Monitoring and preserving historic buildings is of particular interest to the U.S. Department of Defense, which manages the largest property portfolio in the federal government, with more than 500,000 buildings. Of those, 45 are national historic landmarks, 3,032 are national historic landmark contributing places, 2,370 are individual and contributing historic assets in the National Register of Historic Places, and 16,000 are historic assets determined eligible for inclusion in the National Register of Historic Places.<\/p>\n\n\n\n
For its monitoring system, the team will employ fiber-optic sensing networks capable of detecting subtle deformations in a structure. The system works by taking advantage of the physical nature of fiber-optic cables: They are long, narrow strands of glass or plastic that conduct light from one point to another. When light shined along the cable hits an imperfection, it\u2019s reflected. The researchers can use the reflections to interpret where and what type of deformation is occurring in a structure from slow loadings such as temperature changes to fast loadings such as seismic waves.<\/p>\n\n\n\n
Engineers are just beginning to use fiber-optic sensing as a tool to monitor earthquakes through what\u2019s known as distributed acoustic sensing. It\u2019s a technique that Hampton, a civil and geological engineer, says is still in its early stages of development; using it to monitor changes in a structure is a cutting-edge application.<\/p>\n\n\n\n
\u201cIf that cable stretches at any point, those little imperfections that reflect some of that light are going to move further away from each other,\u201d Hampton says. \u201cIf they compress, the response changes because those points are moving closer together. With that information, you can understand how a structure is deforming.\u201d<\/p>\n\n\n\n The fiber-optic networks will be particularly useful for noticing new deformation as it occurs, but Hampton says they may also have value for finding preexisting damage in structures. Structures deform slightly when under load\u2014like from the weight of a car passing over a bridge or the force of the wind against the side of a building. Hampton says that because we know how structural materials should perform under load, it may be possible to use initial readings from the fiber-optic network to infer what kind of damage a structure has accumulated. Additionally, the network can remain in place for long-term monitoring of the structures.<\/p>\n\n\n\n The team will create physics-based structural models of the infrastructure and then will feed data from the networks into the models to better estimate the performance of these structures subjected to anticipated future loading conditions. Blum\u2019s team has experience in creating detailed structural models to analyze behavior.<\/p>\n\n\n\n Employing very detailed LIDAR scans to map out the historic structures, the team also will create detailed point cloud models of buildings. Zoomed out, these models look like a 3D representation of whatever structure they scanned; zoomed in, and they\u2019re made of countless, precisely arrayed individual points.<\/p>\n\n\n\n Blum, Hampton, and their partners at ERDC-CERL and the Department of Defense want to make sure the point cloud models are publicly accessible. \u201cThese are government sites, for non-classified buildings, everyone should be able to virtually interact with them and see what they\u2019re like,\u201d Blum says.<\/p>\n\n\n\n![\"\"](\"https:\/\/engineering.wisc.edu\/wp-content\/uploads\/2023\/12\/CEE-Building_monitoring-IMG_5462-1024x732.webp\")