m BEAMS SUBJECTED TO TEANSVERSE STRAIN. 
483 
Number 
of 
experiment. 
Length 
of 
bearing. 
Breadth. 
Depth. 
Weight which 
overcame the 
elasticity. 
1 
Value of (j) 
computed from 
the formula. 
in 
in. 
in. 
tons. 
tons. : 
8 
33 
1-9 
2-0 
2-5 
3-65 1 
9 
33 
1-9 
2-0 
2-5 
3-65 i 
10 
33 
1-9 
2-0 
2-5 
3-b\5 i 
11 
33 
1-5 
3-0 
4-3 
4-33 J 
12 
33 
1-5 
3-0 
4-.5 
4-33 
13 
33 
1-5 
2-5 
3-25 
4-77 j 
Mean 
4-06 ! 
Mean ratio offto <p : 1 to -406. 
The general mean of these results appears therefore to show, that the resistance of 
flexure in wrought iron, considered as a force acting evenly over the surface, is nearly 
equal to one half of the tensile resistance. It is, however, desirable that further experi- 
ments should be made with this material. 
Appendix to the foregoing pages. 'By Petee Baelow, Esq., F.R.S. 
Received March 25, — Read April 2, 1857. 
Application of the preceding principles to Beams and Girders of non-symmetrical section . 
Ix beams of symmetrical section the neutral axis corresponds with the centre of gra\ity, 
because in that case all the direct forces above and below that point are necessarily 
equal. But when the section is non-symmetrical, it is requisite, in order to determine 
the position of the neutral axis, to find that point in the section in which this condition 
has place, \iz. that point below which the sum of all the direct resistances to tension 
and cunutiu'e are equal to all those above that point due to compression and curvature ; 
then to find the sum of the moments of these resistances separately; and finally, to 
equate them with the straining force. 
The double-fianged girder with unequal fianges forms a good subject for testing the 
general application of the principles developed in the preceding pages. In such a girder, 
a denote the whole depth of the girder ; 
m the thickness of the middle web ; 
d the depth of the bottom fiange ; 
d! the depth of the upper fiange ; 
b the breadth of the former, minus m ; 
h' the breadth of the latter, minus m ; 
X the required distance of the neutral axis from the bottom of the girder ; 
at the distance of the same from the upper face of the girder ; 
t the tensile resistance of the lower fibres ; 
c the corresponding resistance to compression of the upper fibres. 
Now if we consider the centre rib as carried through the two flanges, the sum of the 
direct resistances due to the tension of the metal in the middle rib below x will be \mxt, 
3 E 2 
