Over time, human beings have become better at building structures. We know more about them and we have lighter and stronger materials.
The first man-made structures were carved from rock or were built by stacking rocks or other materials. This left little space between them, like in the Mayan or Egyptian pyramids.
Short stone or wooden lintels were also used to make windows and open spaces, for example, in Greek temples.
With arches and vaults, builders could cover larger spaces and have bigger gaps in the structures.
Vaulted structures are formed by arches and vaults using stones that are cut in such a way that the only stress they support is compression – no problem for hard stone.
The Romans used round arches to build bridges and aqueducts and they used barrel vaults and domes to cover basilicas and pantheons. Later, pointed arches and ribbed vaults were used in mosques and cathedrals. We still use them today.
These structures are made from bars, normally metal or wooden. The use of triangular shapes means they are not easily deformed. This makes them ideal for building bridges (triangular beams), covered with large trusses and vertical structures, like towers and scaffolds.
This type of structure uses cables, called suspenders which the structure hangs from. When they can be adjusted, they are called tension members.
The cables only bear traction stress, but the advantage is that they can adapt their shape to different loads at different times and they are incredibly light.
Cables are used to fasten bridges, marquees, antennas and towers.
There are many kinds of suspended structures which can cover large spaces like stadiums and pavilions, without the need for columns or pillars.
Concrete led to major advances in construction because it could be made into any shape. Concrete resists compression and with steel rebar frameworks it can also bear traction.
It is a very strong material which is used in all types of building, mostly in framework structures like your school:
These are formed by laminates of metal, plastic or composite material like reinforced concrete. Their curved shape and folds give them their strength.
Pneumatic structures are light and easy to transport, set up and dismantle. For this reason, we use them in constructions like field hospitals or funfair attractions for children. These structures use compressed air inside them. When they expand, they stretch the outer plastic surface. This makes them stay upright.
These are three-dimensional structures of bars, which combine the properties of vaults with triangulated structures to create curved shapes and cover large spaces.
They consist of linear bars and nodes that connect them. They use triangles and tetrahedrons, the three-dimensional equivalent of triangles, because these shapes cannot be easily deformed.
Activity 13
Look at the photos:
Activity 14
Find different types of arches in vaulted structures on the Internet and in books about art and architecture and draw them, illustrating the different types of stress they experience. What kinds are they?
Activity 15
Identify what material was used to build the Eiffel Tower. Find out which material we use nowadays for these kinds of structures and list the advantages and choose your answer.
Activity 16
Look at the different types of trusses. Which ones would be better for a bridge? And for a roof?
Activity 17
Look at the bridges and explain how they transfer loads through the various structural elements which you can see in the photos.
Activity 18
Listen and point to the different elements in the structure of this building.
Activity 19
Experiment with laminated structures. Place a sheet of paper flat between two desks. Does it stay horizontal? Try again but, this time, bend the sheet of paper like in the structure in the photo. What happens? Why?
Activity 20
Look at the photo. Can this type of structure bear bending?
Activity 21
Look at the photo. How do the bars join the metal nodes? What kinds of stress are acting on these nodes?
Activity 22
Many structures combine several of the ones we have seen. Examine the viaducts in the photos and say what structure types and materials are used in them. Can you find the relationship between the shape and the material of the parts and the types of stress they bear?
Activity 23
Think about the materials that you could use for your bridge: thread, paper bars, wire, cardboard, balsa wood, etc. How and why will you use these materials for building different parts of the model?
Activity 24
Think about the different types of structures we have looked at. What kind of bridge do you want to build for the unit project? Write it down and draw a sketch in your notebook.
