US2311241A - Method and means for anchoring suspension bridge cable strands - Google Patents

Description

Feb 16, 1943 J. T. MARTIN 2,311,241

METHOD AND MEANS FOR ANCHORING' SUSPENSION BRIDGE CABLE STRANDS Filed June 25, 1940 2 Sheets-Sheet l /4 l ai if m my /lI l i@ I' Y- /I f M a? 7? f4 J4 l [miei/fors JOHN 7.- Maar/N,

Feb. 16, 1943. J. T. MARTIN f 2,311,241

METHOD AND MEANS FOR ANCHORING SUSPENSION BRIDGE CABLE STRANDS Filed June 25, 1940 l 2 sheetsfsneet 2 vPaternal Feb. 16, 1943 UNITED STATES VPATEN'I* OFFICE METHOD AND 2,311,241 MEANS FOR ANCHORNG SUS- PENSION BRIDGE cADLE s'mANDs .101m T. Martin, Elizabeth, N. J. l Application June'zs, 1940, serial No. 342,337

(ci. 1li-21) 11 Claims.

This .invention relates to improvements in method and apparatus for use in the erection of suspension bridges, and relates more particularly to a method and means for anchoring the individual loops of wire constituting the bridge cable strand.

In a typical suspension bridge, each cable may comprise a number of strands, generally "l, 19, 37, 61, or 91 and each strand, as viewed in cross section, may be made up of a number of lengths of wire, generally between 250 and 500, each connected 'by a looped portion at respective ends of th'e bridge. The great number of Wires which appear in a cross-sectional view of a given strand are, in fact, all parts of one continuous' wire or of relatively few continuous wires joined end to end. These wires are spun in place by a known type of spinning wheel which usually carries one or more loops of wire from anchorage to anchorage at opposite ends of the bridge. At each end of the strand the loops are engaged with a strand shoe which in turn is fastenedto a iixed anchorage. The present invention relates to an improved method and an improved strand Y shoe whereby greater eillciency in speed of operation can be attained than is possible byprior practice.

In the erection of recent bridges, the laying or spinning of the wires has beenmaterially speeded up. I'liis has been accomplished by using a conventional spinning wheel carrying two or more loops from anchorage to anchorage instead of only one loop. with each traverse of the wh'eel. Heretofore it has been the practice to assemble all the loops for a given strand on the shoe from one side thereof. This has resulted in an objectionable crossing of the wires in the space beto overcome the above and other problems inherent in prior practice.

Another object of the invention is to provide an improved method whereby a plurality of loops of strand wire may be engaged with a bridge anchorage strand shoe in an orderly, efficient and systematic manner.

A further object is to provide a method wherein the strand shoe is held in a more stable positionv during the engaging of 'the many strands therewith than was possible by methods heretofore in Vogue.

Rotation of the shoe about its longitudinal axis tween the shoe and the chief points o'f support in advance ofthe shoe. Such crossing of wires in good practice limits thenumber of loops which canv be vplaced on a given shoe, and thus limits the number of loops that may-be m'ade by one traverse of the spinning wheel.

Because of the great number of loops of wire per strand, it will be appreciated th'at the wires preferably should be placed in rows in a uniform fashion. It will also be appreciated that it is important to adjust the sag of the wires progressively in the different spans of the bridge. A particular problem is involved in the simultaneous laying of two or more loops, because of the complication in properly placing and adjusting the wires. 'I'his problem makes it necessary to train workmen in the procedure, and prior to the present invention the workmen required longer training time before they became proficient in properly assembling with th'e strand shoe a 'plurality of the loops taken from a given spinning wheel.

It is among the objects of the present invention may be caused by misalignment of the shoe 'ith a line from the shoe to the first ch'ief point of support in advance of the shoe. Rotation of a` shoe in either of the above directions by a considerable amount may cause the wires to be displaced from the shoe and thus damage the strand to such an extent that the wires may have to be removed` and respun, involving great expense. Such happenings also offer grave hazard to the lives of workmen engaged in the cable spinning. -1

Another object is to provide a strand shoe of improved construction wherein the wires of a given strand may be quickly and easily divided into separate groups and arranged symmetrically on opposite sides of the longitudinal center line of the strand.

A further object of the invention is to provide a strand sh'oe with a central longitudinallyextending rib arranged for attachment to a pulling jack or other tensioning device, said strand shoe being provided on each side of said rib with a respective seat, each seat being adapted to accommodate a multiplicity of loops of strand wire.

An additional object ofthe invention is to so construct,arrange, and operate the various instrumentalities hereinafterV referred to that they will individually and jointly perform thelrespec- Figure 2 is a plan view of a strand shoe of the present invention in the position it occupies during the placing of wires in the seat portions thereof, the view also illustrating the relative positions of anchorage eye-bars prior to being permanently secured to the strand shoe;

Figure 3 is a side elevation of parts shown in Figure 2:

Figure 4 is a view similar to Figure 2, but showing the eye-bars permanently connected to the strand shoe therefrom, the tension equipment in this view having been disconnected and removed;

Figure 5 is a side elevation of the parts shown in Figure 4: v

Figure 6 is an enlarged detail view of a strand shoe illustrating certain specific features of the present invention;

Figure 7 is a plan view thereof;

Figure 8 is a section on line VIII-VIII of Figure 6.

