Author(s): Marc A. Maes; Ian J. Jordaan
Linked Author(s):
Keywords: No Keywords
Abstract: During the past few decades there has been increasing acceptance that absolute safety is not a realistic engineering objective and that some element of risk is inevitable in structural engineering. Part of the evaluation of risk is concerned with environmental loading and many aspects have received attention in past years, including potential hazards to offshore structures such as extreme waves or earthquakes. Possible loading of structures offshore eastern Canada by icebergs poses a unique environmental problem. The present paper is devoted to a probabilistic evaluation of such loads. First, problems related to iceberg density and occurrence are addressed, together with the relationship of these factors to flux and directionality of motion. Data on the factors just outlined is used to develop arrival rates of icebergs. It is shown that iceberg loading may be treated analogously to a compound Poisson process. In the evaluation of the loads, the mass, velocity and size (width) must be treated as random. Models for these, based on an empirical analysis of data, are developed. The deduction of probability distribution for mass, velocity and size given a collision is shown and that these are updated versions of the distributions for randomly chosen icebergs. Finally, return periods for calculated kinetic energies are developed, based on a calculation procedure for ice loads which uses the mass and velocity combinations together with added mass. Statistics of extremes are used where appropriate. It is shown that the assumption of independent, identically distributed random quantities is not fully justified and that mixtures of such quantities should be considered. An example of the application of the theory is given.
Year: 1984