The Collapse of Sampoong Department Store

On 29th of June, 1995, the Sampoong department store in Seoul, South Korea, completely collapsed. The collapse is the deadliest modern building collapse until the attacks in New York City and is the deadliest non-deliberate building that collapsed until Savar building collapsed in 2013. The tragedy occurred due to multiple errors made by the designers and contractors who built the store and the negligence of the store owner.

The structure was built on top of a landfill, it was originally designed for an office building but midway through construction, the chairman wanted to make it into a department store. Many engineers that were working on the project warned the owner Joon that the changes were dangerous but he fired them.

In the disaster occurred, they were 1500 people that were trapped in which over 500 died and 937 received non-fatal injuries. The rescue crews did not start to search until the next day and the search was called off because of unstable remains and rescuers would be at risk. Figure 1 illustrates the department facilities for each story.

The construction of the Sampoong started in 1987, it was originally designed to be an office but the future chairman of the building soon Lee midway through the construction, wanted it to be a department store. The process involved cutting the numbers of support columns to be able to install the escalators. The contractors refused to carry these changes as they were not safe, Lee Joon the future chairman ignored their concerns and hired another building company for the construction. 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. (Almarwae Mohammed 2017).

Lee Joon ignored the safety procedures and risked the lives of all those people involved in the incident even after knowing the possible consequences. In April 1995, cracks began to appear in the ceiling of the south wing's fifth floor. The only response byLee 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 it did not want to lose the day's revenue. However, the executives themselves left the premises, as a precaution. (Guo, H.and others2010).

Civil engineering experts were asked to inspect the structure but they only carried a cursory check in which they stated that the building was at risk of collapse. Around five hours before the collapse occurred, several loud bangs were heard from the top floors, as the vibration of the air conditioning caused the cracks in the slabs to widen further. After the cracks already grown 10cm wide, it was realized that the collapse was unavoidable and an emergency meeting was held. In the meeting. The directors suggested that all costumes should be evacuated. However, JoonLee refused over the fear of losing revenues. Joon Lee did leave the building himself as he was aware of the dangers but did not evacuate the customers.

On the 29th of June, the north wing of the Sampoong store collapsed, the disaster killed over 500 people. A large number of fatalities was due in part to a distinct lack of concern by the building owners/ occupiers in failing to take note of signs of serious structural distress before the collapse and evacuating the occupants. The five-story building was a flat plate structure with elevator shafts and services located in rigid shear wall structures between the two wings and the building extremities. (N.J Gardner and others 2002). From the point of the critical failure, it only took around 20 seconds for the entire south wing of the structure to collapse. In figure 2 it illustrates theSampoong Department store after collapsed. In addition, it is estimated that the property damage was around $216 million.

The restaurant floor had a heated concrete base referred to as “ondol”, which has hot water pipes going through it; the presence of the 4-foot-thick(1.2 m) “ondol” greatly increased the weight and thickness of the slab. As a result of the fifth floor's presence, the columns held up four times the maximum weight that they were supposed to support. In addition, the building's conditioning unit was also installed on the roof, creating a 45-tonne(50-ton) load that was four times the design limit. (Guo, H.andothers 2010). In1993, the air conditioning units were moved over the column 5E, where the most visible cracks were, the purpose of the air conditioning was to cover the cracks, the cracks worsened due to the columns supporting the fifth floor.

According to the witnesses, the collapse started from the fifth floor. The committee that was in charge of the inquiry concluded that the collapse started at column 5E on the fifth floor. The reasons for the collapse were noted as design errors, construction faults, poor construction quality control, reduction in the cross-section of the columns support in the fifth floor. Figure 3 illustrates how column 5E was damaged and in figure 4 it illustrates vibrations for AC units.

At around 5.00 p.m. of the local time, the fifth-floor ceiling began to sink, the store workers blocked access to the fifth floor. Before the incident, the store was packed with hundreds of customers, however, Joon Lee did not feel the need to close the store or carry out any repair during that time. When the building 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.

Around 5:52 p.m., the roof gave way, and their 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 pancaked into the basement. Within 20seconds of the disaster, all of the building's columns in the south wing gave way, killing 502 people and trapping more than 1,500 inside. (Alma Rae Mohammed2017).

It is evident that the whole tragedy could have been avoided if they evacuated the customers on time but Joon Lee did not consider such approach necessary. Joon Lee was aware that the collision was unavoidable therefore, it was very selfish to not do anything about it and put the lives of so many people at risk.

After the disaster, Lan Chung, a professor of civil engineering and Professor Oan Chul Choi, head of the Department of Architecture, started investigating the reason why the structure collapsed. The first thing they noticed in their investigation was that the structure of the store was a flat-slab structure as illustrated in figure 5, there are no cross beams or steel framework; without crossbeams, there is a form of load transmission missing, which means the framework must be constructed perfectly. Secondly, they began to look at the site on which the building was constructed and the materials used.

Research revealed that even though the superstructure was built on a landfill, the foundations and basement rested on a rock and survived the collapse well. (Chris McLean and others 2010). The investigation revealed that cutting holes in every slabweakened the structural integrity of each slab. The columns were supposed to be around 31-35 inches thick but were less than 24 inches thick. In addition, the distance between each column was around 36 feet which were very dangerous.

The air conditioning units were placed on the roof in order to keep the noisy machinery away from surrounding skyscrapers. Investigators soon learned that the air conditioning units on the roof had been moved due to noise complaints from surrounding buildings anyway. Instead of hiring cranes and professional moving teams, the units simply had been dragged across the roof, creating huge cracks. Figure 6 illustrates a diagram of forces moving air conditioning units. Chris McLean and others 2010). The constant vibration of the AC caused the cracks to widen column 5E leading it to a critical failure.

The rescue team was on the scene within minutes of the incident, however, rescue crew did not begin searching until the next day due to the risk for the rescue team. The authorities called off the search because of the risks involved for the safety of rescues over the fear that the remains of the store could come down. After two days, some officials assumed that anybody left is dead but one individual survived for 16 days in the collapsed with just a few scratches of drink rainwater to survive.

During the interrogation in the trials. Lee Joon was charged with criminal negligence and received a prison sentence of ten years which was later reduced to seven and a half after an appeal April 1996. His son, Lee Han-Sang, received seven years for accidental homicide and corruption. Two city officials and chief administrator were also involved in taking bribe which as a result were jailed. Other parties involved includedSampoong Department Store executives and the company who was responsible for completing the building. The settlement involved 3,293 cases in which the total cost was around $300-350 million.

All in all, the factors that had the most critical impact on the collapse were the changes in the design and that these changes were carried out without any approval in the process of building maintenance, in addition, a very heavy load was added and the structure was cut and damaged which damaged the structure. In the process of construction, there was a very poor management and supervision which caused poor construction, which was one of the factors that impacted the collapsed. The factors mentioned so far lead to the disaster as the safety factors were not secured. The collapse could have been avoided in many different times throughout the construction and lifespan of the building.