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PERSPECTIVESconducting qualities of wood made it best suited to use for handrails, window sills and other places likely to be touched, as well as for the louvers used to shield against sunlight. From a structural viewpoint, too, since the top floor is supporting only the roof, the use of lightweight timber was the logical structural material of choice. Wood is often thought to be a costly material, but by using timber processed to traditional Japanese measurements and dimensions, which is available on the timber market in greatest quantity, for exterior cladding, interior use and also as a structural material, we were able to achieve cost-effectiveness in timber procurement. Also, in order to make the most of the soft and easily processed qualities of wood, we introduced the use of computer numerical controlled (CNC) fabrication from the design stage, making it possible to cut down on building costs. On the interiors, by putting to good use effective escape and safety verification methods and fire-resistant design, we were able to use timber without fireproofing treatment and without having to fireproof the timber structure. By using the right materials in the right place, we were able to keep costs down and build a safe building.─Possibilities for WoodSeven years on from the completion of the Mokuzai Kaikan, our study of fireproofing technology and fireproof structures for wood has progressed to the point where theory tells us we can design a super-high-rise building of wood. But we are not attempting to use wood for everything; rather, we want to ascertain when and where wood is the optimal material to be used. What we are aiming for is what we might call “wood conscious architecture” which uses wood in the ways for which it is best suited, that is both economical and pleasing to its users, and that we can proudly boast is low-carbon and environmentally friendly.Among the attractive qualities of wood are the ways it weathers and changes color when exposed to sunlight and how wear and tear actually enhances the character of a solid wood finish. Taking advantage of these qualities, it is possible to use wood as a finishing material to foster the kind of attractive aging that is impossible with stone, metal, or tile. As a structural material as well, for the smaller-scale buildings in our cities, lightweight and fire-resistant wooden structures seem to be economically more logical. In large-scale buildings, as was done in the Mokuzai Kaikan, a light weight top-floor timber structure not only offers economic and construction period merit. Timber construction can also provide added value given that top floors often are set aside for boardrooms or other prestigious uses. Top-floor timber structures can be not only logical applications, but can contribute to impressive skylines and the development of superior cityscapes. Further still, with a view to application to today's increasingly long span buildings and factory architecture, study is progressing in the field of “hybrid wood structures” that are reinforced through the combination of the malleability of wood with other materials.─At Nikken Group we will continue to develop wood conscious architecture oriented to the “right place, right material” perspective as well as being economical, safe, and appealing to human sensibilities.を目指しているわけです。 たとえば、日に焼けたり色褪せたりする木材の特性や、無垢材の傷もまた味わいと感じさせる特徴を活かして、石や金属、タイルでは不可能な、エイジングする仕上げ材として木材を利用することが考えられます。 構造材としても、まち中の小型ビルは、軽量かつ耐火性をもった木造架構の方が、経済的な合理性が勝る可能性がありそうです。大型ビルにおいても、木材会館で実現したように最上階の構造を軽量の木構造とすることは、経済的にも建設工期的にもメリットとなる可能性が高いだけでなく、たとえば役員室などの特殊用途に使われるケースが多い最上階に、木造という付加価値をもたせることができそうです。加えて、木造の最上階がつくり出す、合理的でありながら印象的なスカイラインは、優良な都市景観の形成にも寄与するに違いありません。  さらに現在では、より長スパンの大型ビルや工場建築への木構造の適用のため、木材の加工性を活かしながら、他の材料と組み合わせて強化した「ハイブリッド木造」の検討も進めています。─日建グループでは、今後も適材適所の視点を見失うことなく、経済的でありながら、安全で、それでいて人々の感性に訴えかけるような木質建築の開発を進めていきたいと考えています。木材会館最上階に設けた木造ホールの様子。Wood-structure hall on the top floor of the Mokuzai Kaikan.062016 Summer 27Feature | Pushing the Possibilities for Architecture in Wood

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