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Fabric Membranes Cutting Pattern 203
Fig. 8. Strip determined with the stress composition method
The followinggraph represents the values of the principal stresses σ1 and σ2 for
every 40 triangular elements used for the modelling; the ideal solution is drawn
by the horizontal line σ1 = σ1 = σ0 = 250 daN/m (target state). We observe
a regular stress distribution within the surface and the solution appears as
quite satisfactory.
Fig. 9. Principal stresses obtained with the integrated method
If the same strip is now calculated with the simple triangulation method
followed by a reduction, the determined shape may be characterised by a stress
deviance ∆σ L(7)
0 =26, 62% (evaluated after remeshing the plane domain with
40triangular elements by adding internal nodes without altering the geometry
of edges).
The values of the resulting principal stresses are presented in the following
graph.
We point out that, when all the geometry of the domain is not taken into
consideration likewise during the mapping with simple triangulation, increasing
deviances occur. Such result is however not so surprising. A more detailed
analysis of the graph allows noticing a higher distortion between the principal
stresses for the elements located in the top zone of the surface (right part of
the graph). A possible explanation relies in the fact that these elements are