Ep 14 The Sampoong Department Store Collapse

Engineering News - HuggieBot 2.0

Engineering Failure - Sampoong Department Store collapse.


Engineering News:

Sampoong Department Store:

Episode Summary

Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole, and I’m from Calgary, Alberta.

  • I don’t know if I told you this before, but we had a set of world book encyclopedias when I was a kid. A hard copy; boy I haven’t seen one of those in a while. Any time I was curious about something or bored I would read about it in the world. They were sorted alphabetically so sometimes I would just take the “M'' book for example and see what I found. I also used to write little reports on what I learned. I grew up on a farm and needed things to keep my busy mind occupied. But I was thinking not long ago, that it's like I’ve been training for this podcast my entire life.

Before I get into the episode - Housekeeping

  • Based on some listener feedback – I’m making a couple slight changes to the show

  • Don’t worry, no change to content

  • First, I know that you’re busy’ I’m busy, everyone’s busy. And I obviously would love for you to listen to the entire show, but in case you can’t and you just want to get to the good stuff, I’ve added timestamps in the show notes

  • I’m also making an effort to be less scripted – the first few episodes I used the same intro, and then I started telling stories about myself and how I connected with the failure in some way. And I think that being a little less scripted is the next step in this podcast journey. I want to continue to grow and improve each week.

  • Engineering failures – nerdy version of true crime. It's not that I like when things fail, it's just that I’m such a curious camper and I want to know what happened, why and how it failed.


  • Take this week’s failure for example

  • It’s the first engineering failure I’ve covered from Asia. I’m slowly but surely making my way around the globe.

  • It's the sampoong department store collapse

  • Hadn’t heard of until a few weeks ago

  • Saw on the sub reddit catastrophic failure – always a good time

  • I went to the Wikipedia page, my research medium of choice, and immediately read the entire article.

  • This is a fascinating story of greed, ignorance and tragedy. And, like all of the failures I’ve covered on this podcast, completely preventable!

  • Sometimes researching these episodes make me so frustrated because of how many signs there are of failure. But I can’t go back in time, and the show must go on. So I hope we learn the valuable lessons here and don’t let history repeat itself.

Buckle up folks, this one’s a doozy. But first, the news.

This week in engineering news is a feel good story about a robot that hugs users on request

  • I’m not crying, you’re crying

  • Inspired by researchers with family members who lived far away

  • Robot is called HuggieBot 2.0

  • 6 design Goals

    • Soft

    • Warm

    • human sized

    • visually perceive its user

    • adjust the hug to users size and position

    • release when the user wants to

  • Made from

    • two JACO arms (commercially available robotic arms usually attached to wheelchairs)

    • inflatable soft torso that has sensors in it to detect user contact

    • Covered in heating pads

    • Purple robe and grey sweatshirt, with padded mittens

    • 3D printed head, has a computer, depth sensing camera, a speaker and a microcontroller, screen to serve as a face – which shows different animated facial expressions – might be kinda freaky at first, but I think you’d warm up to the idea of a talking robot face that hugs.

  • Natural and intuitive robot

    • HuggieBot’s camera sensed the user, lifted its arms and asked “can I have a hug please?”

    • Torque sensors in arms to detect when user wants to end the hug

    • Sensors in the inflatable torso to detect when the user removes their hands from the robot’s back

  • Current pandemic – in a few weeks it will be a year that we have been living in isolation – there are people living alone or who haven’t had a hug in almost a year. Fortunately I live with my wonderful boyfriend and silly puppy that I can smother with affection against their will. But not everyone has been so lucky.

  • I’m not even a really touchy feely person, but I think a year without a hug would be really really hard. I am fortunate to live with my boyfriend and have a dog I can smother with love.

If you want to read more about the HuggieBot 2.0, check out the link on the web page for this episode, or head to failurology.ca.

Now on to this week’s engineering failure;

  • After standing for 6 years, the Sampoong Department Store Collapse in Seoul South Korea collapsed on June 29, 1995 in the Seocho-gu (so-cho-goo) district of Seoul South Korea.

  • Largest peacetime disaster in South Korean history.

  • Deadliest modern building collapse until the September 11th attacks on the World Trade Center in New York City.

  • Deadliest non-deliberate building collapse until the 2013 Savar (sah-va) Building collapse near Dhaka (dah-ka) Bangladesh

  • There was a large boom in Seoul leading up to the 1988 summer Olympics

  • Bans against international construction contractors signing contracts for projects in Seoul – keep it local

  • Almost all buildings were erected by South Korean companies, built quickly due to number of projects assigned to them

  • Sampoong Group, the developer, began construction of the department store in 1987

  • 4 acres of land was previously a landfill, now affluent area

  • Original plans – residential building with 4 floors, to be built by Woosung Construction

  • Lee Joon, future chairman of Sampoong Group’s Construction division, changed to large department store

    • Cutting away a number of support columns to install escalators

    • Addition of 5th floor

  • Woosung refused to make changes, Lee ignoring their warnings, fired them, used his own company to complete construction

  • Completed in late 1989, opened to public on July 7, 1990 - 1000 employees, 40,000 people per day, 4 million usd per week, Electronic, fashion

