Author: Cusens, A R;Pama, R P
First published: N/A
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Cusens, A R;Pama, R P
Mr. S. Butler: ‘Having read the paper before I came to this meeting, and from past acquaintance with the aeroplane, I should first like to make a statement and then put a question. I was interested in the mention of seven per cent of take-off weight for the pay load; in fact in the paper it says “Only seven per cent”. This was rather more creditable than one tends to think. For a railway train, thought of as a transport vehicle, I believe it is one per cent, if not appreciably less. I think the optimum in percentage pay load goes to a mini car with four hefty men and luggage, and that makes about thirty to thirty-five per cent.'
Mr. F. C. Greenfield : ‘The design-or examination of another’s design - of a modern structure calls for “professional excellence” comparable with any other of man’s skills; it is high time the layman was aware of this. Legislation is badly needed to ensure that the public are protected through structural design, examination of structural design (on behalf of the local authority) and also supervision on site-all under the direction of Chartered Engineers recognised in their profession for their skill in this field. Local authorities should ascertain that they have the necessary professional excellence in their staff; if they do not they should either attract the
right men or engage Consulting Engineers-or do both. For those who rely entirely on their own staff, full responsibility must be shouldered by the engineer-Chief Officer.'
It is shown that an examination of the deformation of a free cable suggests an array of diagonal stays or braces as a means of reducing the deflections. The braces prestress the cable which, since it behaves nonlinearly, produces an increase in the stiffness. Bracing is similar to gravity loading in that it increases the vertical forces acting on the cable. The increased stiffness is thus analogous to gravity stiffness. A theory is presented for analysing this type of structure, and a numerical method of solving the governing equations is given. An experimental investigation verifying the theory is included and finally a theoretical discussion of the significance of the main parameters is given.
T.J. Poskitt and P.R. Stott