P-Delta analysis, notional loads and tension only bracing

[canwesteng]

The combination of these three always seems to create errors in my model. Anyone have any input on how to mitigate this?

 

[Sye123]

Do not use the tension only and Pdelta for the component cases acting alone. For example don’t do such analysis for live load acting alone, or wind or seismic load acting alone. Also I am sure you are using REPEAT LOADs and not LOAD COMBINATIONs. Pdelta effects are only seen when vertical and lateral loads act in conjunction. So here is the recommended command sequence

Define all component cases
PERFORM ANALYSIS
CHANGE
Then define MEMBER TENSION
Define REPEAT LOAD cases
Define the PDELTA 15 ANALYSIS
…

 

[canwesteng]

Yeah, I always use the change command in order to do p delta analysis on load combination cases only

 

[PAstructural08]

If using tension/compression only members you have to use repeat loads and NOT load combinations.

 

[canwesteng]

Sorry for the confusion, but repeat loads are being used.