Low-carbon construction

One big contributor to global warming is the “embodied carbon” in construction material, encompassing emissions from the fuel used in producing and transporting the material and turning it into a building. Now researchers at MIT have created a set of computational tools that could help architects and engineers minimize those effects.

The researchers focused on truss structures—those crisscross arrays of diagonal struts used in everything from antenna towers to support beams. These are typically made of steel, wood, or a combination, but little quantitative research had been done on which material would minimize the structures’ embodied carbon while maintaining the properties a building needs. 

The new system makes use of a technique called topology optimization, which can produce designs optimized for different characteristics given parameters such as the dimensions of the structure and the load to be supported.

In general, wood produces a much smaller carbon footprint than steel and performs very well under forces of compression, but steel performs much better when it comes to tension. From an emissions standpoint, “if you have a structure that doesn’t have any tension, then you should definitely only use timber,” says Josephine Carstensen, an assistant professor of civil and environmental engineering and coauthor of a paper on the research. Steel could then be saved for applications where its properties provide maximum benefit.

In a proposal they developed for reengineering several trusses, the researchers showed that savings of at least 10% in embodied emissions could be achieved with no loss of performance. 

“It’s about choosing materials more smartly,” Carstensen says. The results could encourage what she sees as a positive trend toward increasing use of timber in large construction projects.