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The Structural Engineer

This paper considers first the short-term probabilistic description of random wave loading on offshore structures composed of members for which the Morison form of load mechanism is appropriate. Special consideration is given to dealing with the inherent non-linearity of the drag forces. The general multivariate distribution of loading is derived from the linear Gaussian model of long-crested random seas. The application of the multivariate distribution to yield the probabilistic description of structural response variables is indicated. Probability distributions of peak loads are developed which show the general wideband behaviour contrasted with the simpler distribution which results from appropriate narrow band assumptions. Comparisons of the theoretical models are made with prototype recordings from an offshore platform and laboratory scale experiments. Comments are made on various aspects of the numerical computations necessary in the application of the theoretical models proposed. R.G. Tickell

The Structural Engineer

Through this letter I wish to draw the attention of the readers of our Journal to the fact that there is some ambiguity and error in the above paper, published in March 1973. A.P. Dalvi

The Structural Engineer

Errata The paragraph covering 'cost' on page 382 of the original paper has suffered a couple of printing errors and you may well wonder at such exotic items as 'tar piles' and the finishes to 'structural desks' (lovingly carved with WL/8 no doubt). These should read 'test piles' and 'structural decks' of course!

The Structural Engineer

President's Diary The President and Mrs. Eastwood Will receive some 700 members and their guests at the Institution's Annual Dinner at Grosvenor House, London on Thursday, 5 May, among them Sir Charles Villiers, MC, Chairman, British Steel Corporation and Sir Roy Marshall, CBE, Secretary-General of the Committee of Vice-Chancellors and Principals, with their ladies. Sir Charles will be proposing a toast to the Institution, to which the President is to reply; Sir Roy will respond to the toast to 'The Guests' proposed by Mr. Peter Dunican, CBE (President-Elect).

The Structural Engineer

The term 'stress-ribbon' describes a structure type in which the deck hangs in catenary form. The behaviour and design of an all-steel structure of this type is discussed using a 490m span highway bridge as an example. R.J. Wheen and A.J. Wilson

The Structural Engineer

The doubts expressed by Mr. Gorzelany about plated timber roof trusses (February 1977) are reflected by Mr. R. A. Gill who writes : The probability of a national outcry against the fear that at some time in the future the combination of all adverse effects from excessive moisture, unprotected teeth etc. may affect the strength of plated timber roof trusses is not as remote as some people may think. Verulam