Chris McLean, Brooks Anderson, Carl Peterlin, Kyle Del Vecchio


Abstract


On July 29th, 1995, the Sampoong Department Store located in Seoul, South Korea collapsed(Figure 1) due to a blatant disregard for structural precautions and
corrupt business practices led to the structure collapsing with over 1500 customers still inside the structure. The addition of a fifth floor to the structure and the
dragging of air conditioners along the roof overloaded the structure. The collapse of this structure left 937 people injured and had a death toll of over 500 people.
The progressive collapse of this structure was due to a build up of prolonged weakening of the building leading up to July 29th, 1995. On that day, the structure reached its breaking
point, causing the building to collapse at 5:57 PM. From the point of critical failure, it only took 20 seconds for the entire south wing of the structure to collapse.


Overview


sampoong.jpg
Figure 1: Sampoong Department Store Collapsing (Courtesy of Seconds From Disaster: (Sampoong) Superstore Collapse (Screen Shot)

Location
Seocho-gu district of Seoul, South Korea (previously a landfill)
Completed
1989
Open to the Public
July 7, 1990
Visitor flow
Approx. 40,000 per day
Spec.
Steel Reinforced Concrete
Originally an office building (supports had to be removed for escalators)
North Wing and South Wing connected by atrium
5 stories tall
8 restaurants on 5th floor with heated flooring
Collapsed
June 29, 1995
Damages (in dollars)
210 billion won
(216 million U.S.D.)
Injured
937
Death toll
502

Keywords

  • Punching Shear Failure - a type of failure of reinforced concrete slabs subjected to high, localized forces.
  • Flat-Slab Construction - a construction method that employs concrete floor slabs without beams, using diagonal and orthogonal patterns of reinforcing bars.
  • Joon Lee - chairman of the Sampoong Department Store; sentenced to 10 years of prison for criminal negligence.
  • Hang-San Lee - son of Joon Lee and manager; sentenced to 7 years for corruption and accidental homicide.

Timeline of Events Leading to Sampoong Department Store Collapse


1989: Construction is completed.

July 7, 1990: The store is open to the public.

1993: The department store's three air-conditioning units are repositioned. They are put on rollers and dragged across the roof. The main support columns
of the structure are forced downward. Column 5E receives damage. Cracks occur where Column 5E meets the 5th floor.

June 29 1995:

8:05 AM: Store facility manager investigates note left by night-shift security guard. The security guard heard strange noises on the roof during the night.

10:02 AM: Store facility manager finds large cracks around one of the department stores columns (Column 5E) (Figure 2). Restaurant where column is
located is closed.

Column5E.png
Figure 2: Column 5E Breaking Point (image courtesy of ScienceDirect- Cement and Concrete: Lessons from Sampoong Department Store Collapse


Midday: Customers hear strange sounds, the structure starts to have small vibrations.

12:30 PM: Store facility manager thinks air conditioning units are to blame for vibrations. He shuts them off.

4:00 PM: The store facility manager explains to the head manager that the cracks around Column 5E have increased to 4 inches since the morning. The
structural engineer who built the store complex is present at this meeting. He recommends closing the store immediately for urgent repairs.
The head manager refuses.

5:40 PM: Customers hear a loud noise from the top floor, the ceiling shifts.

5:47 PM: Customers hear an even louder disturbance from the top floor.


5:52 PM: Entire building vibrates violently. Building progressively collapses in less than 20 seconds.




Causes of Failure


In the mid-1980s, South Korea’s economic development lead to a boom in the construction and retail industries.
This, accompanied by the hosting of the 1988 Olympics in Seoul, lead to many construction contracts, too many for firms in Seoul to handle.
International construction firms were not allowed to sign contracts and this caused an overload on already stressed local firms. (Wearne, 2000) Nonstop contracts
lead to constant construction and eventually lax supervision as well as corruption. Mixing greed and loose supervision lead to appalling disasters and horrifying discoveries.


