A new research project led by Nathan Brown, assistant professor of architectural engineering at Penn State, is working to prove how designers could incorporate structural acoustic-optimized concrete slabs in building designs, cutting costs, reducing materials and decreasing the environmental footprint… without compromising areas like acoustics or structural properties.
“If we put innovative ‘optimized’ floor systems in buildings, we might save material and thus cut costs and reduce environmental impact. Yet, if we ignore things like the acoustics early in design, issues that pop up later, during or after construction, might have to be mitigated in a way that cancels out the benefits,” Brown explained. “Our research aims to allow architects and engineers to understand and develop floor designs that achieve all their goals upfront, while still reducing cost and helping the environment.”
Brown noted there has been a lot of interesting research lately on how to minimize the use of construction materials in buildings. Using less material in floors is a viable strategy for improving sustainability in buildings, as it can reduce the structure’s environmental footprint. Prioritizing only this goal, however, can lead to unwanted effects — such as an echo in a room or noise traveling between floors.
“Our research aims to allow architects and engineers to understand and develop floor designs that achieve all their goals upfront, while still reducing cost and helping the environment.”
“Around the world, concrete floor systems make up a large percentage of the material and subsequent embodied carbon that goes into buildings, and people are figuring out how to reduce that impact. Yet as we ‘carve away’ material from floors during design, there are potentially negative consequences we want to avoid, such as poor acoustics in multi-tenant buildings,” Brown said. “My research involves creating, testing and applying computational tools that help building designers manage trade-offs like this, so it was naturally something we wanted to study.”
To begin their investigation, Brown’s team used 3D modeling software to create shaped concrete slabs made up of many curves, connected by movable control points. By providing the program with parameters to follow when moving these points, the researchers allowed the software to generate a variety of possible designs with realistic, customized constraints. Brown and the other researchers then analyzed structural properties, for meeting building engineering standards and acoustic properties, for minimizing undesirable sounds.
“Basic physics dictates what makes a good floor shape. Stiffer, more massive shapes are better at blocking sound, while spreading out material to the top and the bottom of a structure’s cross section usually leads to a more materially-efficient shape. That’s why you often see I-beams in steel or deep beams in concrete,” Brown explained. “Our research concentrates on finding new shapes that range from heavier to lighter, depending on where exactly material needs to go based on performance requirements. The resulting optimal structures often involve curved floor undersides, which are difficult to build using traditional formwork, but are increasingly possible with digital fabrication.”
The study relied on design space exploration techniques such as sampling, multi-objective optimization and constrained optimization to find broad structural-acoustic trends, identify a Pareto front, and identify the best performing shaped slabs at varying acoustic performance levels.
Brown noted that the Penn State Department of Architectural Engineering provided financial and equipment resources to make this work happen. Brown and his team’s project involved constructing scale models of optimized floors for validation, which were fabricated with the help of a local contractor and are being tested in Penn State labs. The findings of the study were then published in the March edition of the Journal of Architectural Engineering by Brown; Micah Shepherd; a research associate in the Applied Research Laboratory and graduate program in acoustics at Penn State; and Jonathan Broyles, a student in the Penn State Department of Architectural Engineering.
“Penn State is a wonderful research community with expertise across many subjects.”
“Penn State is a wonderful research community with expertise across many subjects,” Brown said. “While I concentrate mostly on computational design methods for building structures, this work would not have been possible without Penn State collaborators with deep knowledge of acoustic behavior, including structural acoustician Micah Shepherd.”
The implications of this research study are limitless, as the desire to reduce the carbon footprint of buildings without compromising their acoustic properties or other structural properties continues to grow.
“During this project we realized that floors, or horizontal spanning structures more generally, do a lot beyond holding people up. They block sound, but they can also store energy, act as a radiator to affect thermal comfort in a space or serve as a thermal insulated barrier between [the] inside and outside,” Brown said. “We have begun looking at all of these potential tradeoffs together. Outside of floors, my group also considers how the structural design of buildings and building components might be affected by energy considerations, a desire for access to daylight and constructability.”
For more information on Nathan Brown and his research, visit https://www.bdg-psu.org/.