Nondestructive Evaluation S By Ken Maser
Parking structures play a crucial role in the urban environment, and
both owners and drivers rely on their con- tinued safety and high-level performance. Over time, however, daily wear-and-tear can lead to structural damage that is not always visible to the naked eye. Sustained loads, thermal expansion
and contraction, and chloride ingress from de-icing salts can place serious demands on the reinforced concrete slabs and components of a parking garage. Fur- ther damage, such as corrosion of embedded reinforcement, can occur below the surface and not be seen visibly until it is widespread. To avoid surprises and unplanned
repairs and rehabilitation, owners need to ensure that all components of their park- ing facility were properly constructed at the start. It’s also important to assess and quantify the condition of the facility on an ongoing basis, in order to maintain its structural integrity and to ensure the safe- ty of customers and their property. One way to do this is using state-of-the-art nondestructive
Vehicle-based ground-penetrating radar (GPR).
evaluation techniques, which provide an efficient means of assessing damage so that the most cost-effective maintenance can be performed. Nondestructive evaluation (NDE) uses a number of tech-
niques to determine material or structural properties without causing damage to the structure being evaluated. Because these techniques can be applied to a wide range of structures without
The entire (two-level, 470,000- square-foot, 1,100-space) parking structure was scanned in less than two nights.
adverse effects, they have become a powerful decision-making tool in the assessment of as-built conditions, and in the inspection and maintenance of infrastructure. The type of structure and the condition to be detected
dictates which NDE techniques will be most useful in a con- dition assessment. For example, if the structure was not properly constructed
(e.g., improper placement of rebar), it will overstress and prema- turely crack. Deterioration can also be caused by reinforcing steel corrosion and concrete delamination, freeze-thaw damage, and loss of concrete strength. Two NDE technologies – ground-penetrating radar (GPR)
22 Case Study: Nondestructive Evaluation
(NDE) Techniques in Action Recently, a T.Y. Lin International company employed
ground-penetrating radar (GPR) and impact-echo testing (IET) during a detailed inspection of a two-level, 470,000- square-foot, 1,100-space underground parking structure in downtown Rochester, NY, co-owned and operated by Monroe County and its Local Development Corp.
The inspection of the Civic Center Plaza and parking
garage was part of a program to accurately assess the con- dition of both the parking deck and its supporting mem- bers. A number of additional nondestructive evaluation methods were included in this testing program, including more traditional techniques such as hammer-sounding and visual inspection.
GPR was selected since the elevated deck had a pro-
tective waterproofing membrane system that varied in thickness from 1 to 3 inches and prohibited the deck from being accurately inspected by conventional means.
Infrasense Inc. was contracted to perform the GPR sur-
vey in order to provide deterioration quantities and maps. Using a vehicle-based survey, the entire parking structure was scanned in less than two nights, and 100% coverage was achieved in all accessible areas. – Ken Maser
Parking Today
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