File:An investigation of hooped concrete columns (1914) (14774346311).jpg

Identifier: investigationofh00thom (find matches)
Title: An investigation of hooped concrete columns
Year: 1914 (1910s)
Authors: Thomas, Howard Rice
Subjects: Columns, Concrete Theses
Publisher:
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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For a homogenous material subjected to stresses in morethan one direction, we have the well known formula: exE = Fx (Fy + Fg) eE = P -/fr(P + fc) (P = Fx = Fy) e = 1(P -^(P + fc)But the actual lateral unit deformation . ^ = ;jpy^(P + fc) 1 t £g(i _§. = faJk By a reasonable choice of values ofy^and n, it willbe found that this formula gives fairly close results,up to theyield point of the column. After the yield point is pasBed,^/^-and n becomesuch rapidly changing variables that it would be almost impossi-ble to apply the formula, even if it were a rational one to usefor such conditions. But in deriving this formula it was as-sumed that the column to which it is to be applied is of anelastic homogenous material and subject to the laws governing
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5 such bodies, hile this is approximately true for concrete atlow stresses, it is not even as approximation to the truth athigh deformations. After the yield point of the column hasbeen passed, it is probable that the material acts somewhatlike a granular mass with a thin steel shell around it. Buteven in this case, the granular material is probably one havingan angle of repose (or coefficient of friction) varying with theamount of load to which it has been subjected. It is also proba-ble that there is considerable and variable cohesion among theparticles, and so it ^ould be almost impossible to derive a ra-tional formula that would take account of all of these variablefactors and still be usable. Of course such a formula might bederived for the ultimate strength of a concrete column, but evenin this case the cohesion and angle of repose would be a variablefor each different concrete. Poth the results of tests and the results given by the above formula indicate that the stress in the

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