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Wood Armer Equations 553

The Wood and Armer method incorporates twisting moments into slab design by ensuring that the moment in any direction due to design bending and twisting moments (Mx, My, Mxy) does not exceed the ultimate resisting moment provided by the reinforcement in that direction (Mux and Muα). Mx, My and Mxy are obtained from structural analysis, while Mux and Muα depend on the reinforcement layout and properties. This method aims to prevent yielding in slabs in all directions based on Johansen's yield criterion.

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Balaji Venkateswaran
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693 views2 pages

Wood Armer Equations 553

The Wood and Armer method incorporates twisting moments into slab design by ensuring that the moment in any direction due to design bending and twisting moments (Mx, My, Mxy) does not exceed the ultimate resisting moment provided by the reinforcement in that direction (Mux and Muα). Mx, My and Mxy are obtained from structural analysis, while Mux and Muα depend on the reinforcement layout and properties. This method aims to prevent yielding in slabs in all directions based on Johansen's yield criterion.

Uploaded by

Balaji Venkateswaran
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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Wood and Armer method

Wood and Armer proposed one of the most popular design methods that explicitly
incorporate twisting moments in slab design. This method was developed by considering
the normal moment yield criterion (Johansen’s yield criterion) aiming to prevent yielding
in all directions. At any point in the slab, the moment normal to a direction, resulting due
to design moments Mx, My, and Mxy, must not exceed the ultimate normal resisting
moment in that direction. The ultimate normal resisting moment is typically provided by
ultimate resisting moments Mux and Muα related to the reinforcement in the x- and α-
directions.

Mx, My and Mxy are bending and twisting moments, usually obtained from a finite
element or grillage analysis program. The sign convension needs to be altered if it is
different from above. α is the angle of the transverse steel, measured clockwise, from the
Mx axis.

M*x = Moment to be resisted by reinforcement in the x direction


M* α = Moment to be resisted by reinforcement in the a direction
Ref :

Wood, R.H., “The Reinforcement of Slabs in Accordance with a Pre-Determined Field


of Moments,” Concrete, V. 2, No. 2, 1968, pp. 69-76. (discussion by Armer)

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