Determining Fb for Aluminum shapes

[PostFrameSE]

I'm trying to find out whether using Chapter F of the ASD Steel Construction Manual to determine Fb and Fv for aluminum is acceptable or not. Thanks for the help

 

[Lion06]

No, it isn't.
Aluminum has its own design manual. Additionally, beware of welding with aluminum as it lowers the allowable Fb significantly (at least in the region of the weld).

 

[Bagman2524]

6061 aluminum is pretty strong stuff with yield strengths near 35 ksi. Check out the Aluminum Association at

http://www.aluminum.org/.

They have their own specifications titled Specification for Aluminum Structures and Aluminum Standards and Data.

 

[JAE]

Agree with Bagman2524.

Also - aluminum has a lower E so deflections are a bit higher.

 

[csd72]

buckling of aluminum is very different to buckling of steel.

 

[PostFrameSE]

Thanks for the responses. I'm not welding any pieces. I'm dealing with 6063 T5 extruded small aluminum shapes. I'm laterally loading a "square cornered" U-shape. With one load combination, my compression edge is braced every 9" o.c. while in another combination, my compression edge is unbraced along the entire length.

This doesn't have to be real precise (ie....this is not a commercial structure, and it's for components and cladding) so is using .4Fy or .5Fy a reasonable guesstimate for determining Fb?

Maybe I shouldn't worry about stresses as ultimately, deflections are going to govern........and I understand that the E is much less than steel so deflections are much higher.

Thanks again.

 

[csd72]

Deflections dont always govern, we use 11ksi allowable for welded areas of 6061-T6 this should be okay for an estimate.

 

[Bagman2524]

I believe the modulus of elasticity (E) of aluminum is about 11,000,000 psi. So deflections are about 29/11 = 2.6 times larger.

 

[PostFrameSE]

OK. Thank you all for your help.

 

[msquared48]

You might contact Alcoa - they supply several design manuals for extruded aluminum shapes of all different types of Aluminum - in hopes you will use their shapes...

I believe the publications are produced by the Aluminum Association, Inc.

Good Hunting...

Mike McCann
McCann Engineering