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USFEngineer (Structural) (OP)
6 May 08 12:04
I was wondering if anyone can lead me in the right direction for the allowable bending stress (Fb) of 6061 T6 aluminum? This is my first project designing with aluminum.
 Is there a specific code for design that I should follow or should AISC be used other than the physical properties of the aluminum?

Any info would be greatly appreciated.

Thanks
rb1957 (Aerospace)
6 May 08 12:10
elastic or inelastic ?

i would normally limit elastic bending stress to Fcy = 35ksi.  this supposes that the section is stable in compression (crippling is not a problem, b/t < 8)
pelotoner (Structural)
6 May 08 12:55
The Aluminum Design Manual 2005, by The Aluminum Association.  Very similar design principles, except ASD is easier.  Watch out for proximity to welds, the allowable stress is greatly reduced.

I also graduated from USF (South Florida, right?), Cheers!   
Bagman2524 (Structural)
6 May 08 12:56
rb1957 has the allowable stress correct.  6061 T6 is strong stuff.  The Aluminum Association has a design standard for Aluminum.  AISC should not be used.  Aluminum's modulus of elasticity is somewhere around 10,000 to 11,000 ksi.  A good reference for aluminum design is Aluminum Structures, A guide to their Specifications and Design, J.Randolph Kissell & Robert L. Ferry.
spats (Structural)
6 May 08 13:06
6061-T6 Aluminum is Fy=35 ksi. Fu depends on whether it's plate, extruded, pipe, etc., and ranges from 38-42 ksi. E=10,100 ksi. Allowable bending stress per the Aluminum Design Maual (I have 2005 Edition) varies depending on the shape, and the slenderness of the elements that make up the shape. It even also has to do with whether you're designing a bridge or a building.

For the extreme fiber of a bending member in a building or similar structure, following are some typical values:

   Round Tube Fb=0.71Fy
   Square Tube or Single Web Shape Fb=0.61Fy
   Solid Rectangular or Round Fb=0.79Fy

In any event, you need the Aluminum Design Maual from The Aluminum Association... too many variables here. Also, aluminum allowable stresses are greatly reduced anywhere within 1" of a weld... and on, and on...
 
USFEngineer (Structural) (OP)
6 May 08 13:13
Thanks for the info guys. Much appreciated. I will definatley get the Aluminum Design Manual.

The member I am checking is actually an aluminum angle (L2 x 2 x 3/16) with a point load at its midpoint. The design is straight forward but I needed to get the allowable stress to detrmine if the section modulus is adequate.

Thanks again.

pelotoner - yeah South Florida. (Go Bulls!!) cheers.
lafernandez (Mechanical)
13 May 08 16:50
Hi guys! what is the maximum pressure i can apply to an 6061-t6 Al rectangular tubing of 1.5" x 4" x 0.125" thickness. the total length would be about 40" and the pressure is going to be applied for a max of 20 seg
civilperson (Structural)
13 May 08 19:53
The ny, which is in the denominator below fy (yield stress), is 1.65 for buildings and for formulas in Table 3.4-3. This gives allowable stress for tension in beams, extreme fiber from bending of structural shapes bent around strong axis and tubes of 21.2 ksi. [page I-A-24, 3.4 Allowable Stresses.  "Aluminum Design Manual"
csd72 (Structural)
13 May 08 22:48
This allowable stress is reduced if it is welded, down to about 11ksi.

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