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The design and construction of Skeldergate Bridge, York

Transcriptions of contemporary accounts relating to the design, construction and operation of Skeldergate Bridge, York.

Foreword

The articles quoted below are contemporary accounts that have been extracted from "The Engineer", a journal dedicated to chronicling and explaining British engineering and technical developments.

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The Engineer, March 11, 1881, page 181

THE SKELDERGATE BRIDGE, YORK.

This handsome bridge was opened yesterday with great ceremony. Great interest was shown in the event, the date of which will be easily remembered as that of a curious coincidence, namely, that it was accompanied by the highest flood known for many years. The foundation stone was laid on the 12th June, 1878, and the contract drawings and specification published in THE ENGINEER for the 11th May, in the same year. Designs were submitted for consideration by Mr. Thomas Page, who had been called in as consulting engineer. Mr. Page, however, died before a final selection was made; but the committee obtained the services of his son, Mr. George Gordon Page, M.I.C.E., whose designs were finally adopted. It is of Gothic character, in keeping with the many architectural features of the city. The bridge consists of five arches, three of which cross the river, two being land arches for the waterside traffic. The centre arch has a span of 90ft.; the two side arches have spans of 30ft. each; and the two land arches have spans of 24ft. each. The 30ft. span next the lodge is a Bascule, or opening bridge, and is raised the [sic] lowered by hydraulic machinery. Beneath this opening bridge is an invert 10ft. 6in. below the summer level, formed of brick in cement, 2ft. 6in. deep, supported on a deep bed of concrete on piles. The bascule bridge is formed with eight wrought iron girders, affixed to a horizontal shaft l0in. in diameter, on which they turn. These girders are each 53ft. 6in. long, the portions overhanging the opening being about 35ft. The tail ends carry counterbalance weights, and the connections to the hydraulic machinery. This consists of two hydraulic cylinders, placed side by side, one for opening and one for closing the bridge. The diameter of each cylinder is 12 in., and the stroke 5ft. 6in. The multiplying power is 4 to 1, giving a travel of 22ft. to the chains. The force-pump is worked directly from the crank-shaft of a gas engine. The accumulator has a ram 15in. diameter and 7ft. 6in. stroke, the pressure being 700 lb. per square inch. The machinery is placed in the abutment behind the lodge. The total length of the bridge, including the abutments of the land arches, is 308ft. 8in. and the width is 40ft. The whole of the work is faced with Bramley Fall stone. The springing line of all the river arches is 9ft. 5in. above the summer level, and the soffit of the centre arch is 13ft. 1in. above the springing line. The gradient of roadway of the river arches is 1 in 108. The centre arch is composed of seven main ribs of wrought iron, springing from cast iron skewbacks. The 24ft. land arches are of cast iron. There are wrought iron trams for heavy traffic from end to end of the bridge, the roadway of which is 24ft. wide between kerbs, paved w1th wood blocks set in bitumen. The footpaths, 8ft. wide, are covered with asphalte. The Corporation invited tenders, as our readers are aware, for the construction of the bridge, but ultimately decided upon intrusting the ironwork to Messrs. Handyside and Co., of Derby, and doing the foundations and masonry by its own workmen, under the direction of Mr. Styan, the city surveyor. Mr. Robert Nunn has been the resident engineer under Mr. Page. The approaches have involved a considerable amount of work, and the total cost of bridge and approaches is about £50,000.

The Engineer, July 28, 1882, page 73 and image supplement (see Image 1)

SKELDERGATE BRIDGE, YORK

We give this week as a supplement a permanent photograph of Skeldergate Bridge, which has already been noticed in our columns, The Act for the making of Skeldergate Bridge received the Royal assent on June 14th, 1875. This empowered the Corporation to construct the bridge and the approaches. The style of the bridge is Gothic or medieval, and is consonant with the ancient remains of the city. Circumstances have made the Skeldergate Bridge different in outline and structure to that at Lendal, but a similar style of architecture has been adopted, and except in the standards of the lamps, every detail is dissimilar. The style is of an earlier period and more castellated. The lodge represents the ancient chatelet or small castle, which in the middle ages was always placed at the head of a bridge for defence at the bascule or drawbridge. The similarity of Westminster Bridge, the Victoria and Albert Bridges at Windsor, Lendal Bridge, and others, proves that the style may be applied as an ornament without detriment to the strength of the structure. The parapet is decorated with alternate suns and roses, the collar of the ancient Knights of the House of York.

