User Area > Advice
Wood Armer for Grillages
The Wood Armer equations are commonly used by engineers in
the design of:
- Orthogonal reinforcement for RC slabs which are to resist
a combination of moments (Mx, My) and a twisting moment (Mxy)
- Reinforcement for skew slabs (principle moment directions
inclined to the reinforcement directions). The equations
use Mx, My and Mxy obtained from a plate analysis [more
on Wood Armer with Plates].
To use the Wood Armer equations for grillages, the bending
and twisting moments obtained from the analysis have to be
converted into "equivalent plate moments" in global
directions. LUSAS carries out that conversion as well as the Wood Armer
calculation in post-processing i.e. for a
"pre-determined field of moments" (Mx, My, Mxy).
An extra geometric property (effective
width) has to be defined for the grillage members in
order to compute the "equivalent plate moments".
In the normal way the "effective
width" will be the width of slab assigned to the
member in question. Further information is given in the
Help menu item:
Help Topics > Contents tab > Theory
Manual > Chapter 6 > 6.2 Wood Armer Reinforcement
It should be noted that while general stress
results on a grillage are "per member", Wood Armer
results, reported through the Print Results Wizard or the
Values layer are "per unit width". Reporting Wood Armer
results via the Diagram or Contour layers is not valid.
An outline check may be carried out by any user on the
grillage calculation within LUSAS Modeller by constructing a
grillage and a plate model which can be compared. Allowance must
be made in any comparison for the inherent differences in the
analyses. Similarly a simple test will indicate that the Wood Armer
results, reported through the Print Results Wizard or the Values
layer are "per unit width".
Other Wood Armer related topics
Other Grillage
modelling issues
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