OVERVIEW

The course deals with the application of the finite element method in scantling analysis and design of ship and offshore structures. It includes first engineering principles of the structural assessment methods as well as hints for practical applications according to recent design practices for static and dynamic analyses of the whole hull, of its structural elements as well as of its outfitting components.

AIMS AND CONTENT

LEARNING OUTCOMES

The unit aims at illustrating and enabling to apply advanced criteria and methods for limit state checks of ship and offshore structures in general, according to shipbuilding fundamental principles and to up-to-date classification societies rules in a goal-based standards perspective. Typical case studies are proposed either applying analytical and finite element methods, presenting loading actions on structures as well as global and local checks generally adopted in everyday design working practice.

AIMS AND LEARNING OUTCOMES

Students will be able to apply the finite element method to ship structural design and analysis of ship and offshore structures. Indeed, students will apply to the proposed study cases the concept of limit state design and will be able to carry out various structural design checks, including not only usual robustness checks but also checks typical of in-service condition assessments of merchant ships and naval vessels as well as offshore structures.

Students will be able to implement up-to-date structural design process and technical management approaches typical of shipbuilding industry to guarantee the robustness of a ship construction by identifying boundary conditions, appropriate check criteria of the general scantling problem on the basis of limit states suitably selected with reference to rules, functional and economical requirements, being then able to solve it using knowledge and approaches presented during lectures after selecting relevant variables, limit states and operative requirements. By means of a top-down approach nowadays allowed by numerical calculations, students will be able to describe interactions among structural components of the hull though simulating at the same time the construction as a whole.

In general, students acquire basic skills to be able to use a general purpose, commercial finite element software for structural applications. Students will be able to report the results of their analyses supporting and arguing their design choices.

The following soft-skills will be also gained: alphabetic-functional skill and personal skill at a basic level in developing proposed case studies that simulate real design problems to be presented for examination in the form of professional technical reports.

PREREQUISITES

Knowledge of main theories of structural mechanics (advanced course) and machine design

TEACHING METHODS

Lectures and guided exercises in IT class. Totally, 90 hours of lectures, divided 60%-40% approx.

SYLLABUS/CONTENT

A well-rounded knowledge is provided from theoretical fundamentals with application examples of increasing complexity to pursue the learning aims.

Introduction: structural mechanics models (beam, shell theory), finite element method. Limit state checks and application of structural models to ship and offshore structures

Modern rule checks: IMO Goal Based Standards, rule scantling checks, general principles and idealization of structural components, models selection depending on check types, definition of actions and application to structural models, relevant implications and approximations.

Structural modelling: analytical and numerical models, 2D and 3D models (frames, grillages, plates, orthotropic plates, stiffened panels, complex models). Finite element modelling strategies. Local and global models, primary, secondary and tertiary response, interaction of structural models.

Analysis types: static linear, buckling and modal (Eigenvalues), collapse (nonlinear), dynamic in time domain, stress concentrations and fatigue analysis. Post-processing, critical analysis and presentation of results.

• Planned exercises (to be discussed during the examination):

1. Introduction to FEM software (Kirsch problem, frames, grillages, etc.)
2. Scantling checks on a typical stiffened panel (e.g. deck panel with boundary conditions on bulkheads and side shell)
3. Scantling check of a ship transverse section (e.g. web frame of a longitudinally framed ship)
4. Collapse analysis of a stiffened panel
5. Three holds/tanks model according to classification societies rules (e.g. according to IACS H-CSR, Ch.7)
6. Scantling checks of stress concentration factors and fatigue assessment of typical structural details (including weld seam scantling)
7. Application example of a dynamic analysis
8. Analysis of hull outfitting items (3D models and pressure vessels)

RECOMMENDED READING/BIBLIOGRAPHY

1. Regolamenti per la costruzione e la classificazione delle navi delle principali Società di Classificazione (www.iacs.org.uk) con particolare riferimento ai regolamenti Harmonized Common Structural Rules (IACS)
2. Hughes OF, Paik JK (2010): Ship structural analysis and design, SNAME (ISBN No. 978-0-939773-78-3)
3. Lamb T. Editor (2004): Ship Design and Construction, SNAME (ISBN 0-939773-41-4)
4. Lewis EV Editor (1988): Principles of Naval Architecture, SNAME (ISBN-13: 978-0939773008)
5. Mansour A, Liu D (2008): Strength of Ships and Ocean Structures, SNAME (ISBN No. 0-939773-66-X)
6. Okumoto Y, Takeda Y,· Mano M, Okada T (2009): Design of Ship Hull Structures, Springer (ISBN: 978-3-540-88444-6)

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

As per Polytechnic School calendar

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

Oral exam (including discussion of exercises carried out during the course). Further details will be given during lectures.

ASSESSMENT METHODS

Exercises will be discussed and checked during oral examination considering structural idealization issues, input for modeling and analysis of results. A short technical report is required and it will be checked for completeness and clarity. Oral examination will start discussing the exercises and will continue to ascertain comprehension of theoretical content of the course.