Iconic titanium sphere still shining
Photo: Wikimedia Commons, Mark J. Nelson

Anyone who has spent time in Tokyo will probably haveseen the iconic sphere on top of the Fuji Television Networkbuilding. Constructed of titanium, it has been an icon of thecity since its construction.
Text & images courtesy of Kikukawa
The Fuji Television Network building is
one of the most distinctive buildings inJapan. Located in the waterfront area ofTokyo’s Minato district, the ultra-futuristicbuilding was designed by the architect
Kenzo Tange and completed in 1996. Itserves as the corporate headquarters of
the Fuji Television Network and houses
several studios.
The 25-storey building consist of twotowers connected by three enclosed

The 1,350 ton titanium observation sphere
was an engineering marvel at the time.

24 Stainless Steel World May 2020

pedestrian bridges, called ‘sky corridors’
which are supported by four steelcolumns. The corridors help to strengthen
the overall structure, making it highly
earthquake resistant.

Titanium ball
The centrepiece of the building is thetitanium sphere measuring 32 m
in diameter, and weighing 1,350 tons.
Inside the ball is an observation
platform which is open to the public,
offering unobstructed views of Tokyoand Mount Fuji.
Raising the ball into place was a major
engineering challenge which took a totalof 9-and-a-half hours. It was balanced
horizontally on, and supported by, threebeams, before being raised to its finishedheight of 123 m by hydraulic jacks.
The titanium sphere was constructedby the metal architect Kikukawa. The
massive globe consists of a number ofsmall panels constructed of titanium toavoid corrosion which could otherwise
occur due to the building’s seaside
location. In order to fabricate the globe

Raising the sphere into place was a major
challenge.
with a high degree of precision, thecompany pioneered the use of 3D-CAD in
its product engineering.
Although titanium is a high-strength
metal, which can be difficult to process,the Kikukawa team were able to use
their accumulated expertise to produce
this iconic design.
Project:

Fuji Television Network,
Spherical Observation Room
Material:
Titanium TP270C(JIS H4600 Grade 1) - ASTM
GR1 equivalent
Thickness:
0.8 mmMetal Finish:
Dull finish (ND-15)
Sphere diameter: 31m
Client:Fuji Television
Architect:
Tange Associates
Completion:
1996
Location:
Minato-ku, Tokyo
www.stainless-steel-world.net

[ Titanium ]Art Tower Mito a beacon forlarge-scale titanium projects
Art Tower Mito is acomprehensive cultural
facility symbolized by the
100 meter tall titanium
tower which was opened in1990 to commemorate the100th anniversary of Mito,
Japan, as an official city.
Text & images courtesy of Kikukawa
The 100 m tall titanium tower
is composed of 28 contiguous
tetrahedrons (triangular pyramids)
placed on top of each other, each set ata different angle. Kikukawa participatedin the metal construction of thismonumental project.

The first large-scale Ti project inJapan
Titanium was chosen for the façade of
the tower as it captured the architect’s
vision to “choose high-quality materials
to build architecture that lasts”.
Titanium is known to be a maintenancefree material with excellent resistanceto corrosion and weathering. It is
60% lighter in weight than steel, andis superior to other metals in bothstrength and workability.
Despite such superior properties,
the usage of titanium is limited inarchitecture due to its high materialcost. This project pioneered the use oftitanium on a large scale within Japan:
consequently, it was also Kikukawa’s
first attempt to implement titanium
panels on such a large scale.
Regardless of these conditions,
Kikukawa was able to provide highquality titanium panels by collaboratingclosely with the metal sheet provider
and through repeated experimentation.

9.6 m titanium equilateral triangles
The titanium tetrahedrons composing
Mito tower are formed from 57
equilateral triangles with each side
measuring 9.6m. Each triangle isformed with 8 pieces of 1.5mm thickhairline finished titanium of roughly
1050mm width, ranging in length and42 Stainless Steel World May 2020

The Mito tower is constructed of almost 18 tons of First Grade titanium.
shapes from trapezoids to triangles.
The corners where the panels meet thestructural truss are joined using 1.5mm
stainless steel cut in φ95mm half circle.
The backing frames are composed ofbent 1.5mm stainless steel assembled
into a unit.
To ensure the integrity, wind resistance,
and water sealing, the panels andframes were carefully designed andcalculated. This is evident in details

such as the 230mm risers at the edge ofthe panel.

Stainless steel fittings & louvres
The observation floor at 86 meter highhas 70 circular windows of φ432mm
and φ670mm. The window system has
excellent airtightness and is equippedwith an opening/closing mechanism.
The cross-section of the window
reveals that the glass window is placedwww.stainless-steel-world.net

[ Titanium ]The titanium triangles at the foot of
the tower are equipped with louverstowards the bottom. These louvers
are formed by hairline finished1.0mm thick stainless steel bent intoa Z shape.

Installing large panels sky-high

Built in 1990, the tower was a cuttingedge project in terms of its design, use oftitanium and implementation.
between the interior and exterior
fittings. The 120 mm thick exterior
fittings are tapered, and the interior
fittings are 280 mm thick cylinders, bothpre-assembled into a unit at the factory.
Other triangular sides of this tower are
equipped with a single line of φ432mm
circular windows.

The 9.6 meter assembled equilateraltriangular panels are each roughly 1 tonin weight. Thus, their transportation andinstallation required consideration fromthe detailed design stage.
Frames and hardware fortransportation, ground assemblyand suspension were designed andfabricated, as well as a system to pull in
the lifted panels to the structural truss.
The actual installation was achievedby equipping the panels with bespoke
hinges so that they could be pulled andadjusted into place with bespoke rodshaped installation hardware.

A symbol of Mito
It was a true pleasure for Kikukawa toparticipate in this monumental project.
Art Tower Mito is now known by manyas the symbol of Mito City, and it is also
one of the most well-known works ofthe Pritzker Award-winning architect,
Arata Isozaki.
This was a cutting-edge project in its
design, large-scale usage of titanium
and its implementation. It is projects
like these that challenge our expertiseand hone our metal-crafting technology
which expands our ability to provide
comprehensive solutions for a varietyof architectural projects.

Project Art Tower Mito
Abbreviated
Name:
Client:Architect:
Contractor:

Art Tower Mito
Mito City
Arata Isozaki & Associates
Construction Joint Venture:
Taisei Corporation,Takenaka Corporation,Totetsu Kogyo Co., Ltd.,
Akui Corporation
Completion:
1990
Location:
Mito City, Ibaraki
Material:
Pure Titanium FJIS Grade1,iASTM GR1 equivalent
Material thickness: 1.5t
Finish:HL
Quantity:
Approx. 17.8 ton<285672&. 6(59,&((;3(57)25+,*+3(5)250$1&(0$7(5,$/6WE WILL SOLVE YOUR PROCUREMENT PROBLEM!
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