Span to depth — where it appears
The section that changes along the span
A prismatic beam is checked where the moment is largest, and everyone knows where that is. A tapered one is not, because the capacity is moving too — and for a cantilever with a load at its tip the governing station is exactly where the depth has doubled, with no length, no load and no material in the answer.
The floor is a beam lying down
A floor plate spans horizontally between the walls that resist a lateral load, carries a distributed inertia load, and has chords, a web and a span-to-depth ratio like any other beam. Its stiffness decides whether the walls share the load by their stiffness or by the area of floor nearest them — and the familiar tributary answer turns out to be neither limit.
Named alongside it
The objects these essays reach for when they reach for this one.
Accidental eccentricityBending momentCentre of rigidityChord forceCollectorDeep beamDeflectionDiaphragmErection stabilityFully stressed designHaunchIn plane stiffness