Bending moment unit

Arjumand Anjum

April 10, 2021 18:41

Hi,

PPD exam ahead.

Considering a uniformly distributed load, M= WL²/8. If the load is in kips and length of beam in ft., shouldn't the unit of M be kips-ft²

I have come across notes where it is Kips-ft. I am confused specially when I have to covert the units

Kindly help

Thanks,

Anjum

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Comments

4 comments

rebekkak May 01, 2021 01:04 (Edited May 06, 2021 22:33)

You are correct. Watch the units on the exam. a kip = 1000 lbs. And a kip-ft² is a unit. For that formula you are correct the answer should be length squared.

On the exam I think you’re going to see pounds and feet for the units though.

Hope that helps!

Rebekka O'Melia, B.Arch, M. Ed, Registered Architect, NCARB, Step Up ARE Coaching

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mermann May 02, 2021 01:54

Anjum, I see where you are confused. . . the formula is a LOWERCASE w

w =Uniformly distributed load per unit of length, kips/in

l=Total length of beam between reaction points, in

So M= wl²/8 works out to inch-kips

Let me know if you are still confused and I'll explain more.

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mermann May 02, 2021 11:26

Whoops...I meant kip-inches, not inch-kips

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mermann May 02, 2021 11:27

Whoops...I meant kip-inches, not inch-kips

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