BY R. W. H. HAWKEN. 10 
Continental Engineers specify that columns shall be 
loaded only to a proportion of the Euler Value* (generally 
Da) eiee-a blade —Aocitipions,. <Q... 3», <9 ince dyetayenace a <4» (13) 
To apply the results (1) to (6) to the solution of (11). 
The author considers that in practice we can no more 
realise the Euler condition than we can make a _ perfect 
sphere—we can only approach either to the limit of accuracy” 
of workmanship or of the measuring instruments, 
consequently every material column has some eccentricity 
of loading. Itis quite possible that the deviationf from the 
ideal conditions is not exactly that shewn diagrammatically 
in Fig. 2. The column may be in a bent state though 
unstrained, or the sources of eccentricity may lie in different 
amounts of strain on compressive and tensile sides (vide 
Fidler’s ‘ Bridge Construction’), but the assumption made 
allows of exact solutions and visualising methods and may 
be reasonably considered as a summary of sources of 
difference from ideal loading. 
The phenomena shewn by experiment confirm what 
has been stated above; in the most carefully conducted 
experimental work the Euler condition cannot be realised 
though various experimenters have thought it so: it is 
only a close approximation that has been reached, and 
experimentally ‘unstable equilibrium ’ cannot be attained, 
some residual friction at supportst or want of centrality 
EI 
* . . . “And yet it is this value Q=72 , which has been: 
L2 
stated to be the theoretically (sic) safe (!) load, and the framers of the 
formula who were, of course, perfectly well aware that the formula gave 
results as far away from the results of experiment as the sun is from the 
moon, proceeded gravely to divide the modulus of elasticity E by a factor 
of safety varying from 6to12. . . . The idea of dividing a modulus. 
of elasticity by a factor of safety is sufficiently grotesque in any 
circumstances, but the idea that it may possibly be six or twelve times 
as great as we think it is, is a strange absurdity.” (Extract from Professor 
Smith’s paper on ‘“‘ The Strength of Struts.”’). 
tSee p. 38-39 of “Column Analysis and Design.” 
{This might cause an approach to fixation, consequently the virtual. 
length may be shorter than the actual length and a column apparently 
be able to carry more than its Euler Value. 
