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The University of Southampton

SESS6071 Marine Structures in Fluids

Module Overview

This module provides the fundamental aspects of advanced concepts associated with structural integrity and fluid-structure interactions for ships and ship like floating offshore vessels such as FPSO and FLNG, hitherto referred to as floating vessels. There are two assignments which integrate the structure and fluids and support understanding of the concepts taught through applications to real floating vessels.

Aims and Objectives

Learning Outcomes

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

  • The potential applicability of fatigue, fracture, and fluid structure interactions to the structural design of floating vessels,
  • The concepts and potential application of rational structural design procedures.
  • Safety aspects in structural design.
  • The concepts in long-term structural performance including fatigue and fracture aspects.
  • The fundamentals in fluid-structure interactions, through seakeeping and hydroelasticity methods
  • Deterministic and statistical measures to assess wave loading, floating vessel behaviour in different sea states and to compare performance between ships.
  • The dynamic behaviour of differing floating vessel types through synthesis of concepts into engineering application and design.
  • Analysis, critical assessment and the nuances of dynamics in relation to floating vessel design and operation.


Part A; lectures on: Fluid-Structure Interactions • Introduction to hydroelasticity theory. • Dynamics of flexible beamlike structure in vacuo. • Principal modes and natural frequencies. • Hydroelastic approach to still water problem. • Hydrodynamics of regular waves • Strip theory, boundary value problems. • Fluid actions in equilibrium axes. • Hydrodynamic coefficients • Generalized equation of motion in seaway. • Responses (bodily motions -seakeeping, distortions, bending moments, stresses) in waves. • Random seas and responses in random seas. • Criteria for comparing floating vessel forms - slamming, deck wetness, etc.. Part B; lectures on: Structural Integrity • The rational structural design of floating vessels: - Levels of structural design processes - Limit state design including ultimate and fatigue limits and load effects • Fatigue of floating vessel structures: - Basic concepts of fatigue, fatigue damage mechanisms, S-N methodology, local strain methodology - Life time load determination, wave induced loads, stochastic combination of loads - Load effect determination, FEA approaches and choices of elements, meshing, structural details - Fatigue assessments, voyage simulation behaviour, long term fatigue damage • Fracture modelling in ship and offshore structures: - Fundamental concepts - energy-based and stress intensity based approaches - LEFM, modes of crack extension, useful K solutions, fracture testing, life modelling The integrations of Parts A and B will take place through two group assignments, with contributions and support from staff at Lloyd’s Register. Each assignment is weighted equally, together making 100% of the assessment of the Learning Outcomes. Wave-induced Loads Assignment; where the students perform predict wave-induced loads on a real ship using quasi-static and fully coupled dynamics (hydroelasticity) analyses and design a flexible model for experimentation. Ship Fatigue Life Assignment; where the students analyse stress records (measured or predicted) of a real ship in order to predict the fatigue life of a structural detail.

Learning and Teaching

Teaching and learning methods

Teaching methods include • ~6 lectures on hydroelasticity and fluid structure interactions, including 2 guest lectures on industry application • ~10 lectures on fatigue and fracture related to ship structures • ~5 lectures on design methods • 14 supervised design office sessions focused on the two assignments Learning activities include • Directed reading/independent learning • Example sheets for problem solving exercises • Report-writing for the 2 group assignments • Application of structures and fluid-structure interactions related knowledge to real floating vessels through the two assignments • Use of commercial and academic software to perform the two assignments

Completion of assessment task54
Practical classes and workshops14
Preparation for scheduled sessions14
Wider reading or practice16
Follow-up work30
Total study time150

Resources & Reading list

Blackboard. Resources and reading list: Available on blackboard


Assessment Strategy

Referral Method: There are two assignments in this module. If the mark achieved for the module is less than the module pass mark then a referral will be required in one or both assignments: If the marks for both assignments are less than the module pass mark then both assignments must be referred. Otherwise the assignment scoring less than the module pass mark should be referred and the passed assignment marks will be carried forward.


MethodPercentage contribution
Continuous Assessment 50%
Final Assessment  50%


MethodPercentage contribution
Set Task 100%

Repeat Information

Repeat type: Internal

Linked modules

Pre-requisites: FEEG2005 and SESS2015

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