— 125 — 
For the floor beams of single track bridges tho value of IF may be taken from 
0.06 ton for short panels to 0.08 ton for long panels ; and the corresponding values 
for floor beams of double track bridges at 0.12 ton and 0.15 ton. 
The method of determining the rivet spacing in the flanges of plate girders, 
track stringers and floor beams was indicated in Chapter VI : it will bo further illus- 
trated by an example. To find the mimbcr of rivets necessary to connect a track 
stringer to a floor beam where the former abuts against the latter. 
let W = as before the total reaction upon the floor beam caused by 
the total loads on two abutting stringers, including allowance 
for shock. 
t = thickness of web of floor beam 
t f = tliiclmess of web of stringer 
1 " = thickness of a connecting bent plate 
j) = the intensity of working boariug pressure 
rn = tlie working bending moment for ouo of the rivets used in tlie 
connection 
and cl = diameter of same rivet. 
then tho reaction at one end of a stringer is and the working bearing pressure for 
° Ue r ivet passing through the web of tlie stringer is ノ） " パ ； consequently the total 
dumber of rivets through the stringer web necessary to resist tho bearing pressure 
Wll be given by tlie equation 
JV 
n = 2pt，d 
Tlie stress ^ is equally divided between the two connecting plates, making the stress 
upon each equal to — and its moment equal to ^ X - 十 〆 ’， therefore the number of 
uvets through the stringer web necessary to resist bending will be given by the 
equation 
8 m 
て he greater of the two numbers n and nf is to be taken as tlie proper number of 
U vets to use. Additional strength is gained for this connection by the supporting 
• shelf, but it is well not to depend tlieroon, as the bearing on the slielf may be impel* - 
fect， and this rivet ted coimoction is more affected by impact than any other rivetted 
connection in tlie bridge. 
The number of rivets required to attach each bent connecting plate to tlie floor 
earn as iar as bendiug is concerned will be given by tlie equation 
But for bearing upon the floor beam web, the total pressure being W , tho number of 
ri vets for connecting each beut plate will be given by the equation 
n”， = 
__W 
2p t d 
s before the greater of tlie two numbers n n and n f,f is to be used. 
