Differential shortening — where it appears
Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.
The columns are shorter than the core
Every column in a tall building gets shorter as the building is built on top of it, and the core beside it gets shorter by a different amount. The floors between them tilt by the difference — and the difference is largest exactly half way up, because a floor near the top has almost nothing built above it and a floor near the bottom has almost nothing beneath it.
The deflection that belongs to the support
A beam calculation answers a question about a beam sitting on things that do not move. Real ones sit on bearings, on other beams and on columns that shorten, and every one of those is a spring in series with the member — so a deflection is the sum of two things and only one of them is a property of the beam.
The arm that makes the columns work
The perimeter columns of a tall building are already there, already carrying gravity, and already the furthest thing from the centre. They take almost none of the overturning, because a floor slab transmits shear and not moment — and one storey-deep arm at the right height changes that by nearly a half.
Named alongside it
The objects these essays reach for when they reach for this one.
Axial shorteningCoreServiceabilitySupport settlementTall buildingBearingCompatibilityCompensationConstruction sequenceCreepDeflectionDrift