| Concrete dams
Currently, an extensive amount of steel is used in dams and spillways, especially those with steel spillway gates. FRPs have additional advantages over conventional steel materials used in dam and spillway repair or construction: they are easier to install, impermeable to water, and their fibers can be adapted to include sensors that monitor concrete condition in real time. Concrete dam deterioration includes most commonly cracking, but also corrosion of the spillway gates’ hydraulic steel structure, damaged concrete spillway, lack of monitoring capabilities in real time, and more. Each of these issues could benefit from different types of FRP retrofits, however, such retrofit guidance is lacking. The good news is that after S&T completes this research initiative, guidance will be coming out.
Researching and developing the best
communities – including USACE and its Engineer Research and Development Center (ERDC), the Federal Emergency Management Agency, the Cybersecurity and Infrastructure Security Agency, and the University of Kansas (KU) and Mississippi (UM) – to not only extend the life of dams and other concrete flood risk management infrastructure, but to do so in an environmentally responsible and sustainable way. S&T chose to work on this effort because water poses very challenging and complex situations for concrete. What works for aging water infrastructure like dams and levees, most likely would work for dry-land concrete-based infrastructure like bridges and buildings. This initial use case could become the catalyst for an entire research agenda. S&T is investing in and leading this five-year initiative because disaster or weather-related risks and threats to critical infrastructure continue to rise. This partnership will help better position the US by using innovative retrofitting technologies to create a new economy of more resilient concrete structures. Together, the partners are researching and developing innovative materials that can sense and detect potential stressors for better monitoring of overall conditions, reacting if necessary, and ultimately saving on maintenance costs.
Composite materials are advantageous to infrastructure
FRPs and use cases S&T’s goals for this project include researching how FRPs can help reinforce existing concrete dams to improve performance and extend their service life; surveying dams’ condition using drones to take photos and using deep learning to recognize the damage; and using sensors embedded in FRP fabric or laminates to monitor the condition of underlying concrete. The S&T team has finished the first phase of four overall research phases. Researchers completed extensive literature reviews of FRPs for concrete repairs/retrofits, lab tested selected FRPs in dry conditions to study bond performance to concrete surfaces, and designed a shear test to determine how FRP laminates perform when applied over a lift joint prone to sliding under hydraulic forces. So far, results show promising bonding performance, and the team will soon conduct lab testing under wet conditions as well. The researchers were surprised by the lack of publicly available image sets of damage in concrete dams. Creating such a resource could lead to significantly more accurate damage detection via deep learning. The research team is currently in the second
operations For this effort, the team is studying and working with fiber-reinforced polymers (FRPs), composite materials that typically consist of strong fibers (carbon or glass) embedded in a resin matrix. FRPs, which come in sheets, panels, structural shapes or monolithic structures, are very strong but lightweight, and are not susceptible to corrosion unlike steel. These materials are stronger than steel in strength-
to-weight ratio, meaning much less material is needed than steel for building repair.
research phase, which entails conducting a series of internal lab experiments on simulated components of concrete dams and creating virtual models that can be leveraged to use Artificial Intelligence (AI) for damage detection. To improve and expedite surveying half-a-mile- wide dam structures, S&T is looking at AI. With a drone, surveyors can take thousands of photos, which then must be cataloged and analyzed, which is very time consuming. Here, deep learning can make surveying more efficient by automating the photo processing for damage detection, quantification and documentation. The project team is also facilitating dam
monitoring via self-sensing FRP laminates. Researchers will test two types of sensors embedded in the laminate – carbon fibers, already part of the laminate, naturally possess electrical conductivity; and optical fibers, which will be added to the laminate. The sensors will collect baseline data whenever the FRP material strains from concrete deterioration.
www.waterpowermagazine.com | July 2023 | 35
Left: University of Kansas Ph.D. student Adam Mouak (right) and M.S. student Jessica Diehm (left) prepare concrete specimens to receive epoxy right before FRP application. Photo: KU
Below: Researchers conducted a flexural test on an unreinforced concrete beam with FRP laminate applied to bottom surface, where cracking is expected to develop. The tests will show how well different FRP configurations resist the bending demands and how well they help to mitigate crack propagation. Additionally, the team observed how well the FRP bonds to the concrete. Photo: KU
Below: Annotation of cracking and pop-out damage in an image sample of a concrete dam surface to be used for training a deep-learning model for damage detection. Photo: KU
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