The arch, as a structural element, has been known and used by people for thousands of years. An arch, contrary to a beam, transfers the load without causing tensile stress in the material composing the arch (when correctly designed). This characteristic, which is due to the shape of the arch, allows the arch to create a large span with a thinner wall section when compared to a beam.
When the sides of the arch are properly supported by buttresses, which counteract the lateral forces, the arch can bear huge loads (see the underground tunnels). Whereas in case of a beam, the weight it can bear depends on the resistance of the material and its section. A correct geometry will cause only compressive forces within the section of the arch.
An arch spinning around its vertical axis creates a dome. A dome distributes the load equally and transfers the forces along the wall engaging the full section. The shell structures, even if very thin, can be very resistant. In particular the shell structures are optimized shapes which can achieve maximum strength with minimum amount of material. This is the reason why it is the shape we can often observe in the Nature. Moreover, domes behave better than a post and beam structure during a seismic event thanks to the capacity to spread the resulting loads on a bigger surface and thanks to the compact curved shape.
A dome structure works in compression therefore it has to be built with materials which respond well to compression forces.
When the composition of earth is right, even if it’s not as strong as bricks or concrete, it has a more than adequate compressive
strength (kg/cm2) for the construction of a dome. Nevertheless it is always necessary to make some earth tests in order to verify
its compressive strength.
By building a dome we can avoid cutting trees or using steel, cement and sand to build a roof. This has an important impact on the ecology and on the final cost of the house. The absence of the roof (intended in the classical sense) though requires finding some adequate protection from the rain.
- SUPERADOBE -
Among the different ways to build an earth dome the SuperAdobe technique stands out for its simplicity and efficacy. As the tests conducted by the Cal - Earth Institute
demonstrate, the SuperAdobe domes resist even violent earthquakes. They also withstand hurricanes, fire and floods according to the California standards.
A dome shape creates a uniform space with no corners and no separation between walls and ceiling. This kind of geometry reflects beautifully the shapes we find in nature. Being surrounded by the soft, organic forms has a positive impact on our wellbeing. And at the symbolic level the earth and the dome recall the mother’s womb, a place which preserves and protects life during its growth and transformation.
It is possible to create a small shelter as a single dome or a big house composed of several interconnected domes. The SuperAdobe technique allows building temporary or permanent emergency domes, which can give a safe shelter to people during seismic events as they assure an indoor quality superior to tents or containers especially in the long run.