A panel of experts presented on innovative technological developments and capabilities that enable community resilience. Speakers addressed the vision for built infrastructure in resilient communities for the future. How can new technologies, such as autonomous and adaptive infrastructure and cyber-physical systems, be applied to benefit society? What types of “out-of-the-box” thinking is currently underway? Seymour M.J. Spence, assistant professor at the University of Michigan, served as moderator for the session. Speakers included Jerome Lynch, Donald Malloure Department Chair of Civil Environmental Engineering at the University of Michigan; Daniel Hiller and Alexander Stolz, head of Strategic Management and head of the Department of Protective Structures and Security Technologies, respectively, at Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach Institute EMI, Germany; Maria Feng, Renwick Professor of Civil Engineering at Columbia University; Robert D. Moser, senior research civil engineer in the Engineering Systems and Materials Division—Research Group, Geotechnical and Structures Laboratory, U.S. Army Engineer Research and Development Center (ERDC); and Oral Buyukozturk, professor of civil and environmental engineering and director of the Laboratory for Infrastructure Science and Sustainability at the Massachusetts Institute of Technology (MIT).
Jerome Lynch highlighted the potential and promise of future technologies to deliver community resilience through Cyber-Physical Systems (CPS), an integrated approach that includes sensing, computing, and actuating technologies. Lynch pointed to the increase in large-scale natural disasters, including tropical storms, floods, and earthquakes, such as the 2017 Puebla earthquake in Mexico and the 2011 Tohoku earthquake in Japan, as motivation for his work. He noted that natural hazards are not the only factors that affect community resilience. Climate change, urbanization, aging infrastructure, and extreme poverty also pose major challenges to communities.
Lynch said that the basic definition of resilience has been “the capacity to recover quickly.” When engineers think in terms of resilience, they typically consider technology’s ability to rehabilitate the performance of a component or system as a function of time with respect to a large-scale stressor or disruptive event. Lynch suggested that the opportunity for technology to impact community resilience is better illustrated by the expanded definition of his
colleague, Mohammed Ettouney, chairman of the Objective Resilience Committee at the Engineering Mechanics Institute. Ettouney’s definition includes four properties, four dimensions, and three results. The four properties of resilience include robustness, rapidity, redundancy, and resourcefulness. The four dimensions of resilience are the technical, organizational, social, and economic, and the results of resilience are increased reliability, faster recovery, and reduced consequences (Figure 4-1).1
Emergent technologies can directly impact different dimensions or properties within this framework, said Lynch, including the growth of computing power, increased access to communication interfaces empowered by wireless communications, increased sensing technology, and the interconnectivity enabled by the internet. At the confluence of these trends is
1 For more information about different measures of resilience, see: Bruneau, M., S. E. Chang, R.T. Eguchi, G.C. Lee, T.D. O’Rourke, A.M. Reinhorn, M. Shinozuka, K. Tierney, W.A. Wallace, and D. von Winterfeldti. 2003. A Framework to Quantitatively Assess and Enhance the Seismic Resilience of Communities. Earthquake Spectra. 19(4).
a new area of development in the field of infrastructure, known as Cyber-Physical Systems (CPS).
CPS includes physical infrastructure systems and the sensors and actuators that monitor and control those systems. Lynch explained that CPS is differentiated from classical monitoring and control systems by a direct interface to computing resources, often through the internet. Early earthquake warning systems, intelligent transportation systems, and smart grids are examples of CPS. To illustrate how CPS is impacting community resilience, Lynch explained three different projects.
The first project is developing a smart high rate corridor along Highway 1275, the main artery between Toledo, Ohio and the metropolitan area of Detroit, Michigan. The purpose of this project is to monitor trucks to assess economic utilization, assess bridge and pavement health, and control truck loads to minimize their impact on infrastructure. Data is collected with wireless sensing, cameras, computer vision, and weigh-in-motion systems. The use of cloud-based data analytics allows the data to be stored, and then exposed to a host of analytic platforms in a secure and scalable way. To execute this work, four bridges were outfitted with monitoring systems (Figure 4-2).
