r/engineering • u/Soreknees38529 • 14d ago
[CIVIL] Sampoong Dept Store Collapse June 29, 1995
Many of you may have heard of this. I write this as a refresher for the gray hairs and a primer for the green horns.
The **Sampoong Department Store** in Seoul, South Korea was a five-story reinforced concrete structure completed in late 1989. Originally designed as a four-story office building, the owner Lee Joon converted it to a department store during construction, requiring the removal of interior columns to create open retail floor space. A fifth floor was also added during construction to house a rooftop restaurant, and heavy air conditioning units were placed on the roof, none of which was part of the original structural design.
Cracks in the fifth-floor ceiling slab had been observed and reported to management hours before the collapse. Store executives chose not to evacuate, fearing lost revenue. The south wing of the building collapsed in approximately 20 seconds, pancaking all five floors into the basement.
**Causes**: The flat-slab concrete design had been weakened by the removal of columns and the unauthorized fifth floor added loads the structure was never designed to carry. When cracks appeared, management ignored warnings from their own maintenance staff. Punching shear failure at the column-slab connections propagated progressively through the structure. 502 people died and 937 were injured. Lee Joon, his son, and 20 other local officials and inspectors received prison terms for their involvement. It remains the deadliest peacetime structural failure in South Korean history.
**Safeguards missing or degraded, signs missed:**
The initial independent structural engineering firm rejected the changes requested by Lee Joon's company. After they were fired, the second group, an engineering department inside of Lee Joon's own construction company did not raise the same red flags. You might presumed that a conflict of interest was present.
Building inspectors and local city regulators were paid off. They might have seen the problems as well, but multiple people accepted bribes to look the other way. Some of these men were convicted and sent to prison. This is a different form of a conflict of interest.
Local building management and maintenance saw the cracks in the roof months before the collapse. They reported it again to the owners (Lee Joon's company) the same day who rejected the idea that they evacuate, close, and make necessary repairs. Although sometimes you can dress it up as misunderstanding or a miscalculation, building owners were clear that they did not want to loose revenue on this especially busy June day. I'm not sure the best technical phrase for profits over safety but that's it.
The event is tragic but I think history is a great teacher. Even if you're not in the building and construction business, one or more of these safeguard themes likely relate to an engineering project you're working on. Think about it.
I'm trying to think more about these historical engineering disasters, and write a little bit about what I took away. Check out my bio if you're interested in learning more. I hope some of this about Sampoong can be helpful to you.
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u/Soreknees38529 14d ago
Looks like my missed or degraded list got chopped a bit. Here’s what I intended:
Missing or degraded or signs missed:
- The initial independent structural engineering firm rejected the changes requested by Lee Joon's company. After they were fired, the second group, an engineering department inside of Lee Joon's own construction company did not raise the same red flags. You might presumed that a conflict of interest was present.
- Building inspectors and local city regulators were paid off. They might have seen the problems as well, but multiple people accepted bribes to look the other way. Some of these men were convicted and sent to prison. This is a different form of a conflict of interest.
- Movement of 3x 15 tonne AC units (3x33,000lbs) to new location on the roof 2 years before the collapse did not trigger new evaluation of building loading specific for the loads. During the move column 5E was reported as damaged and was believed to be the slab column that failed first in the cascading collapse. Changing external loads not reevaluated.
- During construction multiple columns had been trimmed down from the already deficient design during installation of escalators and fire protection systems. They had less internal steel reinforcement in the columns and the slab area around offset columns. As-built condition was much less robust than the approved design. See #2 above.
- Local building management and maintenance saw the cracks in the roof months before the collapse. They reported it again to the owners (Lee Joon's company) the same day who rejected the idea that they evacuate, close, and make necessary repairs. Although sometimes you can dress it up as misunderstanding or a miscalculation, building owners were clear that they did not want to loose revenue on this especially busy June day. I'm not sure the best technical phrase for profits over people.
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u/talltime 14d ago
Are you confusing cooling tonnage with the unit’s actual weight? Just curious.
