Demolition of the Old Hotel Plaza (Oyodo-Minami, Kita-ku, Osaka City) Begins Using the Environmentally-Friendly Superhigh-Rise Building Demolition Technology, the Takenaka Hat Down Method

February 22, 2012Takenaka Corporation

Takenaka Corporation (President: Toichi Takenaka) has developed the Takenaka Hat Down Method (※): demolishing superhigh-rise buildings in the centers of cities by installing a movable demolition work space (Hat) so that it encloses the top of the building, then moving it down as the building is demolished from top to bottom. The Hat, in which demolition equipment is integrated including ceiling cranes, is lowered without leaving any gaps while enclosing the demolished building’s body. All the demolished materials are lowered inside the building, permitting demolition safer and kinder to the environment than conventional methods.
Takenaka has selected this method to demolish the superhigh-rise building, the old Hotel Plaza, and will begin work in February of this year. Demolition by this method involves almost no use of conventional breakers or crushing machinery because cutters and wire saws are used to cut the building into blocks inside the Hat, achieving sharp reduction in dust and noise diffusing from the work area. Because the demolished blocks are lowered inside the building by the ceiling cranes, there is no danger of them falling outside the building, so it is a method suitable for use in the centers of cities.
Takenaka developed and used the Takenaka Grip Down Method to demolish the Osaka Tower (September 2009) by repeatedly cutting and jacking down the tower’s exterior column bases. However, Takenaka intends to continue to study and develop safe and environmentally-friendly demolition methods suited to meet varying client needs dependent on the condition of each building.

※Hat Down is a registered trade mark of Takenaka Corporation.

Benefits of the Hat Down Method

[1] The Hat completely encloses the demolition work space, preventing the diffusion of dust and noise outside the space.

[2] Equipped with a roof which can be opened and closed, it can ensure the finest possible interior work environment.

[3] The demolished material is lowered by ceiling cranes inside the building, preventing any of it falling outside the work area.

[4] Integrating the equipment reduces work at high places and avoids breaks to move temporary structures, preventing the equipment from falling.

[5] It includes a mechanism which lets the exterior columns support the integrated unit, ensuring a large working space and permitting it to flexibly adapt to various building shapes.

The above benefits of the Takenaka Hat Down Method have sharply improved safety and environmental problems with the conventional method.

Image of Demolition using this method

Outline of the use of this method to demolish the old Hotel Plaza

The major specifications of the Hat used for this work are height: 19 meters, width: 19.6 meters, length 92.3 meters, and self-weight: 412 tons. Its outside is completely covered with soundproof panels, and its ceiling is constructed so that it can be opened and closed according to the type of demolition work being executed, the weather, temperature, humidity, and other conditions. Twenty-two jacks are installed to raise and lower the Hat, and after the interior of a floor where the Hat is installed has been demolished, the entire Hat is lowered down to the next floor (approx. 2.95 meters) in about one hour to prepare it to demolish the next interior. The floor to be demolished is divided into three sections, with one ceiling crane and lowering opening in each section. Workers work simultaneously in all three sections, breaking the columns, walls, floors, etc. into about 176 pieces per floor, and then lowering these to the first floor through the lowering openings. The work is scheduled to be executed from the 23rd floor (77 meters above the ground), which is the top floor of the building, to the 5th floor (15 meters above the ground) between February and July, while lowering the hat 14 times. (The bottom four floors will be crushed with heavy machinery.)

Background to the development of this method

Superhigh-rise buildings built during a construction rush that started in the late 1960s to effectively use land in the center parts of cities have stood for about 40 years, and are now reaching a period when they are to be renovated or reconstructed because of concern with their earthquake safety and the deterioration of their equipment, and to adapt them to modern IT.
Within Japan, there are now more than 700 superhigh-rise buildings with height exceeding 100 meters, and of these, about 100 were constructed more than 20 years ago. A rise in the number of superhigh-rise buildings which must be demolished is predicted, requiring a safe and environmentally-friendly demolition method.