What I am thinking: structural designer and poet Jun Sato

Jun Sato is Associate Professor at University of Tokyo / Visiting Professor at Stanford University / Chief Executive Engineer at Jun Sato Structural Engineers Co., Ltd.. He has developed transparent, lightweight and ductile structures with geometries of naturalness through his collaborations with architects such as Kengo Kuma, Riken Yamamoto, Toyo Ito, Sou Fujimoto and Junya Ishigami, and through workshops with students. He worked at Toshihiko Kimura’s engineering office from 1995 to 1999. He received the Japan Structural Design Award in 2009.
Sigrid Adriaenssens (SA): What are the research questions that your designs address?

Jun Sato (JS): When we think of structural designs based on manipulating buckling phenomenon and ductility of material, we can develop transparent structures composed with slight elements.
I could expect that those transparent structures have potential to serve as environmental filters to create space of specific naturalness.

Methods in my lab to develop those structural designs are :

Contraction of eigenvalue equation on buckling phenomenon,
Geometrical algorithm such as Fuzzy Node algorithm to create random pattern,
2D power spectrum analysis,
Multiple optimization with objective functions of sturctural performances such as safety ratio, energy absorption, or buckling strength, and environmental performances such as natural light distribution.
Outcomes using those methods are :
Komorebi/Seseragi space which represents specific naturalness,
Lightweight and ductile structure preventing death in the event of collapse,
Lunar/Mars base using such as dimpled shell structure and deployable geometry.

SA: What is “Komorebi naturalness”? Can you exemplify that concept with one of your projects ?

JS: Komorebi is a Japanese term of sunlight falling through leaves in the woods. It is representing natural and comfortable space.
When we look up some 2D power spectrum images converted from some scene of natures, we can find an unique distribution of spectrum for each scene of nature.


Komorebi scene converted into 2D power spectrum image

We can tell which naturalness we could create in each structural design.
A glass pavilion built in the course Transparent Structures at Stanford University could show much similarity with the 2D spectrum of Komorebi.

Glass pavilion, Stanford University

A pavilion using Super Organza, the world thinnest fabrics, could show some similarity with the 2D spectrum of autumn woods.

Autumn Woods

Super Organza + Carbon Rods

Sunny Hills in Aoyama could show some similarity with the 2D spectra of pampas grass field and fleecy cloud.

Sunny Hills in Aoyama, Pineapple Cake Shop, Tokyo, 2013

Pampas Grass Field

Fleecy Cloud

SA: What can you tell us about your latest innovative project?

JS:In this summer 2019, a treehouse could be built in Tokyo. Structural wooden panels assembled in bevel siding are composed into asymmetric egg shape similar to mantis’ egg.
Unique timber joinery could be developed for these panels to be interlocked and the shape of each panel could be generated by parametric geometry. The panels could be carved mostly by CNC and finally finished by expert carpenters.

Treehouse in Tokyo

We are now developing tensegrity façade system using free shape modules. Overlapping modules would provide natural Komorebi light into the building. The module can have the shape of vegetation pot as well. We could build a full scale mock up of the module in this summer 2019.

Tensegrity Façade Project
Vegetated model made by Tucky, Heartland Engineering Co., Ltd.
Full scale mock up of a module made of casted stainless steel, provided by KINZI Co., Ltd.

SA: To what extent do you see yourself as an artist or a scientist/engineer?

JS: Engineering is a technique of omission.We always don’t have enough time to learn every phenomena, nor to provide all the calculations expected. But we engineers still can be realizers who make fascinating structural designs feasible, by manipulating physics and geometry.
When I collaborated with students for the project MOOM, all the calculations which I have provided were only these written on a half pieces of A4 paper.
I have learned a lot from Toshihiko Kimura who was my boss. He didn’t teach me how to calculate but showed me that way of omission. He told me to listen to an architect to figure out which kind of space they are wishing to create. He loved craftsmen and labors on site and thought of structural designs based on their techniques.
Little by little, we are learning Great Nature. When we could learn a little more about oscillation, a little more about waterflow, we can save people a little more.

MOOM, Calculations provided for this project

SA: What is your greatest achievement and why?

JS: In my lab, we are now looking for a method to extract buckling strength of each element in the FEM analysis model and found that contraction of eigenvalue equation can be one of the ways.
We have already found some applicable models of which shape can be optimized to have more buckling strength.

Extracted buckling strength / Jasmine dimples / Lattice x lattice x lattice

Using this method, I am expecting that we can develop some lightweight and transparent structures such as dimpled shell structure or lattice x lattice x lattice structure.
My student could find that Jasmine flower dimples can reinforce a thin sheet a lot. We can optimize the density of the flowers depend on stress distribution. I can expect this structural design can be applicable to Lunar/Mars base shelter.
In 19th century, lattice x lattice (= lattice composed of lattice) structures, for example Eiffel Tower, could be developed. Now we can develop lattice x lattice x lattice structure with optimized patterns of lattice.

SA: What questions do you never get asked but would like to be asked? What would be the answer?


● What was your latest heartwarming project ?
Support project in Barrio Cantera, San Martin de los Andes, Argentina, where is exposed to landslide every year. We could build handmade retaining walls, with local people using local materials, to resist soil pressure when the cliffs fell down. The walls were painted by kids so fascinatingly.


Retaining Walls in Barrio Cantera, San Martin de los Andes, Argentina, 2017
(Photos : Claudia Sakai, Akiko Okabe Lab, University of Tokyo)

● Can we live on the Moon ?
I would like to, even if I couldn’t come back to Earth.


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