The collapse of the Sejong-Anseong Expressway, which resulted in 10 casualties, occurred after the removal of stability facilities (screw jacks) during bridge construction after the installation of the deck (girders) without authorization. The accident was caused by the premature removal of 60% of the total screw jacks for work convenience, despite the stabilization of the girders not being completed. The construction company, Hyundai Engineering, was unaware of the removal of screw jacks for more than a month. The Ministry of Land, Infrastructure and Transport plans to impose strict penalties on Hyundai Engineering based on the investigation results.
On the 19th, the Ministry of Land, Infrastructure and Transport announced the results of the investigation into the Sejong-Anseong Expressway collapse. The Construction Accident Investigation Committee stated that the removal of stability facilities for work convenience was the decisive cause of the accident.
A screw jack is an adjustable device used to temporarily support loads during girder installation. When installing girders, which are concrete beams connecting piers, temporary supports are set up, and screw jacks are used to precisely adjust the height and safely support the load.
Chairperson Oh Hong-seob noted, "This accident was caused by the unauthorized dismantling of screw jacks, which prevent girder tipping, the backward movement of a launcher that had not received safety certification, and the lack of diligence in regular inspections."
On the 25th of February, during the construction of the Sejong-Anseong Expressway, a girder malfunction occurred while moving a launcher (a large piece of equipment for lifting and installing girders) backward, causing the girder to tip and collapse. This accident resulted in 4 deaths and 6 injuries, totaling 10 casualties. The construction companies are Hyundai Engineering and Hoban Industrial.
◇72 out of 120 total girders removed without authorization
The accident appeared to have occurred when workers dismantled screw jacks before the stabilization (horizontal beam placement and curing) of girders after they were erected on-site. Screw jacks should only be removed once the girders are stabilized for safety. It has been reported that the worker involved stated during the committee's hearing that he dismantled the screw jacks upon receiving instructions from a superior, indicating that they needed to be deployed to another site. Of the 120 total screw jacks, 72, or 60%, were removed without authorization. Four screw jacks were found to be damaged or missing. It was also revealed that anti-tipping wires had been dismantled.
It was found that the risk of an accident increased as the launcher moved backward while the girder was in an unstable state. The launcher deployed at the accident site was certified for safety only for forward movement operations under the Occupational Safety and Health Act, making it unusable for backward movement. Workers should have disassembled the launcher before moving it, but they moved it backward without undergoing this process. The construction site had a tunnel entrance, making it practically impossible to disassemble the launcher.
Deficiencies in the construction process were also revealed. The subcontractor provided a different operator in the construction plan compared to the operator listed in the work log. The operator recorded in the work log left the site to operate another crane. Ultimately, these multiple factors led to lift-off between supports and girders, which caused the collapse.
Chairperson Oh said, "The structural analysis results for each collapse scenario indicated that if screw jacks had not been removed under the same conditions, including backward movement of the launcher, the girders would not have collapsed," adding that "removal of the screw jacks was the decisive cause of the collapse."
◇Overall management and supervision deficiencies
Investigations by the committee revealed overall deficiencies in management and supervision. It was shown that the construction company, Hyundai Engineering, did not realize that screw jacks had been removed from the site for more than a month. The removal of screw jacks occurred in January, but Hyundai Engineering failed to detect this despite having installed closed-circuit television (CCTV) on-site.
Chairperson Oh stated, "It is indeed difficult to visually confirm whether screw jacks are installed after girders are positioned," yet emphasized that "because CCTV was available and the video confirmed the removal of screw jacks, I believe Hyundai Engineering failed to manage this aspect adequately."
It has also been found that the review of the safety management plan by the construction company and the contracting authority was insufficient. Although the selection of a launcher that had not received safety certification for backward movement operations and the planned details for backward movement operations were included in the safety management plan for the project, Hyundai Engineering and the Korea Expressway Corporation approved it as is.
Chairperson Oh pointed out, "The subcontractor bid with a promise to move the launcher backwards, and if the backward movement was simply recorded in the safety management plan, a blind spot could occur if the construction company failed to review it carefully." He continued, "The construction company should have been aware that this launcher had not received safety certification for backward movement; however, there were likely aspects they could not sufficiently ascertain due to working conditions."
In particular, confirming the structural safety of temporary structures was also inadequate. While temporary structures should be verified by a third party, it was found that a technician from the subcontractor Jangheon Industrial verified the launcher at the accident site.
The Ministry of Land, Infrastructure and Transport, separate from the committee, established a special inspection team and found 14 deficiencies in the construction site, including four cases of inadequate safety management due to some regular safety inspection results not being submitted, one case of inadequate quality management due to missing concrete compressive strength tests, and nine cases of illegal subcontracting involving unregistered construction workers.
The Ministry of Land, Infrastructure and Transport plans to notify related departments and local governments of the results from this committee and the special inspection. Each administrative agency will determine and notify the level of penalties for construction, subcontracting, and supervision companies. Given that this accident is subject to the Ministry's authority, as the committee has been formed, it will consider imposing strict measures, including business suspension, on Hyundai Engineering.
Kim Tae-byeong, Director General of the Ministry of Land, Infrastructure and Transport, stated, "In the case of Hyundai Engineering, there have been three accidents this year, resulting in a total of six fatalities," adding, "This accident is serious, and the number of deaths makes it subject to authority-related penalties." He further mentioned that the administrative penalties will proceed according to the procedures of the appeals and hearing process and typically take about 4 to 5 months.
Additionally, the Ministry of Land, Infrastructure and Transport plans to confirm the safety of the remaining structures on-site before deciding on repair or reconstruction. Accordingly, the opening date for the Sejong-Anseong Expressway, initially scheduled for next year, is expected to be delayed.