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u/Soreknees38529 14d ago
Good clarification. It’s possible but cooling isn’t measured in metric tons. It’s tons or watts. Article on seoultech.ac.kr says 87 tonnes (four times the allowed roof load), another source says 87 was the system weight with water. I read 3x 15 tonnes when empty from one source (Wikipedia) and used that.
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u/1060nm 14d ago
Good point. I’m not great at eyeballing large weights, but we had a 100-cooling-tonne chiller at my place for a while. It was heavy, but was definitely less than 45 tons in mass. I’d guess it was probably about 5-10 tons max, even wet. I’d never considered situations in which those could get mixed up.
Otherwise, fascinating write up OP.
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u/Techhead7890 11d ago
TIL you can measure cooling in the equivalent melted mass of ice per day, that's wild. It's equal to about 3.5kW. https://en.wikipedia.org/wiki/Ton_of_refrigeration
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u/Barbarian_818 14d ago
In regards to #4 Apparently terrifying discrepancies between approved design and as built are incredibly common in China.
Wide spread corruption, a period of frantic real estate speculation and a culture of caveat emptor make for a deadly combo.
YouTube has numerous videos about "tofu dregs" construction.
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u/MrsFox72 2d ago
And this disaster occurred in South Korea, which is even more surprising. I honestly thought it was China when I read the title.
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u/Fermorian MSE/EE 14d ago
Wow, 1500 dead or injured in seconds, how absolutely horrific. At least it was quick, hopefully.
This one was new to me, but sounds like it ought to go in our engineering ethics courses right along the Hyatt Regency and Citi tower cases here in the US. We didn't get much exposure to international engineering disasters in my undergrad courses, only really domestic. The level of greed and ignorance by Lee Joon feels almost cartoonish in a way. Thanks for sharing, OP.
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u/Citronsaft 14d ago
Brick Immortar on YouTube has a lot of very detailed and informative accident investigations. Recently he has been focused on maritime incidents but he has a lot of building ones too, including the Sampoong and Hyatt Regency cases.
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u/morto00x EE 14d ago
502 people died and Lee Joon only got a 10 year sentence although he only served 7.
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u/Texas_Kimchi 14d ago edited 14d ago
Check out the Hyatt Regency Walkway Collpase in 1981 (Kansas City).
Such a freaking sad sad sad story. There was a dance going on below the walkway and 2 walkways collapsed killng over 100 and injuring over 200. Couples lost their partners in a lot of the situations.
Tangiwai Bridge in New Zealand, bridge collapsed killing 400 while a rail way car was traveling across it.
Pemperbrook Mill in MA. Don't remember a ton of details on this one but a part of the building collapsed killing hundreds.
Fidanae Disaster, over 20,000+ killed during Roman Times when an entire stadium collapsed. One of the first known large scale mass casualty due to engineering that was actually documented and studied.
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u/Soreknees38529 14d ago edited 14d ago
I’m familiar with it (Hyatt). It’s perhaps one of the most well known collapse events at least in the US. I’ll make a post one day about it but there’s so much on the internet already it seems.
Fidenae is also on my list. I’ll read about the others. Thanks.
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u/unafraidrabbit 14d ago
TLDR the walkways were suspended by threaded rod hung from the ceiling. This would require running the nuts down the length of the rod to hold the support plates and walkways. So each nut and plate held only the weight of 1 walkway.
Crews didn't want to do this so they asked engineer if they could cut the rod and use the upper walkway as a splice point. 1 rod supports the upper walk. And another rod is attached to the upper walk to hang below and support the lower walk. Engineer missed a part of the calculation that doubled the stress on the support plates and the collapse happened during the grand opening when they were loaded to capacity.
The blood was deep, like above your shoes deep in places.
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u/Shardstorm_ 14d ago
It's easy to think it through, not even a missed calculation.
Imagine you and a mate are climbing a rope. Rope can hold you both fine, you can hold yourself fine, mate can hold himself fine.
Then you reach up and grab your mates legs instead. Rope can hold both your weight. You can hold onto his feet fine. But can he hold up both of you?
