Structural Engineering & Statics
where the load goes
Generator

The critical-form generator

Rendered here at the parameters it defaults to, with every essay that calls it — which is the same list as the blast radius of changing it.
The count is necessary and not sufficientTwo pin-jointed frames, each satisfying m + r = 2j exactly. One of them folds anyway, because the equations are not independent; the ghosted outline is the motion that costs no member any change of length, drawn at an exaggeration of 0.55 of the span.one panel braced twice, the next not at allm 9 + r 3 = 2j 12 · rank 11a mechanismthe same count, properly arrangedm 9 + r 3 = 2j 12 · rank 12stands up

1 essay calls critical-form. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

one panel braced twice, the next not at allm 9 + r 3 = 2j 12 · rank 11a mechanismthe same count, properly arrangedm 9 + r 3 = 2j 12 · rank 12stands up Equilibrium

The count that does not see it

A frame can have exactly as many unknowns as equations and fold up anyway. The count asks whether there are enough equations; it never asks whether they are different from one another.

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