UA Researchers Develop New Method to Stabilize Older Buildings

TUSCALOOSA, Ala. – Dr. Andrew Graettinger, assistant professor of civil and environmental engineering at The University of Alabama, and Dr. Philip Johnson, associate professor of civil and environmental engineering at UA, have developed a method of drilling long, straight, small holes in typical building materials, without compromising the strength of the structure. This new method will be used for building stabilization, especially in areas that are considered earthquake zones.

Masonry structures can withstand tremendous vertical loads, but problems arise when the structure moves horizontally. Even a fraction of an inch of horizontal movement can produce severe and lasting damage. Steel reinforcing bars inserted vertically and horizontally through the walls can stabilize the structure, but how do you get the bars into an existing wall? Conventional drilling equipment can’t be controlled well enough to stay in the wall.

Graettinger and Johnson wanted something to drill straight, long, small-diameter holes. Their new waterjet drill makes long holes that are smaller and straighter than any other current drill. The waterjet is also portable, making it easy to bring to, and move around, the work site.

The UA engineering professors modified a pressure washer to incorporate grit into the water stream. The mixture of water, polymer and grit shoots out of a one-fourth-inch drill rod that is connected to an abrasive injection system and a 5,000 pounds per-square-inch pressure washer. At 545 miles per hour, the mixture sands and washes away almost any material including steel, concrete and brick.

“The holes allow for post tensioning to be added to older structures to prevent damage from an earthquake,” Johnson said.

The holes can be used to internally tie a structure together to resist shaking. This new method could preserve historical structures and save thousands of dollars in construction costs.

“Cutting materials with high-pressure water jets has been done before, but this method uses lower pressure and an abrasive which makes it less expensive and safer,” Graettinger explained. “We’re trying to preserve the building with reinforcement that no one can see.”

This drilling method also can be used to strengthen older bridges instead of tearing them down and building new ones, which saves taxpayer dollars. The small size of the equipment means fewer lane closures and less traffic congestion as well.

The team submitted a proposal to the University Transportation Center for Alabama for funding. The UTCA conducts transportation education, research and technology transfer activities using faculty members and students from The University of Alabama, The University of Alabama at Birmingham and The University of Alabama in Huntsville.

In 1837, UA became the first university in the state to offer engineering classes and was one of the first five in the nation to do so. Today, the College of Engineering, with about 1,900 students and more than 90 faculty, is one of the three oldest continuously operating engineering programs in the country and has been fully accredited since accreditation standards were implemented in the 1930s.

Note to the Editor: To receive photos of the waterjet drill, contact Mary Wymer at 205/348-6444 or mwymer@coe.eng.ua.edu.