Calculating allowable moment for beam 2

[niltibi]

Hi,

I have to check suitability of the selected beam. The problem is that I'm working with aluminum so I can't find a table that has allowable moments, deflection and shear, which means I have to calculate them myself. (Unless anyone knows of a table of allowable moments and shear?) The beams are simply supported on each end.

I have 3 types of beams (SI units):
1. 100x50x6 Channel
2. 100x10 Solid Rectangle
3. 100x75x6 Hollow Section


They are 6061 T-6 Aluminum which has a 275 MPa yield strength, ultimate 310 MPa and Elongation % on 2" of 12 if that is needed.

The factored loading and lengths are:
1. 6.32 KN/m 2.78m
3. 6.82 KN/m 2.89m
4. 6.13 kN/m 2.21m

 

[JedClampett]

You need to raise $295 and buy the Aluminum Design Manual by the Aluminum Association. Even though this seems like a simple question, there are a lot of nuances that can complicate it.

 

[niltibi]

true, but how do I do those basic calcs anyway?

 

[Ron]

As JC noted, there are many nuances to aluminum and you've asked for "allowable" moments, deflection and shear, when in fact you need to compute the actual moments, deflection and shear and compare those to the design criteria given in the Aluminum Association Aluminum Design Manual (ADM 2005 or ADM 2010). You have given factored loads, so I'm assuming you want to use the LRFD process rather than the ASD method. Both are allowable in aluminum, but each has its own acceptance criteria that you must wade through....and a forum such as this couldn't possible give you all you need to know for that.

I'm not sure where you are located, but the ADM is used in some areas outside the US, including some areas in Canada and other locations.

The ADM does not give deflection criteria.

To answer your question about the calculations, I would suggest that you get a local structural engineer to help you. Even though the calcs you listed are basic and you have a simply supported condition, you need to look at bracing and connections as well.

 

[niltibi]

I'm in Canada so I'll use the ADM. Thanks guys!

 

[MiketheEngineer]

Find the moment of inertia or Section Modulus.

6061 has an Fu of about 34 ksi - if I remember. Look it up in google

The do the normal calcs.

The buy the book to make sure you are correct

 

[boo1]

For bending and shear of aluminum used in architectural applications, you can the provisions of the AISC Code for architecturally exposed structural steel (AESS). “For deflection the Aluminum Design Manual Part I, Section L.3 reads “Deflections caused by service load combinations shall not impair serviceability.” The Specification for Aluminum Structures gives no general deflection limit for aluminum beams since the Specification is used in many different applications, each with its own performance requirements.”

Note: The welded yield strengths of the 6061-T6 are significantly different depending on weld type, rod and, if structure is reheat treated. For example, for 6061-T6 welded with 5356 filler, the 2005 ADM Table 3.3-2 lists Ftyw = 15 ksi.

 

[boo1]

You may also review Canadian standard CAN3-S157-M83 Strength Design in Aluminum and CSA S157-05/S157.1-05.