Arches and Domes

Arches and Domes

Introduction

  • Arches and domes are significant architectural elements throughout history.
  • They contribute to the aesthetic appearance and control weight distribution in structures.
  • Example: Ishtar Gate in ancient Babylon
    • The magnitude of such structures was made possible by the invention of the arch. Evokes specific feelings in people entering the city.

Objectives

  • Understand the historical development of arches, domes, and vaults.
  • Define the anatomy and types of arches, vaults, and domes.
  • Key terms: impost, facoise, keystone, post and lentil, cornice, and pendentive.

Arches

  • Arches can take on various forms:
    • Low arches
    • Rounded arches
    • Cusped or pointed arches
  • An arch controls weight distribution, unlike older systems.
  • Earliest form: Corbel arch
    • Stones are progressively placed inward, distributing weight down the sides at angles.
Post and Lintel System
  • Consists of two posts supporting a lintel.
  • Weight from the lintel is distributed to the posts.
  • The middle of the lintel experiences significant downward pull, causing sagging or crumbling over time.
  • Arches distribute weight down the sides, offering a clear advantage.
Round Arches
  • Babylonians were among the first to use rounded arches.
  • Romans later used them extensively.
  • Example: Arch of Titus (victory arch)
    • Built for emperors returning from war.
    • Evoked specific feelings in those passing through.
Anatomy of an Arch
  • Springing line: The horizontal line where the arch begins to curve.
  • Imposts: Located at the base of the springing line, supporting the arch.
  • Voussoirs: Wedge-shaped stones used in rounded arches to create the curve.
  • Keystone: The topmost voussoir, placed last, distributing weight evenly in two directions.

Vaults

  • Vaults create ceilings using a sequence of arches in a row.
  • Arches spring from a cornice, supported by columns.
Barrel Vault
  • A basic type of vault with a long, tube-like shape.
  • Example: Boston Public Library.
  • Offers advantages of opening up space and utilizing weight distribution properties of arches.
Groin Vault (Cross Vault)
  • An intersection of barrel vaults at a T-junction.
  • Distributes weight down into the corners.
  • Allows for more open space and extension of passageways.

Domes

  • A round, semi-spherical shape created by an arch spun around its vertical axis.
  • Can be oblong or flatter, depending on weight distribution and desired feeling.
Corbel Dome
  • Made by rotating corbel-shaped arches.
  • Resembles a beehive shape from the inside.
Tholos and Rotunda
  • Tholos: A small circular structure.
  • Rotunda: A rounded structure, usually capped with a dome.
  • Example: The US Capitol Building - rotunda topped with a dome.
Onion Dome
  • Used in Islamic architecture.
  • Found on top of buildings like the Taj Mahal and on top of minarets.
Pendentive
  • Used when a dome rests on a square or rectangular shape.
  • Located below the base of the dome and between the archways.
  • Curved triangular shape that distributes the dome's weight onto the rectangular corners of the vaults.

Conclusion

  • Arches and vaults create a striking impression.
  • They offer specific aesthetic appeal and structural stability.
  • These elements can evoke distinctive feelings and contribute to the overall architectural experience.