This breathtaking structure is over 200 years old and still carries the Llangollen Canal over the River Dee Valley. It offers visitors the experience of crossing the world’s longest and highest navigable aqueduct. Both it and the canal are of great historical and engineering importance.
The site is managed by the Canal and River Trust, which has a management plan to guide conservation efforts and continuously works to maintain the integrity of the hydraulic and civil-engineering structures.
The name “Pontcysyllte” comes from the Welsh language and means “Cysyllte Bridge” or “Bridge of Cysyllte.” Cysyllte was a township in the old parish of Llangollen, where the bridge’s southern end is located. This name shows how closely connected the aqueduct is to the local community.
About the Aqueduct
Design and Construction
The Pontcysyllte Aqueduct and Llangollen Canal (originally called the Ellesmere Canal) were built during the late 18th to early 19th century. They used civil engineering techniques that had never been tried before. It is a remarkable engineering feat that uses metal arches supported by tall, slender masonry piers.
The aqueduct has four supporting arches per span, each made of cast-iron ribs. The external arches are cast with an un-pierced web to provide greater strength but at the cost of extra weight. This use of cast iron is similar to that of the stone arch it replaces, utilising the material’s strength in compression.
The canal trough is formed by laying transverse cast plates. The cast iron trough is not fixed to the arches, but lugs are cast into the plates to fit over the rib arches to prevent movement. It was left with water inside for six months to ensure the aqueduct was watertight.
Unlike a road or railway viaduct, the aqueduct experiences virtually constant vertical loading stresses. This is because of Archimedes’ principle. When a canal boat crosses the aqueduct, an amount of water equal to the weight of the boat is displaced into the canal at either side.
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