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Unformatted text preview: Review of section properties: Centroid of an a rea
(M
6:. The centroid of an area refers to the point that ' I
deﬁnes the y
geometric centre for the area. First moment of area \3 [yd/1 jdA
A y: Centroid of composite section ...... ____ NOtB: xi. and y; are coordinates of
centroid for sections
for sections 1,2 and 3
{i=1,2,3) Second Area Moments The area moment of inertia is the second moment of area around a given axis.
For example. given the 0—0 axis, the second moment of area can be calculated by d1=32dA Parallel Axis Theorem IMMW“ = J’ysz: I026 +5026“ : nydA+ bid/1+ I2ych
A A A A A = yfA +1” +234. [yd/i
1 A — i 0'14 is equai to zeto, we have A A IParah'eixx : The moment of area of composite bodies can be calculated by
adding together the moments of inertia of each of its sections The effective seciion shown below is subjected to bending moment Mx. Determine the axial stress. From the BEAM equation
we have M x— 1 xx 0:: ...
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 Winter '09
 S.PinhoandM.Aliabadi
 Second moment of area, JDA, geometric centre, nydA+ bid/1+ I2ych

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