Defence of dissertation in the field of marine technology, Mikko Suominen, M.Sc. (Tech.)

Uncertainty and variation in measured ice-induced loads on a ship hull.

The design of safe structures requires knowledge about the load-carrying capacity of the structure and the loads encountered by the structure. This dissertation focuses on the ice-induced loads on the hull of a ship. As several factors affect the ice breaking process, the process is complex and difficult to define. Thus, long-term measurements are required in order to estimate the variability of the loading reliably. However, the uncertainty related to these measurements has not received a proper attention.

This dissertation focuses on the uncertainty and variation in the ice-induced load measurements on the hull of a ship when the measurements are based on shear strain measurements. The work presents an analytical model, which can be applied to estimate the amount of loading transferred form the loaded frame to the adjacent frames. With the help of the model, it is possible to estimate the uncertainty related to the measurements when the instrumented structure is known.

The work presents the ice trials of S.A. Agulhas II and the measured ice-induced loads during the trial in the Baltic Sea in the winter of 2012. The aft shoulder measurements show that the short ice-induced loads are more common than longer ones, as has been shown by earlier studies. However, the short loads are small in magnitude and the loading experienced by a frame increases as a function of the load length. In addition, the measurements show that the probability distribution of the load magnitude of short loads differs from the distribution of the longer loads. These have not been observed in earlier full-scale measurements. The results of the work can be applied, as an example, when the magnitude of the design ice-induced loads is defined for the ice class rules in future.

Opponent: Claude Daley, Memorial University, Newfoundland, Canada

Supervisor: Pentti Kujala, Aalto University School of Engineering, Department of Mechanical Engineering

Electronic dissertation: http://urn.fi/URN:ISBN:978-952-60-7944-8​

Doctoral candidate’s contact information: Mikko Suominen, Department of Mechanical Engineering, mikko.suominen@aalto.fi, +358 50 433 1338