Can timber replace steel & concrete as building material?

Can timber replace steel & concrete as building material?

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Created from prefabricated timber panels, the 220,000-square-foot building’s structural system was quickly pieced together like LEGO blocks on-site at a speed far exceeding conventional steel-framed and concrete buildings. This building demonstrated that timber can be used for multi-storied structures also and structure can be built much faster than conventional methods

T3 in Minneapolis is perhaps a gamechanger for the commercial building industry and a milestone for mass timber construction in the United States. According to Michael Green Architecture, the architect agency who helped to create T3, it is the first modern timber building to be built in the United States in more than 100 years, and at the time of completion (Sept 2016) the largest in North America. “It celebrates the robust character of historic wood, brick, stone and steel buildings, but provides state of the art amenities, environmental performance, and technical capability needed for competitive businesses in Minneapolis,” says to Michael Green Architecture. Created from prefabricated timber panels, the 220,000-square-foot building’s structural system was quickly pieced together like LEGO blocks on-site at a speed far exceeding conventional steel-framed and concrete buildings. This building demonstrated that timber can be used for multi-storied structures also and structure can be built much faster than conventional methods. 

This project will soon be dwarfed by many other projects announced in Americas and other places. For example, Michael Green Architecture is planning to break its own record by designing USA’s largest timber building in New Jersey. The project, announced a year ago,  will be developed by New York based developer Lotus Equity Group. The project will  be completed in 20 months from the date of signing the agreement.

World’s tallest hybrid timber building will come up in Vancouver, Canada. The renowned Japanese architect Shigeru Ban will design the building for Vancouver-based developer PortLiving. Incidentally, the world’s current tallest timber building, Brock Commons, is also located in Vancouver. The hybrid timber tower designed by Ban is expected to reach 71 metres at its tip. The building will comprise an outer frame of timber and glass top, paired with a concrete and steel core. The building, Shigeru Ban’s first in Canada, is set for completion in 2020.

Sumitomo Forestry Co. Ltd. on its 70th anniversary last year had announced that the company is preparing the concept W350 Plan for creating a 350-meter-tall wooden high-rise building in 2041, which will mark the 350th year since foundation of the business in 1691. The aim is to create an environmentally-friendly and timber-utilizing cities where they become forests through increased use of wooden architecture for high-rise buildings. This concept plan has been prepared primarily at Tsukuba Research Institute, Sumitomo Forestry’s research and development facility. The institute is expanding possibilities for wooden buildings as a roadmap for future technology such as the development of building methods, environmentally-friendly technologies, and trees that become resources and building materials.

The planned structure is a hybrid wood and steel structure made from 90% wooden materials. It will use a braced tube structure in which steel frame vibration control braces (diagonal braces) are positioned inside a column and beam structure, made from a combination of wood and steel. 

Advantages

Timber as a building material has certain a advantages over conventional materials like concrete and steel. “The timber cores will also adopt low-damage seismic design technologies, so that during major earthquakes, damage to the buildings is minimal and occupancy is restored quickly, meaning minimal repair cost and downtime,” says Justin Brown, an engineering doctoral candidate at University of Canterbury (UC). According to him the emergence of engineered wood products has started a renaissance for using timber as a key construction material in mid- to-high-rise buildings. Its less weight vis-a-vis steel while not sacrificing the strength ensures that less pressure in put on foundation during earthquakes.

He further says “We’re seeing a lot of hybrid concrete-timber and steel-timber buildings that still rely on concrete or steel cores to resist seismic forces. I’m exploring whether that part of the building could be replaced with a timber solution and to what height this is practicable and economical.”

Compared with traditionally built mid- to high-rise buildings, all-timber solutions also have a lower environmental impact. Brown is confident that a timber core can be structurally sound and cost competitive, compared with commonly used concrete cores.  The timber cores will also adopt low-damage seismic design technologies, so that during major earthquakes, damage to the buildings is minimal and occupancy is restored quickly, meaning minimal repair cost and downtime. However, currently, there are no design tools and minimal research available to help engineers design timber cores. 

There are many other advantages too.  Timber has natural insulating properties which enhances its thermal performance. As large wooden slabs burn on the outside and while doing so protect the inner structure from burning. Thus, timber provides fire safety much better than other building materials.

Unlike steel and concrete, timber is a natural renewable material that is grown quicker than used. This sustainability factor helps to score Green points as well. In addition, timber is often used close to where it was originally produced, which helps to promote local economies and reduce the effect of long-distance transportation. 

Disadvantages

However, there are certain disadvantages of timber too which often create hurdles in timber becoming the universal building material. For example, it has poor insulation properties as compared to other building materials and this weakness may make it unsuitable as building material in noisy surroundings. Further, when the timber has high moisture content there is very risk of rotting and thus weakening the structure. 

Building codes

Despite these weaknesses of timber, its utility as building material is being recognised by many. Oregon has amended its building code to permit taller buildings made from timber and thus becoming the first U.S. state to do so. Canada’s National Research Council is working on changes to its 2020 building code to allow mass timber construction up to 12 stories. International Code Council (ICC) has plans to make changes to ICC building code models which will allow structures made of mass timber to be built as high as 18 stories, up from the previous limit of six. Thus, things are changing for timber as building material.  

Situation in India

Timber was the traditional building material in India and even today we can see multi-storied buildings with wooden flooring and staircases. Wood was also used as beams before concrete and steel made inroads into construction. However, wood lost its sheen over the years mainly due to non-availability of quality material and today it is rarely used as building material.  Even if timber as building material gains universal acceptability, in India it may not find favour mainly because of its non-availability. 

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