In 2022, global production of construction materials accounted for over 7% of total carbon emissions. But how many of those materials were truly necessary for building houses, buildings, and bridges? A technique called topology optimization can design structures that reduce material usage by as much as 90%, representing a multi-gigaton reduction in building emissions.
Unfortunately, topology optimization is mostly used by researchers for applications like 3D printing, rather than by engineers designing at the scale of buildings and bridges. This is because topology optimization doesn’t create structures that can easily be built on time and budget, which are the primary concerns for builders. MIT researchers have developed a way to make topology optimization designs more buildable. Their framework, described in a new paper in Automation in Construction, allows users to apply constraints to algorithmically generated structures to limit their complexity.
For instance, the approach allows users to limit how many components meet at each design point and how small they want their smallest parts. It also builds on previous work by designing structures with multiple materials and taking into account the properties of those materials to distribute load and specify part connections. "There's an interplay between the materials you're using, the constructability of designs, and the optimization of the structure," says senior author Josephine Carstensen.
The researchers used their approach to design steel, wood, and multimaterial truss structures that support loads in buildings and bridges, showing that carbon emissions associated with materials changed significantly when different constraints were applied. They hope their framework will move topology optimization closer to real-world construction.
In literature, there’s sometimes been a disconnect between the carbon savings achievable on a computer and those for built structures—especially regarding design technologies like topology optimization. The problem lies in the lack of constructability of designs, which are often perceived as too difficult to make with conventional methods. The exciting aspect of this approach is that it allows for constraints, ensuring the resulting designs are feasible to construct.
The researchers compared structures designed with their method to those designed with conventional topology optimization, showing dramatic differences in final designs. Using the Lockport “Upside-Down Bridge” near Buffalo, New York, they applied individual constraints to understand how each constraint impacted final designs.
They plan to build scaled-down structures designed by the model to further validate its predictions and want to add constraints to make it easier for civil engineers to use in designing infrastructure. "As a structural engineer, I was never taught how to design for low-carbon," Schemmer says. Addressing the built environment is a crucial step in tackling climate change, as many early decisions lead to unnecessary material use.
Blogger's Review: This study not only advances the theoretical application of topology optimization but also enhances its practicality in the construction industry through the introduction of actual buildability constraints. As sustainable development becomes increasingly important, effectively leveraging materials to reduce carbon emissions will be a key factor in future architectural design.