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MAROFF-2-Maritim virksomhet og offsh-2

Fundamental investigations of violent wave actions and impact response

Alternative title: Fundamentalt studie av kraftige bølge slag og konstruksjons respons

Awarded: NOK 16.0 mill.

The SLADE KPN project is investigating the response of ocean structures under violent wave impact. The objective is to (1) extend the present knowledge in the area, (2) derive how the response of the structure affects the loads it is being subject to, (3) develop experimental techniques to measure these effects, and finally to (4) develop numerical methods such that the industry can take such effects into account in their development of new ocean structures. The project has carried out advanced experiments representing classical ocean structures in steel and concrete. Hydrodynamic properties and 'global' structural response have been modelled according to present state-of-art. Local deformations in steel plating and concrete shells has been modelled and included in the tests. This is based on cross-discipline collaboration between the model testing teams at SINTEF Ocean and the materials- and nano-technology teams at SINTEF in Oslo. In addition ? to measure the effect of local deformations without sensors themselves influencing the results, SIMLab at NTNU have used their experience with camera-based techniques for measuring response of structures under impact or blast loading. Furthermore, the project has developed experimental techniques to measure the incoming wave field during impact on the structure. I.e. investigated use of laser and camera techniques to measure the temporal and spatial evolution of the entire incoming wave field in front of the structure. With respect to theoretical developments, SLADE has extended the theory of hydro-elasticity to hydro-elasto-plasticity, i.e. when the wave impact leads to permanent deformations in the structure. This development is now extended into development and qualification of practical analysis procedures that are better suited for industry use. Preliminary findings - and projections towards future analysis procedures, has been presented to project partners and received very positive response.

One of the fundamental unresolved problems in design of large volume ocean structures is the accurate prediction of structural response due to wave slamming. Establishing a practical and reliable solution to this problem would make a significant contribution towards safer and more cost-efficient marine operations and installations. Real progress within this field cannot be achieved without the systematic study of practical experience, combined with the development of experimental, numerical and analytical methods. The critical waves causing the largest horizontal slamming loads on ocean structures originates from typical 100 year storms in steep and high sea states. These wave conditions contain massive wave breaking. The present project does not aim at modelling the full problem numerically. The present project will study the local structural response due to steep wave impacts. The emphasis is structural response due to wave slamming on column structures, like offshore and offshore wind structures. The emphasis is on the local structural response due to this type of impacts. This means areas covering parts of a column or walls of the living quarter. The present project will contribute to new knowledge in the field of hydroelasticity and fluid structure interaction. The knowledge on local hydroelastic response of steel structures due to slamming on calm water will be extended in order to describe large plastic deformations. The studies will be compared with original drop tests at a large scale. The knowledge from the drop tests will be used to define original wave tests with flexible local models. These model tests will be compared with a new numerical procedure for calculating response based on slamming force measurements. This in turn will qualify a new procedure for response calculations which can be used by industry.

Funding scheme:

MAROFF-2-Maritim virksomhet og offsh-2