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The Materials Section, in
conjunction with Research and Planning, and the WV College and
University System conduct research into many aspects of transportation
and materials engineering. Some information about current research
projects is provided here.
The following brief
descriptions will be linked to more information for viewing/ downloading
in the near future.
Fitting the Falling Weight Deflectometer with SASW Measurement
Capability
This project is being done in association with the previously discussed
“Evaluation of Backcalculation Algorithms” project. The scope of
this project is to investigate one particular type of pavement found
more and more throughout West Virginia, and that type is called
composite. A composite pavement is nothing more than asphalt overlaying
concrete. New asphalt is being placed over concrete on an everyday basis
during construction season, especially on interstates such as I-79. At
this rate, composite pavements will one day be the dominant type found
throughout the state. Therefore, this class of pavement will become
rather important when it comes to evaluating their structural properties
once rehabilitation becomes necessary.
In general, traditional
backcalculation programs do not perform real well in analyzing a
composite pavement. Their tendency is under predict the modulus of the
asphalt, and to over predict that of the concrete. In this project,
Spectral Analysis of Surface Wave(SASW) techniques is being employed to
determine pavement layer modulus values at several selected sites. This
process involves generating a signal(surface wave) and measuring the
velocities at which that signal travels through the pavement. The speed
at which the wave travels through a certain material is directly
proportional to the modulus of that material. This method is being used
in combination with FWD testing and the two results are then being
compared. A correlation between the two methods (FWD & SASW) is
trying to be established so that we will be better suited to predict
composite pavement layer moduli. Thus far, the results look very
encouraging, and preliminary analysis indicates the two methods are
comparing extremely well. In the near future a correlation will be
established allowing us to analyze composite pavements using FWD methods
with great speed and accuracy.
Evaluation of
Backcalculation Algorithms
for the Falling Weight Deflectometer
This project deals with the evaluation of the many different
backcalculation “algorithms” that are available for the processing
of FWD data. An FWD (Falling Weight Deflectometer) is a device that
imparts a dynamic load to a pavement and measures vertical deflection at
the center of the load, and at various distances from the load. These
deflections can then be used in conjunction with the pavement thickness
to predict the modulus (condition) of the different pavement layers.
This data is primarily used in the overlay design procedure. Basically,
it provides a good assessment of how much asphalt needs to be placed
over a roadway in need of rehabilitation, to achieve a desired life
span.
The problem with these backcalculation algorithms, is that there are
innumerable programs available on the market today that model the
pavement differently, and consequently yielding dissimilar results. Many
of these programs are available in the public domain while several
programs require purchasing from various manufacturers. Some of these
programs are quite costly, however, for the purposes of this project,
the manufacturers have allowed us to evaluate their programs to prove or
disprove their usefulness to us. The way in which these programs are
evaluated is that several sites that have been previously FWD tested
have been modeled by what is known as a finite element computer program.
These results are then compared with those obtained by the FWD. To this
point, we have found one program in particular which is providing
results that compare very well with the results that have been obtained
through finite element analysis. This is a program that is presently in
use by several other states in their overlay design processes.
Performance of Flexible
Pavements Reinforced with Geogrids
This research project has been completed and successfully met the goals
set forth by investigators. Studies proved that the addition of the
geogrid improved the performance of new asphalt pavements. This can be
translated into a longer-lasting pavement that uses less raw material
(asphalt) because pavement thickness can be reduced. When using the
geogrid, the same pavement thickness as conventional designs results in
a longer service life. Moreover, the same service life as conventional
pavements can be extended to geogrid-altered pavements by using reduced
pavement thickness. This is a very important finding from an economic
standpoint. Researchers also learned that the use of the geogrid tends
to impede reflective cracking. The data achieved by this study can play
a beneficial role in the construction of new roads and rehabilitation of
existing pavements in West Virginia.
Durability of Reinforced
Concrete Members
Wrapped with FRP Fabrics
The purpose of this research is to establish durability and long-term
behavior characteristics of steel reinforced concrete members wrapped
with glass and carbon FRP (fiber-reinforced plastic) fabrics. In these
tests, the members will be subjected to the freeze-thaw effect, chemical
and moisture attacks, and sustained stresses to simulate real-world
exposure. Researchers also hope to establish degradation rates of
strength and stiffness of the members due to physical aging. This will
result in long-term performance models for designers to consult when
using concrete members with FRP fabric wraps. This research could
produce an alternative means of rehabilitating concrete members in
structures such as bridges across the state.
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