Cameras placed throughout the corridor identify and track trucks; computer vision of the self-identified truck then triggers the monitoring system. Finally, when the truck drives through the weigh-in stations, a direct, quantitative measure of the load is captured. According to Lynch, this type of system is a game changer for infrastructure health monitoring. Ultimately, the team is able to perform real-time analytics with the data and address questions about the robustness of the infrastructure—a key parameter of resiliency.
As a next step, Lynch and his colleagues aim to go beyond the ability to trigger CPS to explore ways to control trucks via connected vehicle technologies. Research in this area is conducted in collaboration with Gabor Orosz, an expert in connected vehicle technology with the University of Michigan’s mechanical engineering department. Testing is performed in a 17-acre environment at the University of Michigan, designated exclusively for connective and autonomous vehicle technology. Connected vehicle devices used for this research control steering, braking, and acceleration functions in order to self-drive vehicles. Specifically, Lynch referenced a fully autonomous Kia Soul developed within this program, which avoids collision by attempting to detect other vehicles in its path. This technology could be used to improve motorist safety.
Lynch stated that the autonomous vehicle technology and the ability to pair infrastructure response data with quantitative measurements directly impact two of the four properties of resilience. The autonomous capability improves response rapidity to disasters, and the ability to assess the properties of a structure with quantitative data enhances infrastructure robustness. According to Lynch, these capabilities also impact the technical, social, and economic dimensions of resilience.
A second project focused on improving the resilience within watersheds using Green Infrastructure Cyber-Physical Systems. Flooding is the leading cause of fatalities related to natural hazards, said Lynch, noting that his own community in Michigan has recently experienced numerous flash floods. His colleague, Branko Kerkez, created an open source system, Open Storm,2 which can be used to monitor and model urban water systems to predict water flows and demand, and to control green infrastructure to enhance resiliency. Wireless sensor networks are embedded directly into infrastructure and controllable gates are utilized to control flows of water. Sensors examine measures such as rainfall, the level of water within a variety of green infrastructure assets, and the way water enters storm water systems and other built infrastructure. By analyzing the data and using actuators to control urban watershed flows, Kerkez introduces autonomy and controls to community water systems. For example, by offloading the demand on oversaturated infrastructure, flood events can be avoided in the community.
Lastly, Lynch spoke about a project that puts smart technologies directly into the community, called “Sensors in a Shoebox,”3 with the goal of empowering citizens to collect data and solve problems that are relevant to issues to them, in particular communities that experience issues of poverty. In collaboration with Professor Elizabeth Moje, of the University of Michigan’s School of Education, a technology kit is provided to students at schools in southeast Detroit. The kit includes an assortment of cellular-based wireless sensors that collect data and directly connect to a twitter interface. In this project, students measure air pollutants in an area that has an above average asthma prevalence among the community’s youth. Students are
3 More information on Sensors in a Shoebox are available at: https://news.engin.umich.edu/2017/10/sensors-in-a-shoebox.
encouraged to use the kits to monitor local air quality and understand how it relates to illness in their community.
Daniel Hiller and Alexander Stolz introduced work of the Fraunhofer Institute for High Speed Dynamics that demonstrates how engineering methods and innovative technological solutions can improve resilience of critical infrastructure, and thereby support societal resilience. Hiller and Stolz presented several projects that highlighted a continuum of efforts from protecting individual buildings to tools and simulations that address large-scale disasters in complex systems of the urban environment. In their work, resilience addresses both natural hazards and man-made hazards, including terrorism.
An important turning point for civil engineering, said Stolz, came after the 9/11 attacks on the World Trade Center, as it became essential to ask how high-rise buildings could be designed and constructed to withstand this type of attack. A concept designed by the German engineering community, the Security Scraper, features a highly robust inner core that encloses vital supply lines and vertical escape routes, and is made impact-resistant through high-performance materials, such as concrete enriched with steel and propylene fiber. Should destruction of a building’s outer façade and the local destruction of slabs and columns occur, the Security Scraper design still prevents building collapse; the core could resist the impact of an Airbus A380.
