Mar 11, 2022 08:58 PM
(This post was last modified: Mar 11, 2022 09:07 PM by C C.)
https://techxplore.com/news/2022-03-nature-wooden.html
INTRO: Concern about climate change has focused significant attention on the buildings sector, in particular on the extraction and processing of construction materials. The concrete and steel industries together are responsible for as much as 15 percent of global carbon dioxide emissions. In contrast, wood provides a natural form of carbon sequestration, so there's a move to use timber instead. Indeed, some countries are calling for public buildings to be made at least partly from timber, and large-scale timber buildings have been appearing around the world.
Observing those trends, Caitlin Mueller, an associate professor of architecture and of civil and environmental engineering in the Building Technology Program at MIT, sees an opportunity for further sustainability gains. As the timber industry seeks to produce wooden replacements for traditional concrete and steel elements, the focus is on harvesting the straight sections of trees. Irregular sections such as knots and forks are turned into pellets and burned, or ground up to make garden mulch, which will decompose within a few years; both approaches release the carbon trapped in the wood to the atmosphere.
For the past four years, Mueller and her Digital Structures research group have been developing a strategy for "upcycling" those waste materials by using them in construction—not as cladding or finishes aimed at improving appearance, but as structural components. "The greatest value you can give to a material is to give it a load-bearing role in a structure," she says. But when builders use virgin materials, those structural components are the most emissions-intensive parts of buildings due to their large volume of high-strength materials. Using upcycled materials in place of those high-carbon systems is therefore especially impactful in reducing emissions.
Mueller and her team focus on tree forks—that is, spots where the trunk or branch of a tree divides in two, forming a Y-shaped piece. In architectural drawings, there are many similar Y-shaped nodes where straight elements come together. In such cases, those units must be strong enough to support critical loads.
"Tree forks are naturally engineered structural connections that work as cantilevers in trees, which means that they have the potential to transfer force very efficiently thanks to their internal fiber structure," says Mueller. "If you take a tree fork and slice it down the middle, you see an unbelievable network of fibers that are intertwining to create these often three-dimensional load transfer points in a tree. We're starting to do the same thing using 3D printing, but we're nowhere near what nature does in terms of complex fiber orientation and geometry."
She and her team have developed a five-step "design-to-fabrication workflow" that combines natural structures such as tree forks with the digital and computational tools now used in architectural design. While there's long been a "craft" movement to use natural wood in railings and decorative features, the use of computational tools makes it possible to use wood in structural roles—without excessive cutting, which is costly and may compromise the natural geometry and internal grain structure of the wood.
Given the wide use of digital tools by today's architects, Mueller believes that her approach is "at least potentially scalable and potentially achievable within our industrialized materials processing systems." In addition, by combining tree forks with digital design tools, the novel approach can also support the trend among architects to explore new forms. "Many iconic buildings built in the past two decades have unexpected shapes," says Mueller. "Tree branches have a very specific geometry that sometimes lends itself to an irregular or nonstandard architectural form—driven not by some arbitrary algorithm but by the material itself." (MORE - details, the five steps)
We seem to have hit a timber construction ceiling ... https://youtu.be/p_8LlcuV0gc
https://www.youtube-nocookie.com/embed/p_8LlcuV0gc
INTRO: Concern about climate change has focused significant attention on the buildings sector, in particular on the extraction and processing of construction materials. The concrete and steel industries together are responsible for as much as 15 percent of global carbon dioxide emissions. In contrast, wood provides a natural form of carbon sequestration, so there's a move to use timber instead. Indeed, some countries are calling for public buildings to be made at least partly from timber, and large-scale timber buildings have been appearing around the world.
Observing those trends, Caitlin Mueller, an associate professor of architecture and of civil and environmental engineering in the Building Technology Program at MIT, sees an opportunity for further sustainability gains. As the timber industry seeks to produce wooden replacements for traditional concrete and steel elements, the focus is on harvesting the straight sections of trees. Irregular sections such as knots and forks are turned into pellets and burned, or ground up to make garden mulch, which will decompose within a few years; both approaches release the carbon trapped in the wood to the atmosphere.
For the past four years, Mueller and her Digital Structures research group have been developing a strategy for "upcycling" those waste materials by using them in construction—not as cladding or finishes aimed at improving appearance, but as structural components. "The greatest value you can give to a material is to give it a load-bearing role in a structure," she says. But when builders use virgin materials, those structural components are the most emissions-intensive parts of buildings due to their large volume of high-strength materials. Using upcycled materials in place of those high-carbon systems is therefore especially impactful in reducing emissions.
Mueller and her team focus on tree forks—that is, spots where the trunk or branch of a tree divides in two, forming a Y-shaped piece. In architectural drawings, there are many similar Y-shaped nodes where straight elements come together. In such cases, those units must be strong enough to support critical loads.
"Tree forks are naturally engineered structural connections that work as cantilevers in trees, which means that they have the potential to transfer force very efficiently thanks to their internal fiber structure," says Mueller. "If you take a tree fork and slice it down the middle, you see an unbelievable network of fibers that are intertwining to create these often three-dimensional load transfer points in a tree. We're starting to do the same thing using 3D printing, but we're nowhere near what nature does in terms of complex fiber orientation and geometry."
She and her team have developed a five-step "design-to-fabrication workflow" that combines natural structures such as tree forks with the digital and computational tools now used in architectural design. While there's long been a "craft" movement to use natural wood in railings and decorative features, the use of computational tools makes it possible to use wood in structural roles—without excessive cutting, which is costly and may compromise the natural geometry and internal grain structure of the wood.
Given the wide use of digital tools by today's architects, Mueller believes that her approach is "at least potentially scalable and potentially achievable within our industrialized materials processing systems." In addition, by combining tree forks with digital design tools, the novel approach can also support the trend among architects to explore new forms. "Many iconic buildings built in the past two decades have unexpected shapes," says Mueller. "Tree branches have a very specific geometry that sometimes lends itself to an irregular or nonstandard architectural form—driven not by some arbitrary algorithm but by the material itself." (MORE - details, the five steps)
We seem to have hit a timber construction ceiling ... https://youtu.be/p_8LlcuV0gc