Project Dipl.-Ing. Jens Ley
Assessment of loads and the structural behaviour of ships in severe seaways
Even in times of modern shipbuilding total losses of ships occur as a result of global structural failure. Possible reasons vary and, frequently, the reasons cannot be clearly identified. However, extreme sea loads are often the reason for such losses. Especially large and fast container ships with large open decks require detailed structural strength analyses. The investigation of real sealoads and corresponding structural responses are essential for ship design.
For this reason, numerical methods or simulation techniques are being developed which make it possible to reliably forecast sea loads and provide transient structural solutions. First developments were made in the EU project Extreme Seas. These developments are continued and shall include the following aspects:
- Dynamic effects in structural solutions
- Non-linearity of extreme waves
- Application of 3D structural models
By coupling a RANSE procedure (field method) with a Finite-Element solver, the following parameters can be obtained in time domain:
- Sectional loads (Shear-Forces, bending and torsional moments)
- Normal and shear stresses and strains.
Due to the strong interaction between the ship’s structure and the surrounding water (hydro masses, hydro-dynamic damping and restoring forces), a strong 2-way coupling is necessary, causing an enormous computational effort. Therefore, relevant load cases (locally, globally) are firstly identified by fast linear methods and finally examined in detail. Model test results are used for comparison.