Nondestructive Testing
Ground Penetrating Radar (Impulse Radar)
Impulse radar or ground penetrating radar, GPR, has been shown to provide valuable information about structural and non-structural building components nondestructively. The radar data reveals voids, construction layers, the presence of other materials such as metal inclusions, as well as the thickness of the element.
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Tomography
Tomography is a useful technique for imaging defects within masonry or concrete cross sections. The imaging method uses a large number of ultrasonic stress wave velocity measurements, taken from the perimeter of a concrete section, as input into a computer reconstruction program. The program creates a model of the section's velocity distribution that satisfies the measured velocity data. From the velocity distribution, the location, size, and general type of internal feature can be identified. Show Related Projects
Ultrasonic and Pulse Velocity Measurements
Stress wave velocity correlates well with density in concrete and masonry. Using this fact, velocity measurements can indicate voids or higher velocity features in these materials. Ultrasonic measurements are used when the material is dense and the attenuation of the signal is not severe. In material where attenuation is a problem, pulse velocity measurements, made with an instrumented hammer and accelerometer, can be made through several feet of the material. Show Related Projects
Infrared Thermography
Infrared thermography employs a hand-held camera to detect differences in temperature as little as 1/10th of a degree Fahrenheit. This technique allows the identification of structural features and conditions not otherwise detectable by visible light. Some of the applications of this technique include the rapid location of grouted cells within concrete block, moisture infiltration, cracks in masonry, and variations in insulation. Infrared thermography has the advantage over other techniques in that large areas can be surveyed quickly and efficiently.Flatjack Testing
Flatjack tests can determine engineering properties of older and historic structures for structural evaluation, providing a viable alternative to the destructive process of masonry prism removal. The flatjack method is used to determine in situ stress, masonry compressive modulus, and an estimate of masonry compressive strength.A flatjack is a flexible steel envelope, thin enough to fit within a masonry mortar joint. During testing, the flatjack is hydraulically pressurized and applies stress to the surrounding masonry.
Flatjack tests are temporarily destructive, as a portion of a mortar joint must be removed to conduct the test. Following completion of the test, however, the masonry can be restored to its original condition by repointing mortar into the joint -- no visible damage remains.
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The ANA Flatjack
Atkinson-Noland & Associates, ANA, manufactures flatjacks in several shapes and sizes using a unique manufacturing process which results in a reliable flatjack with a superior combination of flexibility and ductility.ANA flatjacks are highly flexible, delivering a linear stress output over the entire working range of 0 to 1000 psi. Strict quality control measures include batch-by-batch calibration checks and a pressure test of every flatjack to 1200 psi.
Each design possesses a specific calibration constant, representing stress output versus internal pressure. Because flatjacks will "soften" with repeated usage, it is recommended that each jack be recalibrated every 5 to 10 tests or when repairs become necessary. Complete repair and calibration services are offered by ANA, using state-of-the-art servo controlled testing machines.
The ANA flatjack is economical; the special fabrication process produces a durable jack which can endure up to 15 test repetitions during its useful service life, thus spreading initial purchase costs to many projects.
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Wisconsin Avenue BridgeWashington, DC
Basilica of the AssumptionBaltimore, Maryland
Cherokee CastleSedalia, Colorado
Flatjack Test
Shearjack Test