Press Information

MBE Delivers 2 "Tuned Mass Damper" Vibration Control Systems
For the 634 Meter Tokyo Sky Tree
- Safeguarding Antenna Support Tower from Vortex Excitation by Wind -

No.1403
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Tokyo, February 1, 2011 - Mitsubishi Heavy Industries Bridge & Steel Structures Engineering Co., Ltd. (MBE), a subsidiary of Mitsubishi Heavy Industries, Ltd. (MHI), has delivered two units of tuned mass dampers (TMD)*1, a vibration control system, for Tokyo Sky Tree*2, which is currently under construction in Tokyo and will become the world’s highest broadcasting tower. The two TMDs will serve to safeguard the supporting (gain) tower of the digital broadcasting antennas from vortex excitation, a response phenomenon caused by wind, at more than 600 meters (m) above ground. MBE believes the customer's high evaluation accorded to its technological expertise and experience in the field largely contributed to the award of the TMD order for the epoch-making landmark tower.

The two TMDs delivered are inverted pendulum type systems whose vibrator base, consisting of a weight and weight frame, is supported by universal joints. Other components of the TMD include push/pull springs and dampers. The TMD weighing 40 tons will be installed at a height of 620m; the unit weighing 25 tons, at 625m. Each unit measures 6m in width, 6m in depth and 4.2m in height. In the TMD installation plan, each unit is required to subdue swing strokes up to plus or minus 70 centimeters (cm) in both the right/left and back/forth directions, but they actually have capacity to control strokes up to plus or minus 125cm. While a single unit of the 25-ton TMD offers sufficient capability to accommodate vortex excitation of that level, installation of two units was selected as a failsafe measure in view of the tower’s mission – broadcasting – which does not allow for service disruptions.

The order for the two TMDs was placed by Obayashi Corporation, the company in charge of the construction of Tokyo Sky Tree. Upon order receipt, MBE conducted design, manufacture and performance testing at its manufacturing plant for one and a half years before delivery. The two TMDs have already been installed in the vibration control equipment compartment which will comprise the top of the gain tower. Going forward the compartment will be jacked up to its designated height by lift-up construction method, with on-site performance testing scheduled for November.

The 634-meter Tokyo Sky Tree, which will be the world’s highest tower either self-standing or wire-supported, is scheduled to be completed in December 2011 and to commence operation in the spring of 2012. Construction work is proceeding on schedule, and the tower is expected to become a new sightseeing landmark in Tokyo while simultaneously constituting the key component of the Tokyo metropolitan area’s broadcasting and communication infrastructure. The area surrounding Tokyo Sky Tree is also currently being redeveloped by Tobu Railway Co., Ltd., and Tobu Tower Sky Tree Co., Ltd., the Tokyo Sky Tree project implementation body.

MBE, which inherited its technological expertise in steel bridges, stacks, water gates, tanks and vibration control & earthquake isolation systems from MHI, where such expertise was accumulated through its related business operations over a long time, has delivered many TMDs to date for various applications, including skyscrapers and long and large steel bridges. Gaining momentum from the latest delivery for Tokyo Sky Tree, going forward MBE will further strengthen its vigorous marketing activities in Japan and other countries.

Notes:  
1.The TMD is a system to absorb vibrations through optimized tuning of natural frequencies by installing weights (mass) and dampers with springs on buildings, structures and machinery requiring vibration control.
2.Tokyo Sky Tree
Project implementation body: Tobu Railway Co., Ltd. and Tobu Tower Sky Tree Co., Ltd.
Design and supervision: Nikken Sekkei Ltd.
Construction: Obayashi Corporation

BUSINESS CONTACT:
Mitsubishi Heavy Industries Bridge & Steel Structures Engineering Co., Ltd.