Plastic Moment

[Nightelf08]

Hi,
How do I find the column shear that corresponds to a full plastic moment developed in a column assuming the column is fixed at top and bottom? My column is a W 8x21.
Thanks.

 

[hokie66]

Not completely sure that I understand your question, but there is no general direct relationship between moment and shear. You can have high shear and low moment, and vice versa.

 

[bookowski]

Not sure what you're after... but in the absence of any external forces along the member V = (M1 + M2)/L or it sounds like in your case V = 2Mp/L

Column being fixed is irrelevant if you are already assuming a full plastic moment.

 

[dik]

Not sure that a W8x21 is a class 1 Section.

Dik

 

[GregLocock]

Depends how long the beam is.

Seriously.

Begin rant/ how about drawing an FBD? /end rant

Cheers

Greg Locock


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

http://eng-tips.com/market.cfm?

 

[rb1957]

do you mean you have a doubly cantilevered beam with a point load applied (= shear) ?

or do you have a column, fixed both ends, with both axial and transverse (= shear ?) loads ? ie beam-column

both cases are available in Roark, etc.

i gather from Dik's post that this section may not be stable in compression (class 1 = stable in compression) so crippling of the compression flange might be the critical compression stress.

Quando Omni Flunkus Moritati

 

[BAretired]

W8x21 is equivalent to metric W200x31 and is a Class 1 section for Fy = 350MPa or 50ksi.

A column fixed top and bottom subjected to a normal force applied at mid-height would require force P where PL/8 = Mp or P = 8Mp/L in which case shear = P/2 = 4Mp/L.

A column fixed at the bottom and free to translate but not to rotate at the top would require a shear of 2Mp/L to produce plasticity at each end (same as bookowski).

BA

 

[dik]

Thanks BA...

Dik