Bridge collapse in Angers

On April 16, 1850, the Basse-Chaîne suspension bridge in Angers collapsed under the steps of a marching regiment, resulting in between 223 and 226 deaths. The disaster was caused by a combination of a violent wind, corroded cables, and a resonance phenomenon triggered by the soldiers' marching step.

Bridge design and deterioration

The bridge, designed by architect Joseph Chaley and inaugurated in September 1838, had been exposed to the humidity of the Maine River and the weather of Angers for over a decade, leading to gradual corrosion of the iron suspension cables. This weakening of the structure played a key role in the collapse.

Military march and structural failure

The regiment, the third battalion of the eleventh light infantry regiment, was en route from Rennes to Marseille as part of a transfer of garrison. Lieutenant Colonel Simonet ordered the soldiers to break step due to the storm, but this measure was too late to prevent the collapse.

Resonance and wind effects

The resonance phenomenon occurred when the soldiers' marching step matched the natural frequency of the bridge, amplifying vibrations and causing the structure to fail. The wind added additional stress to the already weakened cables, leading to a catastrophic failure.

Memorial and reconstruction

The city of Angers established a memorial in the East Cemetery in 1853 to honor the victims. The bridge was reconstructed using stone, a more reliable material, and inaugurated in 1856. The new structure remained in use until 1962.

Legacy and changes in practice

The collapse led to a change in military practice, with armies worldwide ceasing to march in step on suspension bridges to avoid the risk of structural resonance. The new bridge was replaced in 1962 by a reinforced concrete structure designed by engineer J. R. Robinson and architect Henri Madelain.