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Construction Begun on Japan’s First Fire-Resistant Wood Office Building: “Osaka Mokuzai Nakagai Kaikan”

— “Osaka Mokuzai Nakagai Kaikan” changed to a one-hour fire-resistant wood structure office—

July 3, 2012Takenaka Corporation

Takenaka Corporation (President: Toichi Takenaka) has developed “Moen-Wood®,”a fire-resistant laminated lumber for use in the columns and beams of wooden structures, to enable nine-meter spatial spans (the length between columns), the same as with RC structures. This new material is being used in the second and third floor frames (columns and beams) of the “Osaka Mokuzai Nakagai Kaikan” building (Nishi-ku, Osaka), which is a large wooden office building with a total floor space of over 1,000 square meters. Construction of this building began on July 2 this year, and it is expected to be completed in March 2013.

Because “Moen-Wood®”is certified by the Minister of Land, Infrastructure, Transport and Tourism as a one-hour fire-resistant member, a four-floor fire-resistant wood building, or a fire-resistant building with a wooden section of four floors from the top floor to the fourth floor down can be constructed with an ordinary building certification application. Also, to secure “safety and ease of mind” for the client during a large earthquake, the structural planning of this project calls for the use of earthquake-resistant RC walls as aseismic members. Takenaka plans to continue to contribute to the spread and development of large wooden structures in the future in line with the national government’s promotion of more wooden public buildings.

  • Exterior perspective of Osaka Mokuzai Nakagai Kaikan

  • Entrance perspective of Osaka Mokuzai Nakagai Kaikan

Background of the wooden structure market

The “Act for Promotion of Use of Wood in Public Buildings” (which came into effect in October 2010) calls for the promotion of the creation of living environments making use of domestic forest resources which are gentle on people. Presently, the national government is taking the initiative and focusing on increasing the use of wood in public buildings, where use is very low (total floor space of only 7.5 percent as of 2008), and is also proactively promoting use by local governments and private companies, aiming to largely increase overall demand for wood, including ripple effects on the housing and general construction markets.

“Moen-Wood®”will contribute to the spread and development of the construction of large wooden public structures such as schools and hospitals in fire prevention districts, where planning has been difficult up to now because of fireproof and fire-resistant regulations. The use of the product in commercial facilities and large offices in the fire prevention districts will contribute to providing living environments which are gentle on people, the development of the construction and forestry industries, and the conservation of the natural environment.

Using “Moen-Wood®”to realize larger spans

The “Act for Promotion of Use of Wood in Public Buildings” (which came into effect in October 2010) calls for the promotion of the creation of living environments making use of domestic forest resources which are gentle on people. Presently, the national government is taking the initiative and focusing on increasing the use of wood in public buildings, where use is very low (total floor space of only 7.5 percent as of 2008), and is also proactively promoting use by local governments and private companies, aiming to largely increase overall demand for wood, including ripple effects on the housing and general construction markets.

In 2009, Takenaka constructed the New Fire-Resistant Laboratory, the highest-performance facility of its type in Japan (load capacity of thirty meganewtons (MN) over eight hours of heating). Fire-resistant performance can be evaluated using actual-size members, opening up new opportunities for “Moen-Wood®.”

Aid received from the New Energy and Industrial Technology Development Organization and the Ministry of Land, Infrastructure, Transport and Tourism.

How “Moen-Wood®” secures fire-resistance performance

“Moen-Wood®”is a fire-resistant member, consisting of a “load support part,” which is laminated lumber (layered lamina fixed together using adhesive), a “burn stop layer,” and a “substitute burn layer” on the outside.
Larch is used in the “substitute burn layer.” Should a fire break out, the “substitute burn layer” becomes a high-performance fire-resistant char layer, inhibiting burn progression. Mortar and larch are set out alternately in the “substitute burn layer,” so the mortar absorbs the heat, stopping the burning and thereby safely protecting the “load support part” from the fire.

  • Cross-section 1 of a “Moen-Wood” column

  • Cross-section 2 of a “Moen-Wood” column

Outline of the “Osaka Mokuzai Nakagai Kaikan” building

The planning of the new “Osaka Mokuzai Nakagai Kaikan” building began with the concept of pursuing design possibilities, making the most of wood features, with the aim of promoting the use of wood and the spread of large wooden buildings. It is hoped that this building will play the part of a model for the spread of wooden buildings in the Kansai region, and contribute to the promotion of the construction of wooden buildings and the use of more wood both in the public and private sectors.

As a large-scale building made of wood, or using wood, and implementing leading design and construction technology, this project has been accepted as “work promoting wood urban redevelopment” as defined by the Ministry of Land, Infrastructure, Transport and Tourism. As such, aid is available for the construction and design costs.