NZ211354A - Achoring freely oscillating steel tension elements of structural component subject to dynamic stress - Google Patents

Description

21 1354 P i'.-o; ,'iy L Coi'Tipletf.' r,:;d; ««« ■■■■CohMla.-, CoiOtAICQ... j Publication C ! P.O. Jci.fr-' , 3 0 OCT |9Q7 wor::.:: c X PATENTS FORM NO. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "ANCHORING ARRANGEMENT FOR FREELY OSCILLATING STEEL TENSION ELEMENTS OF A DYNAMICALLY STRESSED STRUCTURAL COMPONENT" -It WE LOSINGER AG of Konizstrasse 74, 3008 Koniz Canton of Berne, Switzerland, e_e».-^="ex-Ai_j c"rganl l«ws. «=f . hereby declare the invention, for which ■■[■/we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 2 2 i. 13 u 4 This invention relates to construction components, and more particularly to anchoring arrangements for freely oscillating steel tensior elements of structural parts subjected to dynamic stress.

Devices have previously been available which are suitable for anchoring a stressed tension member for heavy loads in a concrete structural member. The part of the tension member situated within the concrete member is not bonded thereto because it is surrounded by a casing pipe. This part of the tension member can therefore be removed fror the concrete part after the anchoring device has been released and de tached. This makes it possible to replace the tension member later on i it becomes defective, e.g., in the case of a guying cable of a cable-stayed bridge. However, this proposal does not eliminate the breakage caused by deflecting forces acting upon the guying cables, nor does it increase the fatigue strength of such cables.

The device disclosed in U.S. Patent No. 3 866 273 to remedy these shortcomings. For the purpose of taking up the deflecting forces of the wires converging into a bunch behind the anchor body, supporting means against which the wires rest are inserted in the deflection region of the anchor body. Moreover, these supporting means centre the wires i a predetermined position relative to the anchor body. For this purpose, the supporting means are inserted in the spaces between the wires and th respective borehole wall and completely fill these spaces. The supporting means are of a material which is softer than that of the wires and/o of the anchor body. This expedient does reduce friction at the deflection locations of the wires in order largely to avoid breakage from fric tion and corrosion. However, friction and breakage are not totally elir inated precisely because the spaces between the wires and the wall of th respective bore are completely filled with the supporting means, and the wires lie closely agair.st the borehole walls along the whole length of the bores, so that they car.nct oscillate unimpededly.

The most commonly use: solution consists in a filler frictionally bonded to rods, wires, or strands of a suspension cable in the anchoring zone.

In the region of the deflection location at the end of the anchor casing nearest the bracing plate there is provided a 2 ! *> <4 ( 3 ! 3 J ) filler compound of redistilled zinc or zinc alloys having properties preventing friction^l corrosion. The function of such a filler consists t in gradually carrying off the force of the rods, wires, or strands so that it reaches the deflection location either harmlessly attenuated or 5 not at all any longer. This expedient by no means increases the fatigue strength of the rods, wires, or strands.

The anchoring means described in the last two prior disclosures relate only to the deflecting forces occurring in the region of an anchor body or bracing plate and do not at all solve problems caused by deflect 10 ing forces acting upon the second deflection location, where the individual tension elements are bunched into one member.

Thus there is a need for a means for anchoring freely oscillating steel tension elements of a dynamically stressed structural component whereby the tension elements passing through the bores of the anchor body 15 are not exposed to any friction, the force being transmitted to the clarcps by means of which the tension elements are anchored in the bores of the anchor body. The deflecting forces at the first deflection location ought thus to be eliminated. Furthermore, the deflecting forces at the second deflection location, where the tension elements converge into 20 a bunch, ought also to be eliminated.

According to the present invention, there is provided an arrangement for anchoring freely oscillating steel tension elements of a structural component subjected to dynamic stress, which tension elements are deflected twice in the anchoring region, having an anchor body with two 25 bores running parallel to one another, through which the tension elements are led and are anchored at their ends by means of wedge clamps in spaces of the bores opening conically outwards, supporting means, against which the tension elements rest, being provided in the deflection zone of the anchor body for the purpose of taking up deflecting forces, and having a 30 spreader ring for bunching the tension elements leaving the anchor-body bores and passing through the spreader ring, wherein the diameter of each bore in the section from the space opening conically outwards up to approximately the exit end is constant and larger than that of the tension element, that the supporting means are means capable of oscillating pro-35 vided only in the region of the exit ends, and that the spreader ring has i1 2il3ol on its surface facing the tension elements an insert, resting against the tension elaients, which is made of a softer material than that of the spreader ring or the tension elements.

The diameter of each bore is preferably larger than that of the tension elements by 2 to 5 tun.

Several embodiments of the Invention will now be described in de tail, by way of example, with reference to the accompanyin£ drawings, in whi ch: Figure 1 is an elevation, partially in longitudinal section, of an anchoring arrangement with twice-deflected tension elements, 30 Figure 2 is a partial longitudinal section through another embodi ment of the anchoring arrangement on a larger scale, only the anchor body with one tension element being depicted.

Figure 3 is a partial elevation of a perforated, resiliently yielding disc appearing in Figure 1, 2 5 Figure A is a partial longitudinal section through a further em bodiment, the, anchor body being depicted in part with only one bore and e tension element passing therethrough, and Figure 5 is a partial longitudinal section through still another embodiment in which the anchor body is depicted in part with only one 20 bore and & tension element passing therethrough.

