SINGAPORE — An engineer implicated in the collapse of an expressway viaduct near Upper Changi Road in July 2017 that claimed the life of one worker and injured 10 others was on Monday (2 December) jailed for 86 weeks, or about one year and eight months.
Robert Arianto Tjandra, 46, a Singapore permanent resident from Indonesia, was also fined $10,000. If he fails to pay the amount, he will have to spend another four weeks behind bars.
Tjandra was working for subcontractor CPG Consultants when he approved the design for the project and supervised construction works.
He pleaded guilty last month to two charges under the Building Control Act for failing to ensure that building works for the project were designed in accordance with the provisions of the Act and for authorising building works without approval.
He also pleaded guilty to a third charge under Workplace Safety and Health Act for a reckless act which endangered the safety of others at work.
He admitted to two other charges under the Building Control Act, which were considered by Deputy Presiding Judge of the State Courts S. Jennifer Marie in sentencing.
Tjandra knew his team of engineers were inexperienced in designing bridges, but failed to give them guidance or instructions. He also failed to check the design assumptions made for the corbels. A corbel is a piece of material in a wall used to support a heavy structure.
And even after Tjandra realised the errors in his team’s calculations, he failed to take remedial steps.
The company responsible for the works, Or Kim Peow Contractors (OKP), is still contesting one charge of causing the death of a construction worker and injuring 10 others. The firm has already been fined $10,000 for carrying out unauthorised strengthening works on the support structures of the viaduct.
Meanwhile, two other individuals linked to the accident, OKP project director Yee Chee Kiong, 49, and OKP project engineer Wong Kiew Hai, 31, remain on trial.
On 4 July, engineer Leong Sow Hon, 61, an accredited checker appointed by the Land Transport Authority who was working on the project, was jailed for six months. He had earlier admitted that he failed to evaluate, analyse and review the project’s structural design, and did not perform original calculations for the structure’s permanent corbels between 18 November 2016 and 13 June 2017.
The firm’s group managing director Or Toh Wat, 51, was on 31 July given a discharge not amounting to an acquittal for all three charges in relation to the collapse. Or was given a conditional warning from the Building and Construction Authority and the Ministry of Manpower.
Background of the case
Part of the 1.8km-long viaduct, which stretched from Tampines Expressway to the Pan-Island Expressway and Upper Changi Road East, collapsed at about 3.30am on 14 July 2017, killing one Chinese worker and injuring 10 others.
OKP had clinched the contract to build the viaduct from the Land Transport Authority on 23 November 2015.
Tjandra had failed to ensure that corbels supporting the viaduct were designed according to performance requirements. Even after realising the design error, Tjandra told OKP that they could build the corbels and disregarded any risks this might entail.
The engineer had led a team of five inexperienced design engineers from CPG. He failed to consider his team’s lack of bridge-design experience - one of his members was involved in bridge-design for the first time.
During the design stage, Tjandra did not provide guidance on the proper method for the design of the corbels and key support structures, as well as the effective width to be used in the design calculations for the corbels. As a result, the team wrongly calculated the effective width and used the erroneous calculations.
“The accused was not aware, at the design stage, that the design engineers had each used different and wrong effective width assumptions. He did not discuss or check the effective width assumptions used by the design engineers,” said the prosecution.
Even after discovering the wrong effective width assumption used in the corbels’s design, Tjandra also failed to take the necessary steps to ensure that they would be able to support their loads. He also did not take steps to ensure that the corbels were reinforced.
The temporary corbels failed because they had insufficient capacity to support the loads on them at the time of the collapse. “Investigations after the collapse revealed that the temporary corbels...had insufficient capacity to carry these loads even when omitting all load safety factors and material safety factors,” the prosecution said.