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# Re: Cracked Concrete Sections

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Cracked Concrete Sections
• From: "Michael Valley" <mtv(--nospam--at)skilling.com>
• Date: Tue, 21 Dec 1999 17:44:59 -0700
• Comments: Authenticated sender is <mtv(--nospam--at)mail.skilling.com>
• Priority: normal

```Ec is calculated per Section 1908.5.1.

Essentially all researchers and most practicing engineers who think
about it use Ae = Agross for members in compression.  For members in
tension, it probably makes sense to reduce AE, but this is not
usually a significant consideration for most moment resisting frames.

Many researchers and practictioners use Ie = 0.5 Igross.  There is
support for this approach in FEMA 273 and ATC 40 as well as in
past research.  FEMA 273 indicates that Ie = 0.5 Igross for beams and
columns in tension; Ie = 0.7 Igross for columns in compression.

The calculation procedure outlined in Section 1910.12.3 can be used
for stability analyses, so you could argue that it is reasonable for
even simpler approach (with the same rationale) would be to use the
values in Section 1910.11.1 (0.35Ig for beams, 0.70Ig for columns).

**********
> Date:          Tue, 21 Dec 1999 17:21:28 -0800 (PST)
> From:          James Lin <se3949(--nospam--at)yahoo.com>
> Subject:       Cracked Concrete Sections

> What are the effective I, E, & A for cracked concrete
> moment-frame members (beams & columns) while
> calculating the lateral drift per UBC97?

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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

```