Equilibrium matrix — where it appears
Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.
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.
Three equations at every joint
A plane truss is determinate when m + r = 2j. A space frame needs 3j, and that one changed digit is why a cube of twelve bars is six mechanisms short while looking perfectly solid — and why every three-dimensional frame ever built is made of triangles in several planes at once.
Named alongside it
The objects these essays reach for when they reach for this one.
MechanismBracingCritical formDouble layer gridIndependent equationsLoad pathLoad sharingMatrix rankMaxwell rulePin jointRank deficiencyRedundancy