Course content

Buckling and plastic collapse are important potential failure modes for ships and offshore structures exposed to extreme environmental forces. The course addresses analysis and design methods for structural components; bars, beam-columns, stiffened plates, stiffened shells, plate girders and entire frame systems in ships and platforms. Emphasis is placed on providing knowledge of design principles laid down in the most relevant codes and design guidelines for marine structures given by NORSOK, ISO, API, DNV and Eurocode 3.The theory is illustrated with exercise problems on realistic structures. The nonlinear computer program USFOS is used extensively, and one day is devoted to the use of DNV’s software PULSE for buckling assessment of stiffened plates:

Learning outcome

After completion of the course the students shall have a thorough physical understanding of the governing physical phenomena of buckling and plastic collapse and establish simple calculation models for elastic and plastic collapse of components in marine structures.

The students shall be able to:

• Describe the fundamental principles behind code checking according ULS design principles
• Describe the effect of fabrication defects (initial displacements and residual stresses) on the buckling capacity
• Conduct plastic mechanism analysis of beams, frames and plates
• Describe how the plastic capacity is affected by combined loading, notably moment-axial force interaction
• Describe the large deflection behaviour of beams with various boundary conditions
• Understand and describe how elastic buckling stress of columns, plates and shells can be estimated by solving the governing differential equations or by use of the principle of minimum potential energy
• Describe the principles behind 2nd order effects, such as the effective width concept for plates and the tension field theory for plate and box girders in the post-ultimate range
• Understand and describe the basic principles behind the most relevant code requirements for buckling of columns, beam columns, stiffened plates and stiffened shells.
• Calculate the ultimate strength of beams, beam columns and stiffened plates and shells, and conduct code checking by means of Excel spreadsheets.
• Explain the main principles behind the finite element formulation adopted in USFOS
• Conduct nonlinear analysis of components, substructures and offshore platforms with USFOS and interpret the results on the basis their knowledge of the physical phenomena involved.

Learning methods and activities

Lectures, voluntary exercises and use of computer code USFOS and PULS. Exercises and lectures are conducted in English.

Recommended previous knowledge

TMR4105 Marine Technology, Elementary Course, TMR4167 Marine Technology - Structures, TMR4247 Marine Technology - Hydrodynamics and TMR4170 Marine Structures.

Required previous knowledge

TMR4167 Marine Technology - Structures, TMR4247, TMR4170 Marine Structures or similar

Course materials

Lecture notes, exercises and text book: Ultimate load analysis of marine structures, T. H. Søreide, Tapir publishers.

Credit reductions