STAAD PRO V8i and AISC 14th Ch. C - Requirements for Stability

[jray2900]

The question has recently been raised at my company if the way that we are running our analyses using Staad Pro V8i is compliant with the AISC 14th Chapter C requirements for stability. Just to give a little background, I work for a company that designs and builds low occupancy industrial structures. I've been trying to find some relevant information of how to use DAM in staad but I haven't had any luck finding anything readily available on online. I am looking to get a little insight on the way we are using staad to design structures and if this method is sufficient to satisfy code requirements.

Below is an example of the code check section of a generic staad file:

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PDELTA 3 ANALYSIS SMALLDELTA PRINT ALL
PARAMETER 1
CODE AISC UNIFIED
METHOD LRFD
FYLD XXX
LY XXX
LZ XXX
RATIO XXX
STEEL TAKE OFF XXX
CHECK CODE ALL

----------------------------------------------------

Some guidelines we follow:

We always use repeat loads
New construction and newer existing structures are always analyzed using LRFD
Older existing structures are always ASD

Unity Ratios:

Columns < 0.75
Beams < 0.85
Bracing < 0.9
Anything with moving equipment < 0.5


It is our standard practice to be quite conservative with loading and deflections because of the magnitude of some of the equipment that we use in our designs. Thank you for any comments or advice.

 

[canwesteng]

I'd probably use PDELTA CONVERGE instead of PDELTA 3, but for typical industrial structures, these are braced and quite stiff so it wouldn't matter much. As long as you are using notional loads and K factors, you satisfy AISC requirements for analysis. For industrial this is IMO the easiest way to do things. See appendix 7 for effective length method.

 

[dadofranz]

Should we always use P-delta analysis with direct analysis method??
or we can use only (Perform direct analysis)

 

[canwesteng]

Use perform direct analysis, along with appropriate stiffness factors, if you use the direct analysis method. Use P-Delta, with K factors in design equations, if you are using the effective length method