Referring first to Figure 1 of the drawings, I0 represents a structure of concrete or the like, constituting part of the anchorage at one end of the bridge. suitably embedded therein are a plurality of anchor eye-bars, one of which is shown at I2 connected by suitable pins I4 with eye-bars I6. These eye-bars are in eifect part of the anchorage, and at their outer ends they have my improved strand shoes I8 connected thereto by means of pins 20 which are passed through a suitable hole 20* (Figure 3) of the eye-bar. The present invention is directed chiefly to the improved method and means for engaging a multiplicity of cable strand wires in a more emcient and safe manner than can be accomplished by the method and means heretofore in general use.

In carrying out the improved method, I contemplate feeding bridge wires w and `w1 from supply reels R and l?.1 in any suitable or conventional manner. limitation, I have-shown suitable slack take-up devices comprising, for each wire, a fixed guide sheave 22 and a noating sheave 24 which is urged downwardly by weight 2l. Each of the wires w and w1 will be passed around suitable guide sheave 21 and thence will be looped around a spinning wheel 28 which is adapted to be propelled from anchorage to anchorage by a haulage or traction rope 30 in a manner well known to those skilled in the art. According to the teachings of the present invention, a plurality of wires are carried across the span at each-traverse of the spinningwheel, and instead of engaging each loop 3| with the strand shoe from one side thereof, as in prior practice, in which the strand shoe is supported cantilever fashion from a laterallyextending pin, I engage first one loop with the strand shoe on one side of the longitudinal center line thereof and then another loop from the other side thereof. Similarly, if the spinning wheel carries' four loops of wire, two will be engaged from one side of the center line of the strand shoe and the other two at the other side of the strand shoe. To facilitate such procedure, I preferably provide a strand shoe which is constructed and arranged as best shown in detail in Figures 6 to 8 inclusive. As will be readily apparent from an examination of these figures, my improved strand shoe comprises a central rib or web portion 32. Spaced from this central portion are outer flanges 34 and 3B. As thus arranged, separate recessed seats 3l and 4I! are provided, these seats being arranged symmetrically on eitherA side of the center line :c-Iy of the strand shoe. Ear-',istrand By way of example, but notl shoe is of rugged construction and is formed with an inner flanged portion 42 which denes the outline of opening 44, adapted to receive the pin 20 which transmits the stress from the nomple ed strand to eye-bar I6. y As will hereinafter mc :e fully appear, upon adjustment of the strand shoe to its fina1 position, a number of shims 46 are interposed between tlie rearm: face 48 of the aperture 44 and the pin 20 so as to facilitate proper adjustment of the sag of the cable and proper tensioning of the individual strands thereof.

ln constructing a cable according to my improved method, I preferably employ strand shoes such as those shown and described in connection with Figures 6 to 8 inclusive, -and for spinning each strand of given cable I proceed in the orderly and systematic manner which will now be set forth in detail.

'I'he center rib 32 of the strand shoe is secured by means of a plurality of bolts to spaced parallel plates 52 which are coupled by means of a pin 54 and hydraulic jack plunger 60 with a power tension device such as a hydraulic jack 62, capable of exerting a pull of many tons. This tension device is connected at its rear extremity by means of a pin 64 with plate 66 having a hooked portion 68 for engagement with the fixed anchorage pin I4. The plates 52 and 66 during the normal spinning operation are held in fixed spaced relation by means of tension tie-rods 12-.'I2 connected by respective pins 'I4-'I4 and 'I6-16. With the strand `shoes so restrained,A at the end of each trip of the spinning wheel, a plurality of loops of wires are disengaged therefrom by the workmen. Half the number of loops carried by the wheel are engaged with the seat 38 and the other half of the number of loops are engaged with the seat 40. Thus as the cable-spinning operation progresses, the multiplicity of wires constituting a given strand is assembled in an orderly fashion symmetrically about opposite sides of the longitudinal center line of the strand shoe. In this way the tension on the strand shoe is thus equalized and there is therefore substantially no tendency to set up turning moments which would render the shoe unstable. 'I'his is a feature of improvement over prior practice, wherein during the spinning operation the shoe is supported on a cantilever pin, engaging the shoe at a point forward of the point of engagement between the strand wires and the shoe. 'I'he plates 52 carry angle brackets which as shown in Figures 2 and 3 have flanges 53 which overlap the eye-bars I6 and thus serve as means for slidably supporting said plates from said eye-bars.

