Arpley Bridge, Warrington
This is a 180 ft span girder bridge across the River Mersey in Warrington. It is of particular interest because it retains an unusual design of wrought iron box girder from the early 1850s.
It was constructed in 1853-4 for the Warrington and Stockport Railway.[1]. The engineer for the construction of the line was John Lister, and an article in The Engineer credited him with the design of the bridge. In fact Edwin Clark was the designer (see below). The ironwork was constructed by the nearby Bank Quay Foundry Co.
The W&SR was later absorbed by the London and North-Western Railway.
1853 '... The bridge is one well worthy of notice; being designed by Mr. Edwin Clarke, a gentleman whose skill was signalized in connexion with the tubes of the Britannia-bridge, across the Menai Straits. The present structure is to carry the Warrington and Altrincham line across the Mersey, near the bridge at Warrington, and is 200 feet in length. It will be carried across with three girders, the middle girder to be sixteen feet in depth, and those on the outside twelve feet each. As fitted together in the foundry-yard it very much resembles one of the tubes of the Britannia, but is open at the top. ...'[2]
By 1908 the bridge was no longer suitable for the weight of locomotives needing to use it, and it was decided to strengthen it, and also to widen it to current loading gauge standards. This had to be done while maintaining traffic on the railway. The work was the responsibility of William Dawson, who presented a Paper on the subject to the I.C.E. in 1911.[3].
The 1911 Paper also describes the design of the original bridge. There were three large wrought iron plate girders, 190 ft long between bearing centres, with a camber of 9". The central girder was of the box type, 16 ft 9" high, with an unusually wide bottom flange (6 ft). The outer girders were of the single plate web type, 13 ft high. Walkways were provided outboard of the outer girders, supported on wrought iron cantilevered brackets. The railway lines were carried on 9" x 9" timber beams, spanning the full width over the girders and bolted to the bottom of the girders.
An interesting feature was the use of iron castings riveted to the top flange to accommodate compression loading. The castings were each 8 ft long, of semi-circular section with horizontal flanges for bolting to the wrought iron top flanges, with a wall thickness of 2.25". The castings had vertical flanges at each end, allowing them to be riveted or bolted together. The castings are visible on top of the central girder in the high resolution photograph here. See above for lower resolution version.
One of the options considered for strengthening the bridge was the provision of cast iron piers set in the river 120ft apart. Dawson had applied a similar concept when he strengthened the Conway railway bridge in 1899. There were various objections to this, including the fact that to some extent the top flange would be subject to tension. Another shortcoming is that it would not have addressed the narrow passages between the girders which represented a danger to track workers.
The method adopted for strengthening and widening involved replacing the two outer wrought iron girders by steel trusses of the Linville type. The original central box girder was retained, but its loading was partly transferred to the two outer girders by means of overhead lattice girders, in order to reduce the stresses in the bottom flange. This high resolution photo shows the arrangement of the girders. The iron castings on the top of the central box girder are visible.
Another Geograph photo and map here.
During the reconstruction work, traffic used one side of the bridge while on of the new 135-ton girders was assembled on the other side, using an overhead travelling crane running on rails at 10 ft gauge. It was assembled with the same large 9" camber to match the retained centre girder. On completion the new girder was temporarily slid across towards the centre girder to allow removal of the old outer girder.
To remove the old girder it was necessary to move it inboard to align with the existing railway tracks. This was a delicate operation due to the limited transverse stiffness of the girder (the top flange being only 2 ft wide). Removal involved supporting the western end on a low railway wagon, and then bringing a pair of barges under the eastern end, with suitable staging provided to lift the end as the tide rose. A locomotive then pulled the girder across. As the tide fell, support of the eastern end was transferred from the barges to another truck running on temporary trestles. Extra precautions were taken because of the lack of transverse stiffness of the old girder. These ate into the limited time for movement allowed by the tide. However, it was found the girder was much stiffer when supported on the barges, so the precautions were dispensed with on the second girder, and the crossing took just 8 minutes instead of 45.
The work also involved widening the abutments to accommodate the wider spacing of the girders. Also, before altering the second side of the bridge, it was necessary to raise that portion - 320 tons of old centre girder, old outer girder, floor, and rails - by 7", and slew the whole assembly across by 2 ft 7", without disconnecting the rails. The assembly was jacked up and lowered onto greased rails on the abutments, and the whole jacked across. This was done on a Sunday, between trains.
