Substandard scaffolding and construction mishaps may have caused the collapse of a section of a Chao Phraya River bridge during construction in Chai Nat on Sept 30, according to the Council of Engineers.
The incident at the 574-metre concrete bridge in Muang district injured four construction workers, three of whom were critically hurt. The bridge links Nong Rahaeng village in tambon Ban Kluay with tambon Tha Chai.
Amorn Pimarnmat, secretary-general of the council, said yesterday the collapse happened on the 14-metre approach slab, where scaffolding had been set up to support the structure.
The council's experts were sent to determine the cause of the collapse on Oct 3, along with engineers from the Department of Rural Roads (DRR) and a consultancy firm, he said.
Based on the examination, the collapse may have come from two factors, he said.
The scaffolding supporting the bridge's approach slab may have fallen short of the required engineering standard as faults had been found in various spots.
The linkage between its structures were found to be substandard, according to Mr Amorn.
Questions have also been raised about whether the bridge construction complied with the required process since the position of the bridge's joint spots were not consistent with the design, which could have led to the incident, he said.
Further checks are needed to find out whether requests had been lodged to tweak construction design plans, he noted.
Mr Amorn said engineers working on the project will be invited to give information. If they fail to comply with the proper process, they could have their licences revoked, he noted.
Work also is under way to seek the construction design plan from the DRR, the project owner, as well as contacting other state agencies to obtain information for the probe, he said.
"In the process, we will invite the engineers, numbering around 10, to give information, particularly those overseeing the work at the spot where the incident happened," said Mr Amorn, adding the inquiry could last between six months and a year.
Scaffolding had collapsed on other projects before so the council will invite more than 200 civil engineers to undergo a training session on Oct 21 by using the collapsed bridge in Chi Nat as a lesson.
The council is expediting efforts to map out standards and manuals for the design and construction of scaffolding as well as other temporary structures to serve as guidelines, he said.
Chulert Jitjuajun, an engineering expert examining the scene, said the scaffolding's pipe supports did not stand upright.
The connecting spots of scaffolding fell short of engineering principles as they were welded with metal scraps, resulting in instability.
