GB1109243A - Method of fabricating strands and supporting cables for bridges - Google Patents

Abstract

A method of fabricating a strand of parallel bridge wires for subsequent positioning (see Division E1) in spanning relation over and between the cable supports of a bridge for forming part of a main cable, comprises the steps of laying a plurality of lengths of wire between two fixed supports spaced apart a distance corresponding to the calculated length of the main cable, tensioning each length of wire to a predetermined value and anchoring the wires at opposite ends of the strand while so tensioned, securing the wires at the respective ends of the strand to connections suitable for attaching to the cable anchorages when the strand is positioned in spanning relation over the cable supports, and securing the individual wires of the strand at intervals to maintain its form. On each support is mounted a pair of strand shoes and adjacent one support there are two wire drums. The ends of the wires from the wire drums are secured to the adjacent support and a trolley running on rails carries the two wire loops to the other support where the loops are positioned around the shoes. The trolley is returned to the first support where the wires are positioned around the shoes thereon. The trolley makes as many wire carrying trips as required. Tensioning devices are provided at each support and, if desired, at points between the supports and comprise a wire which carries a weight to produce the desired tension and is secured to a winch. To tension a wire at a tensioning device the wire is secured by wire grips to the tensioning wire and the winch operated till the weight is lifted. The wire is unclamped at the previous tensioning device and then clamped at the tensioning device being used, and the tensioning wire released. Ties or wraps are secured to the strand at spaced intervals and clamps are secured adjacent the open end of the strand shoes. To remove a formed strand jacks are provided to move the supports for the strand shoes inwardly to release the shoes. If the strand is to be wound up onto a reel the reel is mounted on a carriage which runs on the rails between the two supports. The tension in the strand between the supports is reduced to 35 lbs. and a wire rope anchored to the reel is attached to one of the strand shoes. The carriage has a motor to rotate the reel and brakes for the carriage wheels so that on rotation of the reel the wire rope and strand are wound under tension and the carriage is drawn along the rails. The strand shoe is secured to a cheek of the reel by a bolt and keeper plate. The strand while being wound is twisted one turn in one direction in alternate convolutions around the reel and one turn in the other direction in the other convolutions so that the wires in the strand are alternately on the inside and outside of the strand while being wound to avoid any tendency in the strand to coil or spiral on being unwound. The twisting may be done manually by means of clamps temporarily secured to the strand as it is being wound, or automatically by passing the strand between two grooved rollers mounted in a support vertically and horizontally adjustable on the carriage and which rotates about the axes of the strand one turn in each direction. Between layers of the strand on the reel a galvanised sheeting is provided.