Author: Drury, F E
1st January 1933
First published: 1st January 1933
Standard: £9 + VAT
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Drury, F E
We very much regret that the following printers' errors occurred in the December issue
of The Structural Engineer :- Page 398- "Stewart & Partridges,Limited" should read
"Stewart & Partners, Limited" Page 404- The figure "330 O.D." should read "300 O.D." Page 409-"Chief Surveyor" should read "Chief Quantity Surveyor" Page 42-"Breaking of cracks" should read "Breathing of Cracks".
To the Editor of The Structural Engineer. Water-Cement Ratio. Sir,-In reference to Mr. C S Gray’s letter,Professor Duff A Abrams states that "Aggregates of equivalent concrete making qualities may be produced by an indefinite number of different gradings of a given material." "Aggregates of equivalent concrete qualities may be produced from materials of widely different size and grading." "In general, fine and coarse aggregates of widely different size or grading can be combined in such a manner as to produce similar results in concrete." The meaning seems to point clearly to the
fact that size or grading may vary widely in each aggregate, but not the different aggregates unless they have equivalent concrete qualities.
W D Williams
Perhaps the most characteristic property of metals at high temperatures is their
ability to flow or creep when under prolonged load, and it is because of that property that the stress necessary to cause fracture of a metal at high temperatures depends on its time of application. Table I illustrates the marked falling away in the stress required to cause fracture, the longer the stress is applied. In the case of nickel-chromium steel at 600°C and brass at 250ºC stresses less than one fortieth of the breaking strengths determined from ordinary tensile tests at 600°C and
250ºC respectively, cause creep of the order of 10-5 inch per inch per day. If, at the stresses given in the last column of Table I, the creep were continuous at 10-5 inch per inch per day a deformation of 1 inch in 100 inches would be produced in 1,000 days, or roughly three years. In many instances, therefore, even such low stresses as those cited are too high for working stresses.
H J Tapsell