In January 2005 Besix undertook to design and build a new LNG marine facility located on Bioko Island, for client Bechtel. The scope included an LNG loading platform and berth, a marine operations platform, a small boat dock, and a trestle connecting the loading platform to a cable stay bridge carrying an onshore piperack. In addition the scope included all topside works such as piping, equipment, utilities and support buildings located on the two platforms.
The project was completed successfully in January 2007 with the first LNG berthing at the facility on 24 May 2007.
Basic design requirements
The jetty was designed to accommodate vessels of 160,000 m3 capacity and it must be able to withstand 100-year storm events with maximum wave heights of up to 5.6 metres.
Hmax is assumed to be equal to 1.85 Hs.
Design was based on American Petroleum Institute (API) and ACI standards. The design life of the jetty is 20 years. In terms of steel pile design this translated as 6 mm corrosion allowance within the splash zone.
Reinforced concrete structures were designed for a crack width of 0.2 mm.
Post-tensioned single-T beams were designed as class two members with a requirement of zero tensile stresses under sustained dead and superimposed dead loads. Under dead plus live loads tensile stresses were permitted as long as the tensile capacity of the concrete was not exceeded, hence ensuring that the sections remained un-cracked under all loading conditions.