The goal of "sustainability" is to reduce humans' impact on the natural environment. These impacts often take the form of facilities and structures such as bridges, highways, and cities that are built and used on an everyday basis.
Oral Buyukozturk, an MIT professor of civil and environmental engineering, looks to develop scientific knowledge and technology to improve this dynamic. Through his Laboratory for Infrastructure Science and Sustainability (LISS), he focuses his research on three areas: durable materials and resilient structures, sensor systems, and energy-efficient buildings. “We can decrease the environmental footprint of the materials and construction methods, and also design and maintain structures so that they have a long lifespan and are more resilient to environmental and in-service deterioration. This is the central aspect of our work.”
Improving the ingredients
Buildings and infrastructure consume a significant amount of natural resources, providing an ongoing challenge for sustainability. Concrete is second only to water as the most consumed material in the world. Its components include aggregate, sand, and Portland cement, a synthetic powder that reacts with water to provide cohesive strength, but it is also a major contributor to global carbon emissions because of the energy requirements for extraction and production, says Buyukozturk. He adds that the environmental impact of these processes is becoming even more significant with the rapid urbanization of the developed world: Concrete consumption has increased roughly from 1 billion to 4 billion metric tons per year during the past 25 years.
A low-cost and high-impact method for improving concrete is to substitute locally available additives for Portland cement. The alternatives could be natural resources such as volcanic ash, or industrial sources such as blast furnace slag, Buyukozturk says. Performance wouldn’t be lost, and certain environmental benefits would be gained. One example is that volcanic ash would help reduce embodied energy — that which is used to manufacture a material — and reduce the overall carbon footprint when cities and neighborhood utilize new materials.
One challenge is optimizing the mix designs for a wide range of potential additives. Buyukozturk says his research group is developing computer models of cement paste for connecting nano- and microscale composition and structure with macroscale engineering properties. These models are informed with experimental characteristics regarding the chemical composition, morphology, and porosity, and take a bottom-up design methodology widely utilized by nature, where biological materials form hierarchical structures through the assembly of smaller building blocks. “Adopting a similar bio-inspired framework for cement-based materials facilitates the design of novel cement-based materials incorporating local additives for tailored sustainable and durable applications,” Buyukozturk says.
Monitoring the buildings
More than improving materials, Buyukozturk looks to improve building performance by understanding their vibrational behavior. To that end, he leads a group that works to develop advanced technologies of sensing and data analytics. “Civil structural systems deteriorate over time due to effects of material aging and hazards, such as earthquakes. We want to make a structure intelligent to ‘feel’ its own health condition through a smart monitoring system,” Buyukozturk says.
The first step is to instrument a structure with vibration sensors, which formulate an embedded “nervous system” to record a building’s motions and responses. By monitoring and processing this response, damage within the structure can be detected at an early stage, which helps to reduce the total repair cost and improve the structural service life, Buyukozturk says.
In one research project, Buyukozturk has been experimenting with monitoring technology on MIT’s Green Building, the tallest building in Cambridge, Massachusetts. To track characteristics and locate possible damage or disturbances, intrinsic vibrational waves propagating in the building are continuously extracted. This monitoring technique is also being tested on the Al-Hamra Tower (412.5 m) in Kuwait City, the world’s tallest concrete sculptured building, which is part of a large-scale project led by Buyukozturk. “Extending such a monitoring system to the city scale is also possible if the technology becomes standardized,” he says. “This would bring benefits to the process of developing smart cities.”
Innovation in vibration monitoring
Traditionally, vibration sensors need to be directly attached to the structure to measure its motions. Another one of Buyukozturk’s research teams is working on methodology that uses cameras for quick structural assessment and quality control.
The algorithm called Motion Magnification, developed by researchers in MIT’s Computer Science and Artificial Intelligence Laboratory, analyzes video for subtle motions of seemingly still objects and exaggerates them to make videos that clearly show the motion. It acts like a microscope, Buyukozturk says, magnifying movements that would otherwise be too fast or too small for the naked eye to see.
In one scenario, a bridge could be measured directly from the video and quantitatively used for vibration analysis for condition assessment. The process would also work for quality control in something like pipes. “The exciting thing is the upside. The potential exists to use a cell phone camera for screening and couple that with a high-powered camera for more in-depth detection. This is a potentially game-changing capability that we hope will be widely applicable to buildings, machinery, and other forms of civil infrastructure,” he says.
Hearing many voices
Buyukozturk says that taking an interdisciplinary approach is a necessary element with all of his work. This approach marks two of his biggest ventures: the MIT-Kuwait Sustainability Project, which involves the Al-Hamra Tower and is funded by the Kuwait Foundation for Advancement of Science through the Kuwait-MIT’s Center for Natural Resources and the Environment; and the Beeview Motion Sensing Project, funded by Shell Global through the MIT Energy Initiative. They both deal with his work on handling natural resources and designing motion detection systems, and, with both, he’s integrated PhD students and undergraduates from a variety of disciplines, such as computer science and artificial intelligence, chemical engineering, earth and planetary sciences, material science and engineering, mechanical engineering, and architecture.
On one level, having different perspectives improves existing ideas, creates new ones, and makes them more practical and market-ready, through the ensuing debate and collaboration, Buyukozturk says. But it’s also required for the nature of the built environment. It’s a field that’s marked by continual change. Systems are becoming increasingly complex and aspirations always rise. “As the population grows, the need for housing will as well. Buildings will become taller and taller, and the energy and material demands will increase. We can meet that challenge, but it takes cooperation between a variety of expertise,” he says. “When that happens, the results are extraordinary.”