Concept

Framed tube — where it appears

A perimeter of closely spaced columns joined by deep spandrel beams, acting as a hollow cantilever against lateral load. The middle columns of each face lag behind the corners because the only route into them is in-plane shear in the spandrels, so the tube behaves as though only part of its width existed.

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

The corner columns take more than their share

A framed tube is a hollow cantilever, and a hollow cantilever's flange ought to be uniformly stressed. It is not, and the reason is that the only route the axial force has into a column in the middle of a face is the in-plane shear of the frame — one bay at a time, from the corner inwards.

structures · framed tube

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.

structures · diagrid

Named alongside it

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

Bracing Drift Effective width Lateral system Racking Shear lag Stiffness Axial force Cantilever Corner column Diagrid Load path

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