The illustrated steel tension member of a dynamically-stressed . structural component, which tension member is, for example, a freely oscillating suspension cable of a cable-stByed bridge, fans out into individual tension elements A (rods, wire, or strands) at the end thereof to 2b be anchored. The part of "the tension member to be anchored is disposed . in a tubular guide casing 6. The casing 8 may be made of plastics or sheet steel and is intended to be embedded in concrete. The end portions of the tension elements A are led through bores 2, running parallel to one another, of an anchor body 1. Screwed to the anchor body 1 is a 30 clamping ring 7 which is in turn welded to the guide casing 8. The anchor body 3 is usually made of steel.

The bores 2 include at one end thereof spaces 2a opening conically outwards, in which wedge clamps 3 are inserted, by means of which the end ' !/ portions of the tension elements A are anchored on the anchor body 1. 35 The diameter D of each bore 2 in the section 2c thereof, which extends 211354 - fror. the conically outwards opening space 2a up to approximately the exit end 2b, is constant and larger than the diameter d of the tension element 4. The diameter D of each bore 2 is 2-5 mm. larger than the diameter d of the tension elements 4.

For the purpose of taking up deflecting forces in the deflection zone of the anchor body 1, there are provided supporting means capable of oscillating, made of a material which is softer than that of which the anchor body 1 or the tension elements 4, resting against the supporting means, are made. The supporting means are provided only in the region of s the exit ends 2b. The supporting means may, as shown in Figures 2, 4, and 5, each consist of a resiliently yielding ring 5, 13, 14 accommodated in a circular recess 11 in the wall of the exit end 2b of each bore 2 and oscillating with the tension element 4. The rings 5, 13, 14 are preferably glued to the wall of the circular recess 11. The resiliently yield 15 ing ring 5, 13, 14 may have a polygonal, trapezoidal, or circular cross-section.

Instead of the rings 5, 13, 14, the supporting means may consist of a perforated, resiliently yielding disc 6 held resting against the end face of the anchor body 1 at the exit end of the bores 2 by means of the 20 cla-.ping ring 7. The holes 12 in the disc 6 are aligned with the bores 2 of the anchor body 1, so that the tension elements 4 coming out of the anchor-body bores 2 pass through the holes 12. In this case, too, as in the case of the rings 5, 13, 14, the edges of the holes in the disc 6 rest tightly against the tension elements 4. Thus, the disc 6 oscillates 25 along with the tension elements 4 passing through its holes 12.

The fanned-out, anchored tension elements 4 leaving the anchor-body bores 2 pass through a spreader ring 9 disposed in the guide casing 8, by means of which ring the tesnion elements 4 are joined to form a bunched tension member (not shown). This is the second deflection loca 30 tior. at which deflecting forces act upon the tension elements. For the purpose of taking up the deflecting forces at this second deflection location, the spreader ring 9 includes on its surface facing the tension elements 4 an insert 10 resting against the tension elements 4. The material of the insert 10 is softer than that of the spreader ring 9 or 35 the tension elements 4. ■i I f. 211.3 5 4 ? - i - It is known that, e.g. at a maximum of 50% of the rated tensile i • l strength of the high-grade steel wire or strands of a suspension cable, j amplitudes of oscillation equal to or greater than 200 N/sq.mm. are j reached. As a result, the wires, strands, or rods, in the anchor-body j bores through which they are led, press against the borehole walls in the i direction of the wire-bundle axis and form a kink upon leaving the anchor body. The same applies to the second deflection location in the region | of the spreader ring. Such kinks then lead to a very considerable reduc- i tion of the fatigue strength and ultimately to breakage of the wires, •» strands, or rods at the deflection locations. In contrast thereto, because of the free space left between the tension elements and the walls of the bores in the anchor body according to the present invention, the tension elements are not subjected to any friction, 100% of the traction >' being transmitted directly to the clamps. By means of the measures de- scribed above, the fatigue strength of the tension elements, and hence J j their service life, is substantially increased in both the first deflec- j tion location at the anchor body and the second deflection location at j the spreader ring.

Claims (1)

1. 2il3u4 ft jTj*;What \AJ£ CL«=II»^ »2>-;1. An arrangement for anchoring freely oscillating ateel tension elements of a structural component subjected to dynamic stress, which tension elements are deflected twice in the anchoring region, having an anchor body with two bores running parallel to one another,;/;5 through which the tension elements are led and are anchored at their ends by neans tf wedge clamps in spaces of the bores opening conically outwards, supporting means, against which the tension elements rest, being provided in the deflection zone of the anchor body for the purpose of taking up deflecting forces, and having a spreader ring for bunching the 10 tension elements leaving the anchor-body bores and passing through the spreader ring, wherein the diameter of each bore in the section from the space opening conically outwards up to approximately the exit end is constant and larger than that of the tension element, that the supporting means are means capable of oscillating provided only in the region of the 15 exit ends, and that the spreader ring has on its surface facing the ten-;si or. elements an insert, resting against the tension elements, which is made of a softer material than that of the spreader ring or the tension elements.;2. An arrangement in accordance with claim 1, wherein the diameter of each bore is greater by 2 to 5 mm. that that of the tension;20 elenents.;3. An arrangement in accordance with claim 1, wherein each of the supporting means comprises a resiliently yielding ring accommodated in a circular recess in the wall of the exit end of each bore, which ring oscillates with the tension element.;25 4. An arrangement in accordance with claim 3, wherein each resiliently yielding ring has a polygonal, trapezoidal, or circular cross-section.;1 SEP [987;8;5. An arrangement in accordance with claim 1, wherein the supporting means comprise a perforated, resiliently yielding disc which by means of a clamping ring is held fast to the anchor body against the anchor-body end face at the exit end of the bores and oscillates with the;5 tension elements passing through its holes.;6. An arrangement for anchoring freely oscillating steel ten-sior. elements of a structural component subjected to dynamic stress, substantially as hereinbefore described with reference to the accompanying drawings.;f*