As it happened: India bridge collapse tragedy

The Gujarat government has announced an inquiry into the cause of the bridge collapse.

While official updates are still awaited, Indian engineers I spoke to believe that the Morbi suspension bridge – a bridge that hangs on vertical suspensions under deck cables – may have collapsed due to poor maintenance at Morbi.

“This is a 140-year-old bridge. You must perform regular and high-quality maintenance. Bridge bearings, joints and rivets should be checked regularly. In India, we are not very strict about maintenance,” says Achyut Ghosh, structural engineering professor and bridge expert.

Delhi-based architect Rahul Raj says the quality of infrastructure maintenance in India “is often compromised because the work is given to a company that charges the lowest fees”.

“Jobs have been cut, companies are cutting fees and the quality of work is suffering,” says Mr Raj.

With narrow walkways, suspension bridges can sometimes sway when people walk on them, and often look precarious.

But Mr Ghosh says hundreds of people standing on a suspension bridge were unlikely to damage the structure. “Bridges are designed and built to carry many loads,” he says.

“But what people shouldn’t do is march along the suspension bridge.”

The reason is that bridges have a natural frequency of vibration. A force applied to the bridge at the same frequency from the run would increase the vibrations of the bridge and lead to its collapse.

It is not clear if people were doing this before the Morbi bridge collapsed.

Around the world, suspension bridges – San Francisco’s 4,200-foot-long Golden Gate Bridge is probably the most famous and an engineering marvel – have come a long way. There are at least 10 suspension bridges in the world that are over 1,300 m (1.3 km) wide, including four in China.

Image Caption: The Golden Gate Bridge spans the bay in San Francisco, California.

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