Princeton Junction, NJ - February 2008 - MISTRAS Group Inc. has announced that Physical Acoustics Corporation
(
PAC) is working with Hampton University and the Virginia Transportation Research Council on a new study to
monitor the stay cables of a major bridge on Interstate 295 over the James River along the I-95 corridor.
Hampton University, located in Hampton, Va., is leading this study on the short-term evaluation of bridge cables
using acoustic-emission sensors provided by
PAC. The Research
Council the research division of the Virginia Department of
Transportation in partnership with the University of Virginia, located
in Charlottesville, Va. will oversee the project on this
VDOT-owned
bridge.
The bridge's supporting cables contain steel strands with individual
wires. The study will determine if the condition of the strands can be
assessed by short-term monitoring with acoustic-emission (
AE)
instrumentation on a single stay cable of the Varina-Enon Bridge during
periods of both low traffic volumes (acoustically quiet) and high traffic
volumes (acoustically noisy).
Scientists will conduct
AE monitoring during high- and low-traffic volumes two times during the year to account for
summer and winter temperature extremes. In addition, this study will evaluate signature sounds and/or wire breaks
that occurred during test periods.
This study will enhance
VDOT's ability to evaluate the health of this structure and to pinpoint regions that might
require more in-depth inspections. It is all part of the overall effort to ensure the continued integrity of the nation's
bridges.
To perform this study, acoustic emission sensors will be strategically attached to a single cable and monitored for
two and a half months during the winter and then two and a half months during the summer.
AE, a non-destructive evaluation (
NDE) technique, has the potential to eliminate subjectivity in traditional manual
(visual) bridge inspections. A critical advantage of
AE testing over other
NDE techniques is its ability to detect active
flaws, making it a principal candidate for real-time flaw characterization and continuous health monitoring of
highway bridges.
AE technique is based on the principal that each flaw is associated with varying types and levels of
deformations that release energy in the form of stress waves whenever a dynamic micro-structural damage, such as
crack growth, occurs.
