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RE: Greetings!

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Arman Rivera wrote:

> should the tower be classified as SPACE or TRUSS?  

In my earlier version of STAAD, it says that TRUSS can be used 
for either a plane or space analysis. If all of your members 
are only to be designed to carry axial loads the TRUSS command 
seems best to avoid the extra work of entering releases. But if 
you want to model the chords as continuous members, the SPACE 
command would be better - but can't you do a "list" of members to 
be defined as "truss" members, rather than entering end releases? 
As others have noted, you make encounter member instability errors 
when entering end releases, which require one end to have rotational 
restraint. 

> Given the allowable soil bearing capacity, how is the modulus of 
> subgrade reaction computed?

Generally there is not direct correlation, although Bowles does give 
an equation for estimating purposes. In a previous thread on modeling 
the modulus of subgrade reaction, it was suggested to "bracket" the 
design by making runs with both a high and a low estimate of subgrade 
reaction, such as 50 pci and 300 pci. Most decently compacted soils should 
have a modulus in the range of 100 to 200 pci, so this seems reasonable.