A KENT BRIDGE
Class 40 Bailey Bridge over River Meuse at Berg (K.613693)
Constructed by 15 (Kent) GHQ Troops Engineers The design of the bridge was governed by the following considerations:
(b) Variation of water level.
(c) Time' available for recce.
(d) Time allowed for construction.
(e) Stores .available.
As regards, (a) the site was that of a flying ferry with a good approach road to each bank. To use the ferry site\ at both sides would have meant an awkward turn at the east end of the bridge and to avoid this the west approach was shifted some 50 yd downstream. This involved the making of about 30 yd of new road and also meant that the pontoons were lying at some 25 degrees to the run of the current. The drive on and off, however, was greatly improved.
As regards (b) only vague details were known originally, and it was believed that the water level would vary between zero and 16 ft. In fact, it varies between 0.98 and 19.16 ft, and the design, therefore, was not ideal.
The design worked out was on the basis of double landing bays at either end to overcome the 16 ft range.
(c), (d) and (e) are related. Reconnaissance was not done until 5th November, 1944, and the bridge had to be open to traffic by 9th November, 1944. There was no time to get in touch with local authorities and make sure of water levels. One design had to be made and adhered to. Owing to a local shortage of accessory and Class 40 landing bay lorries there was only a certainty of double landing bays at one end.
Probable depth of low water meant that pontoons had to be well away from the bank to avoid grounding at lowest water. This necessitated a Bailey crib being built with an approach span. The crib was placed so that the decking should be well clear of the water at highest flood. From it ran double landing bays with a 110 ft TS inshore span and a 60 ft DS offshore span. The intermediate pier was a 6-pier type with Class 70 distributing girders and three Class 40 landing bay transoms across which 16 transoms were laid carrying the grillage which in turn carried the bearings and end posts of the two spans. The single 110 ft landing bay on the west bank would not cope with the full range of water level, but it was proposed to deal with very high or very low water levels by closing the bridge temporarily and jacking up or down at the inshore end and inserting or removing packing under the baseplates.
Unjacked, the bridge could deal with a low water level of 2.38 ft up to a maximum water level of 14.23 ft. Above that level with bank seats raised the bridge could remain open to a level of 16.6 ft, after which the west approach road would have become submerged.
The slide of the bridge was taken up as follows:
The single west landing bay had a maximum slide of 9; in and this was taken up by the bearings of the inshore end of the span sliding on base plates. For the double east landing bay the inshore end of the inshore 110 ft landing bay was fixed by span junction posts, the outer end of this bay on the 6-pier raft took the slide 'which was 5% in by the bearings sliding on a steel plate in lieu of baseplates.
Construction of the bridge was slow due to the following causes:-
(a) The stores were ordered by another formation for a different type of bridge and vital additional stores had to be ordered. Some of these, in particular crib sets and accessory lorries, were amongst the last to arrive.
(b) Reconnaissance was being carried outiand design prepared while the first stores were being unloaded.
(c) The 110 ft TS approach span on the east bank presented considerable difficulty owing to the lack of building space and the height of the pier on which the span had to go.
(d) The launching of the 110 ft inshore landing bay on the east side was particularly difficult.
Launched as separate 11o ft DS girders they were most unwieldy. One fell over at one stage during the night and getting it up again took time. Then a mistake was made. The span junction posts were attached to the separate girders, but these could not be pinned into the junction link until the fixed 110 ft span had been jacked up, thus allowing the offshore side of the junction links to be levered, allowing room to insert the pins.
(e) The river rose 4 ft to 5 ft during construction, and the speed of the current increased from 2.7 to 4.0 knots.
Reconnaissance and stores off-loading commenced at 0800 hrs on 5th November and the bridge was open to traffic at 1610 hrs on the 9th November.
The following are interesting figures:-
(a) Length of bridge between end posts: 626 ft
(b) Weight of bridge: 251 tons
(c) Maximum water level which bridge could take with bankseats normal: 14.23 ft
(d) Maximum water level which bridge could take with bankseats raised :16.60 tt
(e) Lowest water level which bridge could take with bankseats normal and no slope worse than 1 in 10: 3.25 ft
(f) Lowest water level for which bridge was designed with bankseats normal: 2.38 ft
(g) Man hours to construct, including off-loading, approaches and wearing surface 9170