For information about the location, and history of the railway in the vicinity of the bridge, see here and here.
1854: Late Delivery
'WARRINGTON AND STOCKPORT RAILWAY. HALF-YEARLY MEETING. (FROM OUR OWN REPORTER.) ..... Mr. H. L. TRAFFORD asked several questions from the company's engineer, Mr. Lister. He said it appeared to him that there had been great delay in building the iron bridges over the Mersey at Warrington, and the Duke's canal at Altrincham, the effect of which was, as the shareholders had heard, that the opening of the line throughout had been retarded, and the consequent connexion with the St. Helens and Garston Railway at the Warrington end, and with the Manchester South Junction and Altnncham Railway, at the Altrincham end, had been delayed. He should like to know where the blame really lay, he believed it did not rest with the engineer, and he exonerated the directors. The specifications and drawings were out and handed to the contractors long ago. Mr. Lister said they were handed to the contractor, who let them in September, 1852, limiting their completion from that time to ten months, within which time the Bank Quay Company (to whom the iron work had been let) were to have completed their portion of the work, but they had not done so.
Mr. TRAFFORD: Then, am I to understand that it is the Bank Quay Company who are to blame.
The ENGINEER: The Bank Quay Company are the parties really and only to blame. Every means in my power have been used to get the work out of their hands: and I came down from London purposely to satisfy myself whether the delay rested with them.
Mr. TRAFFORD: Was there any penalty attached for non-completion of the work?
The ENGINEER: They are liable to the contractor for non-completion of the work. We expected to have opened the line throughout in August last.
A SHAREHOLDER: I have been told that the bridge over the Duke's Canal at Altrincham, when put up, was upwards of a foot too short, and had to be lengthened. Was that so?
The ENGINEER replied, that Mr. Robert Stephenson had said it was long enough, but though it had been lengthened that had not caused any delay.
Mr. TRAFFORD observed, that, as shareholders, they were suffering considerably from the non-completion of these works at the time specified.
The ENGINEER: The real cause of the delay I believe to be this: Immediately after the contract was entered into, the price of iron rose considerably, and all along they have been waiting for a better market.
Mr. TRAFFORD : And putting you off from time to time by telling you a parcel of falsehoods ?
The ENGINEER: I am afraid that is the case.
Mr. TRAFFORD: Then I consider it is most disgraceful conduct.
Mr. BARRATT asked if there was no time fixed for the completion of the contract by Mr. Brassey.
The ENGINEER replied that as Mr. Brassey, who was a very extensive railway contractor, had always completed his works within the time specified, it was not thought necessary to have any fixed time between the company and him, for the fulfilment of the work.
The CHAIRMAN: Mr. Brassey being a very large shareholder, we thought we had the very best guarantee for the completion of the work at the time stated. Some very strong letters had passed between the directors and Mr. Brassey.
Mr. BARRATT : Then are we to understand that this company has no contract to have the work done at any fixed time?
The CHAIRMAN replied that such was the case.
Mr. BARRATT then asked under what agreement the company stood, as to the expense of locomotive power. Was there any agreement between that and any other company, for the working of the line?
The CHAIRMAN said there was a temporary arrangement with the St. Helens Co. ; but there was no reason why it should not be abandoned almost any day.
Mr. BARRATT said the object of his Inquiry was merely to ascertain their true position. Mr. HEATH asked what was the gross amount of share capital and loans?
The CHAIRMAN said it was about £223,000.
Mr. HEATH said it was very satisfactory to know that they were not called upon to raise further sums of money by mortgages. It was stated that the amount put down for parliamentary expenses, included the payment for a piece of land originally intended for a station, at Manchester, but was subsequently lost, on their failing to procure the act of parliament.
Mr. TRAFFORD again drew attention to the state of the iron bridge over the Mersey, and asked when that "thing" was likely to be completed?
The ENGINEER said it would, or should be, finished in a month. The Bank Quay Company had to-day cleared it out of their hands.
The CHAIRMAN observed that a few days ago, he met Mr. Edwin Clarke, who designed the bridge, and who had immortalised himself by the bridge crossing the Menai, and that gentleman said he was quite confident it would be finished in a few weeks. ....'[4]