Axial force — where it appears
Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.
Two walls that agreed to be one
A pair of shear walls with a row of doors between them is the commonest lateral system there is, and it has two readings that differ by a factor of seven. What decides which one applies is a beam a metre deep over a two-metre opening — and most of the overturning ends up as an axial couple that no bending diagram contains.
The moment the beam left behind
A beam reaction is drawn arriving on a column's centreline. It arrives on a cleat a hundred millimetres out from the face, and the difference is a couple that goes into the column and has to be shared between the lengths above and below it. Nothing about it appears in a frame model whose members meet at nodes.
The columns that lean
A framed tube carries its wind load by bending the spandrel beams between its columns, and it does it badly — the corner columns take nearly six times what the middle ones do. Tilt the columns instead, so the perimeter is triangulated, and the same shear is carried axially. The concentration falls to 1.23 and the tube recovers most of the stiffness the plan said it had.
Named alongside it
The objects these essays reach for when they reach for this one.
StiffnessDriftLateral systemLoad pathBase plateBending momentBracingCompatibilityComposite actionConnectionCoupling beamDegree of coupling