The Gravity Base Structure (GBS) was constructed in a dry dock at Algeciras, Spain. Two LNG tanks, was installed inside the GBS, and was fabricated in a coordinated parallel with the GBS construction. The major part of the Topside modules, off-module equipment and berthing structures was hooked-up and pre-commissioned in the dry dock before tow-out.
Scope of work
The GBS is subject to earthquake loads in addition to waves, water and solid ballast pressure. The foundation area of the GBS is 16.000 m2 and the concrete volume is spprox. 95.000 m3. The water depth is 29m. and the external dimensions (Length-Width-Height) of the GBS are 180 x 88 x 47 m.
Two mooring structures (Mooring Dolphins) were built in Venice and placed close to the main terminal tank structure.
Multiconsult has performed detail engineering of the concrete gravity base substructure. The engineering of the concrete substructure was subcontracted to Multiconsult and partners, working as an integrated discipline in the Aker Kvaerner engineering organization through the front end and detail engineering phases of the project. The services also included follow on engineering and site supervision from the engineering team.
The ALT GBS was designed by means of Multiconsult’s inhouse postprocessor and design program system MultiCon, based on global finite element analysis by ANSYS. By means of this software, a very efficient design procedure was developed. The procedure provides the designer a very good understanding of the structural behavior for complicated load situations. The flexibility of this design procedure enabled the design team to incorporate changes in environmental loads and requirements from topside at a late stage in a very short time without reducing the quality of the final design.