Inspection of collapse cause of Sampoong Department Store

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Abstract

On June 29, 1995, the Sampoong Department Store in Seoul, South Korea, completely collapsed. It was a five story reinforced concrete (RC) building with underground 4 floors and was built using a technique called “flat slab construction”. The collapse is the largest peacetime disaster in South Korean history – 502 people died, 6 missing, and 937 sustained injuries. The Sampoong Department Store was completed in late 1989, and it opened to the public on July 7, 1990, attracting an estimated 40,000 people per day during the building's 5 years in service.

After the collapse, intense investigation was conducted to find out the direct causes of the collapse through (1) survey on the present collapse situation and ground condition, (2) strength test of the concrete and steel collected at the site, (3) design documents and construction/management reports, and (4) structural analysis. The investigation revealed that the Sampoong Department Store collapsed because so many direct and indirect causes such as flaws in design phase and mistakes in construction and management process were overlapped.

Introduction

On June 29, 1995, a building of the Sampoong Department Store, which had four basement floors and five floors above ground in the area of 73,877 m2, collapsed down to the basement floor in a split second, which left 502 persons dead, 6 persons missing and 937 persons injured and caused damage to property worth of KRW 100 billion or higher (the amount of the time when the accident happened) [1]. The collapsed department building had the structure of flat slab. The building had the flat slab system [2], [3], [4], [5] without beam and with slab directly supported by pillar. And it had the structure that collapse of one pillar support led to breakdown of an entire structure in a moment, which means a progress collapse. Therefore, such structure requires a precise design and construction. Even after construction is completed, such structure requires a thorough maintenance.

This study covers only the technological aspect of investigation on the reason for the collapse that was conducted after the accident struck. We decided to review the accident that happened about 15 years ago because the results of the investigation on cause of collapse were not announced. As the accident needs to be regarded as a precedent for the case where a similar accident takes place in the future, we intended to suggest an approach to the technological aspect of structural engineering.

Furthermore, when the investigation was conducted, it was difficult to secure evidence due to rescue work, fire prevention and complete collapse. But we made an engineering analysis based on building survey, foundation ground survey, review of design books, and examination of information on construction and maintenance, which aimed at taking the analysis results as a precedent for prevention of a similar accident in the future.

As shown in Fig. 1 [6], the department store consisted of the building A that was used as a shopping center, the building B that housed a sport center and business facilities, and the core that connected the two buildings. The facilities in the department store were operated as shown in Table 1. The collapsed structure was the building A that was utilized as a shopping center that had sales stores. The structure collapsed at the time when the building was crowded with people, which resulted in the huge loss of people and property.

Section snippets

Before the collapse

Building structure has the life span of around 50 years. While the building structure is being used, it is required to conduct maintenance and retrofit on a regular basis. This can be expressed in life cycle as shown in Fig. 2, which illustrates that performance degradation of the structure and maintenance against the degradation are repeated periodically. It is customary to set the period of repair and retrofit at around 10 years primarily. But the building in this case collapsed about 5 years

Investigation on cause of collapse

The investigation on the site of the collapse was very dangerous and difficult but was very significant in that it was conducted to secure evidence and collect data for estimating the cause of the collapse. In this case, the most urgent task was to clear the remnants of the collapsed building in order to rescue people who were buried in the remnants and recover the dead bodies. Therefore, it was almost impossible to preserve the scene of the accident for investigation. Instead, the scene was

Conclusions

The building construction for the Sampoong Department Store began in July 1987. The department store was opened after it obtained the pre-approval for use on December 1, 1989. Since then, the department store had been in business for 5 years. With respect to structural system, the department store buildings had the flat slab structure that flat slab on the floor supports pillars directly without beam, unlike the common skeletal structure (reinforced concrete frame) that consisted of beam and

Acknowledgement

The Author gratefully acknowledge Professor Lan Chung for advising this research. Also this research was supported by a grant (Code#09 R&D A01) from cutting-edge Urban Development Program funded by Ministry of Land, Transport and Maritime Affairs of Korean Government.

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