EnginSoft Partnership
  next

Simulation and optimization of auxiliary buoyancy tanks for large jacket

PROBLEM OVERVIEW

Tanks are "framed" structures which are connected to the jacket in order to guarantee the required buoyancy during the jacket launching stage, as well as the subsequent self up-ending and floating phases.

Structural Dimensions: Total length: 53 m; total width: 49 m
  Cylinder outer diameter: 5.0 m, 5.6 m
  Buoyancy: 47,000 kN (4,700 t)
NUMERICAL APPROACH
  • Optimization of cylindrical shell thickness as a function of the forces induced on the Buoyancy Tanks (BT) during various phases (slamming, towing, jacket launching and docking, BT removal)
  •  Shell buckling verification and definition of an optimized stiffening ring distribution (light stiffeners along the shells to prevent buckling risk, heavy stiffeners where concentrated loads act)
  • Simulation of tank nodal connections (dedicated finite element models of nodes, analyzed for the required simulation conditions)
  • Simulation of temporary jacket connections
RULES AND REGULATIONS
  • DNV Classification Notes 30.1 "Buckling Strength Analysis, July 1995 
  • DNV Rules for Planning and Execution of Marine Operations "Lifting" 
  • AISC "Manual of Steel Construction – Allowable Stress Design" 9th edition API-RP-2A LRFD
  • Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms – Load and Resistance Factor Design
CUSTOMER

Tecnomare - Italy

AIM
To maintain a dry-weight/buoyancy ratio under 0.25 in order to guarantee the proper dynamic behavior of the jacket during the launching and self up-ending phases. This goal was achieved with a dry-weight of 10,800 kN for each tank and a weight/buoyancy ratio of 0.23