Forensic Investigations Using Nondestructive Techniques

The special section contained in this issue is a continuation of the November 2004 special topic issue on nondestructive evaluation (NDE) applications. Each of the five papers included here presents the use of nondestructive evaluation technologies. In several cases, the results of nondestructive evaluation are compared with laboratory test results.

Readers should refer to the editorial by Michael Drerup introducing the November 2004 issue for background on the collection of these papers and a general discussion of the expanding array of NDE technologies. These technologies provide important tools for inspection, maintenance and repair of the infrastructure.

The first paper, “Bridge Management and Nondestructive Evaluation,” discusses current nondestructive evaluation methods through the lens of a systems-engineering approach being developed in Denver, Colorado. Rens, Nogueira, and Transue note that the majority of U.S. bridges were built during two periods of time—the first as depression-era public works projects, and the second largely motivated by President Eisenhower’s interstate highway construction program. As a result, the vast majority of bridges remains public property and relies on government stewardship. A single municipality may maintain an inventory of dozens, hundreds, or even thousands of bridges. These large networks form practical workshops for the development of infrastructure management systems such as the system developed in Denver. (Please note that this paper was scheduled for publication in Novemeber 2004 issue, but was inadvertently moved to this issue by the publisher.)

Load tests are often conducted on bridges and other structures, and the measured deformations provide critical information about the conditions of the facility. Restrepo, Cousins, and Lesko present the results of such tests using strain gages and deflectometers in their paper “Determination of Bridge Design Parameters through Field Evaluation of the Route 601 Bridge Using Fiber-Reinforced Polymer Girders.” Maintenance and repair recommendations need not require destructive laboratory tests or damage to the structure under investigation.

“Field Evaluation of Marine Structures Containing Calcium Nitrite,” by Bola and Newtson, investigates the corrosion condition of reinforced concrete piers located at five marine sites. Each evaluation uses nondestructive electrical tests, permeability tests, pH tests, and visual inspection of reinforcing bars in core samples. The combination of NDE technologies and carefully selected laboratory tests provides a comprehensive view of the physical condition of the piers.

Dilek, Sorenson, and Chandler, in “Load Testing of the Historic Cast Iron Stairs at the Cape Hatteras Lighthouse,” review their investigation of the condition of an important historic structure. The load testing program was unique because of the dimensional constraints under which it had to be conducted. Of course, such a load test must be carefully considered, or the unintended consequences could involve irreparable damage to the structure.

The final paper, Dilek’s “Evaluation of Fire Damage to a Precast Concrete Structure: Nondestructive, Laboratory, and Load Testing,” presents a comprehensive postfire investigation. Again, nondestructive technologies are combined with accepted laboratory testing methods to provide a more complete view of the condition of the damaged structure.

We hope you find this special issue of interest and welcome your comments. As NDE technologies evolve, introducing new equipment and procedures, the standards for their use will also become more firmly established. We will continue to publish case studies involving practical uses of NDE technologies in the pages of this journal.