GB2415005A

GB2415005A - Suspension bridge cables

Info

Publication number: GB2415005A
Application number: GB0412687A
Authority: GB
Inventors: Thomas John Upstone
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-06-08
Filing date: 2004-06-08
Publication date: 2005-12-14
Anticipated expiration: 2024-06-08
Also published as: GB2415005B; GB0412687D0

Abstract

A suspension bridge cable made up of a large number of parallel steel wires in which a proportion of the steel wires are discontinued to vary the cross-sectional area of the cable at any position along it's length, as required by the design. The ends of the discontinued wires are anchored to adjacent, continuous wires by an adhesive, or solder, or brazing, or metal clamps. Alternatively, a suspension bridge cable made up of a number of steel wire ropes, either parallel or helically twisted, in which a proportion of the steel wire ropes are discontinued to vary the cross-sectional area of the cable at various positions along it's length, as required by the design. The ends of the discontinued wire ropes are anchored with Freysinnet type or other suitable types of socket to suspender clamps, and/or specially provided cable clamps, and/or the main cable supporting saddles.

Description

24 1 5005

SUSPENSION BRIDGE CABLES

This mvenbon relates to a suspension badge cable of varymg cross-secton m any part or parts of it's length from anchorage to anchorage.

There are two different arrangements of suspension bridge cables m general use. In the first design large numbers of parallel steel wires are built into the cable, in-stu, using special spuming equipment. In the second design steel wire rope strands are pre-fabacated, each rope strand comprised of a number of individual wires either parallel or helically twisted. These rope strands are then erected mto place in the bridge cable.

Usually, m the first arrangement, all the wires are continuous from anchorage to anchorage; and, similarly, m the second arrangement, all the wire rope strands are continuous from anchorage to anchorage.

According to the present mventon there is provided a suspension badge cable comprsmg a large number of parallel, steel wires. A proportion of these wires are continuous from anchorage to anchorage. The remainder of the wires are dsconbnued at any position of the cable as required by the design load.

The dscontmued wires are pre-tensoned and terminated at any position m the length of the cable between adlacent suspender cable clamps, or any other cable clamps, as the design load requires. The ends of the dscontmued wires are anchored to adjacent, continuous wires m the cable by an adhesive, or solder, or brazing, or metal clamps. These features enable the cross-sectional area of the cable to be varied at any position in the various lengths of cable between the mam points of support to suit the capacity required to carry the design tension at any position along the cable. This arrangement of wires uses a sgmLicantly reduced quantity of wire when compared with that required for a typical cable as described previously. As the design tension In the cable at it's anchorages Is less than at other positions, the number of wires to be anchored Is also significantly less than that required for a typical cable as described previously; thereby, resulting In significant economies m the structural parts of the anchorages as well.

Also, according to the present Invention there can be provided as an alternative, a suspension bridge cable comprsmg a number of steel wire rope strands. A proportion of these wire rope strands are contmnous from anchorage to anchorage. The remainder of the wire rope strands are discontinued, as determined by the design load, at various positions along the length of the cable.

The dsconhnued wire rope strands are pre-tensoned (to a pre-determined load) and anchored to nearby suspender cable clamps, or to cable clamps specially provided for the purpose, or any of the mam cable supporting saddles at towers or anchorages. These features enable the cross-sectonal area of the cable to be varied at any position m the venous lengths of cable between the main pomts of support to suit the capacity required to carry the design tension at any position along the cable. This arrangement of wire rope strands uses a sgmficantly reduced quantity of wire rope strands when compared with that required for a typical cable as described before. As the design tension In the cable at It's anchorages Is less than at other positions, the number of wire rope strands to be anchored Is sgmficantly less than that for a typical wire rope strand cable as described previously; also, thereby, resulting in significant economies In the structural parts of the anchorages.

Specific embodiments of the mventon will now be described by way of examples, with reference to the accompanying drawings m which; Figure I shows a typical suspension bridge composing a main span, 1-1, and side spans, 1-2. The cables, 1-3, are of parallel wires and are connected to the anchorages, 1-4, from which they pass out and over the rocker splay saddles, 1-5. They then pass over the tower saddles, 1-6, on each side of the mam span. The wires m the cables are clamped at intervals by the cable suspender clamps, 1-7, and, If required, other cable clamps, 1-8, spaced at Intervals along the length of the cables.

Figure 2 is a graph showing the actual design tension, 2-1, In the cable throughout the various spans.

Also plotted is the tensile capacity of the cable, 2-2, together with the varying cross-sectonal area, 2-3, In the cable lengths between main supports due to a proportion of the wires m the cable being dscontmued m the venous spans. The design tension and the tensile capacity of the cable, 2-4, are cahbrated on the let's-hand vertical axis and the cross-sectonal area and corresponding number of wires, 2-5, to provide such capacity Is given on the right-hand axis.

The discontinued wires will be pre-tensoned to a pre-determmed load and anchored to adjacent, continuous wire or wires and the tower saddles.

Figure 3 shows three alternative wire anchorages for the discontinued wires.

