Section modulus for T beam

Break the cross section into two rectangles. Find the area of each and y, the distance their centroids are from the bottom. Multiply the area of each by the y of each. Add those up, then divide by the sum of the areas. That gives the centroid of the cross section.

Next, calculate the moments of inertia of each section, then use the parallel axis transfer theorem to calculate their I at the centric of the cross section and add them up.

Now you can calculate the section modulus.

As I recall, that's how we did it in the old days, someone else will tell you the answer from some computer program shortly!

those

up.

Must have been one hell of a dumpster you found THAT in!

David Merrill

each. Add those

add them up.

ANYBODY that knows of or has a proven subroutine to calculate the section modulus of any reasonable cross section by spreadsheet, or whatever, please let me know. I am sick and tired of doing this by hand!!! A Tee section is tedious but straight forward; try an I-beam section where each of the 4 flange legs is a different thickness!

Wolfgang

I highly recommend the program engineering power tools, at

I drew this so that the base of the web was centered at (0,0), in inches, so the top of the flange starts at (-15.75,78.75) and ends at (15.75,78.75), and got these results:

Area 52.875 Xcg 0.00 Ycg 56.593 Ix 204440. Iy 1953.83 Ixy 0.00 Ix0 35093.14 Iy0 1953.83 Ixy0 0.00 J 37046.98

Where:

Area - Total area (adjusted for any defined voids) Xcg - Centroid of section (distance from X axis) Ycg - Centroid of section (distance from Y axis) Ix - Moment of inertia (about the X axis) Iy - Moment of inertia (about the Y axis) Ixy - Moment of inertia (about the XY axis) Ixo - Moment of inertia (about centroidal X axis, parallel with original X axis) Iyo - Moment of inertia (about centroidal Y axis, parallel with original X axis) Ixyo - Moment of inertia (about centroidal XY axis) Theta - Angle between the principal axis and the XY axis

Ix' - Moment of inertia (calculated at the specified "Delta Angle from Principal Axis" ) Iy' - Moment of inertia (calculated at the specified "Delta Angle from Principal Axis") J - Polar moment of inertia about principal axis

Engineering Power Tools - Copyright 2002, Barry J. Opdahl

Hope this is useful.

-- Regards, Carl Ijames carl dott ijames aat veriz>>

at

Carl,

Thanks very much!

I shall check it out and try it.

Wolfgang

You can find a lot of section properties in the Corus Blue Book,