The collapse is known as the deadliest modern

 

The Sampoong Department Store was constructed in Seoul,
South Korea. It had been collapsed on the 29th of June in 1995. This
collapse is known as the deadliest modern building collapse that has taken
place, up until the attacks that took place in New York. The reasons behind
this disaster were the numerous errors made by the designers and contractors
who built the store, and the irresponsibility on behalf of the store owner.

 

The structure had been built on top of a landfill, which
was originally designed for an office building. However, midway through
construction, the chairman had desired to construct it into a department store,
with an additional fifth floor. Several engineers that had been working on the
project warned the owner, Joon, that the changes were life-threatening. They
stated that the building had high chances of collapsing. However, Joon did not comprehend
with the fact that this was a high probability, and fired his workers instead.

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When the disaster had taken place, 1500 people were present
in the building and got trapped, in which over 500 died and 937 underwent
non-fatal injuries. The rescue team was not able to start their search till the
next day due to the risk of further collapses, therefore rescuers would have been
at risk.

 

Figure 1 illustrates the department facilities for each
story.

 

 

 

Figure 1, Department facilities for each story and
collapsed part

 

https://failures.wikispaces.com/Sampoong+Department+Store

 

 

 

Literature Review

 

The construction of the Sampoong started in 1987. It was
first designed to be an office, but the future chairman of the building, Joon
Lee decided that it should to be a department store instead. The process involved cutting the numbers of
support columns to be able to install the escalators. The contractors refused
to carry these changes as they were not safe, Lee Joon the future chairman
ignored their concerns and hired another building company for the construction.

The Sampoong Department Store opened to the public on July 7, 1990, attracting
an estimated 40,000 people per day during the building’s five years of
existence. (Almarwae Mohammed 2017).

 

Joon undermined the safety procedures, thus he had staked
the lives of the people involved in the event, despite knowing the consequences
that this could lead but he neglected them. In
April 1995, cracks began to appear in the ceiling of the south wing’s fifth
floor. The only response by Lee and his management staff involved moving
merchandise and stores from the top floor to the basement. Eventually the
cracks increased forcing managers to close the top floor and shut the air
conditioning. The store management did not shut the building or make anyone
aware of the situation apart from the executives and chairman, the reason why
they did not want to close the building down was because it was a very busy
store and did not want to lose day’s revenues, However, the executives and
chairman did leave the premises. (Guo, H.and others 2010).

 

Civil engineering experts were instructed to
interrogate the structure. They carried a basic cursory check, in which they
discovered that the building was at a risk of collapsing. About five hours
before the collapse had occurred, a destructive uproar had been heard from the
top floors; the vibration of the air conditioning had caused the cracks in the
slabs to expand further. After the cracks had already developed 10cm wide, the collapsing
of the building was unavoidable, thus an emergency meeting was held. During the
meeting, the directors suggested that all members in the building must be evacuated
for their own safety. However, Joon had inclined this idea, over the fear of
losing revenues. Joon had been successful in leaving the building himself, but
did not evacuate the customers.

 

On the 29th of June, the north
wing of the Sampoong store had collapsed, resulting in the death of over 500
people. The large number of fatalities was due in part to a distinct lack of
concern by the building owners/ occupiers in failing to take note of signs of
serious structural distress before the collapse and evacuating the occupants.

The five-storey building was a flat plate structure with elevator shafts and
services located in rigid shear wall structures between the two wings and at
the building extremities. (N.J Gardner and others 2002).

From the period of the critical failure, it
had only taken around 20 seconds for the entire south wing of the structure to
crumple.

 

Figure 2 illustrates the Sampoong Department
store after it had collapsed. In addition to this loss, it is estimated that
the property damage was around $216 million.

 

Figure 2, Sampoong
Department Store collapse

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The restaurant floor had a heated concrete base referred to as “ondol”,
which has hot water pipes going through it; the presence of the 4-foot-thick
(1.2 m) “ondol” greatly increased the weight and thickness of the slab. As a
result of the fifth floor’s presence, the columns held up four times the
maximum weight that they were supposed to support. In addition, the building’s
air conditioning unit was also installed on the roof, creating a 45-tonne
(50-ton) load that was four times the design limit. (Guo, H.and
others 2010).

In 1993, the air
conditioning units had been transferred over to the column 5E, where the most
visible cracks were. The reasoning of this was so that the air conditioning could
cover the cracks. The cracks were aggravated because of the columns that had
been supporting the fifth floor.

