Concept
Deflection limit
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
Also named here as limit state, serviceability — the same set of essays touches all of them, so they are one junction rather than several.
Stiffness is not strength, and usually it is the one that governs
A beam can be nowhere near failure and still be unusable, because it has moved too far. For most long-span members that limit arrives first, and stronger steel does not help at all.
The water that will not run off
A flat roof deflects, the deflection makes room for water, the water deepens the deflection. It is the same equation as a buckling column, with rain in place of the axial load.
Named alongside it
The objects these essays reach for when they reach for this one.
Limit stateSelf weightServiceabilityStiffnessAmplification factorCritical loadModulus of elasticityPonding