At 6:05 pm on June 29, 1995, the Sanfeng Department Store in South Korea began to collapse. Within 20 seconds, the 5-story department store collapsed into the 4 underground floors, causing a total of 502 deaths and 937 injuries. It was the worst casualties in Korean history in peacetime, and it was also the largest casualties in the world for buildings to collapse on their own.
Accident background
Sanfeng Department Store is located in a prime location in Seoul, the capital of South Korea. Construction in 1987, the building was originally designed as a 4-storey office building, but the building blueprint was changed to the department store building when the foundation was built. Under this change, many load-bearing columns were pulled up to make room for escalators. The original construction contractor refused to continue construction on the grounds of safety. Sanfeng Department Store was finally completed in the second half of 1989 and officially opened on July 7, 1990. It became one of the landmarks in Seoul at that time. It had a large passenger flow on weekdays, marking South Korea's economic prosperity.
Accident passed
April 5, 1995:
The ceiling of the 5th floor of Sanfeng Department Store began to appear. During this period, the only countermeasures of Sanfeng Group Chairman Li and other management teams were to transfer the goods and shops of rooftop to the basement.
June 29, 1995:
at 9:20 am. The cracks on the rooftop became sharply larger, so the management closed the top floor and turned off the air conditioning, and asked civil engineering experts to come and inspect the building structure. After a simple inspection, it was concluded that the entire building was in danger of collapse. However, the management did not close the department store building or evacuate , and the reason was simply because the passenger flow on that day was very large and the management did not want to lose potential huge turnover.
At 17:10 pm, the ceiling on the 4th floor began to sink, and the employees closed the floor.
At 17:50 pm, when a crackling sound came from the building, the staff sounded the alarm and began to evacuate customers and staff.
At 17:52 pm, the rooftop began to collapse and the air conditioner on it fell on the overloaded 5th floor. The originally insufficient load-bearing columns became overloaded and began to fall down one by one, causing the entire north wing of the building to collapse to the basement almost instantly. The landmark building was razed to the ground within 20 seconds, which was an unprecedented tragedy in the disaster of South Korea's buildings.
Affects
A total of 502 people were killed, another 937 were injured, and property losses were as high as 270 billion won (approximately US$216 million). It was once the worst building collapse in the world, and the total number of people killed in the Sava District building in Bangladesh in 2013 was surpassed.
Cause
At first, investigators suspected that this was a collapse caused by a gas explosion or bomb explosion. But no traces of the explosion were found at the scene, which allowed investigators to rule out this. The subsequent concrete compressive resistance experiment also ruled out problems with building materials quality. So the structural design of the building was calculated, and the cause of the accident was revealed: the 80cm load-bearing column in the original design drawing became 60cm in the construction drawing, and the load-bearing capacity was only half of the original one. As the investigation deepens, more and more problems are exposed:
1. Change the purpose and fire the contractor
According to the original design, the building will be built into a 4-story office building, but the chairman redesigns it into a 5-story department store during the construction project. This change has led to the cancellation of many load-bearing columns to make room for escalators and increase floors. The original construction contractor refused to continue construction according to the new design. The chairman fired them as a result and asked his own construction company to do the construction.
2. Cut corners and install the wrong steel bars
In the subsequent investigation, the investigators found that according to the safety standards of the building, the diameter of the columns of the Sanfeng Department Store should be 80cm, but the actual measurement found that it was reduced to 60cm, and the middle steel bars were also reduced from 16 to 8, reducing the building's load-bearing capacity by nearly half.The steel bars used to strengthen concrete floor slabs on the 4th floor were also installed in the wrong position. They should have been 5cm apart from the ground, but actual measurements found that they were 10cm apart from the ground, which was equivalent to thinning the thickness of the floor slab and reducing the strength between the floor slab and column by 20%. This is clearly a systematic neglect of building codes, the investigator said.
3. Drag the air conditioner and destroy the structure
Soon, the fifth floor was added to the building. It was originally planned to be used as an ice skating rink, but the use was changed in the middle and replaced by eight Korean and North Korean food stores. Because Koreans have the habit of sitting on the ground while eating, a layer of floor heating equipment is added under the concrete floor of these restaurants, which greatly increases the burden on the load-bearing structure. In addition, the air conditioning equipment (water cooling unit) of the entire building is now installed on the roof. The three large-scale refrigerators weigh a total of 29 metric tons. When the refrigerator is filled with water, the total weight is as high as 87 metric tons, which is as much as 4 times the load-bearing load that meets the design standard. What made the situation worse was that in 1953, all the chillers at the rear of the building were moved to the front due to complaints from surrounding residents about the chiller noise. This movement should have used a crane, but the result is that all equipment is pushed into place directly on the roof with pulleys, which greatly damages the entire roof structure, and the air conditioner is filled with cracks. In addition, the vibration generated during the operation of the cold machine causes cracks to appear at the connection point between the No. 5E column near the cold machine and the roof, and the pillars cannot play their role.
Processing results
One hour after the disaster, the procuratorate ordered a comprehensive investigation. The outside world initially believed that the cause of the accident was due to the soft foundation of the building. But after in-depth investigation, people soon discovered that the accident occurred due to arbitrary changes to the design by Li and his construction company. Later investigations of the ruins showed that there was no problem with the concrete itself, but the diameter of the load-bearing column was smaller than the original one, and the steel bars in each load-bearing column were also reduced from 16 to 8. The investigation also revealed that Seoul district officials were also suspected of accepting bribes during the process of changing the construction in Sanfeng. As a result, many officials, including the former Ruicao District Administrator, were charged with negligence and sentenced to jail.
On December 27, 1995, the Seoul District Court of South Korea sentenced Lee to 10 and a half years in prison for the crime of aggravated punishment for certain crimes and criminal negligence. His son, CEO Li Hanxiang, was sentenced to seven years in prison for corruption and manslaughter. In April 1996, Li appealed and was given a commutation of his sentence to 7 years.
Reflection on
The disaster is a layer of problems : management is insatiable and lacks basic architectural knowledge, construction units cut corners irresponsible, operation and management careless, and equipment managers lack knowledge of building structure safety. Any link that is done well may prevent tragedy from happening. The 502 dead people are no longer able to accuse them.
25 disasters are still very educational for us in this industry, whether we are doing design, construction, responsible for operation and management, or finally entering the management level.
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