Utilizing Ultrasound to Map and Sustain Existing Structures with Thomas Schumacher

On this episode of PDXPLORES, Thomas Schumacher, Associate Professor of Civil & Environmental Engineering at the Maseeh College of Engineering & Computer Science, discusses employing emerging non-destructive evaluation (NDE) scanning technology to thoroughly map existing structures, from the pyramids in Giza, to bridges in and around Portland. With an eye towards sustainability and environmental conservation, Schumacher sees NDE tools as further aiding in civil infrastructure preservation efforts.

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Transcript

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Welcome to PDXPLORES, a Portland State research podcast featuring scholarship, innovations, and discoveries pushing the boundaries of knowledge, practice, and what is possible for the benefit of our communities and the world. My name is Thomas Schumacher, and I'm an associate professor of structural engineering, and I work in the Department of Civil and Environmental Engineering at Portland State University. If you look around, you'll find that we have built a lot of structures. We live in buildings, we drive on roads and bridges, we use systems that provide us with power, water, and other services, and we have significantly changed and landscaped the natural environment. Structural engineers play a crucial role in designing and maintaining structures, so that they serve their intended purpose and are safe to use by people. These structures represent tremendous investments and play a key role in making our economy function. Once built, we are responsible for making sure we maintain them in a cost effective way, avoiding replacement whenever possible. In my research group, we develop non destructive testing and monitoring tools, also referred to as non destructive evaluation, or NDE tools, that can provide us with information about the health and condition of structures, like buildings and bridges, and how these might change over time. In my group, we are focused on concrete structures. This information helps owners make optimal decisions on how to maintain their structures. I grew up in rural Switzerland and was always tinkering with stuff and building things, mostly following my dad around on the farm. I believe this was the reason for me not only to become interested in structural engineering, but years later also to get into research. While I personally have been fascinated and excited about structural engineering, I do see a general lack of understanding and appreciation of our critical contribution to society. I think this is something we need to work on as a group. Broadly speaking, non destructive evaluation, or NDE, allows measuring properties of structures and the materials they are made of in a way that does not change their integrity. What this means is that after the application of an NDE tool, the structure is still able to serve its original intended function, as well as its strength is not compromised. No harm is done. NDE tools are actually a family of tools that can help determine the properties of materials, such as stiffness and strength, detect defects inside them, such as cracking or corrosion, and document changes of these entities over time. They can be applied on a small scale to characterize defects in a structural member or monitor the deformation of entire structures. The latest tool that we have been working on in my group is imaging using ultrasound. My group aims to work closely with owners responsible for maintaining structures to make NDE tools practical and useful for decision making. NDE is a multidisciplinary field that requires expertise in sensors, data collection, data processing and analysis, and materials and structural engineering. Most of the tools and techniques we use were originally developed to study the makeup of the Earth. The field of geophysics. They were then adapted for medical applications and material characterization. The tool that we have adapted from the medical field for application to concrete structures is imaging using ultrasound waves. Like a doctor scanning a person's body to look for anomalies, we use ultrasound scanners to see into concrete. The scanners, which are commercially available, do look quite a bit different in that they are larger and use fewer transducers or sensors. Even though we are still lagging the medical field, we are now able to create useful images of the interior of concrete, revealing locations of reinforcing steel as well as air voids which might be there intentionally or not. Our work has focused on improving the processing and analysis of the measurements from ultrasound scanners and how to create images useful for an engineer or inspector. We have received funding from a wide range of agencies over the years, including the National Science Foundation, the Federal Highway Administration, local departments of transportation, and industry funded non-profits. A joint seed grant between Portland State University and the Oregon Health and Science University got us started on the research on medical imaging and image fusion for concrete structures. Image fusion is used to combine images based on ultrasound and radar, and potentially other measurements, with the goal to capitalize on the strength of each method. We first applied imaging and image fusion to concrete. Based on a scientific article we published about this work, I got invited to join the Scanned Pyramids team. It didn't take me very long to think about whether I would accept this assignment, which to me was the opportunity of a lifetime. The expertise that they were looking for is combining different NDE measurements. So I became the image fusion guy on the team. I was also involved in taking ultrasound measurements using the same scanner that we have in our group. Some of the data collection was challenging because the surface of the 4,500 year old pyramids has not been spared of aging. Also, the fact that the structure is made up of blocks makes studying ultrasound more difficult, because the waves bounce off the surfaces of the individual blocks. Using computer simulations, though, it was possible to explain many of the features and artifacts we found. In the end, we were able to confirm the existence of a hidden corridor, which made global news on March 2nd of this year. So a major benefit of having an image is that it is an actual visual representation of the interior of a structure. It makes what's hidden visible. Just like when you look at a fetus using pregnancy ultrasound. While I see many opportunities for improvements, we are already able to provide very useful information. For example, I recently scanned an existing local pre-stressed concrete bridge for which the original drawings were unavailable. But even if plans are available, it is not always given that a structure was exactly built according to plans. Or that, for example, reinforcing bars were placed where they were supposed to. As such, imaging can help confirm drawings of existing structures. I'm hoping to connect more to our local transportation agencies and support their needs in preserving their concrete bridge inventory. I believe that NDE more broadly could play a vital role in making sure that we only replace a structure when we absolutely must. There have been instances where decisions to replace a structure were made based on theoretical computer models that predicted a structure was not adequate anymore. NDE can provide the necessary information to make computer models more accurate, in many cases showing that a structure might need some repair, but is still able to fulfill its function safely. I believe preservation is at the heart of sustainability. If we don't have to replace and rebuild a structure, then we can save all those resources and avoid emitting the associated CO2 along with it. Optimal structural preservation does not only save taxpayer money, but it is also the only way forward if we want to be serious about sustainability, which we should. We are in the final stages of launching a new master's level focus area of infrastructure engineering and preservation. We see this as a pressing need in both the private as well as the public sector. Our current graduate focus area, Structural Engineering, is almost entirely about how to design new structures Leaving graduates with little expertise to deal with what already exists. I am personally very excited to launch this new focus area and see it as a great fit for PSU's reputation and sustainability. My name is Thomas Schumacher, and as a structural engineering researcher and educator at PSU, I'm passionate about developing practical NDE tools that will help in the preservation of structures and promote sustainable society. Thank you for listening to PDXPLORES. If you liked what you heard on this episode, please rate and follow podcasts.