Hiller emphasized the need for disaster responders to conduct their operations in the safest and fastest manner possible, and to quickly assess the nature of an event and its location. One solution to improve the efficacy of response efforts is through the development of resilient technologies. Fraunhofer is working to develop models that can assess damages to a building in real time using a sensor network that can collect data to characterize the effects of an event. To render reliable models, Stolz explained, the networks’ sensors must be highly robust and affordable, and preferably energy-harvesting. Further, they must incorporate information concerning a building’s health status prior to an event for residual capacity evaluation. To demonstrate this solution, their team conducted a real-world, hands-on experiment in cooperation with relevant response forces. Using an old industry site outfitted with sensors, they simulated a blast event that caused the semi-collapse of a building. The models produced with these sensor networks provided clear and vital visual information to support the first responders in their response.
Their work also focuses on hazardous events that impact numerous buildings or entire urban areas. They introduced a suite of tools that Fraunhofer developed to both address the need of first responders and to help the systems themselves be better prepared in advance of an event. In responding to a large-scale disaster that impacts multiple areas of a city, first responders face two crucial issues. First, they need to know which area of a city or region is most damaged and how rescue forces can access the area with heavy equipment. Second, upon arrival to a damaged area, rescuers must begin searching for survivors who could be trapped in cavities under the destruction. Stolz described two tools, one capable of indicating potential “hot spots” in the city that sustain the most damage, and a cavity-detection tool to predict the likely locations of cavities after a collapse.
In addition to supporting more effective response, Fraunhofer aims to address how to help urban planners to integrate resilient design into their projects, including understanding the
location of key city vulnerabilities, the potential consequences of possible disasters to both hard and soft targets, and the efficacy of mitigation and counter-measures. Stolz introduced the VITRUV tool,4 which “helps city planners with empirical risk analysis based on the comprehensive terrorist event database (TED) in detecting potentially threatened points in their urban area models.” VITRUV runs multiple simulations and multiple scenarios rapidly to identify hot spots or city vulnerabilities during the planning phase of urban area development.
Lastly, Hiller and Stolz presented their work on designing more comprehensive resilience solutions that connect the physical environment with underlying critical networks and supply grids. To gain the more comprehensive or broader view of resilience, Stolz explained the need to understand how damage propagates within a system as well as how effects cascade through an interconnected environment. For example, in New York City, impacts to the power grid by Hurricane Sandy caused a large portion of Manhattan to lose power. To tackle this need, they first established a tool to simulate interconnected supply grids. Using the city of Helsinki as an example, they simulated a local strong wind event on the interconnected grid of electricity, water, and telecommunication systems. This grid was sized and interconnected within the tool, which then rendered a projection of the initial power grid failure and other interconnected elements of the power grid that would follow consequentially. Visualizations rendered with this tool enable grid operators to easily predict and assess an event’s comprehensive impact on a grid. Additionally, this tool can identify the most vulnerable elements of an interconnected system; thus, grid operators can invest their efforts more efficiently into the system to increase an urban area’s resilience potential.
To conclude, Hiller asserted that new solutions and a new vision are needed to manage the present Cyber-Physical System environment: “Our vision is a truly integrated platform where the many different aspects of resilience can be merged into one… so that future communities can manage and operate the resilience more successfully,” he noted.
During a question and answer session, an audience member asked, “How do you connect the socio-economic systems, which are dynamic in their response, with static engineering systems? What kind of networks can you connect?” In response, Stolz explained that they first look at the engineering system and determine how simulation predictions can be optimized. The next step is to find a way to integrate socio-technical systems; however, finding models that can support and simulate human behavior is yet another challenge.
Lauren Alexander Augustine, Resilient America Roundtable director, asked about next steps and ways that collaboration could take place. Hiller responded that he and Dr. Stolz think it is critical to work with real world scenarios and environments, and with the actors and operators who have direct experiences with the various systems. He noted that the U.S. has recently had more experience with natural hazards, while in Europe they have faced more man-made threats. There is a benefit to working in locations and with people who have experienced events on the ground, including diverse environments such as global supply chain logistics, airport checkpoint design, and community-based resilience. Hiller and Stolz said they believed that working with resilience designers in the U.S. to develop and test resilience models and simulations in the real-world environment could help develop case studies of best practices.
