wood armer is an equivalent moment method - it basically takes the Mxy (twisting) moment and lumps this value to the principal direction moments Mx & My.
A ref for this is R.H.Wood – „The reinforcement of slabs in accordance with a pre-determined field of moments”, Concrete, February 1968
to use the Wood-Armer equations for reinforcement calculations, as follows:
a) Mx, My, and Mxy are fetched or calculated, as described above. They are used to compute the values of design moments, Mxd and Myd.
b) For top reinforcement, the program computes:
Mx1 = Mx + abs(Mxy)
My1 = My + abs(Mxy)
Mx2 = Mx + abs(Mxy2 / My)
My2 = My + abs(Mxy2 / 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 positive, Mxd = 0 and Myd = My2.
If My1 is negative and Mx1 positive, Mxd = Mx2 and Myd = 0.
c) For bottom reinforcement:
Mx1 = Mx - abs(Mxy)
My1 = My - abs(Mxy)
Mx2 = Mx - abs(Mxy2 / 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 positive, Mxd = Mx2 and Myd = 0.
If My1 is negative and Mx1 positive, Mxd = 0 and Myd = My2.
Mxd and Myd are then used in lieu of Mx and My for calculations of the required reinforcing.
