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Student Activity - In Great Shape

INTRODUCTION

The designs of the Sydney Olympic venues - the Dunc Gray Velodrome and Stadium Australia - and the Beijing "Bird's Nest" Olympic Stadium - are interesting, creative yet also highly practical.
The architects were able to design these amazing structures because of the special properties of steel. Steel is strong enough to use as a construction material yet it can be moulded into a wide variety of thicknesses, sizes and shapes such as flat sheets, triangles, hollow cylinders and arches.
Arches are great shapes that can, amazingly, stay up without the support of any pillars or columns!

What makes a metal like steel hard and strong, but also able to be easily shaped?

Metals are made up of crystals that lock together, the interlocking providing strength yet also allowing for easy bending or stretching (shaping) of the metal.

When the shape of the crystals is changed, a different property is given to the metal. The crystals can be changed by mixing different metals (alloying), melting, heating, cooling, or exerting a force.

Some of these processes have been used to produce the different steels at the Olympic venues. For example, chromium and manganese have been alloyed to add toughness and rust-resistance to the arches in Stadium Australia and a treatment called 'cold rolling' has been used to make the thin steel sheets for the velodrome's roof.

Try this Extension Activity - Crystal Creations

INVESTIGATION

In this activity you will test the strength of an arch and take a close look at the use of steel arches in the construction of the Dunc Gray Velodrome, Stadium Australia and the Beijing Olympic Stadium.

WHAT YOU NEED

WHAT TO DO

  1. Place a strip of paper between the wood blocks, as shown
  2. Balance weights on the top (or underneath if you can tie them). Which width is the strongest?
  3. Work out the best distance between the blocks to maximize the strength of the arch.
  4. Look at the arches in the three photos below.

Dunc Grey Velodrome (Joanna Buckley)

The velodrome roof was made using a triangular grid pattern running diagonally to give stiffness and strength in all directions. It contains 11 curved steel arches, fixed at each end to a steel ring pipe that runs around the perimeter of the building.


Stadium Australia - mid-construction (BHP Billiton)

An estimated 32,000 tonnes of BHP Billiton steel (the same weight as about 32,000 cars) was used, 650 tonnes needed just for the two huge (300 metre long), hollow arches that support the roof (14 storeys high at their highest point). The roof area supported by these arches is 30,000 square metres (the same as 115 tennis courts!). It could fit four 747 planes under each side!


Model of the Athens Olympic Stadium, Photo courtesy of www.stadia.gr 

The Athens Olympic Stadium, completed in 2004, can hold 75,000 spectators. Twin 300 metre long steel arches have been designed to support a roof of glass panels. The arches each weigh over 8000 tonnes, are 2/3rds the size of the Sydney Harbour Bridge, and are hollow tubes large enough for a bus to drive through! They must support a roof weighing twice as much as the Eiffel Tower.

DID YOU KNOW?

Each arch of Stadium Australia was pre-assembled in three sections on the ground. Using an enormous crane (with an engine size equivalent to ten V8 engines) each end section was lifted into place.
The middle section of each arch was trimmed by 25 mm at each end, lifted into position at dawn, then as the steel expanded with the heat of the day the gap between the sections closed up (clever, eh?) and they were welded mid-air.
It took 40 hours to weld each section to the next!

QUESTIONS

  1. The use of arches in the construction of these venues has meant that internal pillars or supports do not need to be used. Why is this such an advantage?
  2. Why do you think the arches are made from hollow steel instead of solid steel?
  3. What have you learnt about steel that you think makes it a fantastic metal for use in this sort of construction?