Another audience member asked how Hiller and Stolz secured their soft-target models from those with adverse intentions. Stolz explained that the VITRUV tool was developed to project multiple-hit scenarios, instead of single-shot scenarios. Because it projects multiple-hit scenarios, it cannot be used to analyze the precise consequences of an attack design. Instead, the
VITRUV tool only indicates an area’s vulnerabilities, or where to expect consequences after a general event. In other words, it does not indicate the projected impact of a specific kind of event. In this way, VITRUV is valuable for city planners without the threat of releasing sensitive information.
Lastly, Hiller and Stolz were asked whether they felt that the risk of an airplane attack on infrastructure should be addressed with resilient design or if this problem should be addressed with airport controls. Stolz responded that he believed both resilient design and airport controls should be employed to manage this risk. Airport controls, he explained, cannot ensure total security; on the other hand, with purposed design a building’s fault rate can be virtually eliminated. Due to the limited probability of an airplane attack, constructing a completely impact-resistant building is not a cost-effective solution. Thus, Stolz said he believed that employing both resilient design and airport control to manage this risk would produce the strongest results.
Maria Feng, Renwick Professor of Civil Engineering at Columbia University, examined methods of using technology to make bridges “smart” and infrastructure more resilient. Pointing to the 2017 ASCE Infrastructure Report Card,5 she noted that American motorists cross bridges that are rated structurally deficient 188 million times each day. Nearly $123 billion is needed to fix or replace these bridges; it would take 21 years to finish the job at the current pace of investment. Feng explored what could be done to address bridge safety in the current environment.
Feng explained that load rating testing and analysis are the current methods applied to assess bridge safety. This method pairs visual inspection data with a bridge computer model to assess whether a bridge’s load carrying capacity has decreased. If a bridge’s capacity has decreased, but repairs are too costly to immediately address, the solution is to post a weight restriction on the infrastructure. As a result, 10 percent of the nation’s bridges have received such restrictions, resulting in tremendous economic losses across the nation. Some studies believe this rating system is too conservative, while others worry that periodic visual inspection is ineffective.
Motivated by the need for a more accurate assessment method, research on structural health monitoring has continuously improved over the last 20 years. Feng estimated that thousands of bridges worldwide currently use structural health monitoring technology. For example, following the collapse of the I-35 Mississippi River Bridge in 2007, it was replaced with a smart bridge equipped with state-of-the-art sensors that can measure movement and detect potential bridge corrosion. When bridge sensors register an abnormal reading, an inspection is immediately called, turning a periodic time-based inspection into a condition-based inspection. While this method has many benefits, two significant obstacles challenge the implementation of structural health monitoring technology: high system costs and low sensor data benefits. Feng and her team’s research aims to overcome these barriers, including development of fiber-optic
5 The “Infrastructure Report Card” is a quadrennial publication of the American Society of Civil Engineers (ASCE) that provides a review of the bridge, water, transportation and other infrastructure challenges in the United States. See: https://www.infrastructurereportcard.org/wp-content/uploads/2016/10/2017-Infrastructure-Report-Card.pdf.
sensors to monitor global structure behavior, microwave imaging sensors to detect subsurface local damage, and system identification algorithms to interpret sensor data reliably.
Feng noted that recent advances in ubiquitous sensors, cloud computing, and artificial intelligence provide new opportunities to transform the design, maintenance, and operation of structures with self-sensing and learning capabilities. In particular, she pointed to the potential of computer vision, which offers improved image processing capabilities, cost-efficiency, and early problem detection capabilities. The entire system—comprised of a camera, a computer, and a zoom lens—costs about $1,000. With this system, bridge health monitoring can be done remotely. A single camera placed 100 meters or more away from the bridge can measure bridge movement based on the measurement of vibration characteristics. This technology can also be integrated with sensors already in place, such as with overhead traffic cameras and vehicle sensors, to get a more comprehensive picture of the bridge’s performance and safety. The integration requires no new investment.
