T

he Visual Inspection (VI) method

is, by far, the predominant

nondestructive evaluation (NDE)

technique used for bridge inspection. 

Furthermore, the VI method serves as

the baseline by which all other NDE

technologies and methods are generally

compared. Since inception of the

National Bridge Inspection Standards

(NBIS) in 1971, which mandated regular 

and periodic bridge inspections, a

complete study of the reliability of the VI 

method as it relates to bridge inspections 

has not been undertaken.

 A comprehensive study of VI was

initiated by the NDE Validation Center

(NDEVC) in August 1998 and is

currently ongoing. This significant 

study has three principal parts. First, a

literature review of research related to

visual inspection and human factors was 

completed so that this study could build

on past findings. Second, a survey of

practicing bridge inspectio n 

organizations was completed to establish 

the current state of the practice for

bridge inspection. The final and most

significant aspect of the investigation is

an NDE performance evaluation of the

VI method utilizing the NDEVC test

bridge population.

 The literature review and survey of

States were completed early this year. 

Much was learned from these endeavors. 

For example, the reliability of VI has

been investigated as it is practiced in

other industries, but a comprehensive

reliability study has never been

undertaken for bridge inspection. In

addition, although all States comply with 

the NBIS provisions, there are

inconsistencies in inspection

methodologies between States. 

 The VI reliability study began the

field evaluation phase in early June of

this year. The field evaluation consisted 

of having a representative sample of

practicing bridge inspectors complete

NBIS inspections of the NDEVC test

bridges. Quantifiable information

regarding the inspection environment is

collected in order to establish its

influence on VI reliability. Extensive

information is collected about the

inspector’s physical and psychological 

characteristics, allowing the influence of 

human factors to be assessed. 

 The pool of inspectors participating

in this study comes from the State

department of transportation bridge

inspection groups. The help of all 50

States was solicited for participation in

(Continued on page 2)

An inspector looks for defects in the superstructure of a bridge in Virginia.

Volume 1, Issue 1

Visual Inspection Study Nearing Completion

January 2000

T

here are 367,950 bridges in the

United States that incorporate a

concrete bridge deck design. The

limitations of current visual inspection

practices for evaluating the integrity of

these concrete bridge decks have been

recognized by the Federal Highway

Administration, and a groundpenetrating radar (GPR) program has

been developed in response. GPR has

the potential to evaluate a variety of

bridge deck configurations within the

flow of traffic, thus making it an

attractive alternative to current

inspection practices. 

 Two radar systems have been

designed and built by Lawrence

(Continued on page 3)

Inside this issue:

Visual Inspection Study 1

HERMES Testing 1

Computed Tomography 2

Hanger Pin Testing 3

Dr. Chase’s Farewell 4

HERMES Radar System in Testing at TFHRC

NDEVC News

N ONDESTRUCTIV E E VALUATIO N V ALIDATIO N C ENTE R

U.S. DEPARTMENT OF TRANSPORTATION FEDERAL HIGHWAY ADMINISTRATION

NDEVC News • January 2000 FHWA-RD-00-043 1
A

n x-ray computed tomography and 

digital radiography imaging

system has been added to the NDEVC

research facility. The advanced

computed tomography imaging system

ACTIS 600/420 was built by BioImaging Research, Inc. according to

specifications provided by researchers

at the NDEVC. The system consists of 

dual-focus 420-kV and microfocus 160-

kV continuous x-ray sources. It

includes two digital detectors, with a

512-channel linear array detector for

tomographic imaging and a tri-field image intensifier with a digital camera for 

both real-time radiography and microtomography. The system can benefit

many industrial and scientific applications, including materials research, nondestructive testing, core sample characterization, weld inspection, failure

analysis, and reverse engineering. It is suitable for x-ray inspection of metallic 

and non-metallic items over a wide range of densities. The system produces

cross-sectional computed tomography (CT) images, in-motion real-time 

radiography (RTR) images, and digitized radiographed (DR) images. In

addition to density mapping, CT provides complete 3D morphology of parts

with highly accurate dimensioning capability. The CT data sets can be

converted to line drawings and exported as splines for solid modeling and

comparison to Computed-Aided Design (CAD) drawings. Computed

tomography also provides superior flaw detection capability of extremely small 

cracks, porosities, and voids that are normally not visible with film radiography 

inspection. The system can provide spatial resolution of up to 20 lines per

millimeter or 25-microns. In addition, sample sizes up to a weight of 200-kg 

and a length of 100-cm can be accommodated. The system has been used by

researchers at the NDEVC to conduct projects such as determination of air

void parameters, crack propagation, and internal structure characterization of

portland cement concrete and asphalt concrete structures. 

Computed Tomography Imaging

(Continued from page 1)

this study. The field testing

portion of the study was completed 

in early October. Overall, 25

States participated in the field 

testing by sending inspection teams 

to the NDEVC.

 Results from this study will be 

forthcoming in early 2000.

Visual Inspection Study

Three-dimensional tomographic image of a 

concrete core.

2 NDEVC News • January 2000

NDEVC NEWS is the

newsletter of the Federal Highway

Administration’s Nondestructive

Evaluation Validation Center.

The NDE Validation Center was

established by the Federal Highway

Administration in 1998. The objective

of the NDEVC is to improve the state of 

the practice for highway bridge

inspection. The Center is designed to

act as a resource for State transportation 

agencies, industry, and academia

concerned with the development and

testing of innovative NDE technologies. 

The NDEVC provides State highway

agencies with independent evaluation

and validation of NDE technologies,

develops new NDE technologies, and

provides technical assistance to States

exploring the use of these advanced

technologies. 

