176 Molesworth’s pocket-book
Calculation of Stress on Braced Girdebs.
(C. Lean.)
The coefficients are obtained by writing down the effect of
each unit of load on each member, and taking the totals +
or — for each member.
To find the actual stress on the members of a girder:
1. Find the total amount of dead and live load on the
girder.
2. Divide these amounts by the number of bays to find
tbe unit for one bay.
3. Multiply the units of dead and live loads by their
respective coefficients, and divide the results by
the number of bays. The quotient represents the
greatest possible stress that can come upon the
girder under any conditions of the live load.
For diagonals the amount must be multiplied by the length
of the bay divided by the depth of the girder; if the length of
the bay does not equal its depth the amount must be multi-
plied by the length and divided by the depth. I’he results for
the flanges must be corrected to a similar manner.
Example.-—With live load = 100 tons, dead load =t 50, find
etresses on k. (See Uiagram below.) Units = 10 and 5 tons
respectively in tension and compression,
r ‘ bays, length.
Live load 10 X coef. — 15 — 150 ( — 175 4-10 X 1'41 =
Dead „ 5X „ - 5 = 25 5 - 24-75 tons.
Or Live load 10 X „ +I0= + I00i + 75 4-10 X 1'41 =
„ Dead „ 5X „ - 5=- 25 j +10-6 tons.
a & s b & r e i 1 d&p e & o f Sen g & m i & It
Coefficient) live load J „ dead „ +J-_ 45 I + 45 + ! — 110 - 10 - 36 35 i I « a + | a + + 3 28 25 i- 21 6 + is + » 21 15 il- is io + B I 1 J + I l—« I , I “ 1 1
A&H B4G C&F D&E I&B J&Q K&P L&O M4N
Coef. booms 4-80 -105 4-120 + 125 - 45 45 •* Mi — 06 — 120