171
OF ENGINEERING FORMULÆ.
Thickness of Web Plates of Wkought-ibon Girueu to
resist Diagonal Fokce. (Chas. Light.)
The tabular numbers show safe thrust in tons per foot of
width of plate.
l liiek- jjet unsupported Distances in inches whether between
lie®* i Pillars or Booms.
Web, ins. 24 27 .30 33 j 36 39 42 f 45 48 51
1-5 1-2 1-0 •8 •? • 6 •5 '45 •4 •36
2-8 2’2 1-8 1-5 1-3 1-2 l-0i x-9 •8 •1
i 4-3 3'5 3-0 2-6 2*2 1-0 1-7 1-5 1-3 1-2
A 6'3 5’3 4-5 3-9! 3-4 2-9 2-6 2-3 2-0 1'8
i 8'7 T-i 6’3 5*51 4'8 4-2 3’7 3'3 3-0 2-1
11-2 9-8 8-5 7-4 6-5 5-1 5'1 4'6 4-2 3-8
% 14'0 12-3 10-8 9'5 8-4 7-5 6-1? 6-0 5-4 4-9
H" 17’0 15-0 13-4 n-9'10-6 9-5 8*5 7-6 6-8 6-3
20'0 17-9 16-1 14»"5 WOfll’T 10‘5 9-5 1. ... 8*6 7’8
The tabular number under the distance require«! must not
be less than the shearing force per foot of plate.
t—’-----V—*—\ Latiice Bridge! H f
See ‘ Min. Inst. Civ. Eng.,’ vol. xi. (W. T. Doyne.)
W = Weight distributed.
S = Strain at centre of top and bottom flanges.
æ = Distance of any point from abutment.
y = Strain on any lattice.
a = Distance of centre of any lattice from centre of girder.
I = Length of any lattice. . •
L = Length of bearing of girder or span.
I) = Depth of girder (effective).
WL W
g = S at centre; --j- (Læ — æ«) — s, at any point whose
. distance is x. from abutment.
y = W ; y is for single triangulation, and must be
divided by the number of series of triangulation.
If w = weight applied at centre of girder, ^-jj= strain on
all the lattices.