New Horizons in Structural Design April, 2008

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構造デザインの最前線　　　　FACT　NIKKEN SEKKEI23Light, glassy buildings are increasingly favored in contemporary architectural design. By skillfully concealing earthquake-resistant members, it is possible to give the illusion that no structural mate-rials have been used, resulting in light designs that apparently hide the aseismic capabilities of buildings. Here, we introduce a good example of a light-facade design with thin columns displayed.Quake-Resistant Elements Hidden InsideThe Osaka Bar Association Building harmonizes with the surround-ing landscape, featuring a glass-encased facade that expresses the Bar Association’s openness to the public. Aseismic elements are concentrated at two inner cores on typi-cal floors, where most seismic energy is attenuated. In addition, the building is designed with a focus on total balance that prevents seismic forces from severely affecting the peripheral frame. This enables use of a peripheral frame composed of 45-cm-wide col-umns and beams arranged at 2.7-m intervals that resembles an outer frame and secure high aseismic capability. The exterior of the frame is compactly finished with large, richly textured ceramic plates. Intensive deployment of vibration-damping structures at first basement level helps to minimize seismic forces and gives the facade a light appearance.Skillful Use of Design, Facilities, and SpacesIn the Yodoyabashi Yamamoto Building, structural planning and architectural and building service systems planning have been bal-anced to good effect. Slender precast, prestressed concrete col-umns each with a visible face width of 150 mm are deployed like louvers around the exterior of the building. This design, which delivers highly effective solar radiation shielding, allows for large expanses of pillar-free office space and clearly distinguishes the building from neighboring office buildings. To achieve a quake-resistant and wind-resistant design, steel braces have been adopt-ed for the service core area, and steel earthquake-resistant panels are incorporated to form a large "M" on the entire eastern face of the building. Lighting devices attached directly to the floor slabs enable direct expression of structural beauty while producing a spacious interior with 3.25-m-high ceilings. Kozuki Capital West is located near Osaka Station. This glass facade building has been designed in peristyle, using very thin steel-pipe columns each 19 cm in diameter. Since the office room spaces were only 10 m in depth, the dead spaces had to be mini-mized. We sought column minimization to realize spaces with larger real effective volumes and highly transparent appearance. Extremely thin columns deployed on three sides of each office room bear vertical loads only, while the core section on the eastern side absorbs all of the seismic force. Vibration-damping braces arranged in a well-balanced manner in the hidden core section absorb all seismic energy and resist horizontal and twisting sway actions in the event of an earthquake. With their structural slen-derness, the fire-resistant slim steel-pipe columns of the front facade gives an image of openess.Artful Use of Exposure and ConcealmentWe create new spaces by making full use of reliable aseismic design technologies, cutting-edge materials with high strength, and damping members. We also skillfully deploy "displayed members" and "concealed members" after ensuring close communication among designers and engineers. Focusing on a good balance with architectural planning, we sometimes consider adopting structural materials and members that would normally be used for finishing. By proposing rational solutions, we continue to take up the chal-lenge of materializing better, more aesthetically pleasing propor-tions. Kenzo Taga, Hiroaki Harada, Yukihiro TokudaAseismic elements of Osaka Bar Association Building大阪弁護士会館建築主 : 大阪弁護士会所在地 : 大阪市北区建物種別 : 会館・事務所構造 : 鉄骨造・鉄筋コンクリート造（制振構造）階数 : 地上14階、地下2階延べ面積 : 17005.29㎡竣工 : 2006年7月Osaka Bar Association BuildingClient: Osaka Bar AssociationLocation: Osaka, JapanMajor functions: hall, of ceStructure: S, RC (vibration-damping structure)Number of oors: +14, -2Total oor area: 17,005.29 m2Completion: Jul. 2006大阪弁護士会館の耐震要素の範囲梁Beams柱：φ=300mmColumnsCFT柱CFTcolumnsブレースBraces耐震要素Aseismicelements16.05m72.9m

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