Location: Seoul, South Korea
Type: Structural Overload, Punching Shear
The building began to crack in the ceiling two months prior to its complete destruction. The main causes for the building failure turned out to be its structural overload as well as punching shear in flat slabs. During the construction, the format of the building’s structural system was designed as a residential apartment with four floors. However, the owner of the building changed it to a large 5-level retail facility which required much more load resisting structures. He replaced the original construction team that was being skeptical about the feasibility of the design, and then cut away a number of columns. Moreover, the size of the columns was reduced in order to install escalators and a book store which was not planned in the original project plan. On the fifth floor slab, not only the restaurants with heavy equipment but also the hot water pipes in concrete base for heat radiation transferred extra loads to the columns, and resulted in a failure to support the floor [a].
Another factor that accelerated the collapse was the HVAC units on the roof. The system weighted total 87 tons including the air conditioning fans and cooling towers. After 22months of operation, the department store was receiving continuous complain regarding the noise that the fans were producing. Instead of lifting and mobilizing the system by using crane, the managers decided to drag them to the other side so that they could reduce the equipment cost. Such action pushed down the roof to sink, deteriorating the whole building even more with a phenomenon called punching shear. Punching shear occurs when the slab exceeds its own weight limit by forcing the column to punch through the roof [a].
The failure took place in June, 1995, suffering 501 casualties and approximately 1,400 injuries. Improper structural modifications and building management remarked such event as the deadliest disaster in South Korean construction history [a].