GB1511846A - Cellular concrete off-shore structures - Google Patents

Abstract

1511846 Fabricating concrete offshore structures SEVEN SEAS ENG Ltd 7 Oct 1975 [7 Oct 1974 5 April 1975] 43402/74 and 14036/75 Heading E1H [Also in Division B7] A cellular concrete offshore structure is fabricated completely afloat using a raft formed from a plurality of pontoons which have been built ashore previously, the raft having formwork which permits the pouring of concrete to initially build the base of the offshore structure. When the base has been built afloat in relatively shallow water it is towed to a deeper water location where the concrete offshore structure is completed. In one embodiment, each pontoon has a hexagonal deck 10 which is upwardly domed (Fig. 2) and strengthened by radial webs 12. The deck carries internal formwork 11 which gives the pontoon intrinsic buoyancy and the pontoon is stiffened by a framework comprising stanchions 14 horizontal top members 15 and cross braces (not shown) between the stanchions 14. A steel skirt 18 depends from the deck 10 and the under deck space 10A is in communication with a pipe 13. The pontoons which will be on the periphery of the raft each further include an upstanding bulwark member (not shown) so that when the raft is formed by joining the pontoons together it has a continuous bulwark around its periphery which keeps the deck dry and acts as an external formwork. When pouring wet concrete air may be introduced into the spaces 10A to reduce bending moments in the raft. When grounded at its operational site the skirts 18 buckle to accommodate ground irregularities and afford protection against scouring. Water under pressure may be applied to the undersurface of the decks 10 of the raft to facilitate removal of the offshore structure from the seabed.