Estimation of rainflow damages in container ships
Paper in proceedings, 2012

The distribution of rainflow cycle ranges for fatigue design of ship structures is often obtained from classification rules as an empirical formula in terms of ship geometry, trade regions, etc. It is well-known that this method includes large uncertainties. In particular, it cannot account for the environmental loads and operational profiles for the fatigue assessment of ship structures. A direct fatigue analysis is supposed to be more realistically describe stresses encountered by ships. Using advanced hydrodynamic and structural analysis, the distribution of the rainflow ranges can be estimated using statistics of the more aggregated quantities, e.g. long-term distributions of encountered significant wave height, ship speeds and heading angles etc., and some mathematical models relating stresses to the quantities. In this paper, a very simple model, based on the narrow band approximation, is presented and then validated using the full-scale measurements of two container ships of different sizes. The application of this model for long-term fatigue analysis is also illustrated in details.

full-scale measurements

Fatigue damage

environmental loads

container ships


Wengang Mao

Chalmers, Shipping and Marine Technology, Division of Marine Design

Igor Rychlik

Chalmers, Mathematical Sciences, Mathematical Statistics

University of Gothenburg

Proceedings of the International Offshore and Polar Engineering Conference. 22nd International Offshore and Polar Engineering Conference, ISOPE-2012, Rhodes, 17-22 June 2012

1098-6189 (ISSN)

Vol. 4 688-694

Subject Categories

Mechanical Engineering

Areas of Advance