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RE: Modeling the subgrade modulus in Staad

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Chris,

That's a very interesting viewpoint.......

Trying to implement soil-structure analysis / design from a "design-office" perspective can be a challenge….however, I've found that trying to "bound" (upper & lower) the solution from parametric modeling can be useful…..now correlating that to actual behaviour is a whole different issue…while doing my grad work I spent some time instrumenting the heck out of metal arch culverts (load cells, strain gauges, etc.), collecting data, and then another grad student would start looking at behavior & comparing to FEM modeling……talk about trying to massage numerical / computer applications to fit observed behaiour…what fun !  I think all we can do from a practical standpoint is trying to construct some uppper & lower bound envelopes, understand the effects of different variables involved, and try to "engineer" a practical solution……hopefully a little farther along than snowfall prediction from groundhogs…..but at least there's a fall back plan :^)

Robert Rogers, PE


-----Original Message-----
From: Christopher Wright [mailto:chrisw(--nospam--at)skypoint.com] 
Sent: Tuesday, May 04, 2004 11:45 AM
To: ‡
Subject: Re: Modeling the subgrade modulus in Staad


>Is there any program that is particularly good for this type of 
>modeling?
Soil structure interaction is about as non-linear and indeterminate as it 
gets. You could probably assume a conventional spring rate for the soil 
modulus, once everything has settled, but settling and seismic 
deformations including uplift resistance seem like anyone's guess. I once 
had some docs for a Corps of Engineers program used to characterize soils 
behavior for culvert design. If this were my problem I'd hit the Corps of 
Engineers web site and see what I could find. They may have some software 
to do it or at least some references or buzz words you could use to keep 
searching. try <http://www.scirus.com/> as well as Google. Scirus is 
aimed mainly at science and technology browsing.

I started to get into this with some buried tank designs, and it can get 
extremely complicated. I'm pretty much convinced that soil structure 
interaction isn't a lot more exact than predicting snowfall from the 
behavior of groundhogs.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864) http://www.skypoint.com/~chrisw



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