There Is a self:tghtenmg wire clamp, 3-1, made from sheet steel. The upper and lower halves of the clamp are Identical but turned 'end for end'; the Inside faces of the clamp are punched 'nutmeg' style. Sliding together, theJont, 3-2,is set at a small angle to the axis of the cable, thus exerting pressure on the enclosed wires and providing resistance to the erection load In the discontinued wire, 3-3; 3-4 Is an adjacent, continuous wire. A section, 3-5, shows the sliding arrangement of the clamp. These clamps will be dstabuted along the length and throughout the cross-secton of the cable.

Also shown Is a wedge-operated steel clamp, 3-6. This clamp Is In the form of a letter 'C' and encloses the dscontmued wire, 3-7, and a continuous wire, 3-8. Wedgc-shaped pms, 3-9, Inserted between the two wires exert pressure on them, enabling the discontinued wire to carry the erection load required.

The third alternative wire anchorage, 3-10, shows a discontinued wire, 311, anchored to two adjacent continuous wires, 3-12, by weldmg or brazmg or adhesives, 3-13, to carry the erection load required.

Figure 4 shows a typical suspension bridge comprsmg a mam span, 4-1, flanked by side spans, 4-2.

The cables, 4-3, are of wire rope strands and are connected to the anchorages, 4-4, from which they pass out and over the rocker splay saddles, 4-5; they then pass over their respective tower saddles, 4-6. The wire rope strands in the cables are anchored at intervals to the cable suspender clamps, 4-7, and, If required, by other cable clamps, 4-8, spaced along the length of the cables.

figure 5 Is a graph showing the actual design tension, 5-1, in the cable throughout the venous spans.

Also plotted Is the tensile capacity of the cable, 5-2, together with the varying cross-sectonal area, 5-3, m the cable lengths between mam supports due to a proportion of the wire strands In the cable bemg dscontmued In the various spans. The design tension and the tensile capacity of the cable, 5-4, are calibrated on the left-hand vertical axis and the cross-sectonal area and corresponding number of wire strands, 5-5, to provide such capacity Is given on the right-hand axis.

figure 6 shows the anchorage, 6-1, of a dscontmued wire rope strand to the flange of a nearby cable suspender clamp, 6-2, which Is cast Integrally with the suspender clamp Itself.. The wire ropes are anchored by Freysmnet type anchors, 6-3, which are seated on spherical washers (to allow rotation?).

A secondary cable clamp, 6-4, constricts the wire ropes Into the main cable.

Additional, similar wire rope clamps, 6-5, together with similar constriction clamps, are positioned at other points m the length of the cable as required.

Claims

1) A suspension bridge cable of varying cross-sectional area throughout any part or parts of it's length from anchorage to anchorage.

2) A suspension bridge cable, as claimed m Claim 1, comprising a large number of steel wires m which a proportion of wires are continuous from anchorage to anchorage.

The remainder of the wires are discontinued at any position In the cable as required by the design. 3)

A suspension bridge cable comprising a large number of steel wires, as claimed m Claim 2, In which the ends of the dscontmued wires are anchored to adjacent continuous wires m the cable by adhesive, or solder, or brazing, or metal clamps.

4) A suspension budge cable compusmg a large number of steel wires, as claimed in Claim 3, in which the dscondnued wires are anchored by selftghtenmg wire clamps or wedge-operated wire clamps.

5) A suspension bridge cable, as claimed In Claim 1, comprsmg a number of steel wire ropes In which a proportion of the wire ropes are continuous from anchorage to anchorage.

The remainder of the wire ropes are dscontmued at any position m the cable as required by the design.

6) A suspension bridge cable composing a large number of steel wire ropes, as claimed In Claim 5, m which the ends of the dscontmued wire ropes are anchored to the suspender clamps and/or additional cable clamps as required.

7) A suspension bridge cable comprising a large number of steel wire ropes, as claimed In Claim 6, m which the ends of the discontinued wire ropes are anchored by Freysnnet type sockets to suitably modified cable suspender clamps and/or additional cable clamps, and/or cable saddles.

Amendments to the claims have been filed as follows 1) A suspension bridge cable comprising a number of elongate structural elements, wherem a proportion of the structural elements extend, m use, from a first anchorage on one side of a structure to a second anchorage on the other side of the structure, with the remainder of the structural elements extending along only a portion, or portions, of the length each side of any cable supports; resulting m a cable of varymg cross-sectTonal area throughout any part or parts of it's length from anchorage to anchorage.

2) A suspension bridge cable, as claimed m Claim 1, wherem the elongate structural elements comprise a plurahty of steel wires.

3) A suspension bridge cable, as claimed m Claim 2, wherein the ends of the dsconOnued steel Wires not secured to anchorages are secured to adjacent continuous wires in the cable by adhesive, solder, or brazing' or metal clamps.

4) A suspension bridge cable, as claimed m Claim 2, whercm the ends of the discontinued steel wires not secured to anchorages are secured by self-tightemng wire clamps or wedge-operated wire clamps 5) A suspension budge cable, as clanked in Claim 1, wherein the elongate structural elements comprise a plurality of steel wire ropes.

6) A suspension bridge cable, as claimed in Claim 5, whercm the ends of'the dscontmued wire ropes not secured to anchorages are secured to suspender clamps and/or addTbona1 cable clamps 7) A suspension bridge cable, as claimed m Claim 6, wherem the ends of the discontinuous wire ropes not secured to anchorages are secured by Freysmnct type sockets to suitably modified cable suspender clamps and/or additional cable clamps, and/or cable saddles