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Fwd: [Q] SEAOC-1996: Article C402.10 & C407.3

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I am designing a long and narrow concrete slab
(floor diaphragm) and am required to take into
account the new SEAOC provisions included in the
1996 edition. I ordered the 1996 Blue Book but
until it arrives would like kindly to ask you
the following questions:

1. For what forces shall floor diaphragms be 
   designed? (Rw-factor, overstrenght etc.)

2. My client cited the following articles from
   the new edition of the Blue Book. My question:
   What is the background behind the requirement
   of increased minimum thickness of concrete
   cover for a slab? Do you know of a reference
   (paper or book) which treats this new requirements

Thank you in anticipation.

SEAOC 1996: Article C402.10:

"In response to the 1994 Northridge earthquake damage where
spalling of concrete around these types of bars rendered the
bars ineffective ..."

SEAOC 1996: Article C407.3:

"In Northridge it was observed that large diameter chord and
collector bars and/or closely spaced lap splices tended to
break away the limited concrete cover, especially in concrete
topped precast slab systems. It was apparent that the
reinforcement so exposed underwent large, possibly inelastic,
displacement levels. Once the concrete cover spalled, the chord/
collector bars were rendered ineffective and in some cases
catastrophic building failures ensued"

..."min. concrete cover over tie beams = 2.5 * diameter of 
    reinforcement, but not less than 50 mm"

Peter Rangelow
Deutschherrnufer 29       tel  : + (49-69) 6199-1806
60594 Frankfurt am Main   fax  : + (49-69) 6199-1805  
GERMANY                   rangelow(--nospam--at)

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Subject: [Q] SEAOC-1996: Article C402.10 & C407.3
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Richard Lewis, P.E.
Missionary TECH Team

The service mission like-minded Christian organizations
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