News / Press

Seismology Meeting on Innovative Structures (07/07/2022)

In the meeting prior to this one, it was discussed in the committee that structural engineers should strive to innovative and push the status quo. This meeting, which complimented the last, focused on innovative structures. Professor Jun Sato, from the University of Tokyo, was invited to present on the innovative structures he routinely designs. Architects challenge structural engineers to go beyond their comfort zone. Professor Sato provides novel solutions to the complex problems his architects require from him. He does this by expanding on fundament structural principles in small increments. His presentation and the follow-up committee discussion investigated these concepts and provided insight on how structural engineers can come up with creative designs.

Creativity is developed through small deviations from standard practice. Professor Sato starts with simple concepts and, little by little, these ideas evolve. He has collaborated with architects such as Kengo Kuma, Sou Fujimoto and Junya Ishigami. These architects push him to think unconventional. For example, a visitor center he design in Vijversburg, Netherlands uses curve glass walls as load bearing structural walls. The curvature of the glass walls increases its buckling strength. Knowledge about how to manipulate the buckling strength of thin elements can from Professor Sato’s experience of the design of similar structures and he was able to blend this concept into this design. The probability for earthquakes is low in the Netherlands and the visitor center was designed for wind loads. However, Professor Sato is further trying to go beyond the concepts learned on this project by researching how a glass wall can be used to resist seismic loads. In this way, concepts are transferred to different projects, and this allows for a holistic growth in creativity.

One concept Professor Sato has been exploring is the design of transparent structures which provide a Komorebi environment. Komorebi is a Japanese term which refers to the pattern made from the projection of sunlight going through leaves. This pattern creates a very pleasant environment and Professor Sato attempts to replicate this effect in his work. Similar patterns are Sazanami, ocean ripples, and Seseragi , River Stream. Professor Sato has been designing transparent structures which are assembled in a manner that allows light to enter and create a Komorebi ambience. A workshop he held at Harvard was dedicated to this subject and students developed dome-like structures with PET. The structural elements could be optimized through a computer program. Professor Sato has also been creating tensegrity structures with paper and light weight fabric and these structures exhibit the Komorebi environment as well.

An interesting project which Professor Sato worked with architect Kengo Kuma was the Sunny hills building in Aoyama, Tokyo. This building uses a unique wood structural system in which the wood elements are connected through traditional Japanese joinery called kigumi. While the wood serves a structural purpose, it also defines the architecture of the building. Kengo Kuma wanted a building mimicking scattered particles and Professor Sato took this idea and used it to come up with the building structure. The building, which is shaped like a bamboo basket, serves as a shop to sell pineapple cakes. The geometry was determined through an optimization software. Since the wood elements were very thin, buckling was an important consideration. The generally shape of the building was feed into the optimization software and then the software populated this outline with kigumi units to create the overall shaggy shape of the building. Due to the porosity of the building exterior, the interior of the building has a Komorebi environment.

Professor Sato has a deep interested in buckling and has been studying ways to increase the buckling strength of thin shell elements. He found that adding dimples to the shell structures increases its out-of-plane buckling strength. The scattering and number of dimples is based on the stress distribution. One of Professor Sato’s students found that the flower dimple works especially well. The only issue is that the dimples weaken the structures in-plane stiffness. He is using this concept to design a lunar Mars base, a project he is currently contracted to work on. Test on protypes of this base show a snap through effect when the buckling strength is reached. Professor Sato is furthering this work to understand how dimples effect the energy dissipation of shell structures. He found that the dimples concentrate the damage in localized areas and allow for the structure to remain stable even after damage is incurred. His curiosity in designing buildings with thin structure elements lead to this exploration of buckling.

The Japanese building code is quite conservative, and Professor Sato finds himself fighting with building code officials quite a bit. His desire to go beyond standard practice to beautiful structures which satisfy his architectures but may intimidate traditional structural engineers. In parallel, the Building Seismic Safety Council’s Provision Updated Committee (PUC) is investigating how engineers can incorporate creativity into their designs by going outside of the prescriptive bounds of the building code. These deviations from standard practice may result in greater uncertainty in performance of engineered structures. The work of the PUC and other similar committees will hopefully allow structural engineers to design mores structures which fulfill the vision of their architect clients.