GB584768A - Improvements in floating bridge construction - Google Patents

Abstract

584,768. Pontoon bridges. MAUNSELL, G. A. Nov. 18, 1944, No. 22934. [Class 20 (i)] [Also in Group XXXIII] A floating bridge comprises 'a number of pontoons placed end to end, axially connected by ball and socket joints, tightly bound together longitudinally by tensioned cables, and secured transversely by ground moorings. The terminal pontoons are connected to the shore by hinged girder spans, one of which is shown at A in Fig. 4. The shore end is carried on a roller' carriage F hauled back by ropes attached to a weight L, so maintaining a constant tension in the train of pontoons. A long expansion joint is provided at E. The pontoons designated P, Q --- V, are arranged to have their greatest width on their normal waterline for lateral stability, have a streamline cross-sectional contour underneath to reduce resistance to cross-currents, and low freeboard together with a deck hog-backed transversely to facilitate the overspill of wave crests. They are provided at one end with a knob K and at the other with a socket C into which the knob of the adjoining pontoon fits, and are held firmly together by the tensioned cables H. The roadway D is elevated to be clear from waves washing over the decks of the pontoons. The short junctions of roadway J between adjacent pontoons are articulated to conform to the relative movements of the pontoons. One or more pontoons are submersible to provide a channel for shipping, the submersion being effected by flooding a centrally dispersed chamber in the pontoon of such a size that when completely filled the whole pontoon just loses buoyancy. Excessive submersion is prevented by stools on the sea bed on which the pontoons rest or suspended weights O which on touching the bottom arrest the submersion of the pontoon. The ball and socket joints and shore arrangement of the girder spans allow the submersion without disconnecting any of the pontoons. The submerged pontoons are raised by expelling the flooding water with compressed air. The submersible pontoons are arranged to have their centre of gravity below the centre of buoyancy when submerged, for stability. All the pontoons have fenders N and the moorings are designed to drag before the mooring cables would break to minimise damage in the case of collision with a ship. Suitable dimensions of pontoons for a mile long crossing are given as length 500ft., beam 60ft., and displacement 6,000 tons.