Tag Archives: coastal infrastructure resiliency

Preserving Coastal Infrastructure through the Design and Implementation of Image-Based Structural Health Monitoring (iSHM)

 

 

 

 

 

Camera configuration a) diagram of optical setup and b) field of view, speckle pattern and subsets

It is estimated the average age of bridges in the U.S. is approaching 45 years, suggesting many of these structures may be in a state of disrepair and perhaps even reaching the end of their functional lives. In addition to age-related deterioration, these structures are exposed to weather and environmental hazards, further affecting their longevity.  Take, for example, high-profile infrastructure systems in the Hampton Roads region in Virginia. The Hampton Road Bridge Tunnel and the Chesapeake Bay Bridge are vulnerable to extreme weather events such as hurricanes, sea level rise, exposure to salting during snowstorms and underside exposure to saltwater spray. These environmental hazards cause corrosion and eventually cracking which impact the long-term performance of the structures.

To assess infrastructure for maintenance and repair, structural health monitoring (SHM) is an assessment strategy undertaken to determine the location, severity, and progression of damage. SHM is actually not used frequently and is primarily deployed on high-profile structural systems. Devin Harris, PhD, Associate Professor in the Department of Civil and Environmental Engineering at the University of Virginia, is tackling the problem with a fresh approach.

Harris believes image-based structural health monitoring (iSHM) can be a powerful tool for assessing condition and structural behavior, leveraging vision-based sensing techniques for describing the operational behavior of structural systems. With MATS-UTC funding, he is evaluating the laboratory performance of the iSHM concept. Using standard structural shapes under variable boundary conditions, Harris subjects a representative steel beam to a series of loading configurations, simulating real-world stresses on the structure, with measurements captured using high-resolution cameras. As the beam deforms under the various loads, the contrasting pattern painted on the beam also deforms proportionally. During testing, the cameras capture images of the behavior of the beam as it strains, rotates, deflects or deforms, which are then translated into full-field measurements of these phenomena using a technique called digital image correlation (DIC). These measurement results are then used in a structural identification scheme to update uncertainties in a finite element model of the structural system, which in turn can provide a mechanism to describe structural response and performance under different scenarios.

Preliminary results are promising. The vision-based sensing approach demonstrates real potential for deployment in the field with easy application of painted patterns on existing structures and eventual remote placement of weather-resistant cameras.  Harris envisions that the technology could eventually be used for load testing for bridges all over the country. Next steps include further laboratory studies to refine the approach, extensions to field evaluation of existing structures, and finally the development of smart cameras that are easy to use by DOTs, enabling reliable data collection and analysis and providing a cost effective way to approach health monitoring in the field.

Harris may be contacted at dharris@virginia.edu.

Student Spotlight: Elizabeth (Lizzie) Engel Assesses Resilience of Multimodal Transportation Infrastructure Systems

Elizabeth (Lizzie) Engel knew for a long time that her aptitude for math and science, along with her fascination for bridges and other big structures, would lead her to become an engineer. Now completing her Master of Science degree in civil engineering at the University of Virginia (UVA), she is turning the vision into reality.

Working with advisor, Lindsay Ivey Burden, PhD, a research assistant professor in civil and environmental engineering at UVA, Engel has devoted much of her academic career to studying ‘resiliency’, an approach used in engineering to monitor and revise risk assessments related to system-wide disruptions, failures or malfunctions. For transportation engineering, it refers to the ability of transportation infrastructure, such as highways, bridges, tunnels, rail and seawalls, to withstand and recover from external shock from such events as earthquakes, design failures, terrorism or weather.

Together with collaborator, Nii Attoh-Okine, PhD, a professor in civil and environmental engineering at the University of Delaware, the team is developing a multimodal transportation facility resilience index as a tool to calculate risk assessments. The index will help planning agencies, DOTs and public policy makers prioritize maintenance work and identify systems in need of retrofitting.

Although the resilience index is still under development, the research project is already yielding results. Engel is in the final stages of preparing her master’s thesis, Resilience of Multimodal Transportation Infrastructure Systems, in which she studied the interconnectedness of roads and bridges in Albemarle County. Using graph theory and network science, Engel has modeled the system of major highways in Albemarle County, accounted for traffic volume by weighting the model’s elements according to AADT (annual average daily traffic), and simulated bridge outages using different loss strategies.  Random removal models disruptions that are equally likely to occur at any point in the network, such as weather events, while targeted removal simulates deliberate attacks.  Resilience is tabulated by observing the network’s response to node removal.  This approach can be applied to any transportation infrastructure system, not just highway networks.

Engel presented a poster on the same subject at the TRB International Conference for Sustainability in Transportation in May 2015. It was the only MATS UTC project selected for the conference. “We were very proud that Lizzie’s work was selected to be highlighted at the TRB sustainability conference,” stated Ivey Burden. “It goes to show how applicable her work is to many different transportation systems, and underscores the transportation community’s desire to make sure that the systems we have are as resilient and sustainable as possible.”

Up next, Engel hopes to secure an industry position working on structural design and rehabilitation. “My time at UVA has been extremely productive and inspiring. Now it’s time to take what I’ve learned and experience it as applied knowledge. I’m excited to take the information we’ve compiled and use it to assess system vulnerabilities in an industry setting.”

Engel will receive an MS in Civil Engineering from the University of Virginia in August 2016. She expects to receive Engineer in Training certification in the summer as well.

She earned a BS in Physics-Engineering, double major in Spanish, Magna Cum Laude, from Washington and Lee University where she was a Johnson Scholar. As president of the Washington and Lee Engineers Without Borders, she travelled to San Pedro La Laguna, Guatemala to assess water quality and access needs. The paper she co-authored, Microbiological and Economic Assessment of Ceramic Pot Filters Used Long-Term in Households in San Pedro La Laguna, Guatemala, was selected for presentation at the World Environmental and Water Resources Congress in 2014.

Engel may be contacted at ere8ec@virginia.edu. ‎