Feng’s team developed a phone app called “Citizen Sensors,” which permits citizens to measure bridge elements, like structure vibration, with their phones. Seventy-seven percent of Americans currently own smartphones, which are equipped with multiple sensors. A person crossing a bridge can collect sensor data simply by placing their phone on a structure. To enhance the success of citizen participation, Feng and her team also developed a biomechanics model to filter out human vibration if the phone is left in a backpack or pocket.
To interpret the information being collected, Feng and her team developed a neural network algorithm that takes in vibration data and then renders the stiffness of all of a bridge’s structural elements (Figure 4-3).
With this algorithm, one can continuously monitor changing stiffness to assess infrastructure health. At the time of its conception, one week was needed to train this model. However, recent enhancements to computing power and the ubiquitous state of artificial intelligence have reduced this time to a few minutes. Today, the neural network has deepened and can model more complex systems at very fast speeds. Feng noted that a good application for the neural network is computer vision. For a large-scale structure, mobile computer vision could be used in the form of robots or drones. These robots could also conduct bridge repairs, and if they are equipped with microwave imaging sensors, could detect subsurface damage.
Feng spoke briefly about energy harvesting and suggested that future sensor systems could harvest energy from nature. She expressed her excitement for a possible bio-inspired sensing network that would detect all damage with distributed sensing. For example, piezo sensing nodes and sensing fibers could harness energy when they deform and that energy could, in turn, serve as sensing computing and for future energy harvesting (Figure 4-4).
Lastly, Feng emphasized the need to consider current bridge conditions conjointly with previously collected data. Feng offered an example wherein she and her team integrated sensor data collected over 8 years from the West St. on-ramp in Anaheim, California. Using this data, 4 fragility curves were rendered to represent a spectrum of seismic damage states from minor damage to collapse (Figure 4-5).
When these curves were updated with current monitoring data, the projected fragility increased. “If you don’t consider the current condition, you could get a less conservative prediction of the future performance,” stated Feng. Her team has applied this kind of analysis to the Los Angeles metropolitan area transportation network. By integrating traffic data, bridges can be prioritized for seismic retrofit based on their importance to network performance or cost. Feng concluded, “We’re really living in this very exciting time. Now it’s time to make our bridges smart.”
An audience member asked about the accuracy of displacement measurements taken with a single camera. Feng responded that displacement measurements for a short span concrete bridge were taken with a single camera and were compared to those registered with a high-end laser vibrometer, linear variable differential transformer, and contact sensor. This comparison demonstrated that the single camera’s accuracy was 99.9%. However, the accuracy of a camera’s measurements changes with increased distance from the measurement point. Variables such as heat haze can distort imaging rendered from further distances. Feng noted that she and her team are devising imaging processing algorithms to address this issue.
INNOVATION IN DEPARTMENT OF DEFENSE INFRASTRUCTURE: INSPECTION TECHNOLOGIES, SERVICE LIFE PREDICTION TOOLS, AND ADVANCED MATERIALS INTEGRATION
Robert Moser presented on the United States Department of Defense’s (DOD) approach to infrastructure innovation and the purposes of its science and technology initiatives. Moser pointed to the potential to use technology that historically focused on military applications to study infrastructure issues, noting that DOD’s interest in resilient infrastructure is motivated by several factors. The U.S. military has 800 bases and 560,000 other critical facilities worldwide
that must operate continuously. Many of these, such as the U.S. missile defense facilities in the South Pacific and Artic, operate under extreme environmental conditions. The military has an interest in the domestic transportation network, which can be traced to the National Interstate and Defense Highways Act (1956). The United States Transportation Command (USTRANSCOM) focuses on ways to use the transportation network for military purposes during times of war. DOD collaborates with federal, state, and local agencies to maintain designated strategic corridors that would support military operations and remain operable under extreme conditions. The United States Army Corps of Engineers’ (USACE) focuses on critical water resource infrastructure—dams, levees, locks—which is essential to the nation’s commerce and flood risk mitigation.
