The Sampoong Group, a South Korean trade company began construction of the Sampoong Department Store in 1987 over a tract of land previously used as a
landfill. Originally designed as a residential apartment with four floors, it was changed to a large
department store during its construction by Lee Joon, the future chairman of the building. This involved cutting away a number of support columns in order to install
escalators.[SUP]
[2][/SUP] When the original
contractors refused to carry out these changes, Lee ignored their warnings and fired them, instead using his own building company to complete construction.
The building was completed in late 1989, and 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. The store consisted of north and south wings, connected by an
atrium.
Later on, a fifth floor was added, which was first planned to be a skating rink to comply with zoning regulations that prevented the whole building from being used as a department store. Lee changed the original plan for the fifth floor to include eight restaurants instead. When a construction company tasked to complete the extension advised that the structure would not support another floor, they were fired, and another company was hired to complete the project. The restaurant floor also had a heated
concrete base with hot water pipes going through it, as patrons sit on the floor of traditional Korean restaurants, which added a large extra load due to the increase in thickness of the
concrete slab.
In addition, the building's air conditioning unit was installed on the roof, creating a load of four times the design limit. Two years before the collapse, the air conditioning units were moved across the delicate roof, which is where the cracking started. The units were moved over the column 5E from which the most visible cracks in the floor of the fifth level were seen before the collapse.
Collapse
In April 1995, cracks began to appear in the ceiling of the south wing's fifth floor. During this period, the only response by Lee and his management staff involved moving merchandise and stores from the top floor to the basement.
On the morning of June 29, the number of cracks in the area increased dramatically, prompting managers to close the top floor and shut the air conditioning off. The store management failed to shut the building down or issue formal evacuation orders, as the number of customers in the building was unusually high, and they did not want to lose the day's revenue. However, the executives themselves left the premises as a precaution.
Civil engineering experts were invited to inspect the structure, with a cursory check revealing that the building was at risk of collapse; the National Geographic documentary series
Seconds From Disaster indicates that the facility's manager was examining the slab in one of the restaurants on the fifth floor, eight hours before the collapse, when, unknowingly, vibration from air conditioning was radiating through the cracks in the concrete columns and the floor opened up.
Five hours before the collapse, the first of several loud bangs was heard emanating from the top floors, as the vibration of the air conditioning caused the cracks in the slabs to widen further. Amid customer reports of vibration, the air conditioning was turned off, but the cracks in the floors had already grown to 10 cm.
At about 5:00 p.m. Korea Standard Time (UTC+9:00), the fifth floor ceiling began to sink, resulting in store workers blocking customer access to the fifth floor. According to
Seconds From Disaster, the store was packed with shoppers 57 minutes before the collapse, but the owner did not close the store or carry out repairs at that time. When the building started to produce cracking sounds at about 5:50 p.m., workers began to sound alarms and evacuate the building, but by then it was too late.
Around 5:57 p.m., the roof gave way, and the air conditioning unit crashed through into the already-overloaded fifth floor.[SUP]
[3][/SUP] 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, all of the building's columns in the south wing gave way, trapping more than 1,500 people and killing 502.
