A chain hanging freely takes the one shape in which it is in pure tension; turn that shape upside down and it is the shape of an arch in pure compression for the same loads.
free-hanging chain (catenary) ↔ ideal arch under its own weight
Rules · Structure · Materials · Theory
Construction first, then art-form
Begin every design from its construction; the architect’s task is to turn the construction into art-form, never to hide it behind forms borrowed from another material.
Wagner held that every architectural form began as a construction and became, with time, an art-form. His own works show the process at small scale: the Karlsplatz station pavilions of the Stadtbahn (1898–99) are steel frames, painted green and left visible, faced with thin slabs of marble, crowned by curved roofs and gilded sunflowers; the Post Office Savings Bank (1904–06) fixes its marble cladding with visible aluminium-capped bolts.
Related rules
Hang a chain (or a model of strings loaded like the building) from two points; the curve it takes, turned upside down, is the ideal shape of an arch carrying the same loads, in pure compression.
A masonry arch stands if a line of thrust (the path of the compressive force through it) can be drawn entirely within its thickness; the catenary arch contains its own line of thrust exactly, the semicircle only if it is thick enough.
catenary: thrust line = centre line · semicircle: needs t ⁄ R ≳ 0.11
A new material calls for new forms: iron should be used in slender members that show its strength in tension and bending, not cast in imitation of stone columns and vaults.
Instead of applying ornament to a structure, shape the structure itself, especially exposed iron, into lines that are both constructive and decorative.
Omit applied ornament from buildings and everyday objects: it wastes work, money and material, dates quickly, and adds nothing that fine material and exact workmanship cannot give.
Cite this page Chris Paton, “Construction first, then art-form”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/wagner-construction-art-form. Text, drawings and models licensed under CC BY-NC 4.0.