The collapse of the 40m segment of the viaduct under construction next to the slip road from Upper Changi Road East to the Pan-Island Expressway surprised many.

The corbels might have given way for various reasons, including design oversight, overloading, concrete not achieving the required compressive stress and poor workmanship.

The Land Transport Authority has in place a stringent inspection regime (Questions loom over collapse of viaduct segment; July 16).

During the tender process, it was aware of Or Kim Peow Contractors' (OKP) September 2015 incident, in which one worker was killed and four others injured in a major breach of the Workplace Safety and Health Act.

However, it still awarded the contract to OKP, despite the fact that the Manpower Ministry was still investigating the incident.

Whether OKP's safety performance was considered during the tender assessment is not known.

A thorough investigation should be carried out into the reasons for the structural failure, the tendering process, the safety track records of OKP's present and previous projects, and the OKP project management team's competency.

Sreenivasan Sreenath (Dr)