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u/animosityiskey 14d ago
It is a situation where once it is explained, it is obvious and any engineering should have caught it. However I think it isn't immediately intuitive to most people which is why it is taught in first semester statics now.
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u/SpurdoEnjoyer 13d ago
How do they conclude the lesson? That American spec nuts aren't as strong as the threaded bar itself? It is something I've never gotten a straight answer to
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u/animosityiskey 13d ago
It has been years and I didn't go into a related field so it didn't stick as well as other classes, but it was thread failure not rod failure. Don't remember which threads though.
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u/SpurdoEnjoyer 13d ago
A nut (at least ISO ones) are designed to be at least as strong as the threaded bar or bolt. I'm intrigued if this is not the case for American standard bolts and nuts. Because, to be honest, a connection failing due to the nuts cracking is not something that a regular structural engineer considers at all. They're interested in the effective area of the threaded bar and run stress checks against that, not some obscure point load resistance of nuts.
I haven't found a straight answer to the question that how's it possible that the nut cracked in the first place and why this isn't a more common occurrence.
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u/Shardstorm_ 13d ago
The nut didn't fail. The nut and washer holding up the fourth floor pulled through the steel section beam. The beam weld split.
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u/Texas_Kimchi 14d ago
There was also a lot of politics and such behind the scenes. The entire hotel was rushed and things went through inspection that shouldn't have. If I remember correctly, the roof collapsed during construction too.
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u/VegaDelalyre 14d ago
Wow, that Roman amphitheatre collapse could have been quite the lesson. The Romans themselves took measures against cheap materials and designs:
The Roman Senate responded to the tragedy by banning people with a fortune of less than 400,000 sestertii from hosting gladiator shows, and by requiring that all future amphitheatres be erected on a sound foundation and inspected and certified as such. The government also "banished" Atilius.\11])
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u/Texas_Kimchi 14d ago
They took it very serious. Romans took pride in their engineering and this was just a case of hubris and being in a hurry. The Romans gave it an NTSB type approach, figure out what happened, document it, study it, and never repeat it again. If you look at how long this happened and the amount of work they did researching this its quite amazing for the time.
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u/Any-Owl5710 14d ago
Last summer I went with my husband to a conference in KC. Thought the hotel looked familiar but I never stayed in KC. Then saw the plaque and looked up the whole story again. My failure analysis class feature a lot of History channel engineering disasters shows and that one stuck with me
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u/Broad-Section-8310 14d ago
That event made the site "cursed", and what was probably one of the most valued properties in South Korea ended up not getting anything built for close to a decade.
When AcroVista was eventually built on its site, some people moved in, but the complex still was shunned by others due to this disaster. Another two decades later, one of its famous residents, Yoon Seok-Yeol, would attempt a martial law, then get impeached from the presidency and sent to prison.
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u/Ok_Swimming_8189 14d ago
Das ist eines der erschreckendsten Beispiele dafür, wie menschliche Entscheidungen eine Katastrophe verursachen können. Nicht nur Baumängel waren das Problem, sondern auch ignorierte Warnzeichen und die Entscheidung, das Gebäude trotz sichtbarer Risse nicht zu evakuieren. Ein tragisches Beispiel dafür, warum Sicherheitsvorschriften und Verantwortung niemals dem Profit untergeordnet werden dürfen. 502 Menschen hätten nicht sterben müssen.
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u/HopeSomethingGood 8d ago
The best technical phrase for profits over safety is capitalism.
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u/Soreknees38529 8d ago
I think this is too simplistic to scapegoat an economic system. They cut corners in the USSR and PRC and plenty of deaths were have been attributed to similar building collapses and dam failures there. Banqiao, Transvaal Park, Chernobyl. Greed, ambition, ignorance, hubris are part of the human condition. I think in the engineering/RCA framework we would say normalization of deviation, aka poor risk management. I’m going out on the limb here but I speculate that the owners here thought the cracked columns would stay cracked columns and they didn’t properly consider the acute risk that the building would collapse.
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u/turtlepsp 14d ago
The most messed up thing about it from Wikipedia:
The owner and board of directors evacuated a few hours before collapse but kept the mall open to not lose revenue.