Aluminum beam design

[S.K.G]

Hi,
I am trying to design a scaffolding system that uses aluminum beams. I have a copy of the 2005 version of the aluminum design manual and in there, they specify to design a beam for bending you have to check the tension bending, compression bending, and shear bending. However, the final values for each state gives you the value in stress. For example, for tension bending I would get a final answer in units of ksi which means I cannot exactly compare it to the max moment the beam experiences due to the applied load. Would I simply multiply this value by the section modulus of the beam on the bottom (tension side) to get my moment capacity like we do for steel, and the same thing for compression bending (but use the section modulus at the top (compression side))?

 

[driftLimiter]

The actual section properties and effective section properties are used to compare with the limiting stress.
In the newer versions of the code/specification there is an example section (similar to AISC examples). In there you can find simple beams and the design checks.

 

[S.K.G]

@drift sorry, could you elaborate on what you mean by, "the actual section properties and effective sections properties are used to compare with the limiting stress"? Like are you saying there are section properties for the designated beam and you would compare them with the applied moments/loads kind of like beam selection tables? Also if so, I guess I should ask my boss to buy the latest version then.

 

[driftLimiter]

No, what I mean is you use the section properties to determine the stress. Basic Mechanics P/A, My/I, V/Ac.

Those examples I provided are the gross section properties. But aluminum is notoriously designed with instabilities locally. So the ADM provides different methods of calculating effective section properties that include local slenderness effects. This procedure varies significantly depending on the section in question... i.e. doubly symmetric, singly symmetric, with slender elements or without.

You really need to go over those examples to do this correctly.

 

[driftLimiter]

The examples can be found in ADM section VII. (I'm using the 2015 edition).

 

[S.K.G]

@drift, okay will talk to my boss about buying the new version. Thanks a lot!