Moment curvature — where it appears
The section that yields from the outside in
A rectangle has half again as much moment in reserve past first yield as its elastic capacity suggests, and an I-section has a seventh. Read as a ranking that gets it backwards — the reserve is bought with curvature, and the rectangle pays four times as much of it.
The stress that was there before the load
A rolled steel section leaves the mill carrying eighty N/mm² of stress with nothing applied to it, in a pattern that sums to no force and no moment. It is invisible to every calculation and it is the knee in every column curve.
The section that cannot reach its own strength
A section classification looks like a table of arbitrary numbers. Set a plate's buckling stress equal to the yield stress and the numbers fall out of a formula written three phases ago — larger than the quoted ones by a constant factor, at every grade.
Named alongside it
The objects these essays reach for when they reach for this one.
DuctilityImperfectionResidual stressRotation capacityColumn curveEffective widthFirst yieldLocal bucklingNeutral axisPlane sectionsPlastic modulusPlastic moment