Ariake Gymnastics Centre in Tokyo boasts of the world’s largest spanning timber roof

The streamlined Ariake Gymnastics Centre, built for the recently concluded 2020 Tokyo Olympics and Paralympics Games, boasts of one of the largest timber-framed roofs in the world. Designed by Nikken Sekkei in collaboration with Shimizu Corporation, the structure spans 90 metres and is a triumph in the use of natural materials and sustainable design while reflecting the area’s history.

Located in Ariake, Koto Ward in Tokyo, Japan, the arena was conceived as “a wooden vessel floating in the Bay Area,” where generous use of 2,300 cubic metres of sustainably sourced timber plays an extensive role throughout the three-story building.

The project was conceived for dual functions, initially as a temporary international sports competition facility. Upon completion of the Games, spectator stands were removed, allowing its transformation into a permanent exhibition hall. The wooden roof beams that crown the structure are free of any steel framework, which enabled the creation of a large and open expanse, without any pillars, in the venue’s centre.

“This is a positive realization of ‘wooded facilities’ and ‘sustainability as announced in the (project’s) candidacy file,” the contributing Japanese architects share. The venue is also an effective exercise in showcasing traditional Japanese craftsmanship, embodying aspects of Japan’s timber-based construction culture.

When the prior Tokyo Olympic and Paralympic Games were held in 1964, Japan’s economy was in rapid growth mode, and the last of Japan’s premier sports facilities were built with concrete and steel. This time, as a modern equivalent to that legacy, the designers opted to make the most of wood, whose utilisation perhaps best protects the environment. The use of timber also serves as a memorial to the site’s heritage as a timber storage pond. Timber is used in the roof structure, facades, spectator seats, exterior walls and elsewhere - all with careful consideration for the characteristics of the material. The designers note that each unit of timber is certified material from domestically planted and sustainably managed forests.

A gently sloping entrance path along the canal guides visitors to the 12,000-seat Centre, with the imperceptibly arching roof in eyesight. The surface of the walkway slope is covered with water-retentive wooden chips that reduce air temperature through evaporative cooling. Deep timber eaves, with their rich, sculpted contours, usher entrance to the structure. A feeling of warm weightlessness envelopes visitors upon entering the arena, surrounding them with the comforting hue of wood. The huge ceiling’s timber frame looms protectively above, while timber benches stretch leisurely below.

The wood-framed ceiling is designed specifically to reduce the weight of the overall structure, while the timber dressed facade sports acoustic and thermal insulation properties. A corrugated steel roof shelters the structure, outlining the trapezoidal volume of the timber beams underneath to create the Centre’s characteristic shape. Larch wood from Nagano and Hokkaido Prefectures was used in the roof, cedar from Mie Prefecture was used in the benches, and cedar from Shizuoka, Miyazaki and Akita Prefectures were deployed in the eaves.

Achieving beauty and richness in simplicity

Evocative of a Japanese-style engawa (veranda), the expansive concourse space has been intentionally placed in an outdoor setting to generate seamless dialogue with the bayside. Outside positioning of the concourse avoids the impenetrable exterior typically found on large-scale sports facilities that are characterized by monolithic walls. "(The concourse) evokes the age-old traditions of Japanese wooden architecture, and…brings a welcome breeze from across the canal,” says Hidemichi Takahashi, lead architect, Nikken Sekkei.

The project stretches in the middle of a wide-open canal-side landscape, mindful of a nearby residential area full of condominiums. The maximum height was kept low to avoid an overbearing silhouette. It is Japan’s first complex structural system using timber beam strings structure and cantilever trusses to create the large spanning wood frame. Designers employed low-profile large glued laminated timber with high heat capacity to achieve both fire resistance and structural stability.

Wood is weaker than steel per cross-section area, yet stronger in compression strength-to-weight, making wood appropriate for a roof structure whose critical load is its own weight, the Nikken team explains. They share that one of the typical long-span structures using compression strength is the arch, which typically needs a bulky profile with a high rise. So, they contrived a complex structure with steel cables to cancel the thrust that occurs in low-rise timber arch beams without steel frames, allowing for a streamlined profile that blends in with the surrounding Tokyo Bay area.

The Ariake Gymnastics Centre hosted Olympic artistic, rhythmic and trampoline gymnastic events, as well as Paralympic boccia. The main arena space achieved a clear span of 88.8m x 117.6m. The arching profile of the roof was also designed to efficiently and effectively clear smoke in case of fire.

“Function, structure, and space are tightly combined to achieve beauty and richness in simplicity, which is the essence of Japanese traditional wood architecture that we hope spectators and athletes from all over the world appreciated,” according to Nikken Sekkei.

Be better, together - for the planet and the people, the underlying sustainability concept of the Tokyo 2020 Olympics, was realised in full capacity and vigour with the Ariake Gymnastics Centre. In addition to other features and facets of the Games, it delivered powerful green solutions that respond head-on to global challenges of practical sustainability.

Project Details

Name: Ariake Gymnastics Centre
Location: Ariake, Koto-ku, Tokyo Japan
Total Floor Area: 39,194.30 square meters
Client: The Tokyo Organising Committee of the Olympic and Paralympic Games
Schematic design/ Design development review/ Construction supervision: Nikken Sekkei Ltd.
Developed design: Shimizu Corporation, Masao Saito (engineering adviser)
Construction period: November 13, 2017 - October 31, 2019
Construction: Shimizu Corporation