardener with good flowability, the very fine-grained, high-strength fillers, such as Quartz grains, your steel balls or chips or other micro-balloons made of one for material suitable for this purpose can be added, in similar wheat. as in the claim 2 is indicated, rising from the bottom to aen control port - z.r. according to Fig. 2 numbers 12 and 13 - this presses in all existing cavities up to the point of entry of the tension member in the anchor body must be filled in a non-positive and sealing manner. 4. Process according to claims 1-3, characterized in that the gap extrusion material after pressure-retaining sealing of the potting cone space both ends - for example: Fig. 2 numbers 9 and 10 - by exercising a strong Grouting pressure is forced, especially inside the spread wires in the area in which the tension member enters the anchor body and where im In general, the potting material often just fill the gaps between them due to premature solidification, cannot completely fill the air to push out of the cavities and by their full closure a complete To cause oxygen exclusion from any wire friction points. 5. The method according to claims 1. 3 and 4, characterized in that that simultaneously with the pressing out of the interior of the anchor head, which is sealed against high internal pressure not just the gap that may have arisen, the voids between the wires but with certainty the ones that remain at the outer edge of the potting cone every now and then Blowholes or even larger cavities are positively filled and reliable Verification of functional safety is carried out. 6. The method according to claim 1, characterized in that in addition for pressing out the gap after hardening or independently for all Types of potting, including spherical plastic potting, that are cone-like or in the longitudinal direction also curved surface of the steel anchor head transversely to it several annularly extending wave crests and valleys obtained in a suitable manner so are designed that a toothing between the anchor sleeve and the material of the Potting cone arises - for example fig. 3 items 16 and 17, which is the longitudinal shift of the inner potting cone restricted and thus the concentration the contact pressure removed from the entry area, this over the entire length while reducing the absolute values are distributed and thus also the breadth Truncated cone part is used to generate pressing pressures even if through A certain detachment has occurred. II. Stand. It is common to use the wires or strands that make up the tension members assemble in the frustoconical interior of the anchor heads (also Xnker- or rope sleeves) through the poured potting material after it has hardened to compress by means of the tensile force exerted in the cone area and thus to close anchor - Fig. 1 -. The potting cone is dimensioned so that the U amount of the minimum breaking force from the tension members to the anchor body is guaranteed. In DIN 83 315, the is to be replaced by the new version of DIN 3092, the required are Minimum dimensions driveway. Potting with 1. Metal and metal alloys with as much as possible are known low melting temperature. 2. Plastics that have fillers to increase pressure resistance are added z. 3. 6% by weight epoxy resin + hardener 14 - - 16% by weight zinc dust 80 - 78 Gew. Ffi steel balls # 1.2 - 2 mm with great hardness or also epoxy resin mixed in Quartz grains and similar hard material. As is known, lead-tin alloys are used as casting metals with casting temperatures of 320 - 440 ° C. Zinc alloys and fine tin "" 420 - 480 ac. In the Federal Republic of Germany it is common for anchoring of bridge members for which a high creep strength is required, i. a. a zinc alloy ZN 16 Cu1 (e.g. Zamak 610 from Goldschmidt, Essen) or similar, which have a lower casting temperature than pure zinc having. In the United States and Japan, zinc is generally used in fairly large quantities for these purposes pure kind used. In addition to the permissible tensile loads also the fatigue strength decisive, which is particularly for steel bridges with low dead weight and bridges with high traffic loads such as B. Rail transport applies. According to the provisions of DIN 1073, for an upper stress in the tension member equal perm # amplitude # # of 150 N / mm² for ropes of 200 N / mm² for parallel wire and strand bundles can be endured after 2,106 load changes. There may only be enough wire breaks or cracks that the remaining residual breaking force is still 75% for ropes and parallel wire and strand bundles 80% of the nominal breaking force reached. The experiments carried out here and there in recent years convey the impression that these demands can often not be achieved and the the high mean value based on the current state represents an inadequate "steady state" Confidence range ". The consequence arose, either that stipulated in the standard Reduce vibration coefficients or significantly improve anchoring technology. The following approaches have become known: 2.1 a transition that is as even as possible of the individual wires from the composite of the ropes or parallel wire bundles into the more or less spread open position within the frustoconical interior of the anchor body. In the case of ropes, the necessary "rope broom1, non-elastic deformations inevitable, which turns out to be disadvantageous. In the case of parallel wire bundles, the wires can be adequately covered Bend large radii elastically so that the ender. threaded into the perforated plate (Fig. 1 and 2, item 4) and with sufficient mutual distances after pressing from small "heads" - Fig. 3, item 19 - in an orderly position, aligned with the axis can be fixed. In order to enlarge these radii of curvature and thus the expansion dimension To be able to flatten something was first known in 1970 at the Mannheim Rhine Bridge Pre-sleeves (tubular extensions see Fig. 1 and 2, item 6) in the anchor heads get involved. If you adapt to the corrosion protection on the free tension member length for this pre-sleeve a different metal than the steel casting usual for the anchor head must choose, so an electrolytic potential is due to corrosion protection a subsequent joining two-part plastic bushing, e.g. made of polyamide - Fig. 2, point 7 - should be avoided. Since the "rope brooms" do not have the same precise order as the Spreading of the parallel wire bundles can be formed for the ropes Pre-pods have not yet been considered useful. 2.2 There has recently been a move towards the smallest diameter expand the anchor head cone at the entry point of the tension members so that they of a cast metal ring with a thickness of 10% x D + 1.5 mm at this critical one Position can be included. The inner bore of the pre-sleeve also has to be attached to this Make a diameter of at least 1.2. D + 3 mm (D = tension member diameter). 2.3 In some cases, instead of the metal casting, one already has the Above mentioned ball plastic potting executed, with the elimination of the heat influences a 33 to 45% higher amplitude appears to be achievable. x) x) indrä Saul: Experiments with bundles of parallel wires and strands for the north bridge Mannheim-Ludwigshafen and the tent roof Munich, "Bautechnik" 51 jg. (1974) Hafte 9, 10 and 11.