After the requisite number of wires for a given strand has been spun, the hydraulic jack is actuated to bring about the proper adjustment of sag in the strand and also to slightly retract the shoe to a position which will permit the pin 20 to be inserted through the eye-bars I6 and placing of the proper number of shims 46 to effect the deboth. By following the procedure described, the stresses are maintained in balance during the progress of spinning the wires of the strand, and upon completion of each strand, the operating step of connecting the strand shoe permanently to the eye-bars is carried out in a safe manner because, unlike prior practice, the `stresses are balanced on opposite sides of the longitudinal Acenter line of the strand shoe and the shoe is thus connected in a stable manner with the tensioning jack. This is to be contrasted Awith the hazardous prior practice'wherein the strand shoe was supported in a horizontal position on a cantilever pin during the spinning, and wherein a bridlel was engaged with the front end of the shoe, which, it will be seen, is a considerable distance forward of the point where the strand wires transmitted their pull to the shoe. In short, my present method o f holding the strand shoe and moving it during the adjustment of the cable strand insures great stability and safety, as compared with the instability and hazard under conditions which are inherent to prior practice. The present method has the further advantage that the shoe during spinning is held in a verticaly plane, and thus does not require the turning of the strand shoe upon completion of the strand,

through an angle of 90, with the attendant labor and hazard of this operation.

The advantageous features of the invention herein referred to have been demonstrated in a practical sense in connection with the erection of the Bronx-Whitestone Bridge in New York State.

While I have described quite precisely a cer tain sequence of steps in the improved method and have shown a specific design of strand shoe, it to be understood that the drawings and the detailed description are to be interpreted in an illustrative rather than in a limiting sense, since various modifications can be made by those skilled in the art without departure from the scope of the invention as defined in the appended claims.

I claim:

1. In the spinning of suspension bridge cables,

the method which comprises arranging the component Wire loops of a given strand in respective groups permanently segregated on opposite sides of a single strand shoe extending lengthwise of the bridge, applying a pulling force to the thus grouped strand loops along the center line of said shoe so as to properly adjust the strand as a whole, and then fastening the thus adjusted strand shoe to an anchorage.

2. In the spinning of suspension bridge cables, the method which comprises providinga strand shoe and arranging the component wire loops of a given strand inrespective groups on opposite sides of the longitudinal center line thereof and maintaining the identity of the groups so segregated, applying a pulling force to the strand shoe at a point to the rear of the arc of contact between said loqps and the strand shoe, and fastening the strand shoe to an anchorage.

3. In the spinning of parallel wire bridge cables, the method which comprises the nove1 procedure of alternately engaging the wire loops of the strand with portions located on opposite sides of the longitudinal center line of a strand shoe and maintaining the loops so separated on such opposite sides in the finished cable.

4. In the spinning of parallel wire bridge cables, the method which comprises providing a strand shoe with grooved seats on opposite sides of the longitudinal center line thereof, attaching thel shoe to a xed support, engaging respective loops of the strand wire with each of said seats and maintaining the loops so separated on such opposite sides in the finished cable.

5. In the spinning of parallel wire bridge cables, the method which comprises engaging loops of the bridge Wire with grooved seats located symmetrically on opposite sides of the longitudinal center line of a strand shoe while the shoe is supported in such manner that the tension imposed thereon by the pull of the strands is distributed substantially uniformly on opposite sides of such longitudinal center line and maintaining the loops so separated on such opposite sides in the nished cable.

6. In the spinning of parallelwire bridge cables, the method which comprises providing a strand shoe with a respective grooved seat on each side of a longitudinal center line thereof and attaching the shoe centrally to a fixed support at a point to the rear of the loops so that a stabilized support is provided to the rear of the loops while they are being successively assembled with, the shoe.

7. In the spinning of parallel Wire bridge cables, the method which comprisesproviding a strand shoe with arespective grooved seat on each side of the longitudinal center line thereof, positioning said shoe between eye-bars, engaging loops of bridge wire from opposite sides of the shoe with the respective seats thereof, placing the shoe under tension applied centrally to effect proper adjustment of the strand, and coupling the strand shoe with said eye-bars.

8.V In the spinning of parallel wire bridge cables,

the method which comprises providing a strand -to the rear of thegrooved seats with a tensioning device connected to a fixed support, engaging approximately an equal number of loops of bridge wire with each of said grooved seats from the opposite sides of said shoe, causing said device to impart an endwise movement to the strand shoe, connecting the shoe'to an anchorage member, and thereafter breaking the rst connection between said rib and said tensioning device.

9. In an anchorage for parallel wire bridge cables, a strand shoe comprising a center rib with grooved seats symmetrically arranged on opposite sides thereof, an extension at the rear of the shoe disposed in a plane between said grooved seats, and securing means carried by the extension for attachment toa tensioning device.

10. Inl an anchorage for parallel wire bridge cables, a strand shoe comprising a center rib with grooved seats symmetrically arranged on opposite sides thereof, said center -rib having an extended portion rearwardly of the grooved seats and carrying means for facilitating attachment to a tensioning device.

11. An article of manufacture constructed and arranged for engagement with the looped ex tremities of bridge cable strands, comprising a strand shoe including a centrally disposed rib having formed symmetrically on each side thereof respective curved grooved seat portions for the accommodation of loops of bridge wire, the body portion of the shoe being apertured for engagement with an eye-bar pin, said rib having a portion extended rearwardly of the grooved seats connection with a tensioning device.

JOm T. MARTIN.

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