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# Re: Greetings!

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Greetings!
• From: Scott E Maxwell <smaxwell(--nospam--at)engin.umich.edu>
• Date: Thu, 5 Oct 2000 11:53:44 -0400 (EDT)

```Arman,

a while since I used it, but I can give a response on the modulus of

The modulus of subgrade reaction really needs to come from a geotechnical
engineer.  I am not aware of a way to determine it from "allowable"
bearing pressure, but there are some geotechnical types on the list (they
like to see how those of us on the darkside, aka structural engineering,
live) who be able to offer some input.

Basically, the modulus of subgrade reaction is the load required that must
be applied to a plate of a set dimension (and stiff enough to behave as a
"rigid" plate) to make that plate "settle" a some distance.  For
example, take a plate that is 600mm diameter and apply some rather sizable
load.  Measure how much it deflects/settles.  With that information (plate
size, load, and deflection) the modulus can be determined with some
adjustment for the flexibility of the plate.  Basically, the modulus is
the pressure determine from taking the load divided by the plate area
which is then divided by the deflection.  The resulting value is in the

Therefore, I would suggest that you need to get some additional
geotechnical information.

Hope that helps.

Scott

On Thu, 5 Oct 2000, arman s rivera wrote:

> Dear fellow engineers!
>
> Greetings!
>
> I am Arman Rivera, a practicing structural engineer in the Philippines.  Our firm recently purchased the software Staad Pro 2000 and from the limited hands-on I have had on it, this software is remarkable.  However, as I've been reading the manual that came with the software, I have many questions regarding it.  Is anybody familiar with Staad Pro 2000 that won't mind answering questions from a novice user?
>
> I've been using Staad Pro 2000 to design communication towers.  My first question is, should the tower be classified as SPACE or TRUSS?  What I've done is to treat it is a space and then assign the moment releases at the end of the diagonals and verticals only (not the main posts), so that these members would carry only axial forces.  Is this correct?
>
> My next question is on the support conditions.  I have modeled the mat foundation using finite elements in Staad Pro 2000.  I have defined the joint supports as ELASTIC MAT by specifying the modulus of subgrade reactions (kv).  Given the allowable soil bearing capacity, how is the modulus of subgrade reaction computed?
>
> I have many more questions regarding this software, any help you could give me would be greatly appreciated.
>
> Thank you very much.
>
>
> Regards,
> Arman S. Rivera
>
> __________________________________
> www.edsamail.com
>
>

```