Design analysis and optimization of offshore module

Abstract

The structural analysis of topside module presents many technical challenges that have to be designed to overcome in efficient manner to meet a proper weight and strength control with respect to transportation, installation and operation. The topside modules form an integral component of the structural system of the platform. Fabrication and installation tolerances as well as testing of key components are very important.

Structural analysis of offshore structure above the sea bed is highly exposed to live and environmental loads. To achieve intended result with respect to design rules and standards the following acceptance criteria shall be considered.

• The verification of an element consists of comparing its characteristics resistances to a design force or stress. It includes: • A strength check, where the characteristic resistance is related to the yield strength of the element. • A stability check for elements in compression related to the buckling limit of the element. • An element is checked at typical section (at least both end and mid span) against resistance and buckling. • Tubular joints shall be checked against punching. These checks may indicate the need for local reinforcement of chords using larger thickness or internal ring stiffeners. • Element should also be verified against fatigue, corrosion, temperature and durability wherever relevant.

The ongoing developments of technologies and studies on offshore topside structure are necessary for long-term performance of the structure. This master thesis presents the design and analysis of offshore topside module which has a dimension of 40m x 20m x 20m length, width and height respectively. The mail goal of this master thesis is optimization of structural member profiles and this thesis illustrates the strategy or procedure of performance of a design optimization of the topside offshore structure considering all the construction phases.

On this report in-place, lifting and transport analysis are performed using SESAM software package for global analysis of the topside structure.

However local analysis of lifting padeyes and joints will be performed. The global and local analysis covers the ultimate limit state and is carried out in accordance with prevailing design rules and standards.

Key words: • Topside module • Design Optimization • Construction Phases • Environmental loads