1June 29, 995 Why did Sanfeng Department Store in Korea close down?

1In the summer of 995, Seoul, South Korea flourished and was the representative of the Asian economic miracle. The fashionable TheSampoong department store is a landmark and symbol of Seoul's rapid and successful rise in the world. On the afternoon of June 29th, it became the center of a terrible disaster. Within 30 seconds, the five-story department store collapsed layer by layer, causing 50 1 person to be crushed to death. Angry Koreans asked: What caused the worst peacetime disaster in Korean history?

The fashionable Sanfeng Department Store 1989 opened. Department store is located in the most expensive section of Seoul, which is the representative of luxury goods. The two wing buildings are connected by huge chrome-plated glass in the atrium, and the walls are decorated with Italian pink marble. High-end clothes, all kinds of furniture and luxury goods are displayed on the shelves, and there are many fashionable Korean restaurants on the fifth floor, targeting the people working in urban areas with amazing spending power. The performance of Sanfeng Department Store in the first five and a half years was very good, with an average daily turnover of more than 500,000 US dollars. But on June 29th, 1995, it all fell apart in an instant.

There was an early warning before the collapse.

Park Sung-hyun works in the children's clothing department in the basement. She remembered that the air conditioner on the roof was broken, so the store was extremely stuffy. "Even if the air conditioner is broken, we still go to work. On that day, as usual, customers shop as usual and employees work as usual. It seems that there is no difference. "

Actually, that day was a little different. Between 8: 00 and 9: 00 in the morning, some staff found that the floor tiles of the Spring Garden Restaurant were broken and the floor seemed to be deformed. The vibration of the building rattled the glassware in the tableware department. 10: 30, many shop assistants heard a loud banging in the store. Everyone thought it was all right and went to work as usual. Near noon, the kitchen staff on the fifth floor heard a crack on the ceiling.

On the same day 14, Li, president of Sanfeng Group, called the directors to discuss the countermeasures of cracks and inexplicable sounds. They invited experts to identify the damage and assess the risk. 15, structural engineer Li came to the building for inspection. He photographed the cracks in the ceiling on the fourth and fifth floors and the big bumps on the kitchen floor of the dining room. At this point, the cracks in the roof have spanned the whole building and some areas have collapsed.

Li 16 reports to the top management of Sanfeng Department Store. Although the evidence showed danger, he said the building was still safe. Cracks can be temporarily filled, and the upper structure can be repaired after closure. The director of Sanfeng ordered the department store to continue its business and the employees to continue their work-a decision that killed 50 1 person.

Disaster only takes 30 seconds.

Before dinner in the evening, at the peak of business, the aisle was crowded with shop assistants and people shopping on their way home from work. 17: 30, there was a loud noise on the fifth floor and a pillar broke from the ceiling. 17: 47, there was a loud noise upstairs. Four minutes later, the alarm sounded in the store, the building shook, the dust fell, the lights went out, and the sound similar to a subway station came from the other end of the store. At first, Park Sung-hyun tried to stay calm. When she found that she couldn't escape, it was too late. A piece of cement hit her head and she fainted.

Pedestrians in the street could hardly believe the horror scene that happened next. Within 30 seconds, the five floors above the ground collapsed continuously, and all the four floors below were crushed. At the moment after the accident, the scene was very quiet, then the injured people appeared from the dust and rubble, and then chaos began. ...

Why did Sanfeng Department Store close down?

South Korea is also asking the same question: Why did Sanfeng Department Store close down? Is there any hidden danger in the design of the building? Is the foundation sinking or the structural concrete strength too weak? Forensic engineers and professional criminal investigation teams will uncover the truth behind the biggest peacetime disaster in South Korea. The earthquake is the first suspicious factor that investigators can immediately rule out. By comparing the seismograms, the investigators found that there was no earthquake activity on the Korean peninsula that day.

Could it be a bomb explosion or a terrorist attack? Investigators searched the scene carefully for traces of bombs or explosives, but found nothing. The focus of the investigation turned to the foundation where the building was located, where the first reliable clue was found. Sanfeng Department Store is built on top of an old landfill. If the ground is not cleaned, the foundation will be unstable. Investigators drilled a core sample from the ruins for analysis.

Engineer Zheng led a team to drill soil core samples of the foundation to determine whether the foundation structure of the building was the cause of the collapse. There are usually two reasons for collapse: the construction method of the building or the foundation. We need to find out whether the foundation is enough to support the building. If the foundation is too weak and the building sinks, it will destroy the structure of the building.

