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Menai Suspension Bridge

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The Menai Suspension Bridge is a major engineering landmark in Wales. It spans the Menai Strait, which separates the island of Anglesey from the Welsh mainland.

Menai Bridge at dusk
Menai Bridge at dusk

This bridge is a Grade I listed structure, meaning it is of special historical importance. It was one of the first major suspension bridges in the world. It was also only the second major suspension bridge designed to carry vehicles. The first was the Union Chain Bridge, completed in 1820. The Menai Bridge remains a vital link for travelers today.

The geography of the Menai Strait made a bridge necessary. The strait was formed by glacial erosion during the Pleistocene epoch. This period of glaciation lasted from about 2,580,000 to 11,700 years ago. Moving ice sheets scoured the bedrock to create deep channels. As the ice receded, the sea flooded these hollows to form the strait. The water there is very dangerous due to strong tidal flows. Twice daily tides create four strong flows that cause whirlpools and currents.

The suspension bridge, over the Menai
The suspension bridge, over the Menai

Before the bridge, crossing the strait was a high-risk task. In 1785, a boat with 55 people sank during a gale. Only one person survived that disaster. Moving cattle was also difficult and expensive. Farmers often drove cattle into the water to swim to the mainland. This caused many valuable animals to be lost. The need for a reliable route grew after 1800. When Ireland joined Great Britain, more people traveled between London and Holyhead. Holyhead was the main port for ferries to Dublin.

Select Sketches - Menai Bridge 2
Select Sketches - Menai Bridge 2

Civil engineer Thomas Telford designed the bridge to solve these problems. He was tasked with building the Holyhead Road. He chose a site near Bangor on the mainland and Porthaethwy on Anglesey. This location had tall banks that allowed sailing ships to pass underneath. Telford proposed a suspension design to cross the fast waters with a wide span. Parliament authorized the project through the Roads Between London and Holyhead Act 1819. Construction began in 1819 with the building of the towers.

A plan & view of a chain bridge - erecting over the menai at Bangor Ferry 1820
A plan & view of a chain bridge - erecting over the menai at Bangor Ferry 1820

The bridge mechanism relies on massive iron chains to support the roadway. The two towers are made of Penmon limestone. These towers are hollow and contain internal cross-walls for strength. Sixteen huge chain cables support the entire span. Each cable consists of five parallel bars of wrought iron links. This means there are 80 iron bars and 935 links per cable. The chains rest on cast iron saddles with rollers. These rollers allow the chains to move when temperatures change.

Building these chains was a massive undertaking. William Hazledine supplied the required wrought and cast iron. To prevent rust, the iron was soaked in linseed oil and painted. Workers assembled most of the chains link by link on site. They used platforms near tunnel mouths and scaffolding to reach the tower tops. For the final central section, workers used a raft and a pulley system. It took 150 men to lift the chains into place. The bridge opened on 30 January 1826. It reduced the London to Holyhead journey by 9 hours.

A plan & view of a chain bridge - erecting over the menai at Bangor Ferry 1820
A plan & view of a chain bridge - erecting over the menai at Bangor Ferry 1820

The bridge has undergone many changes to stay safe and useful. The original roadway was unstable in the wind because it lacked stiffening trusses. W. A. Provis strengthened the deck in 1840. In 1893, Sir Benjamin Baker designed a new steel deck to replace the wood. The original 4-ton weight limit became a problem for freight. In 1938, the wrought iron chains were replaced with steel ones. This was done without closing the bridge.

The suspension bridge, over the Menai
The suspension bridge, over the Menai

Modern maintenance continues to be a challenge for the structure. In 1999, the bridge closed for a month for resurfacing. During World War II, a Wellington bomber was even flown under the bridge as a bet. More recently, the bridge has faced several closures. In 2022, it closed for essential maintenance following engineering advice. It reopened in early 2023 with a 7.5-ton weight limit. In October 2025, it closed again due to weight limit policing issues. The bridge remains a candidate for a World Heritage Site.

Menai Bridge at dusk
Menai Bridge at dusk
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🖼️ Images & Media (5)
File:A plan & view of a chain bridge - erecting over the menai at Bangor Ferry 1820.jpeg
A plan & view of a chain bridge -...
File:The suspension bridge, over the Menai.jpeg
The suspension bridge, over the Menai.jpeg
File:Bangor, View on Suspension Bridge (8571590364).jpg
Bangor, View on Suspension Bridge (8571590364).jpg
File:Select Sketches - Menai Bridge 2.jpg
Select Sketches - Menai Bridge 2.jpg
File:Menai Bridge at dusk.jpg
Menai Bridge at dusk.jpg
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