Mixing steel and wood to reduce construction emissions

A new computational tool developed by researchers at the Massachusetts Institute of Technology could allow architects and engineers to reduce the carbon footprint of buildings and bridges. The tool helps designers select the best materials that reduce carbon emissions from trusses, those cross-beam and truss structures used to construct bridges, antenna towers and buildings.

Civil and Environmental Engineering Professor Josephine Carstensen, who led the new work published in engineering structures.

Buildings are responsible for 40 percent of global carbon emissions, some of the largest energy consumers In the world. This is partly due to the energy-dense materials used in modern construction, such as Builds and steel.

Efforts to reduce the carbon footprint of buildings have mainly focused on Reduce energy consumption. While there are a few nascent efforts to decarbonize cement and steel industryand made large wooden structuresthere has not been much progress on a large scale in reducing The environmental impact of building materials. A new computational tool developed by Carstensen and colleagues could help counter this effect.

The researchers focused on gables, which are usually made of wood, steel, or a combination of both. These materials contain internal carbon emissions that come from the way they are produced. Mining and smelting steel, for example, requires a huge amount of fuel. Production per ton of steel versions About 1.85 tons of carbon dioxide On average, it results in about 8 percent of global carbon emissions.

Wood also contains some carbon embodied from the fuel used to cut and process trees. But the carbon footprint is generally smaller than that of steel. The compromise is that it does not have the best properties of trusses in some applications. For example, it is excellent in resisting compressive forces, but not like steel when it comes to the tension forces that separate materials apart. It is also heavier.

Choosing the correct combination of the two materials for the truss design will provide optimum performance while generating lower carbon emissions. MIT researchers have come up with an algorithm that helps designers do just that.

Designers will enter factors such as the load that the structure must bear, the cross-sectional area and the physical composition of each truss element. The algorithm takes these variables into account and calculates the best truss design made from a combination of glue-coated timber and steel elements to reduce the global warming potential of the structure.

To illustrate the tool, the researchers used it to re-engineer different trusses. New designs reduce emissions by at least 10 percent. Carstensen says the tool can help save double to three times that amount. “It’s about choosing materials smarter.”

source: Ernst Cheng, Josephine F. Carstensen. Optimizing the truss topology of wood and steel structures to reduce the embodied carbon design. engineering structures2021.

picture: flickr

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