Engineer's texts after PIE viaduct collapse suggested incident was due to design mistake

The viaduct collapsed in the early hours of July 14, 2017, resulting in the death of 31-year-old Chinese worker Chen Yinchuan. Ten other workers were hurt, two seriously. PHOTO: MINISTRY OF MANPOWER

SINGAPORE - Hours after the collapse of a PIE viaduct in July 2017, professional engineer Robert Arianto Tjandra, who had been overseeing the design of the project, said in WhatsApp messages to a former colleague that the incident had been a result of a "design mistake".

The text messages were revealed in court on Friday (Sept 13), during the cross-examination of prosecution witness Liu Xiayu, who was a former subordinate of Arianto Tjandra at subcontractor CPG Consultants at the time. Mr Liu joined CPG in 2010, but resigned in Feburary 2018.

Arianto Tjandra, 46, was the qualified person from CPG who had approved the design and supervised the construction works for the project.

He is facing five charges under the Building Control Act and the Workplace Safety and Health Act.

The viaduct collapsed in the early hours of July 14, 2017, resulting in the death of 31-year-old Chinese worker Chen Yinchuan. Ten other workers were hurt, two seriously.

On Friday, the court heard that about five hours after the incident, Mr Liu messaged Arianto Tjandra, saying that he felt "so sorry about the accident". "Please let me know if I can help (with) something," he added in the text message.

In response, Arianto Tjandra asked Mr Liu to check calculations for piers 40 and 41 - vertical columns on which the viaduct would have rested.

After making the calculations, Mr Liu told Arianto Tjandra that the support structures had not been sufficiently designed to support the weight of the viaduct.

In response, Arianto Tjandra said to Mr Liu: "Then no deck slab can be cast?"

Mr Liu replied: "Yes. Not allowed deck slab." Deck slab refers to the slab of concrete that would have acted as the carriageway for vehicles on the viaduct.

"Die. My prop also failed," Arianto Tjandra had said to Mr Liu, referring to the temporary structures to support the weight of the viaduct that was under construction.

Referring to the text messages, defence lawyer Tay Peng Cheng from WongPartnership, acting for Or Kim Peow Contractors (OKP), asked Mr Liu whether he believed Arianto Tjandra had made similar calculations relating to the support structures before giving OKP the instructions to construct the deck slab.

Mr Liu said he was not aware, as he did not know details of the discussion between Arianto Tjandra and Mr William Wang, another member of the CPG design engineering team for the project.

When pressed by Mr Tay on whether he knew if any discussions took place between Arianto and Mr Wang, Mr Liu said: "I couldn't answer this. But I guess there must be some discussion."

Subsequent WhatsApp messages between Arianto Tjandra and Mr Liu also revealed that after the collapse, the Land Transport Authority questioned CPG's design for parts of the viaduct, including piers 40 and 41.

In one message, Arianto Tjandra told Mr Liu: "LTA boss already questioned our design for flyover 7 & 8. The design not consistent. Some piers heavily reinforced, some are not."

Mr Liu responded: "We try to explain. That's why we use propping. Anyhow, I may not know the full story. But let me know if you need help at anytime. I am also responsible for it."

When Mr Tay asked Mr Liu if he had meant in the WhatsApp message that the PIE viaduct collapse was due to design inadequacies, Mr Liu said: "Correct."

Earlier this year, in July, OKP was fined $10,000 for carrying out unauthorised strengthening works on the permanent corbels - support structures - of the PIE viaduct.

Its group managing director Or Toh Wat was also given a discharge not amounting to an acquittal for all his three charges.

These were two charges under the Building Control Act, in relation to carrying out unauthorised works, and another charge of failing to ensure the safety and health of his employees under the Workplace Safety and Health Act.

However, OKP still faces one remaining charge for causing the death of a Chinese worker and the injuries of 10 others under the Workplace Safety and Health Act - which it is contesting in this trial.

Besides Arianto Tjandra, two other individuals allegedly linked to the incident are also involved in the trial: OKP project engineer Wong Kiew Hai, 31, and OKP project director Allen Yee Chee Keong, 49.

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