Structural Engineering & Statics
where the load goes
Concept

Rank — where it appears

The number of independent equations in a set, which decides whether a structure stands rather than the number of equations there are.

Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.

56.8 kN13.6 kN49.6 kN120 kNthree legs · rank 3 · determinateΣV, ΣMx and ΣMy all close to 1e-14 kN

Six equations, and the drawing shows three

Ninety essays have taken place on a piece of paper, where equilibrium is three equations and a structure is a diagram. The real object has six, the extra three are the ones nobody writes down, and the difference between three legs and four is not a matter of degree.

equilibrium · three dimensional equilibrium a square with both diagonalss = 1 · m = 0Maxwell's count: +1nothing to stiffentwo bars in a straight lines = 1 · m = 1Maxwell's count: +0prestress stiffness +1.000

The forces that are there with nothing applied

Maxwell's count is the difference between two dimensions, and it knows neither of them separately. A frame can satisfy it exactly and still both fold and be prestressable — and when it does, the second of those is what stops the first.

structures · self stress

Named alongside it

The objects these essays reach for when they reach for this one.

DeterminacySelf stressCable netEquilibrium matrixFree bodyGeometric stiffnessIndeterminacyInfinitesimal mechanismMaxwell countMechanismMoment about an axisNull space

All concepts