The analysis was first started with the
possibility of earthquakes although South Korea was in a stable landmass. The
seismic charts indicated no earthquakes activity on the day of this incident.
There was a possibility of act of
terror from communist North Korea as 50 years after the Korean War, the two
countries are still in strong military tension. This possibility was discard as
there was no trace of act of terror after inspecting the rubble.
The investigation of the collapse of
the department store was continued with inspection of the ground as after the
collapse, a part of the building stayed standing while other part ended up in
The ground was originally a landfill
before the construction of the store, therefore further inspection of the
foundation was imperative to verify that the land. After studying the land by
drilling deep into the buildings foundation, concluding that the ground
structure beneath the construction was solid enough for the department store as
this was firmly attached to a layer of bed rocks.
The building was based in flat slab
construction which is popular and cheap choice for buildings. This type of
construction is strong than any other but required to be planned and
constructed precisely. As the building was made on a solid land, it was
suspected that construction of the department store could had caused the
collapse. Sample of concrete was examined thoroughly in a laboratory to test
the strength by using a compressor. To achieve strong and solid concrete, the
components must be precisely mixed. The examination concluded that the concrete
was solid enough for the building.
The investigation continued by
examining the original blue prints of the building and hints of the collapse
were hidden on them. During the construction of the store, the original
construction company hired for building were not allowed to finish the
structure as the executives demanded several design modifications of the buildings.
According to the engineers, the modifications could put the people and the
entire construction at risk.
The original construction company was
replaced by another one as the boss wanted to continue with the modifications.
The danger was ignored, and the construction continued to meet the executive’s
Originally, the building was only
designed for 4 floors. However, as mentioned, management wanted to incorporate
a fifth floor. The modifications were based on the fifth floor which was
originally designed for roller skating rink. However, this was replaced by a
floor of restaurant. This multiplied the weight of the floor by 3 times due to
restaurants and its appliances. Moreover, Korean restaurants normally used
water pipes for heating systems travelling through the floor. Therefore, the
floor thickness had to be increased by 30 cm, adding more weight than the
Figure 12 – Design and real load
of 5th floor (T. Won Park, 2012)
Furthermore, investigators found that
huge water cooling systems that weigh around 30 tonnes were moved along the
floor due to neighbours’ complaints. This action put the slabs into huge
stresses leading into irreversible damages.
The structural drawings indicated that 16 columns on 4th and
5th floor were designed to be 80 cm diameter. However, this were
replaced by 8 pillars of 60cm of diameter with 22 mm diameter of reinforced
bar. This changes the structure of the floor by including two types of pillars,
reducing 56.3% of the cross-sectional area and 50% reduction of reinforced bar.
Figure 14 –
Reduction of cross sectional area of columns. (T. Won Park, 2012)
Another important point to add to the
findings was the omission of drop panel construction. Drop panels increase the
shear strength of the flat slab floor by handling with punching shear which is
critical to flat slab structure. The investigation proved that some pillars
were reduced and other did not have drop panels installed, reducing the overall
strength of the structure.
– Punching Shear
preventions and performance estimations.
As described, the construction and
performance of the building was clearly poor as the safety factor had been
dramatically reduced. The pillars experienced extreme shear failure on the 5th
floor and the roof leading to progressive destruction of the entire building.
Sampoong department store failure could
have been prevented if the original blue prints and structural calculations
were followed during the construction. The following ways for failure
prevention are listed below as case interventions:
Case 1 – 5th floor
This case is the clearest and easiest
to evaluate among the rest to prevent the failure of the department store. The
5th floor was not included on the initial design as the building was
specially designed as a 4-floor department store. The restaurants and
appliances have added considerable weight increasing the dead load. If this had
not been constructed, the building would not have collapse on the 29th
of June 1995.
Case 2 – Water cooling systems
The installation of water cooling
systems on the roof added had added more weight, specially when they were full
of water. Due to complaints, the systems were moved and dragged along the floor
placing concentrated stresses on the column, causing cracks up to 25mm wide
according to investigations. These heavy cooling blocks could had been lifted
by using a crane to prevent structural damages on the building. The vibrations
caused by the cooling blocks when operating also contributed to widen the
cracks produced on the floor This was also prevented by adding more columns to
distribute the load of the cooling system.
Case 3 – Irregular construction
According to the structural drawings,
the pillars on the 4th floor and 5th floor were designed
to be 80 cm diameter. However, some of the columns were 80 cm diameter such as
pillar of C1A and some other were reduced to 60 cm diameter with 22
mm of reinforced bar as seen above in Figure 3. By regulating the size of the
columns and reinforcement bars throughout the entire floor would have
contribute to reducing the possibility of the collapse.
Figure 16 –
Comparison of columns between structural calculations and design. (T. Won Park,
Case 4 – Drop panel construction
As mentioned, sizes of several pillars
were reduced and drop panel construction were omitted on the columns. The force
from the slab is transfer to the drop panel and consequently, transfers it to
the column. Drop panel construction helps to distribute the load applied to the
slab by reducing the stress concentrated on the column area. If drop panel had
been kept, possibility of punching shear would had been reduced positively.
Analysis of the stress of the structure
was carried out by using FEA software such as Siemens NX. The following images,
graphically shows the stress concentration and distribution when the load is
applied on a column:
Without drop panel construction
With drop panel construction