The Structural Engineer > Archive > Volume 12 (1922) > Issues > Issue 5 > What is the use of the modular ratio? Part II
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What is the use of the modular ratio? Part II

Coming now to the consideration of reinforced concrete beams, if we turn back to the early pioneers we find first of all that their work was done with next to no calculation; slabs and beams were tested to destruction, and in the light of such experiments buildings and parts of buildifigs were constructed, the sizes being roughly proportioned from the data thus obtained. The first attempt to formulate some method of calculations that is known to the author was that given in a book printed at Chiswick in 1877 for private circulation by Thaddeus Hyatt, the inventor of pavement lights, who came over from New York to establish a business therein in England, and had a number of experiments on reinforced concrete bearns conducted by David Hirkaldy. The method of calculations put forward in the book was a simple comparison with iron joists embedded in concrete. It was pointed out that the upper flange of a steel joist was in compression, and the lower in tension, and that the web and compression flange might be omitted, the purpose served thereby being fulfilled by the concrete. All the concrete above the middle of the steel joists was taken as being in compression. The ultimate compressive resistance of the concrete was taken as 2,000 lbs. per square inch, but this was reduced to a mean stress of 1,000 lbs. per square inch, which looks like a triangular stress distribution, but the centre of gravity is taken halfway, thus suggesting rectangular stress distribution. Mr. Hyatt acknowledged his indebtedness to Mr. Thos. Rickett, of Birmingham, formerly, as he says, in the employ of the London and North-Western Railway. Probably Mr. Rickett was responsible for the method of calculations, which are merely sketched in the book. It is interesting to note that Mr. Rickett and Mr. Hyatt did not lose sight of the possibility that the neutral axis might become displaced by reason of the different deformations of concrete and steel under a similar stress, because they record an experiment that they made to ascertain the amount of deformation, but apparently through the roughness of the apparatus they were not able to get any difference between wrought iron and cement, so assumed the same for concrete (the book states) "the effect of which in the compound beam is to keep the neutral axis at the central line of the beam, the entire tensional strain being thus thrown on the metal tie." H. Kempton Dyson