Re: FEMA 273 "First Draft" -- Equations F7-1 and -2

• To: seaint(--nospam--at)seaint.org
• Subject: Re: FEMA 273 "First Draft" -- Equations F7-1 and -2
• From: "Michael Valley" <mtv(--nospam--at)skilling.com>
• Date: Wed, 19 May 1999 16:02:54 -0700
• Comments: Authenticated sender is <mtv(--nospam--at)linux.skilling.com>
• Priority: normal
```Bill:

Yes.  I_g is the gross uncracked moment of inertia in the long
direction of the wall (which is the direction that we normally
consider shear wall to work).  The equations are based on the
initial, elastic conditions.

Section C7.4.2.1 of the FEMA 274 Commentary says, "Because the
unreduced forces are ficticious, they cannot be used to assess the
expected amount of cracking in any component. ... Therefore, only
initial, uncracked linear stiffnesses can be used with the equivalent
linear procedures.  Any nonlinear action is accounted for by applying
the m factor to expected strengths."

-Mike

***************
> From:          "Bill Polhemus" <polhemus(--nospam--at)insync.net>
> Subject:       FEMA 273 "First Draft" -- Equations F7-1 and -2
>
> These formulae, for "k" (stiffness of wall or 'pedestal') use I-sub-g
> (Moment of Inertia for gross uncracked section).
>
> Since they are "in plane" stiffnesses, should this be the gross uncracked
> section of the LONG DIRECTION of the wall? (i.e. the shearwall or pedestal
> with forces acting horizontally in the in-plane direction)

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Michael Valley                                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201

```