The new bridge consists of five arches, three of which cross the river, the two others being land arches for the waterside traffic. The centre arch has a span of 90ft., springing 9ft. 5in. above the summer level of the river. The headway at the crown of the arch above the summer level is 22ft. 6in.; the depth of the ribs carrying the roadway is 2ft. 6in., and the level of the roadway at the apex is 25ft. 7½in., and the level of the footpath next the parapets at the crown of the arch is 25ft. 9in. above summer level. The gradient of the roadway of the bridge is 1 in 108, falling each way from the centre to the abutments. The arch is composed of seven wrought iron ribs springing from cast iron skewbacks bedded in the masonry of the pier. The whole of the ironwork is strongly braced together transversely from one face rib to the other by a system of continuous bracings, nine in number which, in addition to bracing the bridge, serve as continuous cross girders to distribute the load over all the ribs. The roadways of the bridge, with the exception of the bascule, which is planked, are carried on deep corrugated wrought iron plates, 5in. deep, the corrugations being 1ft. 4in. from centre to centre, and flattened top and bottom to get more metal for increased strength, and is made up with Portland cement concrete to the requisite level for laying the trams and the preserved wood pavement, and the asphalte of the footpaths. The preserved wood pavement is composed of blocks 6in. deep, 6in. to 12in. long, and 3in. wide, with ⅜in. spaces between the rows of blocks, run in with asphalte and small gravel. The whole of the wood pavement is bedded on a layer of sand, and this preserved wood pavement is stated to be more lasting than any other wood pavement yet laid down. The surface of the blocks is so hardened that they are rendered impervious to the action of the weather. The parapets, cornices, bosses, and all the ornamental parts of the bridge over all the arches are of cast iron. The Skeldergate 30ft. river span is carried by seven girders, forming a continuation of the top longitudinals of the centre arch; the facia girder having ribs forming a pointed Tudor arch, with spandrils harmonising with the centre arch and the opening out spandrils and ribs of the bascule bridge. The two land arches are each 24ft. span, and composed of nine cast iron ribs, braced together with cast iron bracings. The bascule or drawbridge next the lodge or chatelet has an available opening for the passage of masted seagoing vessels of 30ft. in the clear, and the depth of water over the invert is l0ft. 6in. below the summer level. The ironwork of the movable portion of the bascule is composed of eight wrought iron girders affixed to a shaft l0in. in diameter, upon which the whole turns. The total length of each of these eight girders is 53ft. 6in. They are strongly secured and braced together by six continuous cross girders extending over the opening. They also assist in carrying the platform of the roadway on rolled joists. The hydraulic machinery for opening and shutting the bridge was manufactured and fixed by Messrs. Sir Wm. Armstrong and Co. It consists of two hydraulic cylinders placed side by side, one for opening and one for closing the bridge. The diameter of each cylinder is 12in., and the stroke 5ft. 6in. The multiplying power is 4 to 1, giving a travel of 22ft. to the chains. The hydraulic force pump, adapted to work up to a pressure of 700lb. per square inch, is worked directly from the crank shaft of an Otto's silent gas engine. The accumulator has a ram 15in. diameter and 7ft. 6in. stroke, with cast iron weights, &c., and a self-acting apparatus for cutting off the pressure from the pump when fully charged. The machinery is placed in a watertight. cellar in the abutment behind the lodge.

