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Afterthoughts : Re: STAAD-Concrete sectional properties

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Dear John,

Just had some afterthoughts in progression to your questions. As previously stated, they are more related to the software & modelling than the codal requirements

1) Be very careful of the modeling of the shearwalls, as that can result in results that are way "off the mark".(This precaution is specially necessary, when dealing with circumstances that assume that a software does things "automatically". I had an experience in a peer review of a design in which the design of a RCC element by the software was "automatically assumed" to take into account very large axial forces in primarily flexural members. The software "did", but only after telling it to do so, not by default. ....the downside of technology.....)

2) This is a question. Is there any software available which does this "third degree analysis", i.e for example, taking into account the cracking of concrete? And if there is, then what is the hardware requirement to run such a software?

Regards

Pankaj Gupta
Structures Online
India


From: "John Holliday" <john.holliday(--nospam--at)chemtex.com>
Reply-To: seaint(--nospam--at)seaint.org
To: <seaint(--nospam--at)seaint.org>
Subject: STAAD-Concrete sectional properties
Date: Thu, 11 Oct 2001 23:09:12 -0400

I am reviewing the STAAD input for a Reinforced Concrete six story
industrial building and have a few questions that I hope someone can answer.
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 the
east-west direction (in combination with moment resisting frame) and only a
moment resisting frame in north-south direction. Can I use gross section
properties?

3.	STAAD PDelta analysis has been performed. The engineer who done this
analysis informed me that the PDelta analysis in STAAD takes into account
(automatically) reduced section properties due to cracking, therefore it is
acceptable to input gross section properties. Is this correct?

4. I reviewed the UCB on this subject. Section 1633.2.4 states that flexural
and shear properties shall not exceed one half of the gross section
properties unless a rational cracked-section analysis is performed. Could
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 1633.2.4
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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