Structural Engineering & Statics
where the load goes
Concept

Sway — where it appears

Horizontal movement of a frame under load, which lengthens every lever arm and so manufactures moments the first-order analysis lacks.

Named by 2 essays across one field — each of them below, with the objects they name alongside it.

20H 10.0 M 22.2H 10.0 M 22.2the two base shears add to the applied 20 — the split came from stiffness, not staticsthe sway is exaggerated; a real frame at this load moves a fraction of a millimetre

The frame that leans, and what stops it

A rectangle of pinned bars folds flat. Make the corners rigid instead of adding a diagonal and it does not — which buys an unobstructed opening and costs bending in every member of it.

structures · portal frame wall 146 mmframe 140 mmtogether 58 mm20 storeys at 3.5 m · 40 kN per floor

How a tall building stands still

A shear wall bends and a framed tube shears, and the two deflected shapes are the wrong way up for each other. Tie them together at every floor and the pair is stiffer than the sum of their stiffnesses — because near the base the wall holds the frame back and near the top the frame holds the wall.

structures · lateral system

Named alongside it

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

IndeterminacyInteractionJoint rigidityLateral systemMoment connectionMoment diagramOutriggerPortal frameShear wallStiffnessStiffness distributionStorey drift

All concepts