Contains the full lesson along with a supporting toolkit, including teachers’ notes.
For 150 years the 40 metre high Nelson Pillar stood in the middle of Dublin’s O’Connell Street until it was demolished in 1966 after being damaged by an explosion. In 1998 Dublin City Council launched an international architectural competition for a replacement monument. There were 205 entries and the winning design was an elegant spire by Ian Ritchie Architects. It is a 120 m high cone that is three metres wide at the base and tapers to 150 mm at the top. Although it is essentially art, architecture and sculpture, it is also, as we will look at in this lesson, engineering, science and technology.
How was the Spire designed?
The spire was manufactured in eight sections of up to 20 m in length each of which is a frustum – a truncated cone. The sections were made from rolled sheets of stainless steel. A thickflange with holes in it was welded at the ends of adjoining sections to enable them to be bolted together. The top two frusta are joined by a threaded connector.
What effect has wind?
The force of the wind must be taken into account in the design of tall structures. The moment of a force, i.e. its turning effect, is the magnitude of the force multiplied by the perpendicular distance from its line of action to the point about which it can turn (the fulcrum). The force is a function of the wind speed and the surface area on which it acts.
For example, if a force Fdue to wind acts at a heighth then the moment of the force around the point A isF x h.