The dome of the US Capitol building

Dome – a feature of architecture that usually looks like the upper half of a sphere on top of a building. It is a feature that makes many religious and government buildings stand out, because if someone is speaking to others inside or under a dome, the voice sounds louder. Also a dome makes it easier to identify an important building, for example a temple or a palace.

The Capitol dome – The capitol has a large dome in the center, above a rotunda—a large space that is shaped like a circle. The capitol was designed by William Thornton. Construction started in 1793, but it was not completely finished until almost twenty years later. The dome in the center of the building was smaller and made of wood. In 1814, the capitol was set on fire by the British Army during the War of 1812. In the 1850s and 1860s, the capitol was fully repaired, and the wooden dome was replaced with a larger iron dome.

Expo 67 American Pavilion, Montreal, Québec, Canada

Geodesic dome – R. Buckminster Fuller named the dome “geodesic” from field experiments with artist Kenneth Snelson at Black Mountain College in 1948 and 1949. Snelson and Fuller worked developing what they termed “tensegrity,” an engineering principle of continuous tension and discontinuous compression that allowed domes to deploy a lightweight lattice of interlocking icosahedrons that could be skinned with a protective cover. Although Fuller was not the original inventor, he developed the intrinsic mathematics of the dome, thereby allowing popularization of the idea

Metrodome – A large stadium with a roof over the playing field is often called a “dome”.

What’s the problem?

Design for the cupola of St Paul’s Cathedral, London. Around 1705-1706, Sir Christopher Wren was working on the design and drew these two half-sections, showing the relation of the inner and outer domes.

  • Ask – At this time many great churches were being built with tall dome to create impressive and bright interior spaces. The tall dome roof would be seen from miles away.
  • Imagine – Architect and engineer Sir Christopher Wren was familiar with designs for domes. He wanted to get the most height and light into the church, so he worked out a way to make the dome support the weight by curving to the base.
St Paul’s – the final design
St Paul’s Cathedral Interior Dome 3, London, UK
  • Design, BuildThis free-hand drawing was made to show the relation of the inner and outer domes. The outer dome is supported on a massive, circular drum surrounded by giant columns. This lighter outer dome is built of timber covered with lead, hence its distinctive grey colour. It rests partly on the brick cone which rises from the inner dome. This cone, which rests on the supporting drum, also supports the crowning stone lantern, ball and cross which can be seen from the floor below, through the domes. The design of a dome within a dome, and supporting the heavy lantern via the cone to the drum, is a marvellous mix of design and engineering.

Engineering ideas

  • tensegrity, geodesic, tension, continuous, compression, discontinuous, lattice, interlocking, icosahedrons

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