Wood-Armer & Twisting Moments
Wood-Armer & Twisting Moments
(OP)
Just getting myself up to speed with everything discussed and presented in thread744-341206: Mxy moments in concrete floor design - v2
I understand twisting moments can be significant and therefore considered carefully in design.
However reading my RC textbook... Link
"In general, for reinforced concrete slabs, it is required to design for Mx and My only. Special reinforcement detailing is sometimes necessary to cover twisting moments at the exterior slab corners."
Setting up a test file in RAM Concept and quick hand calculations shows that using Wood-Armer can significantly change the design actions present.
So why would this textbook say that? When is it critical to consider the twisting moments? Always? Or only at the slab corners?
My gut says that the Wood-Armer method is much more comprehensive and correctly generates design actions for reo in the orthogonal directions.
I understand twisting moments can be significant and therefore considered carefully in design.
However reading my RC textbook... Link
"In general, for reinforced concrete slabs, it is required to design for Mx and My only. Special reinforcement detailing is sometimes necessary to cover twisting moments at the exterior slab corners."
Setting up a test file in RAM Concept and quick hand calculations shows that using Wood-Armer can significantly change the design actions present.
So why would this textbook say that? When is it critical to consider the twisting moments? Always? Or only at the slab corners?
My gut says that the Wood-Armer method is much more comprehensive and correctly generates design actions for reo in the orthogonal directions.





RE: Wood-Armer & Twisting Moments
If you use a method of analysis that produces Mxy moment as apart of equilibrium, than you must include it in your design.
Wood-armer isn't the only solution for converting Mxy to Mx and My resultants. It can be conservative in situations and consideration to its use should be given.
http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."
RE: Wood-Armer & Twisting Moments
When using Ram I keep the wood-armer on.
I also reduce the torsional stiffness to 10%. It gives a more realistic deflection plot.
RE: Wood-Armer & Twisting Moments
Asixth - am I correct in saying that the default option of "none in regards to torsion design in ram is making the program ignore Mxy? Here's hoping just allows for the extra twisting moments in the Mx and My moments.
RE: Wood-Armer & Twisting Moments
RE: Wood-Armer & Twisting Moments
The Mx and My moments in strip methods are not the same as Mx and My in FEM.
FEM produces node moments. To convert them to useable orthogonal design moments for an element, Mx and My cannot fully describe the situation for an element unless the moments at the corners are basically symmetrical. So for most elements a twisting moment Mxy is needed to define the twist in the element.
You will find in a regular structure that the FEM Mx and My, after being adjusted by a contribution from Mxy will be basically the same as the strip method Mx and My.