Incremental Launch Bridges: UK Practice and Some Foreign Comparisons

‘It is unwise to pay too much, but worse to pay too little; when you pay too much, you lose a little money, that is all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the things it was bought to do...' P.L. Campbell I see that the question of a suitable definition of engineering has again been raised by Professor Happold and others. As engineering is an activity carried out by engineers, and as most of our institutions are of engineers rather than of engineering, possibly we should, instead, focus on the definition of an engineer. My own preferred definition of a structural engineer is ‘someone who can efficiently design any structure in the most appropriate material.’ T.A. Erskine Britain’s professions are currently under great pressure which threatens their survival. If I talk about structural engineering, it is not because the threat on it is any greater, but because it is the profession that I know best. S.B. Tietz

Mr J. A. Emery (Advanced Construction Materials Ltd) The authors of this paper have made a valuable contribution to our knowledge of the performance of limestone concrete aircraft pavements under thermal shock conditions. Their development of new concretes having improved jetblast resistance is of great interest, but the following comment from World Air Power Journal, Vol. 6, Summer 1991, p47, does beg the question should a specialised concrete surface be necessary at all?

Bond and flexural behaviour of concrete beams with fusion-bonded epoxy-coated reinforcing bars have been investigated under static load, repeated load, and sustained load. Embedment lengths were varied in the static load tests, (16, 20 and 28 diameters for 25mm bars, and 16, 20 and 33 diameters for 12mm bars). Both coated and uncoated bars were employed in all three series of tests. Relative bond behaviour and flexural performance of epoxy-coated bars are evaluated and discussed in comparison with uncoated bars. Professor A.R. Cusens and Z. Yu