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The WSDOT conducts many tests on the states
routes to be used in the construction, reconstruction, or rehabilitation of pavements. Most of this data is collected yearly or every
other year and is stored in the WSPMS.
The distress identification van collects pavement distress,
wheelpath rutting, and roughness (IRI) every year on the state route system. These condition measures are processed into
pavement performance measures and include PSC (Pavement Structural Condition), PRC
(Pavement Rutting Condition), and PPC (Pavement Profile Condition - IRI).
Another test
that is conducted on 100 percent of the state route system is surface friction. This test
is conducted in the Northwest, Olympic, and South Central Regions during even numbered
years and in the North Central, Southwest, and Eastern Regions during odd numbered years.
The FWD (Falling Weight Deflectometer) is used typically on
routes that are scheduled for an upcoming rehabilitation or where subgrade failure is
suspected. This data is used in the Evercalc
program to help characterize the pavement structure.
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Distress Identification
In 1999, WSDOT purchased a data distress collection van
that records pavement profile (ride, faulting, and rutting) and video images of the
pavement surface, ahead view, and shoulder view. This data can be collected at highway
speeds and will significantly enhance the accuracy of the data collection process as well
as provide a variety of research and analysis options concerning pavement performance. In
years previous to 1999, this data was collected with a "windshield" survey. The
raters would ride in a van over portions of the state routes, drive approximately 10 mph,
and rate the roadway from what they could see. The collection van greatly improves the
accuracy and quickness of the data collection process.
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Pavement Distress Identification Van
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| Being able to quantify the condition of the existing
roadway will provide an increased understanding of past performance and an indication of
how well the roadway will perform in the future. Knowing when and how a pavement
distresses will inform the pavement designer of potentials for underlying base or subgrade
problems, inadequate structure, insufficient material properties, increased truck loading,
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 The information collected by the van is stored in a database
that is included in the Washington State Pavement Management System (WSPMS). The WSPMS is
a valuable tool to the pavement designers and with the improved accuracy of the roadway
rating, the easier and more accurate the designer’s job becomes.
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Camera Views |
Friction
Tester
Surface friction is measured on the complete WSDOT route
system every two years. In essence, a coefficient of friction is measured via a
locked-wheel towed trailer between a tire and the pavement surface (the actual value is
called Friction Number). Vehicle speed is maintained while water is applied to the
pavement surface in front of the test wheel and a brake is applied to the test wheel. When
the test wheel stops rotating (locked-wheel state), the drag and load (horizontal and
vertical force) are measured.
The friction of most dry pavements is high. Wet pavements are the problem. Thus, the
Friction Number testing process involves application of water to the pavement surface
prior to determination of the friction value. Such data allows WSDOT to identify
potential low friction pavements that in conjunction with accident history and roadway
geometrics are used to minimize wet weather skidding accidents.
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Friction Tester
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Falling Weight Deflectometer
The FWD (Falling Weight Deflectometer) is a non-destructive
testing device that is used to complete structural testing for pavement rehabilitation
projects, research, and pavement structure failure detection. It is used for
conventional and deep strength flexible, composite and rigid pavement structures.
The FWD is a device capable of applying dynamic loads to the pavement surface, similar in
magnitude and duration to that of a single heavy moving wheel load.
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Download the FWD Software
FWD
Software Readme.txt
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 The response of the pavement system
is measured in terms of vertical deformation, or deflection, over a given area using
seismometers. The use of a FWD enables the WSDOT to determine a deflection basin
caused by a controlled load. These results make it possible to treat pavement
structures in the same manner as other civil engineering structures by using
mechanistically based design methods. FWD generated data, combined with layer
thickness, can be confidently used to obtain the "in-situ" resilient elastic
module of a pavement structure. WSDOT uses this information in a structural
analysis to determine the bearing
capacity,
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| estimate expected life, and
calculate overlay requirements over a desired design life. Selecting the type of
rehabilitation to be implemented on a given pavement is of considerable economic
significance and to reach that decision without an adequate knowledge of the structural
condition of the pavement may have very costly consequences. |
FWD Load Plate and Sensors |
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