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Re: Modeling of soil with superstructure

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Sadanand,

For most structural designs, modeling the soil as linear (one way) compression springs with a plus or minus 50 percent range under your foundation is plenty accurate and is required for dynamic analysis per ASCE 7-05 Section 12.13.3.  I suppose you could use nonlinear soil springs but the problem would be how do you accurately define the linearity when soil properties in general are not that well known and can vary considerably over a project site.  Putting a few extra decimal points into your solution does not necessarily make the results any better especially when it comes to soil properties.

Thomas Hunt, S.E.
Fluor



sadanand_ojha(--nospam--at)yahoo.com
11/03/2008 08:10 PM
Please respond to seaint
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Modeling of soil with superstructure





Can any one has some clue how to model non linearity of soil with structure any software for that
Sent on my BlackBerry® from Vodafone Essar

-----Original Message-----
From: "Doug Mayer" <doug.mayer(--nospam--at)taylorteter.com>

Date: Mon, 3 Nov 2008 13:52:28
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Horizontal Irregularities


Hmmm...not sure what happened with that last message.  Anyway, here it is again in a (hopefully) readable format.

Agreed that the (possible) increased nailing requirement would only be along the boundary edge.  However, the way the code table reads is that to achieve the listed diaphragm capacity, the specified boundary AND edge nailing must be used.  It doesn't seem it would follow the intent of the table if you used 2.5" spacing only at the boundary edge and then immediately switched to 6" o.c. for all other edges after removing the 25% increase.

Doug Mayer, SE


-----Original Message-----
From: William Haynes [mailto:gtg740p(--nospam--at)gmail.com]
Sent: Monday, November 03, 2008 12:39 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Horizontal Irregularities

I knew that question was coming next... It says "connections of
diaphragms to vertical elements" so I take that to be along the
immediate edge of the diaphragm to vertical element (ie. boundary
nailing), so anywhere interior of this would not have the 25% increase
applied. So I would say it is required only along the boundary and not
at any locations interior to the very edge of the diaphragm (my
interpretation). Therefore, you should be able to step it immediately
to a lower shear value even though it seems a little counter
intuitive.

Will




On Mon, Nov 3, 2008 at 3:19 PM, Doug Mayer <doug.mayer(--nospam--at)taylorteter.com> wrote:
> If that is the case, then how would you deal with stepped diaphragm nailing
> zones?  At what point away from the boundary edge would you be able to
> remove the 25% demand load increase?
>
>
>
> Doug Mayer, SE
>
>
>
> From: Gerard Madden, SE [mailto:gmse4603(--nospam--at)gmail.com]
> Sent: Monday, November 03, 2008 11:42 AM
>
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Horizontal Irregularities
>
>
>
> It applies to the boundary nailing in wood diaphragms, deck welds and shear
> studs to boundaries in metal deck w/ conc. etc...
>
> Where the diaphragm shear is not at a boundary (i.e. support in your
> diaphragm shear diagram) it does not apply per this wording.
>
> -gm
>
> On Mon, Nov 3, 2008 at 10:54 AM, Doug Mayer <doug.mayer(--nospam--at)taylorteter.com>
> wrote:
>
> Hmm, I worded that poorly.  Yes, the demand should be increased 25% per this
> section, but does it apply to the diaphragm shear values that you would then
> compare to the code allowable diaphragm shear?
>
>
>
> Doug Mayer, SE
>
> Structural Engineer
>
>
>
> TaylorTeter
>
> Partnership
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>
>
> 7535 North Palm Ave., Suite 201
>
> Fresno, CA 93711
>
>
>
> (559) 437-0887 Ph.
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> (559) 438-7554 Fax
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> doug.mayer(--nospam--at)taylorteter.com
>
> www.taylorteter.com
>
>
>
> From: David Topete [mailto:d.topete73(--nospam--at)gmail.com]
> Sent: Monday, November 03, 2008 10:46 AM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Horizontal Irregularities
>
>
>
> It appears the demand must be increased 25%, while the "allowable" shear
> values remain unchanged.
>
> On Mon, Nov 3, 2008 at 10:26 AM, Doug Mayer <doug.mayer(--nospam--at)taylorteter.com>
> wrote:
>
> Section 12.3.3.4 of the ASCE 7-05 states:
>
> "For structures assigned to Seismic Design Categories D, E, or F and having
> a horizontal structural irregularity…the design forces determined from
> Section 12.8.1 shall be increased 25 percent for connections of diaphragms
> to vertical elements and to collectors…"
>
>
>
> Does this requirement apply to diaphragm shear values taken from the code
> tables?  As I read it, it does not, but I would appreciate confirmation.
>
>
>
> TIA,
>
>
>
> Doug Mayer, SE
>
>
>
>
> --
> David Topete, SE
>
>
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