Marley Kunzler

Fiber grating traffic monitoring systems

Previous studies have shown the capability of fiber Bragg gratings (FBGs) to monitor components of strain on bridges and structures. In past months, Blue Road Research and the Oregon Department of Transportation embedded long-gage FBG sensors into the Interstate 84 freeway east of Portland, Oregon to determine the feasibility of retro-install and for use of these sensors in monitoring freeway traffic speeds under conditions similar to loop inductors, piezo-ceramic weigh-in-motion (WIM) systems, and other vehicle monitoring devices. The objective of the study was to develop a working traffic sensor system with the potential to be more durable, reliable, informative, and cost-effective than currently available traffic sensors. A primary purpose of the freeway installation was to test the sensors for vehicle classifier and counter applications. In addition to discussion of the advantages of using FBGs for traffic classifiers and systems over conventional sensing methods, this paper overviews the installation and summarizes the use of FBG traffic sensors for vehicle counting and classification.

Fiber grating systems for traffic monitoring

Blue Road Research has designed, built, and installed fiber grating sensor systems onto bridges, and most recently into an asphalt and concrete highway test pad. The sensitivity levels of the fiber grating sensors are sufficiently high to enable detection of people standing on the bridge or highway. This paper briefly overviews the usage of these sensors for traffic monitoring.

Traffic monitoring using fiber optic grating sensors on the I-84 freeway and future uses in WIM

Blue Road Research has demonstrated the use of fiber optic Bragg grating sensors in roads and highways to develop traffic sensors that could count and classify traffic usage on roadways, providing statistical information for maintenance, safety, and growth. This paper reviews the progress by Blue Road Research that led to installation of traffic sensors on the I-84 freeway and outlines the benefits of developing a fiber optic weigh-in-motion sensor.

Structural damage assessment via modal property identification using macro-strain measurements with fiber Bragg gratings as an alternative to accelerometers

In this article, the use of long-gage fiber Bragg gratings to provide dynamic strain measurements in conjunction with a damage detection algorithm is investigated.

Real-time damage assessment of civil structures using fiber grating sensors and modal analysis

In this effort, long gage fiber Bragg grating sensors are used to provide dynamic strain measurements in conjunction with a damage detection algorithm to provide a real-time assessment of the health of a civil structure such as a abridge or a building.

Use of multidimensional fiber grating strain sensors for damage detection in composite pressure vessels

Arrays of multi-axis fiber grating strain sensors have been integrated into a composite pressure vessel test article, and are used to monitor changes in the transverse and axial strain fields during curing and pressure cycling near cut tow and Teflon tape defects. These changes in the multi-axis strain due to four pressure cycles and repeated impacts are measured and compared to ultrasonic and eddy current scans. Examples of the remote detection of damage using transverse strain and transverse strain gradients is given as well as data showing the ability of the system to distinguish broken tow and delamination defects.

Using multi-axis fiber grating strain sensors to measure transverse strain and transverse strain gradients in composite materials with complex weave structures

Multi-axis fiber grating strain sensors have been used to quantitatively measure axial strain and temperature; transverse strain and transverse strain gradients in composite weave structures. This paper overviews the multi-axis fiber optic grating strain sensors and how they can be applied to measuring multidimensional strain fields interior to composite parts with complex composite weave structures. Experimental results are given for the case of a bi-axially woven composite coupon as well as for an E-glass/epoxy composite sample.

Second-generation fiber grating traffic monitoring systems on the I-84 freeway

This paper highlights the installation and monitoring to date, as well as key findings of a second generation of fiber Bragg grating traffic sensors installed into the I-84 freeway near Portland, Oregon for the purpose of counting and classification of traffic.

Nondestructive evaluation of composite materials using multi-axis fiber grating stain sensors

Fiber optic sensors may be used to monitor strain and temperature in composite materials. These measurements can be useful in determining rate and degree of cure of composite. Multi-dimensional strain measurements enabled by fiber gratings written onto polarization maintaining optical fiber enable monitoring changes in transverse strain, transverse strain gradients, and shear strain internal to composites and adhesive joints. This paper provides a brief historical overview of the usage of fiber sensors to provide strain measurements in composite parts, leading eventually to multi-axis strain sensing.

Fiber Grating Strain Sensors

The need to measure strain occurs in a variety of industries, ranging from aerospace design to civil engineering to traffic sensors to robotic manipulators. Measuring the deflection of a structure gives design engineers data needed to build safer and more efficient systems. Typical measurements can be approximately an inch of deflection over a 100 foot gage length (8 millistrain) for structural applications, to a micron of deflection over a meter gage (1 microstrain) for materials testing. Strain measurements are made along one, two, or three spatial axes, depending on the need.