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GWR Route: Banbury to Wolverhampton

Solihull Station: gwrs1567

Dynamic testing of the new plate girder bridge over Hillfield Road, halfway between Solihull and Widney Manor Stations

Dynamic testing of the new plate girder bridge over Hillfield Road, halfway between Solihull and Widney Manor Stations. Four King Class locomotives coupled in pairs and running side by side tested all of the seventeen new bridges after the quadrupling of the track between Olton and Lapworth was completed in May 1933. Here 6017 King Edward IV and 6005 King George II are steaming in company with No.6001 King Edward VII and 6014 King Henry VII. The 60XX King Class locomotive had a maximum axle weight of 22 tons 10cwt and with their tender, each locomotive had a total weight of approximately 136 tons loaded.

At this time steel plate girder bridges were considered to be the most economical and efficient type of structure for spans ranging from 15 to 80 feet. The normal arrangement was the ‘through floor’ arrangement where the bridge floor was carried on the bottom flanges of the main girders as this maximised the road headroom beneath. The flooring system was important as poor drainage could lead to corrosion of the steelwork. Here what is termed a three girder, free flooring system was constructed with regular cross girders at right-angles to and resting on the bottom flange of the main girders. Two rail girders of similar size to the cross girders rested on the lower flanges of each pair of cross girders, arranged so that each one provided maximum support by being directly under the rails positions and finally a steel plate floor was riveted above. One inch of asphalt was spread over the plate floor to prevent water ingress and approximately four inches of ballast laid above, on which conventional trackwork was constructed. This produced a simple and economical arrangement with good structurally capabilities, but was limited to double track spans of 36 feet and single track spans of 60 feet.

The reason for these span limitations was that in order to have sufficient structural strength, the main girder size needed to increase as the span increased. Above these span lengths the typical height of the main girder became so large that it infringed the Board of Trade clearance requirement which stated that ‘No standing work is to be nearer to the side of the widest carriage in use on the line than 2ft 4in and this at any point between the level of 2ft 6in above the rails and the level of the upper parts of the highest carriage doors’. This same regulation explains the offset position of the bridge parapet on the outer side of the main girder.