Area Moment of Inerita simple rectangle composite I'm lost

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SUMMARY

The discussion focuses on calculating the moments of inertia for a Z-section about its centroidal x0 and y0 axes, specifically at distances of 80 mm and 90 mm, respectively. The user expresses confusion regarding the necessity of setting up a chart for the calculation of \bar{I}x and \bar{I}y, which are derived from the individual moments of inertia of the three parts of the section. It is confirmed that the parallel axis theorem is essential for determining the overall Ix and Iy values, which must include the contributions from the individual centroids of the designated areas.

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  • Understanding of moments of inertia and their significance in structural engineering.
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frozenguy
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Homework Statement



Determine the moments of the inertia of the Z-section about its centroidal x0 and y0 axes.
I didn't draw them in, but the x0 axis is 80[mm] up from the bottom and the y0 axis is 90[mm] from the left most point. So it is in the middle of the piece.

The Attempt at a Solution



So I guess I'm confused as to whether or not I need to even set up this chart since its only asking for \bar{I}x and \bar{I}y. Its just the sum of each from the three different parts? If I do need the chart, what is dx a distance from/to? I don't think my numbers are right at all.

I have the answers in the book.
staticsprobA43.jpg
 
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Your values for dx an dy appear correct (d = distance from centroid of area to centroid of shape). But your chart is missing the Ix and Iy values, of the areas you designate as 1 and 3, about their individual centroids. You need the parallel axis theorem to compute the Ix and Iy of the overall shape.
 

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