MENAI SUSPENSION BRIDGE MAP

MENAI SUSPENSION BRIDGE MAP

FIRST MAJOR SUSPENSION BRIDGE MAP; LONGEST SUSPENSION BRIDGE MAP 1826-1834

Crossing Menai Strait, Anglesey, Wales Designer/Engineer Thomas Telford Completed 1826 Span 579 feet (176 meters)

Materials Iron, limestone Type Suspension

You can still drive over Telford’s masterpiece, the world’s first suspension bridge.

Once Ireland was linked politically with Britain in 1801, a reliable mail connection between London and Dublin became imperative. Standing in the way of the route over the Irish Sea were the notoriously unpredictable waters of the Menai Strait and the equally resistant residents of Caernarfon, Wales, who for decades were vehemently opposed to a bridge because their livelihoods were based on shipping. Expensive international conflicts, such as the American Revolution and the Napoleonic Wars, delayed its realization as well. Over the years various plans were proposed, including cast-iron arch designs, but none were realized.

Thomas Telford (1757-1834), a self-taught Scottish engineer, was unequaled in his masterly and prolific construction of roads, canals, harbors, and bridges. One of the first to understand civil engineering as an art separate from architecture, he articulated its goals as efficiency in materials, economy, and appearance standards that remain today. His resume includes many monuments of eighteenth-century engineering, most of which still stand, including Pontcysyllte in Wales (1805), the Craigellachie Bridge in Scotland (1814), and the Conwy Suspension Bridge in Wales (1826). Telford was the first civil engineer consciously to move away from the old canons of architectural taste…. For Telford, the possibility for beauty must come internally from what the technical and economic constraints suggest.

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DAVID P. BILLINGTON, THE TOWER AND THE BRIDGE MAP, 1983

Finally, in 1818, Thomas Telford began work on what is considered by most to be his masterpiece, the Menai Suspension Bridge. Telford, then at the peak of a mighty building career, was assisted by Captain Samuel Brown, whose interest in ship rigging eventually led to his designing an early suspension bridge, the Union Bridge over the Tweed in 1820. Together Telford and Brown executed hundreds of load tests to satisfy themselves of the strength of wrought iron. No doubt the pair was aware of the work of an American, James Finley, who had published his “Patent Chain Bridge” in The Port Folio (1810) and would eventually build some forty suspension bridges, albeit small and crude ones.

To prevent rust, the wrought-iron chains were treated with boiled linseed oil; they were replaced with steel chains in 1942. Major repairs were made in 1999, and the bridge was repainted in 2005, for the first time since 1940.

Construction on the Menai began in 1819. When the masonry towers were completed in 1824, there was “breathless silence” as the first chain was floated out and linked to the chain hanging from the Caernarfon pier. Ultimately, sixteen wrought-iron chains were anchored to cast-iron frames embedded in the abutments. The chains were suspended from the two piers, creating a dramatic curve and the necessary leverage to support the center span’s unprecedented length of 579 feet (176 meters). Four hundred and forty-four vertical suspension rods hanging from the chains supported the roadway.

Impressive limestone arches, four on the island of Anglesey and three on the Welsh mainland, lead to the central span between the two 153-foot (47-meter)-tall towers. After the cornerstone was laid, three hundred men battled the weather and the tides for four years to build the stone approaches. Telford himself had begun as a stonemason.

Telford’s pioneering design would inform all suspension bridges to follow. His achievement is even more noteworthy when one considers that the bridge was built twenty years before the steam engine was fully developed. Telford harnessed manpower, horsepower, and the tides themselves to bring the bridge, stone by stone, link by link, to completion.

“[London Bridge] stands as one of the strangest monuments to our sense of possession over purpose.”

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