" Folded plates and shells."

A folded plate is an example of a 3-dimensional or space structure. To consider the effectiveness of the folded plate look at the following experiment.

When a thin sheet of paper rests between two supports it will bend due to the fact that it has insufficient strength to carry its own weight.

If the same piece of paper is folded then it will be capable of supporting one hundred times its own weight.

If the load is increased past this point then the structure will fail and the folds will flatten out.

This problem can be rectified by using transverse stiffeners at the ends. The folded plate acts as a beam and can support even greater loads.

Try this Experiment at home or in school, make sure to use sheets of paper equal area.

Folded plates consist of straight pieces joined with sharp edges. It cannot be made as thin as a shell due to the fact that it is subjected to bending.

The result of this bending can be seen in the animation opposite.

Folded plates can be seen as a space version of a rigid frame. Folded plates are best formed from reinforced concrete due to the fact that they can be easily cast. Folded plates can take the form of frames as seen above or domes.

Geodesic Domes.

Geodesic domes are an example of a curved space frame. They were invented by R.Buckminster Fuller and as was seen in section 1 Structures in Nature examples of Geodesic domes can be found in nature. As was also discussed earlier, domes are not an new development, they have existed for hundreds of years. The geodesic dome is referred to as a braced dome due to the fact that there are bracing members present so that the dome keeps its shape.

The geodesic dome is made up of a network of triangles, this results in the maximum amount of strength and rigidity being obtained while using the minimum amount of materials.

The varying number of triangles is referred to as the frequency and the higher the frequency the greater the resistance of the structure to collapse.

Click on the icon to see how the different frequencies change the shape of a Geodesic dome.

Geodesic domes can be constructed from metals or plastics and they have many advantages.

Speed of construction - In 1955 he built domes for the air-force and they only took fourteen hours to erect.

Size - the clear span of a dome constructed by Fuller in 1958 was 117m and it had a total weight of 12MN. If you then compare this to St.Peter's Cathedral in Rome which has a diameter of 40m and weighed 100MN.

Using drinking straws and connections try and make a geodesic dome.