The Skeldergate bascule bridge is the largest of its kind in the world. The area of the whole surface of the bridge in front of the axis is 1484.3 square feet; the area of the Copenhagen Bridge, the next largest, being 1155 square feet, or 329.3ft. super less than the Skeldergate bascule flap. There is one great point in this bascule bridge which is an innovation in advance of nearly all opening and movable bridges. This is that it has been so designed and arranged that the whole character of the design is not marred by unsightly girders, &c., as is usually the case with opening bridges.
The foundations of the Castlegate pier, invert, and abutments were put in by means of a coffer-dam, so constructed that the lower portion formed part of the structure. The foundations of the piers are 63ft. long by 15ft. 4in. wide, giving an area of foundation for each pile of 812ft. super. The area of the foundations of invert is 1290ft., being 30ft. by 43ft. The aggregate area of the Castlegate abutment, invert, and pier amounts to 3870ft., or a square, the side of which is a little over 62ft. Owing to the treacherous nature of the bottom it was found necessary to pile over a total area of 2850ft. super. The interstices between the main piles were all excavated and dredged out until a good bottom was found, and the whole filled in with Portland cement concrete. The piles of the Castlegate pier and abutment were cut off about 10ft. 3in. below the summer level of the river. The Skeldergate pier and abutments are very similar to those on the Castlegate side. The invert, however, has only 6ft. 6in. of water over it at centre below the summer level.

There are six approaches to the river bridge - two on the Castlegate side having an inclination of about 1 in 40 - the first commencing from Tower-place with a sweep of 140ft.. radius, joining the second from the entrance to the new baths, near Castlemill Bridge, with a sweep of about 340ft. radius, at a point 90ft. from the centre of the St. George's under-bridge. On the Skeldergate side, one from Bishopgate-street, one from Skeldergate, one from Baile-hill, and one from the down-stream riverside property, have the respective gradients of 1 in 40, 1 in 30, 1 in 50, and 1 in 25. The ruling width of the approaches is 40ft., with the exception of the riverside approach, which is 20ft. wide. All the retaining walls of the approaches are faced with Bramley Fall stone ashlar, with a cornice running along the same, surmounted by a solid stone parapet, which has small pedestals growing out of it at distances along its length, and four bold octagonal terminal pedestals, on which are placed the lamp standards and lamps.

In addition to the approaches there are three flights of approach stairs, viz., the St. George's-fields footpath flight, the flight adjoining the St. George's under-bridge, and those adjoining the Skeldergate under-bridge. There is also a flight of stairs to the new terminal bastion, making in all four flights. The tollhouse has a ground floor about one foot above the flood level, which comprises kitchen, scullery, larder, bedroom, large cellar, coal collar, &c., and a passage leading to the hydraulic machinery cellar. On the first floor is the tollhouse proper, bedroom, &c., also steps to the open look-out tower or lantern, the floor of which has a lead flat, and the roof of which is surmounted by a lead flat, flagpole, and chimney. The river wall and deep-water channel upstream have a length of about 72ft. and downstream 270ft. The wall is composed of about forty main piles, 33ft. long and 13in. square. These piles are driven at distances of 10ft., with sheet piling between, secured by a continuous waling at the summer level, a top waling at the level of the quay, and top rail for the protection of the piles. The whole is securely bolted together, and tied back with long wrought iron tie rods fixed into counter piles driven about 20ft. inland. The foundations of the wall are of concrete, and are carried out down 10ft. 6in. below the summer level. Above this level the wall is faced with Bramley Fall ashlar backed with concrete. In order to keep the navigation in its proper course, and to protect the cut-waters of the stone piers from collision, a set of dolphin piles and guide booms have been placed up and down stream.

The total length of the bridge, including the abutments of the land arches, is 308ft. 8in., and the total length from the end of one retaining wall to another is 861ft. 8in. The outlay on the bridge, approaches, lodge, river wall, deep water channel, land, &c., has amounted to £56,000. The foundation stone was laid on the 12th June, 1878. The bridge was opened to the public on the 10th March, 1881. The bridge was designed and carried out under Mr. George Gordon Page, M. Inst. C.E. London, Mr. Robert Nunn being the resident engineer. The Corporation originally invited tenders for the construction of the bridge, but ultimately decided to divide the work, entrusting the ironwork of the superstructure to Messrs. Handyside and Co., and doing the foundations and all the other works by its own workmen, under the direction of Mr. Styan, the city surveyor.