Two separate construction companies built the Sampoong Department Store on the site of a former landfill. (Wearne, 2000)
Woosung Construction had originally been contracted to build the entire structure but were dropped after they refused to drastically change the building plans,
which included adding a fifth floor. With only a foundation and lower levels completed, Sampoong executives hired their own construction company to finish
the superstructure.


The changes implemented by Sampoong’s in-house contractors changed the entire layout of the building. Originally, the building was designed to be an office block,
but became an open-plan department store. The additional fifth floor was intended to be a roller-skating rink, but became a traditional Korean restaurant. (Wearne, 2000)
By the time construction was completed, the building was a far cry from its original plans.


After the collapse, Lan Chung, professor of civil and structural engineering at Dan Kook University, and Professor Oan Chul Choi, head of the department of
Architecture at Soongsil University, began investigating why the structure collapsed. (Wearne, 2000) The first thing they noticed was that the store had been a flat-slab structure.
In a flat-slab structure (Figure 3), there are no cross beams or steel framework; without cross beams, there is a form of load transmission missing, which means the
framework must be constructed perfectly. Secondly, they began to look at the site on which the building was constructed and the materials used. Research revealed
that even though the superstructure was built on a landfill, the foundations and basement rested on rock and survived the collapse well.The concrete used was questioned,
but sampling and testing revealed that the concrete was adequate. Finally, the investigators began to review the plans.
concrete_slab_construction.jpg
Figure 3: Example of Slab Construction (Copyright Chris McLean)

The plans revealed many disturbing secrets about the collapse. The conversion from an office block
to a retail store meant escalators would be necessary on every floor. Cutting holes in every slab for an
escalator weakened the structural integrity of each slab. Floor columns had been weakened to meet fire
regulations as well – columns that were supposed to be thirty-one to thirty-five inches thick were less than
twenty-four inches thick. Also, the span between each column was nearly thirty-six feet, a dangerously large
spacing made in an attempt to maximize floor space. The crucial element of collapse came from the fifth floor
Woosung Construction refused to build. The fifth floor added extra weight to the entire structure, but its conversion
from a skating rink to a restaurant added significantly more weight. Traditional Korean restaurants do not have
chairs and customers sit on the floor. Sampoong execs wanted heated floors for their customers, and that added
four extra feet of thickness to the fifth floor slab. Also, the fifth floor’s columns did not align with the columns
underneath, leading to load being transferred from the column to the slab and through another column instead
of column to column. Furthermore, the roof structure was found to be extremely inadequate for the heating and
cooling systems they were supporting – the slabs were found to be one-fourth of the required strength.
Yet, the building had stood for over 5 years; what actually caused the building to collapse?




The air conditioning units were placed on the roof in order to keep the noisy machinery away from surrounding skyscrapers. Investigators soon learned that the air conditioning units on
gfff.jpg
Figure 4: Diagram of forces of moving air conditioning units (Copyright Chris McLean)

the roof had been moved due to noise complaints from surrounding buildings anyway. Instead of hiring cranes and professional moving teams,
the units simply had been dragged across the roof, creating huge cracks (Figure 4). (Seconds from Disaster, 2006) It also created a downward force on the support columns and
column 5E was critically damaged and cracked (Figure 5). When the air conditioning units were turned on, the vibrations were sent through the
cracked roof, down the mismatched, undersized columns, and through the rest of the building. (Wearne, 2000) The constant vibrations of the air conditioning units
caused the cracks to widen in column 5E leading to critical failure on June 29th, 1995. On that day column 5E completely separated from the 5th
floor floor-plate (Figure 6). Although these dangers were present for years, the executives ignored others’ warnings. Even on the day of collapse,
structural engineers determined the building unsafe, but the store remained open.

column_damage.jpg
Figure 5: How Column 5E Was Damaged (Copyright Chris McLean)

sfsd.jpg
Figure 6: Vibrations from AC units cause further damage to Column 5E (Copyright Chris McLean)



The public outcry was extraordinary. A government survey of high-rise construction in South Korea revealed that 14% of all high-rise structures in
the country were unsafe, 84% needed repair work, and only 2% met government safety standards. (Wearne, 2000) In the end, Joon Lee, chairman of Sampoong,
was found guilty of criminal negligence and jailed for 10 years. His son, Han-Sang Lee, was jailed for 7 years for corruption and accidental homicide.
The Sampoong collapse was the largest loss of life in a single construction disaster. (Seconds from Disaster, 2006) Pitifully, it was due to corporate corruption and greed.

