Concept
Span to depth ratio
2 essays name this object, across 2 fields. What follows is each of them, and the objects they name alongside it.
Depth is the cheapest strength there is
Doubling the depth of a truss halves its chord forces without adding a gram of material to the chords. Nothing else in structural design is that cheap, and almost every structure has already spent it.
Plane sections stay plane, and what the assumption costs
Beam theory rests on one sentence about geometry. It is very nearly true for a slender member, wrong for a deep one, and everything in the subject that fails does so where it stops holding.
Named alongside it
The objects these essays reach for when they reach for this one.
BucklingChord forceDeep beamEfficiencyLever armNeutral axisPlane sectionsSaint-Venant's principleSecond moment of areaSelf weightStrain distributionStrut and tie