Human-induced vibrations may have caused FOB collapse: BMC

Going deep into scientific reason to save the engineers arrested over the Himalaya bridge collapse incident, the BMC Engineers' Union advocated that vibrations induced by human beings could be the reason behind the accident. The engineers' union has written to the civic chief requesting him to investigate the Himalaya bridge collapse from this angle as well.

They claimed that one of the well-known causes of bridge collapse incidents is resonance from human vibrations. They said mishaps caused due to such reasons happen suddenly without any warning sign.

Sainath Rajadhyaksha, executive president of the BMC Engineers' Union said that there was no prior signal that the bridge was not safe and it suddenly collapsed.

He said, "It is not known how many people were walking over the bridge at that time and it is studied internationally that major cause of foot-over-bridge slab collapse is due to resonance also called human-induced vibrations." They also included pages of a book "Dynamic Loading and Design of Structures," with the letter.

Rajadhyaksha takes the example of soldiers marching in unison over a bridge is not allowed. "We all know that soldiers are not allowed to march in unison across the structure as it applies a force at the frequency of their step," he said, adding that if their frequency is closely matched to the bridge's frequency, the soldiers' rhythmic marching will amplify the vibrational frequency of the bridge. If the mechanical resonance is strong enough, the bridge can vibrate until it collapses from the movement.

Even, the BMC officials alleged that the bridge was overused by the Railways. Earlier, the foot-over-bridge was meant to be used only for suburban commuters. However, it was later connected to long-distance commuters. "The pressure increased and it collapsed during peak hours when it was used by maximum commuters," said Rajadhyaksha.