Author: Johnson, P H
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Johnson, P H
The Structural Engineer, Volume 13, Issue 9, 1935
THE work of demolishing Waterloo Bridge is now reaching the final stages and the nine arches will soon have completely disappeared. Owing to the tremendous amount of work involved and the necessary care which had to be taken, the task has been somewhat difficult, and it has taken some months to arrive at the present stage. It was necessary to erect steel overhead trusses on, and to suspend steel centering beneath, all but the centre arch, which is supported by piles.
In the design of reinforced concrete structures certain assumptions are made which are known to be unfulfilled in practice. It is usual when designing for specified working loads to use formulae based on a linear relation between stress and strain or a constant modulus of elasticity for concrete. This assumption, though true for steel within the limit of proportionality, is known to be incorrect for concrete and other building materials and has resulted in much controversy. Furthermore, while the value of the modulus remains sensibly constant for all steels, that for concrete varies considerably with the richness of the mix, quality of the aggregates, water-cement ratio, age at testing, methods of curing and of loading, range of stress and with the interval of time during which the concrete is under stress. It is therefore desirable to examine the effect of a change in the assumed value of the modular ratio on the calculated stresses and deflections of reinforced concrete members. R.H. Evans
In presenting the paper, Mr. Snow added that for the 21 flats in the block at Berners Street, Stepney, there were 300 applications; and for the 320 flats at Amhurst Road, Hackney, there were 1,200 applications.