Investigators were this week focusing on whether a failed steel connection triggered a footbridge collapse in New Delhi last week, injuring 23 people (News last week).
The 100m-long footbridge was to connect a car park to the main Jawaharlal Nehru stadium and was due to be opened for Commonwealth Games, which start on Sunday.
The bow string arch bridge collapsed as labourers were pouring concrete on the deck.
Engineers said images of the collapse suggested a pin connecting the bridge deck to cable hangers, suspended from the arch, could have snapped.
Photographs following the incident show that the lugs at the end of the deck hangers, through which a connecting pin would have run, had splayed but not broken.
Chain of events
Failure of a pin could have overloaded adjacent hangers, setting in motion the chain of events that resulted in the collapse.
Once one hanger connection failed, it is likely the other connections followed suit.
The deck broke into three parts as it fell.
After the collapse, the two deck ends were left leaning against the abutments while the main central portion lay on the ground.
Bridge experts said that if a single pin had failed, there should be enough redundancy designed into the structure to prevent such a collapse.
“The design should allow for at least one of the deck hangers failing,” said Buro Happold associate director Simon Fryer.
Government official and Delhi commissioner Sheila Dikshit this week launched an investigation into the collapse. It is unclear who designed the bridge, but Delhi State Public Works Department said it held overall responsibility for the structure and construction was contracted to Chandigarh-based P&R Infraprojects.