Sanfeng Department Store consists of two identical wings, which are connected by a glass atrium in the middle, but only one wing collapsed and the other is still standing. Investigators found that the south wing built above the landfill collapsed. The north wing that did not fall was built on solid ground. This seems to be in line with the saying that unstable foundation leads to disaster, but the investigation results rule out the possibility that the building foundation is laid correctly.

The design has changed a lot.

Investigators feel that the problem must be the building itself. Investigators * * * collected about 150 groups of concrete samples in the ruins and extracted them to the engineering laboratory for strength testing.

One of the conditions for concrete to achieve the best strength is correct mixing, otherwise the strength is not enough. If bubbles are not excluded during condensation, honeycomb pores will be formed inside. Is the closure of Sanfeng Department Store related to this? The results of pressure test show that the strength of concrete is sufficient. So the investigators were forced to expand the search scope again.

At this time, a team member made an amazing discovery: the original blueprint of the building contained unknown secrets.

Sanfeng department store belongs to the so-called "plane" structure, which was widely used at that time, with low cost and short construction period. The floor is composed of thick concrete slabs, and the supported concrete wall columns transfer the weight of the building to the foundation. The construction of horizontal organization has many advantages, but it is very sensitive. Its planning must be more precise, and nothing can go wrong. 1968 in London, England, a woman caused a small explosion when she lit the fire, which destroyed the supporting structure of the building and caused the side building of a 23-story apartment building to collapse. 1987 In Qiaogang, Connecticut, USA, a 16-story plane structure building collapsed during construction.

After reviewing the architectural blueprint of the building, the architects of the investigation team found that the construction company hired to build Sanfeng Department Store had no chance to complete it. Shortly after the foundation grouting, the director of Sanfeng Department Store asked for a big change in the design. The engineers warned that it was dangerous to change the whole building to horizontal organization, but President Li simply fired them and took over by his own construction company. Despite the danger, Sanfeng Construction Company continued to carry out the construction according to the greatly revised design drawings.

The problem is on the fifth floor.

The investigation team found that the most critical change was on the fifth floor. The fifth floor used to be an ice rink, but later it was changed into a traditional Korean restaurant, which led to a three-fold increase in the weight of the floor. Turning the fifth floor into a dining room is the biggest mistake. In traditional Korean restaurants, the floor under the guest's seat is heated by hot water pipes, which requires a lot of extra space. In this way, because there is an extra layer of concrete on the fifth floor, the thickness is increased by 1 foot. Each restaurant is equipped with large kitchen equipment, and these extra weights have never been included in the structural calculation. Then, the investigators found a major modification of the roof: because the neighbors complained about the noise, they moved the large cooling water tower from the ground to the roof, and the water tower could hold 30 tons of water.

The weight of the upper floors has increased a lot and needs to be strengthened, but the builders are doing the opposite. When comparing the skeleton of the building with the blueprint, the investigation team found that there is no supporting plate between some columns and the floor, but the supporting plate is an important element of the plane structure because the supporting plate of the stigma can disperse the load of the concrete floor. The result of the actual investigation is that many pallets are too small in size, and some stigmas even have no pallets.

The bigger secret that was discovered next was that the diameter of the columns supporting the fourth and fifth floors was greatly reduced. The weight of the top floor is greatly increased, but the structural support is greatly reduced. These two factors have brought fatal results.

Looking at the blueprint of Sanfeng Department Store, investigators can see that disaster will happen sooner or later. He believes that the building was in a "damaged state" at the beginning of its construction, but why did it last for more than five years? What was the last straw that crushed it?

the last straw

Ironically, it was the newly added security facilities that eventually destroyed the building. Seoul's law requires department stores to install firewalls next to escalators. In case of fire, the firewall will be automatically closed to prevent the fire smoke from spreading to other floors. In order to make room for installing a firewall, workers must cut the concrete column next to the escalator. This behavior reduces the important support of the building by more than 25%. This series of deadly combinations is like a time bomb. The main culprit of the closure of Sanfeng Department Store is the so-called "through shear force". When a column that is too thin bears too much weight, it will pass through the ceiling above, just like a finger piercing a wet tissue.

In the final report, the investigators said that the reason for the collapse of Sanfeng Department Store was to change the drawings during construction. Li Yin, president of Sanfeng Company, was sentenced to 10 year for negligent crime. The cause of the tragedy is the constant mistakes and negligence in the construction methods and procedures. Sanfeng department store has lived for more than five years, but in the end, this gamble cost 50 1 life.