DOD is primarily invested in four areas of resilience science and technology: diagnostics, prognostics, innovative material solutions, and innovative structural solutions. With diagnostics, there is a focus on assessments and new ways that facilities can be inspected. As an example, Moser cited the use of unmanned aerial systems (UAS) to assess difficult-to-reach areas on dams. UAS can be mounted with multiple remote sensing systems that collect data and perform different structural interrogations; using sensor fusion technology multiple sensing modalities can be condensed into single data sets that provide information about the state of the infrastructure. Another method employs a type of infrasound technology, based on nuclear proliferation monitoring technology, which uses a structure’s low frequency acoustic signatures to monitor that structure’s behavior. This technology has the potential to assess multiple structures in an urban area using a small number of sensors, indicating whether or not infrastructure is behaving with the same integrity before and after an event. If a structure appears to be compromised, then an inspector can be sent to that location.
Where prognostics are concerned, DOD is primarily invested in forensic analysis. Often, inspections performed by structural engineers note symptoms of distress, such as cracks or displacements. However, these notations do not demonstrate the underlying causes of the distress. DOD is using different material science analysis techniques to investigate how materials are deteriorating, which would enable engineers to model deterioration and develop rehabilitation strategies. Improved understanding of a structure’s present state of distress, and the fundamental drivers of that state, can help predict the future health of that structure. Ultimately, this can inform decisions about how to financially invest in structure maintenance and operability.
Developing service life tools to predict the future state of distress of structures is core to DOD’s science and technology research. Moser suggested that a large gap in knowledge is the link between the state of distress on a structure and how the stress will impact the structure’s performance. Making the link between future degradation and its impact on performance of a structure is critical for decision-making. An example of this kind of translation can be found in how DOD is addressing issues of alkali aggregate reactions, which can degrade the strength and integrity of concrete. These issues are pervasive to the military’s concrete structures on airfields, bridges, and dams; many of the problems stem from construction prior to knowledge that these mechanisms existed. Due to high costs, structure replacement is not a reasonable solution. When these reactions are identified in a structure, accelerated laboratory-based testing is performed to assess the problem. Service life models help project future structure behaviors, which supports decisions about how best to provide facility maintenance.
Moser discussed innovations in materials science and structural solutions that result in new approaches to infrastructure design and construction. He pointed to materials that are
stronger, tougher, and more durable, or that offer new capabilities, such as self-sensing materials that can be integrated with health monitoring technologies. Moser noted that advanced materials often address logistic obstacles that challenge structure operations. For example, composite materials or alternative cement materials that can be installed in hours rather than days, even at a higher cost, offer many advantages for operation of a facility. One important advantage is that a facility’s operations do not have to shut down, as it would for conventional construction. Additionally, innovations in design are often spurred by the rapid evolution of new technologies; for example, additive manufacturing has changed the way components and structures are designed based on the functions they will serve over their lifetime.
Moser concluded by acknowledging that new technologies enable us to simulate things we could not simulate before. Within the next five to ten years, the user community may be able to simulate advancements that currently require the use of the DOD’s super computing resources. DOD investments in science and technology are enablers of infrastructure innovation; however, finding ways to transition that innovative technology is a formidable challenge. Moser believes the government research organizations have a responsibility for developing methods of integration and emphasized the importance of developing guidance documents, specifications, and applications to benefit the user community.
Oral Buyukozturk, George Macomber Professor of Civil and Environmental Engineering at the Massachusetts Institute of Technology, began his presentation by acknowledging that the country’s infrastructure is deteriorating. Despite recent technological developments in structural engineering, a major problem is that these developments have not been completely transferred for implementation. As it pertains to infrastructure, Buyukozturk defined resilience with three components: safety, durability, and sustainability. In particular, he pointed to material behavior as having a key role in the sustainability of infrastructure. Structural failures, for example, are often related to a material’s response to degradation or extreme loading. A focus on increasing our understanding of material behavior could lead to major innovations that could then solve large-scale infrastructure problems. Ultimately, these innovations would increase the broader resiliency of a system, and therefore, of a community.
