Structural Engineering & Statics
where the load goes
Concept

Self stress — where it appears

A set of internal forces in equilibrium with no load at all, which a redundant structure can carry and statics cannot see.

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 free at one end10.8 mmno stressheld at both ends75.6 MPaheld by a spring of 100 kN/mm53.2 MPaE·α·ΔT = 210000 × 12×10⁻⁶ × 30 = 75.6 MPa, at every length

The movement nobody applied

A temperature change is the only load in this collection that a structure can decline. Let it move and it produces a movement with no stress; hold it and it produces a stress with no movement — and that stress contains no length, no area and no second moment, so a bracket and a bridge girder carry exactly the same one.

deflection · thermal movement

Named alongside it

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

IndeterminacyBucklingDeterminacyExpansion jointFree bodyMoment about an axisRankRestraintServiceabilitySupport reactionThermal gradientThermal movement

All concepts