Concept
Three pinned arch
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
The hinge put in on purpose
An arch with two pinned feet cannot be solved by statics. Add a third hinge at the crown — deliberately weakening it — and the whole structure falls out of one moment equation.
The line that must stay inside
A masonry arch does not stand because its shape is right. It stands because some line of compression can be drawn inside the stonework — any one will do, and there are infinitely many to choose from.
Named alongside it
The objects these essays reach for when they reach for this one.
Horizontal thrustThrust lineBending momentDeterminacyFunicularGeometrical factor of safetyHingeLower boundSafe theoremSupport settlement