NAGI Terrace | 奈義町多世代交流広場 ナギテラス

The building features a composition of simple rectangular floor plans combined with gable roofs that do not align in direction or shape with the underlying forms. Columns are placed at the intersection points between the axes of the purlin beams and the centerlines of the exterior walls, supporting the purlins directly. Although the continuous columns appear slender and tall, they are laterally braced using steel braces and horizontal timber members, connecting them to the horizontal structural planes to provide effective buckling restraint.
The dominant short-term load for this building is wind load. In particular, the area of Nagi Town is known for a local strong wind phenomenon called “Hirotokaze,” which has been recorded with peak gust speeds of up to 70 m/s and is widely feared by local residents. The cross-section of the long cantilevered eaves was also determined based on wind loading. For this project, the design wind load was set at twice the velocity pressure defined by the Building Standard Law of Japan (equivalent to 1.4 times the average wind speed), ensuring a high level of wind resistance.
The shear walls are designed as structural plywood walls applied on both sides of the exterior walls and interior partitions, providing sufficient lateral stiffness and strength throughout the building.

Architectural Design: Eureka
Structural Design: Eureka
Program: Community Facility
Year of Completion: 2018

Photo courtesy of Kurome Photo Studio

平面プランは整形な矩形の組み合わせだが，その上に，棟の向きも外形も整合しない切妻屋根が載っているのが特徴である。母屋梁の軸と外壁芯の交点位置に柱を設け，母屋梁を直接支持させている。一見，細長比が大きな通し柱は，鋼管ブレースや木造横繋ぎ材等を利用して水平構面と接続し，座屈補剛している。
本建築物における支配的な短期荷重は風荷重であり，奈義町の「広戸風」はその強烈さで町民に恐れられており，最大瞬間風速70m/sにも達した記録がある。長い片持ち庇の断面も，風荷重が決定要因となる。本計画では，設計風荷重は基準法により求まる速度圧の2倍（平均風速1.4倍に相当）とし，高い耐風性能を確保した。耐力壁は，外壁・内部間仕切りを満遍なく合板両面貼りの構造壁とすることで十分に確保できている。

意匠設計：Eureka
構造設計：Eureka
用途：交流施設
竣工年：2018年

写真：黒目写真館