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Running Load Combo's and Cases

Running Load Combo's and Cases

Running Load Combo's and Cases

(OP)
Why does Risa run each load combination rather than running the load cases and then superimposing them. I know that you need to run each load combination for a P-Delta analysis, but if you're not using P-Delta then why can't you superimpose the load cases? Is there a reason for this because its much quicker and RAM does is.

RE: Running Load Combo's and Cases

RISA used load combinations because that is more accurate.

That's because of various non-linear effects (P-Delta, Tension only members, compression only springs, Direct Analysis Method's stiffness adjustmenst...et cetera,).

Technically, it would be possible for us to use one solution strategy (Load Cases) whenever non-linear effects should not be present and a seperate solution method when those effects are present.  However, we have not chosen to do this at this time.  

By the way, when are you allowed to solve without P-Delta these days?  Wood design?  It seems to me that all the new codes are really emphasizing these types of second order analysis requirements in their analysis requirements.  

Josh

 

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