Design flaw not ‘Act of God’ brought down Kolkata flyover, say experts

A design flaw led to the collapse of the flyover in Kolkata, experts said after visiting the spot on Friday, dismissing the construction company’s argument that the incident was an “act of god”.

Structural and civil engineers with decades of experience in building bridges across the country, told HT that structural flaw of a T-shaped pillar -- technically a cantilever pier --led to the collapse. A cantilever bridge rests on structures that project horizontally into space only on one end.

A portion of the flyover caved in on Thursday afternoon killing 24 people and injuring more than 90. A few hours after the crash an official of the construction company, Hyderabad-based IVRCL, described the disaster as an “act of god”.

“The design of the pier head (the t-junction) was inadequate. The arms simply buckled under pressure of the steel and concrete,” said Achyut Ghosh, a bridge expert and visiting professor at IIT Kharagpur, Jadavpur University and IIEST in Shibpur.

“The bridge was yet to be inaugurated, and therefore, there were no pressure of vehicles that a functioning flyover carries. This proves that it was simply a design failure,” added Ghosh.

“This was preventable. It can’t be called an accident,” he added.

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Experts pointed out that cantilever piers are one of the most unstable structures and are usually avoided. If absolutely necessary they are meticulously designed and need perfect implementation with strict quality check of materials.

“It appears to be a technical failure. What was running on two pillars (at the start of the bridge) has converged on to one pillar. But this single pillar did not have adequate strength,” said professor Arun Chakravarti of IIEST, Shibpur.

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Another civil engineer Snehasis Sinha, who visited the crash site earlier in the day, reinforced the ‘flawed design’ angle. He also alleged that there could have been serious lapses in quality control and even execution.

“Apart from the flawed design there could be compromise in quality of materials and even lapses on the implementing authority’s part while the flyover was being built. There could have been lapses in monitoring and checking,” he said.

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