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RE: Interpreting Analysis Results
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 Subject: RE: Interpreting Analysis Results
 From: "David Handy" <dhandy(nospamat)trg.ca>
 Date: Mon, 27 Dec 2004 13:58:22 0500
Title: Message
Bill:
I have attached a chunk of the help notes from my Robot software in the ways it
deals with the Mxy value in getting estimates of Mx and My:
Robot allows one also to use the Wood&Armer method (the
European code supplement [ENV 199211 EC2 Design of Concrete Structures –
Appendix 2, point A.2.8 Reinforcement in Slabs]). The conception
of determining equivalent moment is authored by Wood and Armer. Details
concerning the method can be found, for instance, in R.H.Wood – "The
reinforcement of slabs in accordance with a predetermined field of moments",
Concrete, February 1968, August 1968 (correspondence)].
Calculation procedure
For a selected direction "x" (and the corresponding perpendicular direction "y") one calculates two types of design moments M*: the "lower" ones (positive, causing mainly tension in the bottom parts) and the "upper" ones (negative, causing tension in the upper parts). The general procedure takes the following form: Determination of the "lower" moments Mxd*, Myd*: Mxd* = Mx + Mxy Myd* = My + Mxy However, if Mx < Mxy (i.e. the calculated Mxd* <
0)
Mxd* =
0
Myd* = My + Mxy*Mxy/Mx. Similarly, when My < Mxy (i.e. the calculated Myd* < 0) (*) Mxd* = Mx + Mxy*Mxy/My (*) Myd* = 0 (*) If any of thus obtained moments Mxd*, Myd* is smaller than zero, one should assume the zero value (the design moments for tension in the upper layers are determined further on in the text). Determination of the "upper" moments Mxg*, Myg*:
Mxg* = Mx  Mxy Myg* = My  Mxy If Mx
> Mxy (i.e. the calculated Mxg* > 0) (*)
Mxg* =
0 (*)
Myg* = My  Mxy*Mxy/Mx (*) Similarly, when My > Mxy (i.e. the calculated Myg* > 0) Mxg* = Mx  Mxy*Mxy/My Myg* = 0. If any of thus obtained moments Mxg*, Myg* is bigger than zero, one should assume the zero value (such moments would design the lower reinforcements, which is already guaranteed by the formerly calculated "lower" moments Mxd*, Myd*) I
would not fully rely on this but you can use it as a starting point anyway.
Robot does all this for me.
Good
Luck
David
Handy, P.Eng.

 References:
 Interpreting Analysis Results
 From: Bill Allen, S.E.
 Interpreting Analysis Results
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