Bridge collapse

Read an interesting theory behind the collapse of the freeway bridge in Minneapolis. It is a simple physical law about expansion. When materials heat up, they expand. They do so at different rates.

The bridge in Minneapolis was a concrete and steel structure. Temperatures in the city were reported to have been between 90 and 95F on the day of the collapse. As the mercury began to fall, the structure contracted. However, the steel would contract more than the concrete. This process had been going on for the lifespan of the structure, and occurs in each and every structure on earth. It induces metal fatigue and cracks in the concrete. When the construction workers were using jackhammers and a train passed below, it introduced vibrations.

A famous case where vibrations caused a bridge to collapse was the Tacoma Narrows Bridge, which collapsed in 1940 after being battered by force 7 winds. Each and every structure and object on earth has a frequency at which it will start to vibrate increasingly violently. The bridge at Minneapolis is thought to have been set off by the workers, contractions and the train. It failed because of a combination of concrete and metal fatigue. The full story can be read here.