light gage purlin allowable deflection 1

[shei]

Hello everyone!

I would just like to know what is the allowable maximum deflection according to AISC. I'm quite confused what to use
between L/360 for liveload only or L/240 for deadload and liveload combination. Also, i have read some that uses L/150 using liveload. Thanks....

 

[SperlingPE]

Use what you deem appropriate. AISC provides minimums.

 

[Lutfi]

You need to be more specific and the answer really depends on your situation.

I use L/360 for floors that have ceilings. This criterion was developed many years ago and it was based on the use of plaster. Using L/360 prevents plaster from cracking.

If you have a roof, I would use L/240 for criteria. Keep in mind potential ponding. In some areas, I have used L/180 for live load deflection.

If you plan on using light gage steel purlins, you will find that controlling deflection is hard due to their inherent low moment of inertia of a thin section. Also keep in mind most of these sections are not true prismatic sections.

You need to use your engineering judgment.

 

[pmkPE]

What is the alloable deflection for the roofing being supported?