Broughton Suspension Bridge

The Broughton Suspension Bridge was a chain bridge over the River Irwell between the villages of Broughton and Pendleton, now City of Salford, Greater Manchester, England. She was one of the first suspension bridges in Europe and became famous because they are likely due to resonance vibrations collapsed on 12 April 1831 caused by marching troops.

Bridge

The bridge was built in 1826 on behalf of a local contractor at his expense. Your design is attributed by some to Samuel Brown, others think it was built by a local machinery manufacturers. She was the local pride since it was opened immediately after the Menai Suspension Bridge. She had a wingspan of 44 m (144 ½ feet). The supporting chains consisted of two arranged in parallel, long iron rods which were connected to a two- pin and three short flat iron joint with the next two iron rods. So that the pins passed through five closely spaced iron, the load relatively evenly distributed on the bolts. Only the last link consisted only of a single bolt that connected the two bars of the chain with the cast-iron anchor plate in the masonry abutments. The chains were supported by four cast iron pylons at the ends of the bridge.

Collapse in 1831

On April 12, 1831, two groups of soldiers had already crossed the bridge without problems, as another group wanted to return of about 70 soldiers in four rows in the barracks. The group marched first probably not in lockstep. Animated by the vibrations of the bridge, some soldiers whistled a marching song, whereupon the soldiers probably adapting their step the song and the vibrations of what these significantly enhanced. As the head of the procession had reached the other side, there was a loud bang, followed by one of the pylons crashed into the bridge and fell parts of the road about five feet deep in the river. About forty soldiers rushed against the chain parts and into the water, which was very shallow at the time. There were no deaths, but about twenty wounded, including six seriously injured.

Investigation

The investigation revealed that the bolt of the last chain link were broken with the anchor plate and bent some other bolts. Because of this a broken bolt in the chain was missing the rear anchor, so they outline the pylon and brought the bridge to collapse. The vibrations caused by the soldiers had caused the break, but it was felt that the bolt would be broken sooner or later in any case. Criticized the construction to attach the chain with only one bolt on the rear anchor, also the quality of the forged bolt was doubted.

Follow

Although the collapse was the construction of additional suspension bridges do not stop, but the problem is amplified by the resonance vibration was generally perceived consciously. The British military issued a general order that troops can not march in lockstep over bridges. Painting is still at the Albert Bridge in London a sign with the warning All troops must break step (all soldiers must march without impact ).

The bridge was built in amplified form and with chains again, which were performed twice, not even on the rear anchor. However, the bridge was provided with temporary restraints, if larger crowds on the bridge were expected. This bridge was used until 1914, when it was replaced by a steel truss bridge for pedestrians.

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