4. Semicircular staircases

4.1 General

• Definition

  Semicircular staircases represent the second family, and correspond to structures with a non-rectilinear tread line.

  This is made up of one or more (usually two) circular parts (quarter-circle or half-circle) connected to straight lines.

  This layout requires irregularly shaped steps in sections where the stride line is circular (balanced steps).

  The layout of these steps is called the swing.

• Types

  Semicircular staircases include :

  • flights with a "turning quarter", i.e. a part of the flight (generally at a...