No tension material — where it appears
Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.
The middle third
A material that cannot be pulled imposes a condition on where the load may land, and the condition is a region rather than a point. For a rectangle it is the famous middle third; for every other section it is a shape nobody quotes, and one ordinary section's is nearly twice as generous as the rule allows.
The force nobody put in the model
A slab strip whose ends cannot move apart is not the strip in the yield-line calculation. Deflecting shortens the chord between its ends, the ends do not come in, and the strip is forced into an arch — worth four times the load it was designed for, at a movement nobody would see.
A section made of two materials, one of them pretended away
Multiplying a material's width by the ratio of the moduli produces a fictitious section of one material with the right neutral axis and the right forces. It is not a trick — it is compatibility and Hooke's law written down — and it says a stiff material takes what its modulus asks for.
Named alongside it
The objects these essays reach for when they reach for this one.
Alternative load pathBearing pressureCatenaryCentroidCollapse mechanismCompatibilityComposite actionCracked sectionCreepEccentricityElastic modulusHorizontal thrust