In reference to sustainability, Buyukozturk highlighted the role of concrete in society, noting that it is one of the most commonly used materials on Earth because it is inexpensive and relatively durable. However, because its use results in high carbon emission, it also has global societal implications. As examples, he noted that for every person in the world, 3.8 metric tons of concrete is used each year; and currently Portland cement production accounts for more than 6% of the world’s carbon emissions alone. Buyukozturk also noted the recent construction of the Al Hamra Tower in Kuwait, which is 414 meters tall and constructed using 490,000 metric tons of concrete (Figure 4-6). The total embodied energy of the Al Hamra tower is an estimated 150,000 metric tons of carbon dioxide. Although this is an extreme case, many structures built today use large amounts of concrete.
To reduce the energy required in concrete manufacturing, Buyukozturk proposed the use of locally available natural or waste materials as additives to replace a percentage of traditional cement. This requires the development of a new material just as durable but with less waste and emissions. His proposal draws from the Roman approach to engineering, which was used to establish structures in diverse parts of the world with materials that were locally available, such as volcanic ash; these structures have lasted nearly 2,000 years. He suggested that concrete made with materials like volcanic ash could address durability challenges while also increasing sustainability by producing a smaller carbon footprint. Buyukozturk also noted, however, that the Romans were able to employ trial and error methods that would not be possible in today’s environment.
According to Buyukozturk, by starting from the molecular level, material resilience problems can be solved as a material science problem. Exceptionally resilient bio-materials are nanocomposite. These materials use a protein and have some ceramic composition; thus, he proposed that concrete should be redesigned as a nanocomposite material. Additives are chemically diverse, so evaluating possible additives requires multi-scale analysis using computation and simulation. Advanced computational techniques have been used to perform parametric studies on the influence of changes in material at the molecular, meso-, and micrometer scales. Figure 4-7 shows experimental images and computational models of concrete with additives that were organized hierarchically from the atomistic representation to larger scale representations.
To transfer this work into practice, Buyukozturk and others are assembling a multi-scale framework for translating atomistic behavior to engineering scales (Figure 4-8). This framework would make this developing capability available as a black box. He explained: “You will put the additives into the concrete and, from the black box, we will get the constitutive relations and durability-related characteristics…. If a solution like that is possible, we will solve our material problems.” Structural strain concentrations occur as colloids develop at the molecular level. This behavior, Buyukozturk noted, occurs in the same manner at the macro level.
The main innovation in Buyukozturk’s work is the inclusion of cohesive frictional behavior into the model’s prediction. The plausibility of the creation of a computational framework that could make this resilient material approach available to practitioners is increasing.
To conclude, Buyukozturk emphasized that supplementing a certain percentage of concrete with waste material allows engineers to produce material similar to Portland concrete. If materials like this were used in the construction of the Al Hamra Tower, embodied energy would have been reduced by 9 to 10 percent. The use of materials like these in the structures of an entire neighborhood or city would translate into even greater energy savings and sustainability. In this way, Buyukozturk’s approach opens further development opportunities in areas like long-term response prediction and creates opportunity for innovation in resilient design. Finally, Buyukozturk urged for increased public education on the importance of infrastructure engineering. He expressed his belief that a more fully aware public is more likely to influence their decision makers toward better policies for implementing advanced technologies.
An audience member asked Dr. Buyukozturk whether his model—in addition to factoring in microscopic and nanoscopic compositional differences—could also account for different physical environmental parameters. Buyukozturk explained that he and his colleagues are attempting to model the thermodynamic process that concrete undergoes as it strengthens. If the local material in a certain region has different chemistry, this chemistry is plugged into the tool as an additive, and the framework will incorporate and process that chemistry. Although modeling that accounts for material variation and environmental impact is much more complex than modeling a finite element analysis, Buyukozturk said his framework enables these considerations to be factored through the tool. Furthermore, the effects of temperature can also be incorporated into this model.
Finally, Buyukozturk was asked about how the variety of materials found in bridges interact with one another. He explained that the use of various materials in structures is a system-level issue that requires study and optimization of interaction between the different materials. He indicated, “what I’m emphasizing here is the strength and durability of the concrete material itself.” In a composite system that consists of concrete and steel, there will be an interface, and if the concrete is a low-grade, then the interface of concrete and steel is likely to also be low-grade and affect the integrity of the composite system. Ultimately, Buyukozturk said he believed that better solutions begin with the resilience and material composition of the concrete itself.