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Collapsed Can Tho bridge engineers knew scaffolding was inadequate

Design checks on falsework for the 2.75km Can Tho bridge in Vietnam which collapsed last week warned four months ago that the scaffolding was inadequate for the loads it was expected to carry.

According to local reports this week, a Japanese engineer wrote an internal memo to his supervisor in June warning that the section of the collapsed bridge did not meet standards.

The reports quote Hiroshi Kudo, a project supervisor and engineer with Nippon Koei, as warning that the design of the scaffolding supporting the two spans between columns 13, 14 and 15 should be revised because of its "very low" safety coefficient.

"The work's safety coefficient stands at 1.15, which is lower than the required construction standard at 1.25," he said in his memo. "The coefficient of the wind force, which is 0.5, remains far lower than the 1.5-2.5 as required."

Kudo asked the Japanese contractor to re-work the drawings and an adjusted drawing was submitted to his supervisor in July.

However, two spans of the approach structure to the cable stayed Can Tho bridge collapsed whilst under construction on 26 September. An 87m-long section of concrete deck between piers 13 and 15 fell after the 30m-high scaffolding system gave way, killing 53 and injuring 80.

The concrete girder deck had been poured just one day before. More than 250 people were working on and under the bridge at the time of the collapse.

The cause of the Can Tho bridge collapse is still being investigated. Minister of Transportation, Ho Nghia Dung told a press conference this week that suspicions about the construction and design of the bridge were logical. He previously said that the scaffold foundation might have settled and caused the collapse.

But according to the local police, the contractor removed the falsework sooner than recommended by the designer. Eyewitness testimonies have also indicated that the subcontractors used poor quality scaffolding, which had been re-used several times

The Vietnamese government has established a national committee to investigate the collapse. The committee will be chaired by the construction minister Nguyen Hong Quan, chair of a state construction council. The 10-member committee will include a representative from the Japanese department of bridges and roads technology.

The prime minister has ordered that a report on the group's activities be delivered to him in a month.
The Ministry of Transport has temporarily stopped the work on the bridge until the committee has reached a conclusion.

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