Lecture 10
Example Problem
Principle of Moments
Given:
the following truss with the loading indicated
Determine:
the moment of each of the loads about point A; the combined moment of all the loads about point A; the required reaction at B to satisfy equilibrium
Solution:
First find the moment caused by each of the loads around point A, which will equal the force, or its components, multiplied by the moment arm. Clockwise moment will be posative.
Moving from left to right through the truss:
(185#)(8ft) = 1480#-ft
(300#)(6ft) = 1800#-ft
(260#)(12/13)(12ft) = 2880#-ft
(260#)(5/13)(16ft) = 1600#-ft
(-252#)(cos 40)(6ft) =
(252#)(sin40)(24ft) =
(100#)(32ft) = 3200#-ft
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