  • 4 basement levels and 5 stories above ground – north and south wings connected by an atrium

  • Rigorous inspections for public buildings

  • Sampoong passed regular inspection – question the integrity of these inspections based on what I’m about to tell you

  • In the months before 2 gas explosion, bridge collapse 150 deaths - poor building practices to blame

    • One of the gas explosions was at the underground construction site of a subway. They didn’t call the gas company before digging. Over 100 people died. People. Always always call before you dig! Alberta 1 call. Its

    • Seongsu bridge – cutting corners and metal rusting – people driving over – over 30 people died


  • April 1995 cracks appears in ceiling of south wing’s fifth floor – Lee, the chairman of the Sampoong Group, moved merchandise and stores from top floor to basement

  • Civil engineering experts inspected the structure, a cursory check found it was at risk of collapse, but nothing was done

  • Could have put re-shore or columns to reinforce the slab, probably could have made them hidden, and got creative. In all reality, should have closed the store for repairs

  • Days leading up to collapse - Disturbing sound heard / loud bangs on 5th floor - Vibrations felt on basement level 1

  • By June 29th, the day of the collapse, Facility manager has a note from night security about noise on roof

  • Due to unusually high numbers of customers in building the management failed to shut down and evacuate the store – didn’t want to lose revenue – but executives themselves left as a precaution

  • Collapse was inevitable – emergency board meeting held – directors suggest evacuation, Lee refused for fear of revenue losses – Lee left before collapse – didn’t inform his own daughter-in-law Chu Kyung Young who was an employee – she ended up getting trapped in the rubble and rescued days later

  • 10am Large crack noticed around column 5E and floor looks buckled at base - closed restaurant - tells restaurant workers to say nothing

  • 1230pm - facility managers think air conditions are causing vibrations, turns them off – crack already 10cm

  • 4pm - facility manager lee briefs store owner about cracks (4in wide since morning) - structural engineer recommends to close for urgent repairs, owner refuses

  • 5pm Korean Standard Time – fifth floor ceiling began to sink – customer access to fifth floor was closed

  • 540 pm - loud bang heard in top floor, slab shifts.

  • 545pm - packed with shoppers, ac still off 32C

  • 547pm - loud bang from top floor

  • 5:52:30 - shock wave rocks building, alarms go off. Staff exit on upper floors. Starts to collapse - 20 seconds - entire store except ends

  • AC units crashed through already overloaded fifth floor – main columns weakened from escalators, collapsed and south wing pancaked into basement – 20 seconds all columns in south wing gave way

  • 270 billion won (216 million USD at time, equal to 364 USD in 2020) in property damage


  • 1500 people trapped inside - rescuers on site in minutes

  • 1000 rescue works and volunteers, 30 cranes and excavators, work through night Remove huge slabs

  • 200 rescued by morning, 44 dead, many still missing

  • North face tilting and could fall - end of second day have to abandon search – if you go to failurology.ca you can see a picture of the building after collapse. You’ll see the north face that’s left standing is a tall, skinny structure that without the building isn’t really supported

  • 500 protesters take to the streets to keep up the search

  • Morning of 3rd day north wing is stabilized by guy cables

  • Day 4 - death toll 107

  • Rubble is compressing, further trapping those inside

  • After a week - authorities decide there’s little hope bc there’s no water (weather about 85f heat)

  • Rescue turns into recovery - 5 days go by, 21,000 tons of debris removed - just after 330pm 12 days after collapse - (yu) survivors found alive 285 hrs trapped, drinking rainwater to survive

  • 16 days after, site is mostly clear, last person is rescued 377 hrs trapped – Park Sung Hyun (Hun) - she was supposed meet her friend after work the day of the collapse


  • Within an hour of disaster, full scale inquiry is ordered. Professor Lan Chung of civil engineer at Dankook university’s engineering school

  • Gas related? 80-90% sure, but it’s not – remember two gas explosions occurred elsewhere in the City that year

    • Fires in the rubble were from burning automotive gasoline from crushed cars in the underground garage (called a parkade in Calgary) – gas explosion would have been larger

  • Terrorist bomb? Damaging interior columns (North Korean militants)

    • Korean War – 1950-53 – south and north korea have been in conflict for years

    • Bears resemblance to April 19, 95 Oklahoma bombing, just a couple months before

    • Oklahoma can see debris blown out sideways from explosion - forming a pattern

    • Sampoong, debris inwards, collapse straight down. Bomb ruled out

  • Structural failure caused it

    • Prosecutors office to arrest owner, chief architect, ceo and facilities executive under suspicion of professional negligence

    • Original design - 4 floors above ground, half way through the build they added a floor. Construction company refused and was fired. In house hired to finish job

    • Drawings look ok. Basic concept - original dwgs

    • Engineer calculates column sizes and enters them back into the building. Like Quebec bridge – assumptions are made at first and then recalculated later once the design information is known. Column diameter is reduced on dwgs from calculations - 80cm diameter, dwgs 60cm

    • Designed to be 2.5x stronger than needed. Actual columns reduced by half but still ok – a bunch of problems

