Sampoong Department Store collapse


The Sampoong Department Store collapse was a structural failure that occurred on June 29, 1995, in the Seocho-gu district of Seoul, South Korea. The collapse is the largest peacetime disaster in South Korean history, killing 502 people and injuring 937. It was the deadliest modern building collapse until the September 11 attacks in New York City, and the deadliest non-deliberate building collapse until the 2013 Savar building collapse near Dhaka, Bangladesh.

Background

In the events leading up to the 1988 Summer Olympics, there was a large development boom in the Seoul area. Because of bans against international construction contractors signing contracts for projects in Seoul at the time, almost all buildings were being erected by South Korean companies, who typically built the structures quickly because of the large number of projects assigned to them.
The Sampoong Group began construction of the Sampoong Department Store in 1987 over a tract of land previously used as a landfill. The building's plans originally called for a residential apartment with four floors, and the apartments were to be built by Woosung Construction; however, during construction, the blueprints were changed by the future chairman of the building, Lee Joon, to instead create a large department store, which involved cutting away a number of support columns to install escalators, and the addition of a fifth floor. After Woosung refused to carry out the changes, Lee ignored their warnings and fired them, using his own building company to complete the 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.
The completed building was a flat-slab structure without crossbeams or a steel skeleton, which effectively meant that there was no way to transfer the load across the floors. To maximise the floor space, Lee Joon ordered the floor columns to be reduced to be thick, instead of the minimum of in the original blueprint that was required for the building to stand safely, and the columns were spaced apart to maximize retail space, a decision that meant that there was more load on each column than there would have been if the columns were closer together.
A fifth floor was originally planned to house a roller skating rink, added later to comply with zoning regulations that prevented the entire building from being used as a department store. However, Lee Joon changed the plan for the fifth floor to include eight restaurants instead. The construction company tasked with completing the extension advised that the structure would not support another floor, but was promptly fired, with another company being hired to complete the project. The restaurant floor had a heated concrete base referred to as ondol, which has hot water pipes going through it; the presence of the ondol greatly increased the weight and thickness of the slab. As a result of the fifth floor's presence, the columns were supporting four times the maximum weight that they had been designed to bear.
In addition, the store's three 15 tonne air conditioning units were also installed on the roof, creating a load that was four times the design limit. In 1993, the air conditioning units were dragged across the delicate roof, resulting in cracking. The units were moved over column 5E, where the most visible cracks in the floor of the fifth level were seen before the collapse. The cracks in the columns worsened because the columns supporting the fifth floor were not aligned with the ones supporting lower floors, causing the load of the fifth floor to be transferred through the slab.

Collapse

In April 1995, cracks began to appear in the ceiling of the south wing's fifth floor, but 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 parts of the top floor. 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 it did not want to lose the day's revenue. However, the executives themselves left the premises as a precaution.
When civil engineering experts were invited to inspect the structure, a cursory check revealed that the building was at risk of collapse; the National Geographic documentary programme Seconds From Disaster indicates that the facility's manager was examining the slab in one of the restaurants on the fifth floor only hours before the collapse, when, unknown to him, 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 complaints of vibration, the air conditioning was turned off, but the cracks in the floors had already grown to 10 cm wide. Around then, it was realized that collapse of the building was inevitable, and an emergency board meeting was held. The directors suggested to Lee that all customers should be evacuated, but Lee angrily refused to do so for fear of revenue losses. However, Lee himself left the building safely before the collapse occurred. He did not even inform his own daughter-in-law, Chu Kyung Young, who was one of the employees in the building, of the imminent danger. She became trapped in the rubble and was rescued only days later.
At about 5:00 p.m., Korea Standard Time, as the fifth floor ceiling began to sink, store workers closed off all customer access to the fifth floor. According to Seconds From Disaster, the store was packed with hundreds of shoppers 57 minutes before the collapse, but Lee did not close the store or carry out repairs during that time. When the store started to produce cracking sounds at about 5:52 p.m., workers began to sound alarms and evacuate the building, but it was too late: 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 began pancaking into the basement. In less than twenty seconds, all the columns in the store's south wing had given way, killing 502 people and trapping more than 1,500 inside. The disaster resulted in about ₩270 billion worth of property damage.

Rescue and recovery

Rescue crews were on the scene within minutes of the disaster, with cranes and other heavy equipment being brought in the next day. However, Seoul's then mayor, Choi Byung Yol, announced the rescue would be called off, due to fears the unstable remains of the store would collapse. Massive protests, especially from friends and relatives of those still missing, compelled officials to continue looking for survivors, with the remains of the store being steadied by guy cables. At one point, Korea Telecom was transmitting a signal, every half hour, designed to trigger cellphones or pagers that trapped survivors might be carrying.
After nearly a week, the focus was on removing the debris, but construction crews were careful to check for victims.
Two days after the collapse, some officials said that anybody who was still in the building must have already died; therefore, further efforts would be made only towards "recovery", not "rescue" despite the possibility of victims being able to survive for much longer. Despite the sweltering heat, some who were not rescued in the first few days avoided dehydration by drinking rainwater. The last to be rescued, 19-year-old Park Seung-hyun, was pulled from the wreckage 17 days after the collapse with a few scratches. 18-year-old Yoo Ji-hwan was pulled out after nearly 12 days. A man rescued after 9 days reported that other trapped survivors had drowned from the rain and from the water used for fire suppression.

