STANDARDIZED LOAD SEQUENCE FOR OFFSHORE STRUCTURES–WASH 1

Abstract

Abstract WASH 1 is composed of a defined series of six seastates for a yearly return period; the two lowests seastates 1 and 2 being eliminated, because they do not influence the fatigue life of offshore structures, and the three highest seastates 8, 9 and 10 were combined. The sequence and the duration of the resultant six seastates correspond also to long term observations in the North Sea. A generated load history with the power spectrum of the strain measuremnts used as a basis, is the result for each seastate. The return period of the standardized load history WASH 1 decided upon is 5 × 10 5 cycles coresponding to one year of wave loads. It is fixed sequence of peaks recorded on tape. Testing frequency and signal shape are optional. The basis for the derivation of standardized load histories is always formed by strain histories measured in operation. WASH 1 was derived on the basis of strain measurements on the FRIGG DP2 platform of IFREMER, Brest, supplemented by measurements of Germanischer Lloyd, Hamburg, on the Research Platform NORDSEE. As even comprehensive measurements can only be samples over a limited period of time, the strain measuremments were supported by the results of long‐term observations of seastates in the North Sea.