Shimonoseki-shi Kawatana Onsen Koryu Center (Kawatana no Mori) 4

下関市川棚温泉交流センター (川棚の杜) 4

This structure consists of folded triangular plates making a bumpy surface. Trying to make this structure look random was a valuable attempt. Basically, the rise made by these bumps work like a depth of a beam and this structure can span a long distance by the beam-like ridge intersecting with each other. I was eager to realize this structure because this project was the first time I applied my “Manual Form Finding” software.

However, this kind of architecture apparently seems impossible when the budget and time of a general official construction is considered. It can be realized only when all situations are satisfied. I feel like this all the time when I design architecture. My manual form finding software was used in the past when I taught students designing and making a polyhedric structure named “Mori no Kyoshitsu” (Classroom in the Forest) made by plywood in a lecture at Keio University. Fortunately the software was also improved through other project and it was almost completed before applying to this Shimonoseki project. Using the software, at first I looked for what kind of form can be made by the given materials and then changed the form again and again to decrease the amount of steel used in the structure. I grasped the form by simplifying the member into a wire frame model, but at the same time, I imagined the depth of the member and the way of connecting each member and building the structure. This has a big effect on the expense of the structure. As Mr. Fujiwara say, the way of setting the coordinates of the member influences the cost a lot, so I discussed it a lot with Mr. Saita, who was in charge of this project.

In this way, we polished the plan again and again, but unfortunately, it was expected to be too expensive. It was also fortunate that a member of Nippon Steel Corporation helped us quite timely. We decreased the amount of steel by refining on the member, its configuration, and the joint. My office didn’t have enough time to draw the detail, and Nippon Steel Corporation helped us finish on time before the construction period. The final plan was a relatively complicated way―using a pipe as a chief member and connecting H-shaped and T-shaped plate to the end of it, and connecting to a ball shaped joint with a bolt. However, the member of Nippon Steel Corporation told us that this was the cheapest way thinking of making the structure using 3D-CAD and Numerical Control machining. Also, this structure was realized thanks to the consideration of the people living in Shimonoseki city, and the favorable cooperation of Kosei Corporation, which is a contractor.

Maybe, we could think of a structure using lattice girder in order to thoroughly save the amount of steel. In this project, I didn’t consider all the concrete skin into the structural strength to avoid complicated analysis and finish in time. However, if we design the structure considering the strength of both steel and concrete, another form may be invented. There is a lot of possibility in this structure and it is true that it has room for improvement. But the realization of this structure tells us that we can go for a more sophisticated one.

Jun Sato
Jun Sato Structural Engineers Co.,Ltd.
Associate Professor, the University of Tokyo