- #1
dbaliki918
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Homework Statement
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Statement: Find the principal axes of the section shown:
The origin is on the top left corner.
Homework Equations
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Centroid equations:
Second moments of area:
Mohr's Circle for I equations:
Coordinates
Centre
Angle from principal axes:
The Attempt at a Solution
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Finding the centroids:
Finding Iy, Iz, and Iyz (Finding Iyz is where I'm having some difficulties):
THE PROFESSOR-PROVIDED SOLUTION FOR Iyz (I don't know how to determine whether or not y1, z1, y2, z2 are positive or negative) (My prof's answer was Iyz = -1.188×106mm4) Here is his provided solution:
I know where his values come from, I just need a surefire trick on determining the sign of y1, z1, y2, z2.
Mohr's Circle for I (I know I'm missing the axis labels. x-axis is Is, y-axis is Ist) Each point is multiplied by 10-6:
Centre:
Angle of Principal axes:
TL;DR Need a trick on determining the sign of y1, z1, y2, z2 from the Iyz equation.