Arch

St Louis Gateway Arch

Arch illustration

Arch action English

Analogy between an arch and a hanging chain and comparison to the dome of St Peter's Cathedral in Rome

Maqueta funicular

Arch refers to a curved structure that spans an elevated space and may or may not support the weight above it, or in case of a bridge, the dynamic loads of the traffic on the bridge itself. The arch has been used since ancient times for both its engineering efficiency and its aesthetic appeal. In architecture, an arch is a structure that spans a space while supporting weight from above, often in the form of a curved symmetrical structure from end to end.

History

The origins of the arch can be traced back to the ancient Mesopotamia where the arch form was first used in buildings. The Romans, however, were the ones who realized the full potential of arches. They incorporated it extensively in their architecture, leading to the development of the Roman aqueducts, bridges, and the grand Colosseum. The Roman adoption of the arch allowed for structures to be built stronger and taller than ever before, revolutionizing architectural possibilities.

Types of Arches

There are several types of arches, each with its own structural and aesthetic characteristics. These include:

• Round Arch: Also known as the Roman arch, it is a semicircular form and is one of the most commonly used types.
• Pointed Arch: Characteristic of Gothic architecture, this arch type distributes force more efficiently, allowing for taller and more slender structures.
• Segmental Arch: A segment of a circle, this type uses less material and exerts less thrust at the base, making it suitable for bridges.
• Ogee Arch: With a double curve, this arch is often found in Islamic architecture and English Gothic architecture.
• Relieving Arch: Used primarily in ancient and medieval architecture, this arch is built above a lintel or another arch to distribute weight away from a vulnerable point.

Construction and Mechanics

The construction of an arch involves careful consideration of the forces at play. The key component of an arch is the keystone, the topmost piece which locks all other stones into position, allowing the arch to bear weight. This is possible due to the arch's shape, which efficiently distributes the forces of compression through its curve to the supports or abutments at either end, effectively stabilizing the structure.

Cultural Significance

Throughout history, arches have not only served structural purposes but have also been imbued with cultural and symbolic meanings. In Roman architecture, the triumphal arch was erected to commemorate victories and achievements. In Islamic architecture, arches symbolize the divine, reflecting the infinite nature of the universe.

Modern Usage

Today, arches continue to be a popular architectural element, featured in both historical restorations and modern designs. They are used in the construction of bridges, gateways, and buildings, showcasing the enduring legacy of this ancient form.