The President 1990 - 91

Potential for catastrophe in building alterations Mr P. S. Rhodes of Bangor, Northern Ireland, relates our correspondence on this topic (raised by Peter Mawer on 20 March, with subsequent contributions in our columns for 15 May and 19 June) to a previous article under his own authorship: I refer to The Structural Engineer of September 1974 (Vol. 52, No. 9), p332, the top four paras on the second column, and also to p333, second column and ‘Lessons for the future’. Verulam

The use of centrifuges to improve similarity in geotechnical model studies has developed rapidly over 2 decades, in the UK and elsewhere. With increased numbers of machines of varying size, power and sophistication, the opportunities for engineers in practice to avail themselves of this technology are increasing. A review is presented of what has been achieved to date, and some conclusions are drawn. A new era of model testing, with the inclusion of greater precision in simultaneously modelling above- and below-ground components of complex structures, is foreseen, for both static and dynamic situations. W.H. Craig

U-frames are an available option used to brace the compression flanges of beams used in deck-type composite bridge decks and in halfthrough bridges. E. Jeffers