Investigation

The investigation was headed by Professor Lan Chung of Dankook University's engineering school. Shortly after the collapse, leaking gas was suspected as the probable cause because two gas explosions had occurred elsewhere in the city that year. However, the fires in the rubble were from burning automotive gasoline coming from crushed cars parked in the underground garage, and a gas explosion would have been significantly larger. In addition, it was widely feared that there had been a terrorist attack, with North Korea as the prime suspect. However, the fact the building collapsed downward, with little debris thrown outward, ruled out a significant explosion, according to US and South Korean experts.
Once the investigation focused on structural failure, it was initially believed the building's poorly-laid foundation and the unstable ground that it was built on, both led to the failure. Investigation of the rubble revealed that a substandard concrete mix of cement and sea water and poorly-reinforced concrete was used for the ceilings and walls.
Further investigation revealed that the building was built with incorrect application of a technique called "flat slab construction". Reinforced concrete buildings are often built by using columns and beams, with the floor slab supported over the full length of the beams. "Flat slab construction" does not use beams but supports the floor slab directly on the columns. The area of floor around the columns must be reinforced in order to carry the load; if the columns are too narrow, they can punch through the slab. Examination of the building showed the concrete columns installed were only 60 cm in diameter, below the required 80 cm shown in the plans. Worse still, the number of steel reinforcement bars embedded into the concrete was 8, not the required 16, which gave the building only half its needed strength. Steel reinforcements intended to strengthen the concrete floor were placed 10 cm from the top instead of 5 cm, decreasing the structure's strength by about another 20%.
Ironically, one of the changes that contributed to the collapse was the installation of a safety feature. Fire shields were installed around all escalators to prevent the spread of fire from floor to floor, but to install them, the support columns were cut, further reducing their diameter. The reduced diameter concentrated the load on a smaller area of the slab, leading to an eventual puncturing of it. Those factors, along with the addition of a fifth floor including restaurants and heavy restaurant equipment, all contributed to the building's eventual failure. The original building design would have been more than twice as strong as needed to remain erect, and the flawed structure managed to stand for almost five years.
Investigators finally pinpointed the direct cause of the collapse, known as the "trigger" or tipping point, in the building's history. It was revealed that two years before the collapse, the building's three rooftop air-conditioning units had been moved because of noise complaints from neighbors on the east side of the building. The building's managers admitted noticing cracks on the roof during the move, but instead of lifting them with a crane, the units were put on rollers and dragged across the roof, further destabilizing the surface by each unit's immense weight. Cracks formed in the roof slabs and the main support columns were forced downward; column 5E took a direct hit, forming cracks in the position connected to the fifth-floor restaurants. According to survivor accounts, each time that the air conditioners were switched on, the vibrations radiated through the cracks, reaching the supporting columns and widening the cracks, over the course of two years. On the day of the tragedy, although the units were shut off, it was too late; the structure had suffered irreversible damage, and the fifth floor slab around column 5E finally gave way.

Trial

During his interrogation with Professor Chung, Lee Joon sparked further controversy by saying that his main concern was that the collapse of the store not only harmed the customers, but also inflicted great financial damage to his company. On December 27, 1995, Lee Joon was found guilty of criminal negligence and received a prison sentence of ten and a half years. Prosecutors originally asked for Lee Joon's sentence of twenty years, but was reduced to seven and a half years on appeal. Lee Joon died on October 4, 2003, months after his release from prison, of complications from diabetes, high blood pressure and kidney disease.
Lee Joon's son and the store's CEO, Lee Han-Sang, received seven years for accidental homicide and corruption. Following his release from prison in 2002, Lee Han-Sang worked as an evangelist in Mongolia.
City official Lee Chung-Woo, who was a chief administrator of the area where the store was located, was sentenced to three years in jail for bribery. Hwang Chol-Min, a former chief for the area, was found guilty of accepting a ₩12 million bribe from Lee Joon, and was sentenced to 10 years in prison.
Other participating officials, including a former chief administrator of the Seocho district, were also jailed. Other parties sentenced included a number of the store's executives and the company responsible for completing the building.

Compensation

At first, families of the victims were asking for an average of $361,000 each. However, the City of Seoul, representing the store's owner, offered to pay $220,000 for each victim, arguing that he cannot afford to pay more.
Two months after the collapse, Lee Joon and Lee Han-Sang submitted a jointly-signed memo to Seoul, offering their entire wealth to compensate the families of the victims. As a result, the Sampoong Group was disbanded immediately.
The settlement involved 3,293 cases, totaling ₩375.8 billion. Payouts were complete by 2003.

Reaction

The initial reaction of the disaster was an enormous public outrage that led to months of public demonstrations on the streets of Seoul. The disaster led to skepticism and fears regarding safety standards on other engineering projects undertaken as South Korea had experienced an economic boom during the 1980s, and it resulted in a review of South Korean safety regulations; the disaster also revealed the level of corruption and greed among city officials, who were willing to accept payoffs to families of the victims with little regard for public safety.

Site today

The remains of the store were demolished shortly after the collapse and the recovery operations; the site remained vacant until 2000. The families of the victims requested that a memorial be built on the site, but it was opposed by the Seochu District government, forcing the Seoul Metropolitan Government to mediate the dispute. In a controversial move, the memorial was built elsewhere and the land sold off to a private developer. The site of the collapse is now home to a luxury apartment complex, Acrovista Apartments, whose construction began in 2001 and was completed in 2004.

Memorials

The Yangjae Citizen's Forest has a sculpture made in memory of the collapse. The twelve-meter high marble memorial was designed by Ewha Womans University professor and sculptor Kim Bong-gu, and funded by the Sampoong Group as compensation to the victims.

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