2010. The Society of Naval Architects and Marine Engineers
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This technical note evokes directionally nonuniformloading field effects on exposures of marine objects and structures in service under environmental conditions. The note firstly reveals the statistical variability of distributions of probabilities and the entropy concept of uncertainty of systems of events for identification, ordering and presentation of probabilistic seasonal nonuniformities of wind wave loading fields. This paper provides diagram of variability of wind wave directions and the chart of ocean-wide directional nonuniformities compiled from the Global Wave Statistics (GWS). It also considers seasonal loading field distributions of wind wave heights against wave directions as well as methods for calculation and presentation of directional exposabilities of marine objects and structures. The study introduces two methods for favorable placement and selection of sustainable directions of marine objects and structures exposed seasonally to nonuniform wind wave loading fields based on criteria for minimal average exposure and on robust uniform exposures during service period. The note elaborates examples of favorable placement of a marine object on six piles near the east Brazilian coast and of an oil tanker in the Gulf of Mexico. The note at the end illustrates the use of the multiple-criteria approach either to support decisions about optimal placement and sustainable headings to waves or for avoidance of unfavorable directional field effects and their combination on marine objects and structures.