Prediction of Design Response for North Sea

Abstract

The methods to predict long term extreme structure responses induced by environmental loads are reviewed. Due to the variability of both environmental condition and response in a given environmental condition, the prediction should be performed statistically. Generally, one should carry out a full long term response analysis, i.e. convoluting the variability of response in a given environmental condition with the variability of environmental characteristics. One may consider the response distributions during all sea states or storm peaks. However, full long term analysis can be quite time-consuming if the problem under consideration is of complicated non-linear nature. In this condition it is more convenient to perform short term response analysis. The most common method in connection with this is the environmental contour lines method. Extreme heave motion of a semi-submersible in the North Sea is evaluated as an example.

Key Words: Characteristic response, all sea states, peak over threshold, environmental contour lines.