    • Poorly-laid foundation, unstable ground – contributed to failure

    • Substandard mix of cement and sea water and poorly-reinforced concrete used for ceilings and walls

    • Flat slab structure without cross beams for steel skeleton – no way to transfer load across floors

      • Floor slab is supported directly on columns

      • Area of floor around columns should be reinforced to carry load

      • If columns are too narrow, they can punch through slab

      • Number of rebar embedded into the concrete was 8, not required 16 – half needed strength

      • Rebar are in wrong place - 5cm from top of slab but are 10cm - critical - lower makes it thinner and weakens by 20% where slab connects to columns

      • Any of these on their own may not have resulted in failure, but combined they are not good

      • Installation of fire shields around escalators, a safety feature to prevent fire spread, cut support columns reducing diameter further

    • Columns reduced from 80cm to 60cm – spaced further apart at 11m to maximize retail space – more load on each column than if they were closer

    • Fifth floor was original planned to be a roller skating rink – zoning regulations prevented entire building from being used as a department store – changed to 8 restaurants instead – heavy equipment

    • Construction company advised the structure would not support the extra floor, they were fired

    • Heated concrete floor (ondol) with hot water pipes going through it

    • 1.2m thick ondol increased weight and thickness

    • Diners sit on floor - installed floor heating - thickened slab - even more stress on column connections - lee seen cracks and photos - restaurant pillar has crack around base size of mans fist, slab has separated with only rebar

    • Three 15 tonne AC units were installed on roof – adding 45 tonne load – four times design limit

    • Moved over column 5E – most visible cracks seen before collapse

    • Columns supporting fifth floor were not aligned with ones supporting lower floors, fifth floor load was transferred through the slab

    • Stood for 6 years - nearly 8 acres of retail floor space

    • Critical point - 1993 2 years before, 3 large ac units move bc neighbours complained about noise – rollers and dragged, rather than relocated by crane

    • facility manager - confirms they were moved with photos - show cracks

    • How they were moved - dragged across roof - very concerning - made entire roof unstable - 15 tonnes each- column 5e most – crane may have delayed collapse

    • Vibrating on collapse - every time unit is turned on it sends vibration across roof down to 5th floor, radiating, crack gets wider around 5e until is breaks, let’s go and pancakes

    • Lee turns off ac but it’s too late, crack is 10cm – they must have had roof leaks.

    • 20 seconds before - shock wave through building

    • Slab around 5e gives way

    • Blames on human ignorance, negligence, greed


  • Lee Joon, chairman, complained during interrogation with Professor Chung that his main concern was that collapse inflicted great financial damage to his company

  • Dec 27, 95 Lee Joon was found guilty of criminal negligence – 10.5 years – prosecutors asked for 20 years – reduced to 7.5 yrs on appeal – died Oct 4, 2003 months after release from prison, complications from diabetes, high blood pressure, and kidney disease

  • Lee Joon’s son, Lee Han-Sang, store’s CEO received 7 yrs for accidental homicide and corruption. Release from prison in 2002 – worked as an evangelist in Mongolia

  • Lee Chung-Woo, city official – chief administrator of the area, sentenced to 3 years in jail for bribery

  • Hwang Chol-Min, former chief for area, guilty of accepting 12 million wan bribe – sentenced to 10 years in prison

    • 12 million is equivalent to about $13,000 canadian dollars. Can you imagine 10 years in prison for 13k!

  • Former chief administrator Seocho district also jailed

  • A number of store executives and company responsible for completing the building were also sentenced


  • Families of victims asked for $361,000 each, and the city of Seoul, representing the store’s owner, offered to pay $220,000 for each victim.

  • Two months after collapse, Lee Joon and Lee Han-Sang liquidated the Sampoong Group and offered their entire wealth to compensate the families

  • Settlement of 3,293 cases, 375.8 billion wan – payouts complete by 2003


  • 21 others, 13 city officials found guilty, widespread corruption

  • 1 of 7 rebuilding , 1 of 5 major work

  • 1 in 50 was safe

So there you have it

  • Demolished what was left shortly after collapse and recovery

  • Remained vacant until 2000

  • Families requested a memorial – opposed by Seocho District government – Seoul Metropolitan Government to mediate dispute – memorial built elsewhere

  • Land sold to private developer – luxury apartment complex – Acrovista Apartments – began in 2001, completed 2004

  • Would you live there? I think the site might have bad juju

  • Yangjae Citizen’s Forest has a sculpture made in memory of the collapse – 12m high marble memorial – funded by Sampoong Group

Check out the podcast page, link in show notes, for photos and sources from this week’s episode; or visit failurology.ca. On there you will find an image of the

If you’re enjoying what you’re hearing, please rate, review and subscribe to failurology, so more people can find it. And if you want to chat with me, my twitter handle is @failurology or you can email me at thefailurologypodcast@gmail.com.

Thanks everyone for listening. And tune in next week for the Q&A episode; where I answer all of your questions about the podcast. It’s kind of like a behind the scenes look at failurology. But more on that next week. Bye everyone, talk soon!