Art Tower Mito is a comprehensive cultural facility symbolized by the 100 meter tall titanium tower which was opened in 1990 to commemorate the 100th anniversary of Mito, Japan, as an official city.
^ The 100 meter tall titanium tower 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 at a different angle. Kikukawa participated in the metal construction of this monumental project.
The first large-scale Ti project in Japan
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 maintenance free material with excellent resistance to corrosion and weathering. It is 60% lighter in weight than steel, and is superior to other metals in both strength and workability.
Despite such superior properties, the usage of titanium is limited in architecture due to its high material cost. This project pioneered the use of titanium 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 high quality titanium panels by collaborating closely 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 is formed with 8 pieces of 1.5mm thick hairline finished titanium of roughly 1050mm width, ranging in length and shapes from trapezoids to triangles. The corners where the panels meet the structural truss are joined using 1.5mm stainless steel cut in φ95mm half circle. The backing frames are composed of bent 1.5mm stainless steel assembled into a unit.
To ensure the integrity, wind resistance, and water sealing, the panels and frames were carefully designed and calculated. This is evident in details such as the 230mm risers at the edge of the panel.
Stainless steel fittings & louvres
The observation floor at 86 meter high has 70 circular windows of φ432mm and φ670mm. The window system has excellent airtightness and is equipped with an opening/closing mechanism. The cross-section of the window reveals that the glass window is placed between the interior and exterior fittings. The 120 mm thick exterior fittings are tapered, and the interior fittings are 280 mm thick cylinders, both pre-assembled into a unit at the factory. Other triangular sides of this tower are equipped with a single line of φ432mm circular windows.
The titanium triangles at the foot of the tower are equipped with louvers towards the bottom. These louvers are formed by hairline finished 1.0mm thick stainless steel bent into a Z shape.
Material: Pure Titanium FJIS Grade1, iASTM GR1 equivalent
Material thickness: 1.5t
Quantity: Approx. 17.8 ton
Installing large panels sky-high
The 9.6 meter assembled equilateral triangular panels are each roughly 1 ton in weight. Thus, their transportation and installation required consideration from the detailed design stage.
Frames and hardware for transportation, ground assembly and suspension were designed and fabricated, as well as a system to pull in the lifted panels to the structural truss. The actual installation was achieved by equipping the panels with bespoke hinges so that they could be pulled and adjusted into place with bespoke rodshaped installation hardware.
A symbol of Mito
It was a true pleasure for Kikukawa to participate in this monumental project. Art Tower Mito is now known by many as the symbol of Mito City, and it is also one of the most well-known works of the 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 expertise and hone our metal-crafting technology which expands our ability to provide comprehensive solutions for a variety of architectural projects.
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