Construction
At 2:33 p.m. on May 26, a section of the deck collapsed at the demolition site of the Seosomun Overpass in Seodaemun-gu, Seoul.
The accident claimed the lives of three people—including the construction company’s site manager, the head of the supervision team, and an external structural engineer—and left three others injured.
Notably, all three fatalities occurred immediately after the victims had entered the space between the girders (the main structural beams) to conduct a “safety inspection.” As such, this accident goes beyond a mere construction safety incident; it directly challenges how we actually implement the concept of “safety.”
In this article, we will summarize the full details of the Seosomun Overpass collapse and examine one structural challenge that this incident highlights.
The crux of this accident is clear: the very people who ventured closest to assess the danger were the ones who fell victim to that danger.
The accident began around 2:30 a.m. on the 26th when a 2.9 cm subsidence was detected while cutting the viaduct’s slab (the topmost concrete slab of the bridge). Work at
the site was suspended in the early morning, and at 2:00 p.m., inspection personnel entered the space between the girders to conduct a safety assessment.
About 30 minutes later, the girder they were inspecting collapsed, causing the workers inside to fall.
Lee Jong-woon, head of the Disaster Safety Division at the Seodaemun Fire Station, explained during a site briefing, “It appears that after suspending work in the early morning, personnel entered the space between the girders at 2:00 p.m. for a safety inspection, and the girder collapsed.” Choi Jin-woo, head of the Civil Engineering Department at the Seoul Metropolitan Government’s Urban Infrastructure Headquarters, also stated, “The girder is about 80 cm high. It is understood that the girder collapsed while personnel were inside conducting an inspection, causing them to fall.”
The deceased are Mr. Lee, a site manager in his 60s employed by the contractor Heunghwa Construction; Mr. Ahn, a supervision team leader in his 60s; and Mr. Lee, a structural engineer in his 50s who was an external expert.
All three were personnel who had entered the interior of the structure to inspect the cause of the subsidence. A total of nine people participated
in the inspection that day, including the three who died, as well as officials from the Seoul Metropolitan Government’s Civil Engineering and Roads Division, representatives from the safety inspection firm, and external advisory committee members. The three injured individuals were identified as employees of the Seoul Metropolitan Government’s Urban Infrastructure Headquarters and the Seodaemun-gu Community Service Center. It was reported that the Community Service Center employee was caught up in the accident while passing under the overpass, unrelated to the construction work.
The question raised by this accident is clear: “Who made the decision to send people into that structure immediately after subsidence was detected, and on what basis?”
The Seosomun Overpass, built in 1966, is a 335-meter-long, 14.9-meter-wide road consisting of 18 piers.
Due to deterioration, an incident occurred in March 2019 in which concrete fragments fell onto the road, and following a detailed safety inspection that rated it a Grade D, a decision was made to demolish it.
Demolition work began last August and was scheduled to be completed on July 29 of this year.
In other words, the work was being carried out on a structure that had already been officially deemed “structurally unsafe.”
If a 2.9 cm subsidence was detected in such a structure, all on-site decisions from that point onward should have been based on objective data regarding “the stress state of the structure.”
However, after detecting the subsidence in the early morning, the site waited approximately 12 hours before sending nine workers directly into the structure for a safety inspection, during which the girder collapsed. This is why
the police have stated that they will investigate whether the safety inspection was conducted recklessly despite signs of impending collapse.
The structural challenge highlighted by this accident ultimately boils down to one question: When warning signs are detected on-site, are those signs and the history of actions taken in response shared on a single screen with all decision-makers?
RenameDP has been examining construction site accidents from the perspective of drawing and document management. Whether in the GTX Samsung Station rebar omission incident or the recent Seosomun overpass collapse, a common issue emerges: “Where and in what form is the basis for judgment documented?”
Demolition sites require a different kind of information flow than construction sites. The stress state of a structure changes with daily work, and a girder that was safe yesterday may become dangerous today.
In such an environment, the moment a safety inspection is decided, what is needed is a chronological record of “which section was cut, what displacement was measured immediately afterward, and who ordered what measures.” Only when this record is shared in the same format with the contractor, supervisor, client, and external experts can the decision to “enter the structure for inspection” be made on a rational basis.
This is precisely why RenameDP is developing its service to automatically organize drawings and documents while preserving their history. When a single drawing, a single line in a daily work log, and a single page of a safety inspection report are all connected without omission, the site can operate based on “evidence” rather than “intuition.”
This accident did not occur because inspections were neglected.
Rather, it is all the more serious because it happened while personnel were inside the structure to conduct an inspection. This accident is teaching us, in the most costly way possible, that it is not the frequency of inspections that matters, but that every step—from deciding to inspect to carrying out the inspection—must be documented and managed.
Yonhap News - "Seosomun Bridge Collapses During Demolition… 3 Dead Including Site Manager and Supervising Engineer (Comprehensive Report 2)"
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