The Sampoong Department store collapsed due to ignorance and punching shear failure (Figure 7). The flat-slab construction allowed for the
entire building to fall like a house of cards after the roof collapsed. In hind sight, this disaster should have been prevented long before construction
was completed.

sc00089baa.jpg
Figure 7: Diagram of Punching Shear on Coulmn 5E (Copyright Carl Peterlin)





Conclusion


In conclusion, the collapse of the Sampoong Department Store could have easily been prevented. From the beginning, signs of danger were evident. The addition of the fifth floor was completely
unnecessary; greed lead the executives of Sampoong to hastily make decisions that only benefited their business. Their oversights and stubbornness throughout construction doomed the building
before it was even completed. In addition to incorrect construction and structural practices, executives refused to heed the advice of structural engineers repeatedly. Sampoong's management had
seen the inch-wide cracks on the roof and at the base of column 5E with ample time to correct the problem and/or evacuate the building. Once again, Sampoong's executives balked at closing the
store to correct their problems. The collapse on the afternoon of June 29th, 1995 was the largest loss of life in a single construction disaster.

Lax inspections, change of the engineers and architects plans without permission, and miscalculated dead loads were the norm in Korea in the late 20th century. The Sampoong collapse only
made the public aware of a deadly problem that plagued their structures. Out of the investigation, 14% of South Korean skyscrapers were unsafe, 84% needed repair, and only 2% met codes and
government standards. Unfortunately, the Sampoong disaster could have been avoided many different times throughout it's construction and lifespan. Luckily, the collapse made Korea aware of
its backward business practices and sub-standard construction. Structures are central to economy and life as we know it and are used for many different things. In the future, however, those in
charge of what goes on inside the building don't necessarily control the building. Engineers and architects plans and calculations are of the utmost importance and when altered, can lead to large
losses of life.



Bibliography



Books:

  • Wearne, Phillip. Collapse When Buildings Fall Down. New York: TV, 2000. Print.
The subject of this book is forensic engineering. The author focuses on the specifics of failure as well as the effect of the human element in 11 in-depth cases. The
book offers insight to past catastrophes so we may prepare ourselves for, and hopefully avoid, future failure.


Video:
  • Seconds from Disaster: (Sampoong) Superstore Collapse. National Geographic. DVD. Darlow Smith Productions 2006
This video goes through a chronological process of events leading up to the day of the disaster and concludes with a detailed analysis of why
the structure fell with testimony from people who were in the structure the day of the collapse and testimony from civil engineer experts who examined why
the structure collapsed.


Journal:
  • Gardner, N.J., Jungsuck, Huh, and Chung, Lan (2002). "Lessons from the Sampoong Department Store Collapse." Cement and Concrete Composites, 24(6), 523-529
This journal provides an in depth mathematical analysis as to why the structure collapsed.

Webpages:
The article gives a factual overview of the collapse, rescue and recovery effort, and investigation and trial of the Sampoong Department Store.
The article describes the chain of events that lead to the structural collapse of the Sampoong Department Store. It also speculates about the WTC collapse and it's relation
to the structural failure of the department store.

This online journal provides an in depth mathematical analysis as to why the structure collapsed.
A factual account about the structural failure and events leading to collapse.
A form of this article appeared in the NY Times on June 30, 1995. It connects human error with human emotion unfortunately through disaster. Also, it offers details about
the rescue effort.

A factual account about the structural failure and events leading to collapse.