Structural Engineering & Statics
where the load goes
Concept

Plane sections

2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
neutral axiscompressiontensionI = 29.97 × 10⁶Z = 299.7 × 10³peak stress 200.2σ = M y ÷ I, at every height

Bending is a pair of forces, pushing and pulling

A bending moment is not a mysterious twisting. It is a push near the top of a section and a pull near the bottom, separated by a lever arm — a couple, made out of stress.

sections · bending stress span ÷ depth = 8plane sections holdspan ÷ depth = 4plane sections holdspan ÷ depth = 2off by 19%span ÷ depth = 1off by 31%the assumption is the theory — everything else is arithmetic on top of 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.

sections · plane sections

Named alongside it

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

Neutral axisCentroidDeep beamElastic limitLever armPlastic momentSaint-Venant's principleSection modulusSpan to depth ratioStrain distributionStress blockStrut and tie

All concepts