TIMBER BRIDGE CONSTRUCTION IN. N.S.W. V. 
The author therefore has dealt with the case in what he submits, 
isa practical way of looking at the question. 
_ Starting with the end bay there is a stress of 27-72 tons which 
_ extendsfor the whole length of the chord (70 feet). Taking the least 
di meter, the ratio of length to least diameter is 48 to 1 and the 
ultimate buckling strength of a timber column of this proportion, 
ing 2-36 tons per square inch, the area required on the point of 
buckling would be 11-74 inches, whilst at the ends of the column 
the area required, when on the point of failure by direct crushing 
would be 5-87 inches. 
‘Setting up these ordinates and plotting in as a parabola, the 
area shown on diagram, Plate 4, is obtained ; in the second 
y the stress is 48-51 tons extending for a length of 50 feet 
but as part of this stress (27°72 tons), has already been 
vided for, it leaves only 20-79 tons to be dealt with ; 
ing the ratio of length to diameter this gives a column 
he proportion of 36 to 1, requiring an area of 6°77 square 
es when the column is on the point of buckling at the centre, 
an area of 4:4 square inches when on the point of failing by 
t chrushing at the ends, the required additional area being © 
on the diagram, Plate 4. 
Th the third bay there is a stress of 62°37 tons extending over 
distance of 30 feet, 48°51 tons of this stress has already been 
ealt with, leaving only 13-86 tons to be provided for, proceeding 
s before, the area shown in green is arrived at ; in the middle bay 
€ stress is 69-3 tons extending over 10 feet of which 62°37 tons 
been provided for, leaving 6°93 tons to be arranged for. 
The whole of the varying stresses having now been dealt with, 
is heavy dotted black line, represents the total area required 
When the column would be on the point of failing. 
The actual net area of timber provided is 156-16 square inches, 
te 4, and as the maximum area required at the centre is only 
“09 square inches, the column has a factor of safety of 6°6 
buckling, irrespective of the stiffness imparted by the 
Ying of the feet of braces. 
