Correspondence on the Superstructure of Bangor District General Hospital by J.G. Roddick and F.C. S

After the manuscript had been submitted to the Institution, comment came back that nothing had been included about the actual design of individual silo bins; arising from this, Appendix B was added. Notwithstanding, we feel it desirable to elaborate further.

Progressive collapse We have received the following excellent letter from Mr Jan Korff who writes: The President is to be congratulated for returning to the subject of progressive collapse. I, too, in my small way, revisited Ronan Point and now, when the last cathartic act has been played out and the Court had its final say, I cannot but help reflecting whether it was all worthwhile. Was the price of hundreds of millions of pounds, that we all had to pay and will continue to pay in perpetuity, not too high a penalty for this minor (albeit spectacular) accident. I say minor advisedly; 6 % of the volume of the building collapsed, but virtually all the remaining structure survived in mint condition. The loss of life-five persons-was far less than could have been expected, bearing in mind the volume destroyed. The accident occurred only because of the perverse conjunction of adverse factors, i.e. a very severe explosion in the vicinity of a gable wall near the top of the building. Here the Tribunal made their fatal error in suggesting that there was a 2 % probability of significant damage in a 60-year life of such a building. In fact, a more likely figure is 40 times less. To put it in perspective, we can expect one unstrengthened block in 2000 or so to suffer the fate of Ronan Point in a life span of 60 years. Verulam

A new way of thinking about the teaching of structural analysis and design, a new paradigm, is proposed. This is based on the 1O-year study of the development of an understanding of structural behaviour in groups of recently-qualified graduates. D.M. Brohn