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RE: Staad loading

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The question is what the “bottom chord” loading is.  The title for Load 3, as I see it, is “Floor Live Load”.  This might not be the right loading.  You are likely looking at a model of a truss, and I don’t know what member 3 is, that is, if it is the top chord of the truss or the bottom chord.  Without seeing the entire input file, really ANY conclusion drawn from this is completely speculation.  The only thing you can determine is that this member is loaded with an 80 plf load in the global y (downward direction).  If these trusses are assumed to be at 2 foot centers, then yes, this is a 40 psf loading.  However, what member 3 is as far as the model is concerned, can NOT be determined by the information presented.


You can send me the file personally and I’ll take a look at it to verify.  I’ve used STAAD quite a bit and I’d be willing to clarify.  I would have no problem with this and it shouldn’t take long at all.


Dave Maynard, PE
Gillette, Wyoming


From: Joe Grill [mailto:jgrill(--nospam--at)]
Sent: Tuesday, May 23, 2006 12:13 PM
To: 'seaint'
Subject: Staad loading


A quick question for you staad fans, and probably a very easy one at that.


An engineer in one of our other offices is out on vacation.  He uses staad, where I don’t.  Anyway, a client of his has a question on some work he did, which I only have to verify the loading on the bottom chord of a truss.  The truss is a light pre-manufactured wood roof truss over a garage with an attic space.  The truss is going to be altered slightly and are at 24” spacing.  The client wishes to confirm that a 40psf load was used for the lower chord of the trusses.


I got the file from their office which included the staad output.  He used a load at the bottom chord as follows:




45 3 UNI GY -.08


I’m assuming that this is a 40 psf live load at 2’ centers which is 80 plf or .08 klf.  I’m pretty sure that is right, but just checking.



Joseph R. Grill, PE




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