Stone arches are built using a specific method involving wedge-shaped stones and a temporary support structure. Here's a breakdown:
- Keystone: The keystone is the most important stone in an arch. It's located at the very top and locks all the other stones in place, distributing the weight evenly.
The Construction Process
- Preparation of Stones: The arch is constructed from wedge-shaped stones, also known as voussoirs. These stones are carefully shaped so that they fit together snugly.
- Temporary Support (Centering): A temporary wooden framework, called centering, is constructed to provide support for the arch during the building process. This centering mimics the shape of the arch.
- Placement of Voussoirs: The voussoirs are then placed on top of the centering, starting from the supports (abutments) on either side and working their way up.
- Keystone Placement: Once all the voussoirs are in place, the keystone, which is the final wedge-shaped stone, is inserted at the top. The keystone's shape and position force the other stones into compression, making the arch self-supporting.
- Removal of Centering: With the keystone securely in place, the centering is carefully removed. The arch is now able to support its own weight and any load above it.
Key Elements Explained:
| Element | Description |
|---|---|
| Voussoirs | Wedge-shaped stones that make up the arch. |
| Centering | Temporary wooden support structure. |
| Keystone | The final, central stone that locks the arch in place. |
| Abutments | The supports at either end of the arch that bear the arch's thrust. |
Principles at Work
The arch works because it transfers the weight of the structure and any load above it down to the abutments through compressive forces within the stones. The wedge shape of the voussoirs ensures that the force is directed along the curve of the arch, preventing it from collapsing.