The NDE Validation Center utilizes a

series of unique resources to evaluate

and assess the factors affecting the

reliability and performance of NDE

systems. The Validation Center is

located at the Turner-Fairbank Highway 

Research Center in McLean, Virginia. 

To supplement the capabilities of these

laboratory facilities, a series of bridges

located in Northern Virginia and

southern Pennsylvania are utilized to

conduct field investigations. In

addition, a collection of component test 

specimens are used in various test

programs.

NDE Project Manager

Glenn Washer

202-493-3082

Email: glenn.washer@fhwa.dot.gov

A bridge inspector measures the 

opening of an expansion joint.

NDE Validation Center

Phone: 202-493-3118

Fax: 202-493-3126

Web: www.tfhrc.gov
T

ests using a number of different

NDE technologies were recently

completed on a set of hanger pins that

were removed from an in-service bridge

in the Midwestern United States. The

techniques included ultrasonics,

radiography, and computed tomography.

 Initially, misalignments were

noticed in a few hanger assemblies

within this particular bridge. The State

DOT then investigated further,

contracting for field ultrasonic

inspections to be completed on each

hanger pin in the bridge. This field

ultrasonic inspection identified seven

hanger pins that contained possible

defects. The defects identified ranged

from significant wear grooves to cracked 

cross-sections at the level of the shear

plane. The defective pins were removed 

from the bridge and sent to FHWA’s 

NDEVC.

 At the NDEVC, the pins were first

studied using ultrasonics in an

immersion tank. This is a non-contact 

automated technique that provides

highly repeatable results. A C-scan 

image recorded during the immersion

tank testing is shown below. For this pin 

in particular, the immersion tank testing 

showed that the pin cross-section at the

level of one of the shear planes had

decreased to approximately 25% of its

original area. Overall, the immersion

tank testing confirmed the results

obtained from the field ultrasonic testing 

prior to pin removal.

 Radiographic testing was also

performed on several of the pins at the

NDEVC. These tests, although not

practical for field use on a bridge

component of this type, were useful for

comparison purposes between different

techniques.

 Finally, several of the pins were sent 

to Lawrence Livermore National

Laboratory in Livermore, California, to

be tested using computed tomography. 

Tomographs of a pin section at the shear 

plane were consistent with the ultrasonic 

results. In addition, the images

indicated longitudinal cracking near the

shear plane defect.

Various NDE Techniques Used on Hanger Pins

(Continued from page 1)

Livermore National Laboratory under

the sponsorship of FHWA. The

HERMES (High-speed Electromagnetic 

Roadway Measurement and Evaluation 

System) bridge inspector is a GPR

system built into a towable trailer. The

design facilitates survey of the deck

condition without the need to disrupt

traffic flow. This system is based on a

64-channel antenna array covering 1.9-

m in width with a sampling density of 3-

cm.

 To investigate specific areas of a

bridge deck that require detailed

inspection, a robotic cart-mounted radar

system has been produced. This system,

PERES (Precision Electromagnetic

Roadway Evaluation System), has a

density of data coverage of 1 cm, 

with an average of 100 samples

taken at each location to improve 

the signal-to-noise ratio. 

 Images of the deck interior

are reconstructed from the

original synthetic aperture data

using diffraction tomography.

This technique refocuses the 

diffuse, original data with the aim 

of producing an image that is a

closer representation of the

internal structure. The goal of

these systems is to accurately

locate steel reinforcement,

corrosion-related delaminations, voids,

and disbonds. 

 The testing phase of these systems

has commenced. To date, HERMES

measurements have been recorded on inservice bridge decks in California, New

Jersey, Tennessee, and Virginia. PERES 

has been tested using deck slabs that are 

part of the bridge component specimen

collection held at the NDEVC, as well as 

in select field locations.

 Currently, the GPR systems are

completing a series of field tests, which

have include stops in St. Louis (July 14-

16); Denver (July 28-30); Minneapolis

(August 10 -12); Harrisburg, PA

(October 26-28); and Washington, D.C.

(November 9). Further testing and

demonstration of the system will

continue into winter.

HERMES Radar System in Testing

HERMES Bridge Inspector performing radar imaging of a 

bridge deck outside Nashville, TN.

C-scan from the ultrasonic immersion tank 

testing of a hanger pin.

NDEVC News • January 2000 FHWA-RD-00-043 3
I

n early summer of this year, Dr. Steve Chase moved on from the NDE Group at the Turner-Fairbank Highway Research 

Center. However, he has not left the FHWA family. Dr. Chase is now working in the field of Hydraulics and is located at 

the FHWA’s Baltimore Resource Center.

Shown at right, the NDE Group came together just before his

farewell luncheon. Starting from the back left are:

 Mark Moore – Project Manager

 Dr. Mike Scott – Research Engineer

 Dr. Habeeb Saleh – Research Scientist

 Dr. Fassil Beshah – Research Engineer

 Dr. Steve Chase – FHWA Baltimore Resource Center

 Dennis Rolander – Research Engineer

 Glenn Washer – FHWA NDE Project Manager

 Ben Graybeal – Research Engineer.

In the front row are:

 Fariba Parvizi – Administrative Assistant

 Dr. Brent Phares – Research Engineer

 Dr. Nigel Davidson – Former Research Scientist

 Dr. Paul Fuchs – Research Engineer.

Staff members not pictured include Research Engineer Dr. Ali

Rezaizadeh and Research Engineer Richard Walther.

NDE Staff Says Goodbye to Dr. Steve Chase

FHWA NDE staff pauses for a picture just prior to Dr. Chase’s farewell.

4 NDEVC News • January 2000

U.S. Department of Transportation

Federal Highway Administration

Turner-Fairbank Highway Research Center

NDE Validation Center

6300 Georgetown Pike, HRDI

McLean, VA 22101-2296