mom net of inertia of beam with holes

[bhart192]

this should be pretty basis but its been a while i wanted to check how do I account for the moment of inertia of a beam that has a slot in the center .

 

[appot]

Parallel Axis Theorem. And then add (or subtract in your case) the moments of inertia

 

[BAretired]

If the slot and beam are doubly symmetrical, I = I_beam - I_slot; otherwise I = ΣI_s where I_s is the moment of inertia of solid parts about the c.g. of the section.

BA

 

[dik]

Unless it's a big hole, the reduced moment of inertia reduction will be small. Subtrace w*d^3/12 from the original I of the beam, if hole is in middle... w-web thickness d-hole diameter.

Dik

 

[msquared48]

Agree with dik...

Mike McCann, PE, SE (WA)

 

[GregLocock]

How much of the shear web can you cut away (along the axis of the beam) before it starts to act as 2 small T beams in parallel rather than an I beam?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[dik]

If any significant shear, I treat it as two T beams...

Dik