4. Man-made structures

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Over time, human beings have become better at building structures. We know more about them and we have lighter and stronger materials.

4.1. Massive structures and lintels

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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.

4.2. Vaulted structures

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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.

4.3. Triangular structures

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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.

4.4. Suspended structures

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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.

4.5. Reinforced concrete structures

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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:

• Under the floor you are on there is a horizontal structure called slabs, which consist of small beams called joists and material in between them (ceramic blocks, bricks or polystyrene).
• The slabs transfer your weight to the beams (made of concrete and steel rebar) and then to the columns (vertical supports).
• The columns don't sit directly on the ground because they would sink. Between the columns and the ground are the foundations, which spreads out the weight of the building and its load.
• Reinforced concrete can be used to build huge arches, bridge piers, plates and roofs, as well as pillars and beams in structures.

4.6. Laminated structures

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These are formed by laminates of metal, plastic or composite material like reinforced concrete. Their curved shape and folds give them their strength.

• The curved shape makes the laminates bear the stress of traction and compression on their surface.
• The folds and ribs give rigidity in exact points. So, for example, the rim on a plastic cup prevents the cup from deforming when we drink and the grooves on the side make it stronger when we hold it.

4.7. Pneumatic structures

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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.

4.8. Spatial and geodesic

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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.