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RE: STAAD-Concrete sectional properties

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He is correct...... to my knowledge as well, it only accounts for
deflections and does not automatically adjust stiffness values
representative of the degree of cracking.....

Robert C. Rogers, PE
Senior Structural Engineer
A.M. Kinney, Inc. 
Consulting Engineers / Architects
150 East Fourth Street, 6th Floor
Cincinnati, Ohio 45202
PH: 513-421-2265, ext. 125
FX: 513-345-1318

-----Original Message-----
From: Structures Online [mailto:soldetail(--nospam--at)]
Sent: Thursday, October 11, 2001 11:41 AM
To: seaint(--nospam--at)
Subject: Re: STAAD-Concrete sectional properties

Dear John,

I am not very much familiar with American codes, so I cannot reply to
questions, but I can answer Q #3.

The answer is that STAAD does not take reduced section properties due to
cracking. P-delta analysis performs a secondary level analysis, in which
takes into accounts the forces generated by the deflections caused by
first order analysis, and that is all.


Pankaj Gupta
Structures Online

----- Original Message -----
From: John Holliday <john.holliday(--nospam--at)>
To: <seaint(--nospam--at)>
Sent: Friday, October 12, 2001 8:39 AM
Subject: STAAD-Concrete sectional properties

> I am reviewing the STAAD input for a Reinforced Concrete six story
> industrial building and have a few questions that I hope someone can
> 1.  Is it usual practice to use the member properties in ACI 10.11.1?
> 2.  Section R8.6.1 talks about using gross section properties for all
> members in braced frames. My building has two parallel shear walls in
> east-west direction (in combination with moment resisting frame) and
> moment resisting frame in north-south direction. Can I use gross
> properties?
> 3. STAAD PDelta analysis has been performed. The engineer who done
> analysis informed me that the PDelta analysis in STAAD takes into
> (automatically) reduced section properties due to cracking, therefore
> acceptable to input gross section properties. Is this correct?
> 4. I reviewed the UCB on this subject. Section 1633.2.4 states that
> and shear properties shall not exceed one half of the gross section
> properties unless a rational cracked-section analysis is performed.
> someone explain to me what a rational cracked-section analysis is.
> 5. Section 1910.11.1 of the UCB gives similar member properties as ACI
> 10.11.1 but seems to contradict the requirements of UCB Section
> i.e. using 50% of gross. Can someone clarify this for me.
> Thanks in advance for any help.
> John Holliday  P.E.

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