File:The elastic properties of concrete under bi-axial loading (1912) (14779282264).jpg

Identifier: elasticpropertie00mill (find matches)
Title: The elastic properties of concrete under bi-axial loading
Year: 1912 (1910s)
Authors: Millard, Floyd Hays
Subjects: Concrete Theses
Publisher:
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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with a differentarrax:igement of apparatus. The results of the second test areshown in Fig. SI. The rather high values of 0.70 and 0.79 forthe ratio of deformation on the cross to that on the arm in thefirst two stages of the second test of 2050 may have been duepartly to Lhe earlier test. The apparent initial modulus ofelasticity of concrete is usually increased ?:hen a piece istested after having been previously loaded, vjhile the stress-deformation relations at stresses higher than those reached bythe preliminary tests are not changed. This is brought out inBulletirxs 4 and 10 of the University of Illinois EngineeringExperiment Station. The apparent initial modulus of elasticityis foixnd in both cases from the experimental stress-deformationcurve and it must be remembered that t-.e zero readings of thelater test are not those of the first test by the amount of theset produced by the first loading, and that the origin of thestress-deformation curve is changed in the second trial. At
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108 least a part of the difference must have been the result of adifferent method of applying the load and lack of experience indeallnj v^ith test specinona of this sort. The average ratio of deformation on the cross to deformationon the arm for the complete second test of 2050 made tvo daysafter the first, is 0.74. The separate ratios at each incrementof load do not vary greatly from the mean. It would probablybe T^ell to drop the results of tests of this preliminary specimen,but the average of the two tests is the same as the average ofthe three later tests and it is of no consequence whether theyare dropped or kept. In comprossion specimen 2051 the ratio of the unit deforma-tion on cross to that on the arm, as determined from the stress-deformation curves, varied from 0.S2 to 0.S9 and averaged 0.63for the test. The very small variation of this ratio with thestress at loads higher than the first 11. evident. The values of the ratio of the deformation on the cross tothe deformation o

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