Witnesses had claimed that
the collapse had rooted from the fifth floor. The committee that was in-charge
of the inquiry concluded that the collapse started at column 5E on the fifth
floor. The causes for the collapse were taken into account as design errors,
construction failures, substandard construction quality control, and reduction
in the cross-section of the columns to support the fifth floor. Figure 3 illustrates
how column 5E was damaged. Figure 4 illustrates vibrations for AC units.

 

Figure 3, How Column 5E
was damaged (Chris McLean)

Figure 4, Vibrations from
AC units cause further damage to column 5E.

https://failures.wikispaces.com/Sampoong+Department+Store

At around 5.00 p.m. of the local
time, the fifth-floor ceiling had started to sink, and so the store workers had
blocked access to the fifth floor. Prior to the incident, the store was occupied
with countless customers. However, Joon did not desire to close the store or
carry out any repair during that time. When the building started to produce cracking sounds at about 5:52 p.m.

The workers began to alert the building with sound alarms and evacuate the
building, but it was too late to be able to take any action. Around 5:52 p.m.,
the roof gave way, and the air conditioning units crashed through into the
already-overloaded fifth floor. The main columns weakened to allow the insertion
of the escalators, collapsed in turn, and the building’s south wing pancaked
into the basement. Within 20 seconds of the disaster, all of the building’s
columns in the south wing gave way, killing 502 people and trapping more than
1,500 inside. (Almarwae Mohammed 2017).

It is evident that the
whole tragedy could have been avoided if they evacuated the customers on time,
but Joon Lee did not consider such an approach to be necessary. Joon Lee was
aware that the collision was unavoidable, therefore he did a self-serving act
by saving his own life and putting others at a risk.

 

After the disaster, Lan
Chung, a professor of civil engineering and Professor Oan Chul Choi, head of
department of Architecture, started a thorough interrogation of why the building’s
structure had been a failure. The first thing they observes was that the structure of the
store was a flat-slab structure. As illustrated in figure 5, there are no cross beams or steel framework; without cross
beams, there is a form of load transmission missing, this means that framework
must be constructed perfectly. Secondly, they started 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. (Chris McLean and others 2010). The investigation revealed that cutting
holes in every slab had weakened the structural integrity of each slab. The
columns should have been around 31-35 inches thick, but that wasn’t the case as
they were less than 24 inches thick. In addition to that, the distance between
each column was around 36 feet which was hazardous.

 

Figure 5,
Example of Slab Construction (Chris McLean 2010)

 

https://failures.wikispaces.com/Sampoong+Department+Store

 

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 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 6 illustrates diagram of forces moving air conditioning units. Chris
McLean and others 2010). The constant vibration of the AC caused the cracks to widen
in column 5E leading it to a critical failure.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6, Diagram of forces moving air
conditioning units (Chris McLean 2010)

 

 

The Sampoong Department had collapsed
due to the ignorance of safety issues, and punching shear failure, which is
illustrated in figure 7. The construction of a flat-slab permitted the entire
building to collapse.

 

 

Figure 7, Diagram of Punching
Shear on Column 5E.

 

The rescue team made an
appearance during the event within minutes, however, the search had not begun until
the next day due to the life-threatening risks for the rescue team. After two
days, some officials assumed that any member trapped would be dead, but one
individual survived for 16 days, with the help of drink rain water droplets
falling in.

 

While the investigation in the
trials had taken place, Joon was charged with criminal negligence and received
a prison sentence of 10 years, which was later deducted to 7.5 years after an
appeal in April 1996. His son, Lee Han-Sang, underwent 7 years for accidental
homicide and corruption. Two city officials and chief administrator had also
participated in taking bribe, and so they were also jailed. Other parties that
had been participating included Sampoong Department Store executives and the
company who had had a responsibility for constructing the building. The settlement
involved over 3000 cases (3,293 precisely), in which the overall cost was
around $300-350 million.

 

All in all, the factors that
had had the gravest impact on the collapse were the changes in the designing,
and also the fact that these changes were carried out without any approval in
the process of building maintenance. Furthermore, a heavy load was topped and
the structure was cut and damaged which damaged the entire structure. In the
process of the construction, there had been a poor management and supervision,
which resulted in poor construction, and so it had been the main factor of the
building’s collapse. These factors had been a contribution to the disaster, as
the safety factors were not secured. The collapse could have been avoided in
several occasions throughout the construction, and there could have been a life
span of the building.