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Re: Interpreting Analysis Results - UPDATE

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Bill,
 
Thanks for clearing that up - I think.
 
By the way, have you noticed that STAAD uses the minimum flexural reinforcement ratio to size the steel even when the moment strength does not control the design.  I wish they would incorporate an option to use "1/3 greater than required by analysis" which is often significantly less than what STAAD comes up with using the minimum reinforcement ratio.
 
Best regards,
 
 
Ken
 
Kenneth S. Peoples, P. E.
LVTA
Lehigh Valley Technical Associates, Inc.
1584 Weaversville Road
Northampton, PA 18067
 
Phone: 610-262-6345
Fax:610-262-8188
Email: kpeoples(--nospam--at)lvta.net
----- Original Message -----
Sent: Wednesday, December 29, 2004 11:51 AM
Subject: Interpreting Analysis Results - UPDATE

The good folks at Research Engineers have guided me to the section of their technical reference which describes how STAAD.Pro interprets Mxy, p. 3-32.

 

The user has an option to either ignore Mxy or to use the Wood-Armer equations.

 

For the top reinforcing, the following quantities are calculated:

 

Mx1=Mx+abs(Mxy)

My1=My+abs(Mxy)

Mx2=Mx+abs(Mxy^2/My)

My2=My+abs(Mxy^2./Mx)

 

If both Mx1 and My1 are positive, Mxd=Mx1 and Myd=My1.

If both Mx1 and My1 are negative, Mxd=0 and Myd=0.

If Mx1 is negative and My1 is positive, Mxd=0 and Myd=My2.

If My1 is negative and Mx1 is positive, Mxd=Mx2 and Myd=0.

 

For the bottom reinforcement:

 

Mx1=Mx-abs(Mxy)

My1=My-abs(Mxy)

Mx2=Mx-abs(Mxy^2/My)

My2=My-abs((Mxy2/Mx)

 

If both Mx1 and My1 are positive, Mxd=0 and Myd=0.

If both Mx1 and My1 are negative, Mxd=Mx1 and Myd=My1.

If Mx1 is negative and My1 is positive, Mxd=Mx2 and Myd=0.

If My1 is negative and Mx1 is positive, Mxd=0 and Myd=My2.

 

Mxd and Myd are then used in lieu of Mx and My for calculations of the required reinforcing.

 

Regards,

 

T. William (Bill) Allen, S.E. (CA #2607)

ALLEN DESIGNS

Consulting Structural Engineers

http://www.AllenDesigns.com

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