Laser Scanning Unearths Secrets of Aging Wall
These days, the benefits of laser scanning in the construction industry aren’t just hard to miss. They’re also pretty hard to ignore. Recently, our team at Hawthorne Academy of Health Sciences
witnessed first-hand the advantages of obtaining accurate, three-dimensional images of current building conditions. The data collected enabled the project team to provide the owner with a reliable recommendation for repairs that will save money over the life of
the project and, most importantly, make the building safe upon occupation.
Begun in June 2014, this project encompasses the complete renovation of nearly 100,000 square feet to accommodate a new, medical magnet school – a first for Charlotte Mecklenburg Schools. The facility, which has undergone a number of renovations over the years, was originally constructed around the 1940s. Needless to say, obtaining an accurate as-built for such a building was hardly viable.
From the outset of construction, the project team knew that a 28x13 foot, CMU block wall in the mechanical room would require substantial repairs. Not only was the wall leaking, as evidenced by exterior water damage, but after selective demolition of several small block segments, the team realized there were numerous inconsistencies with regard to cell grouting. Rebar was also missing, further affecting this partially load-bearing wall’s structural integrity. At the request of the owner made during initial constructability reviews, the project team also performed a GPR scan of the wall. The scan established that the rebar and cell grouting issues were pervasive problems throughout the entire wall.
Although these methods were helpful, they didn’t fully reveal the magnitude of the wall’s structural instability. Thanks to laser technology, however, that important discovery was no more than a scan away. Our team created a digital thermal map of the wall
with the aggregate data we collected using a FARO laser scanner. As pictured above, the heat distribution points revealed the wall deviations in 96 distinct quadrants. In the purple areas, the wall was bowed in as much as one full inch. Once the project team had access to this precise analysis, it didn’t take long to decipher the root of the problem. The purple areas – representing the greatest degrees of deviation – just so happened to overlay an area of the wall that jutted up against an abandoned mechanical tunnel. Due to the movement of the earth among other factors, the tunnel had pushed in the wall over the life of the building.
Armed with the full knowledge of the wall’s conditions, the project team worked with structural engineer, Case Consulting, to devise several possible repair options. Knowing the addition of a new freezer in the building’s second floor would
only compound the forces acting against the wall, the owner ultimately decided on a solution that would reinforce the area for the long haul. A new concrete wall was built behind the existing wall, and the two walls were tied together. In addition, the project team tore out the problematic tunnel, which had not been in active use for some time, and thoroughly waterproofed the original wall.
The project team knew the wall was structurally compromised, but it was only with the laser scan that we were able to pinpoint the true extent and cause. The owner was thoroughly pleased with the degree of accuracy Balfour Beatty was able to provide.
“With the GPR and laser scanning reports, we were able to make a sound decision about the best avenue to resolve the wall’s issues,” says Chip Lofton, project manager for CMS Schools. “It was a good process that did what it was intended to do from a structural standpoint.”
Efficient building practices, field-accurate information, and a happy owner. It’s another one in the books for laser scanning.