■Combining Nature and Metal

Together with the completion of ‘GranRoof Front‘ of Tokyo Station Yaesu-Exit, the central ventilation monument tower within the square in front of the exit was completed.
To implement the concept ‘creation of relaxing space with greenery’, Kikukawa fabricated the greening sharp stately metal structure that also serves as the central ventilation tower.

■Pearl Vibration Finished Duplex (Two-phase) Stainless Steel

The overall size of the independent shell-shaped structural monument is 17m in length, 6.7m in maximum width, 4.8m in height. Given the environment of the project and the function as a structural panel, the material selected was a two-phase (Ferristic-Austenitic) stainless steel*, SUS329J3L, which is higher in durability and resistance to rust and stains.
The monument is crafted as a one-piece structure manufactured from 9mm thick stainless steel finished with pearl vibration.

*Two-phase stainless steel (also called duplex stainless steel): Stainless steel with a two-phase microstructure which consists of a mix of Austenitic and Ferritic stainless steel. In comparison to SUS304, the typically used stainless steel sheet in architecture, its strength is roughly two times and has better corrosion resistance and mechanical properties.

■Dual Curving Stainless Steel Structural Panel

The shell-shaped ventilation tower required the use of Kikukawa’s 3D-CAD and dual curving technology. To better understand the curvatures of the structure, a 3D-CAD model was created. Based on this model, the 9mm thick stainless sheets were shaped within the factory, then welded and finished within the factory and on-site by our expert craftsmen.
As the monument was to be independent as structural panels, Kikukawa’s certification as the ‘stainless steel building structure manufacturing factory’ within Japan was a necessity in crafting the steel beam frames that line the inside of the ventilation opening.

Click here to find out more about Kikukawa’s dual curving technology

■Welding 24 pieces of Dual Curved Panels

This stainless steel structure is crafted from 1067mm tall individually shaped 24 pieces of dual-curved stainless steel sheets. Every two pieces were factory welded into a unit, then all units were welded onsite after installation to create the giant one-piece independent structure. By doing so, the shell-shaped structure without the interior base steel frames was implemented.
Due to the location with heavy traffic and the required machinery, the timeline for the installation work was limited. To optimize the process, Kikukawa created a detailed plan that was precisely implemented.

■Merging into the Surrounding Landscape

As its’ function as a ventilation tower, as a designed monument, and as a greening construction, the requirements for this project were unique. From the selection of the material to installation, Kikukawa was able to provide solutions for these new challenges and further our expertise.
Given the project’s contribution and preservation of the surrounding landscape, the Yaesu-exit square received the 2017 Civil Engineering Design Prize hosted by the JSCE, Japan Society of Civil Engineering. Kikukawa is honored to have participated in such an outstanding and unique project that fully demonstrates our metal craftsmanship and metal construction consulting capabilities.

Click here to find out more about the ‘Civil Engineering Design Prize’ (Japanese link)