Structural Factors of Jointed Plain and Concrete Pavements: SPS-2 - Initial Evaluation and Analysis
CHAPTER 7. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
The SPS-2 project, Strategic Study of Structural Factors for Rigid Pavement
of Jointed Plain Concrete Pavements, is one of the key experiments in the
LTPP program. The main objective is to determine the relative influence and
long-term effectiveness of the JPC pavement strategic factors that affect its
performance. There are some concerns about the ability of the SPS-2 experiment
to meet those expectations, given that several SPS-2 sites were not constructed.
In addition, at the SPS-2 sites that were constructed, some construction deviations
and data collection deficiencies exist.
This study provides the first comprehensive review and evaluation of the SPS-2
experiment. Issues of experimental design, construction quality, data availability
and completeness, and early performance trends are addressed in this report.
The key findings are summarized in this chapter. This chapter also presents
the research team's recommendations on improving the SPS-2 experiment and its
data availability, expectations of the SPS-2 experiment, and future data collection
and analysis topics.
SPS-2 Experimental Site
Status
As of January 2000, 13 SPS-2 sites have been constructed throughout the United
States. An additional site in California has been nominated and is currently
under construction. The full factorial of the original experimental design
is not completely satisfied by the constructed sites, leaving a portion (31
percent) of the desired inference space (subgrade and climate) with no experimental
sites.
These 14 sites fill in 11 of the 16 SPS-2 experiment factorial cells and provide
good coverage of major areas of the United States. Five sites (31 percent)
are missing from the original experiment design, as listed below:
- Two sites in a wet no-freeze climate
(southeast United States) with a coarse-grained subgrade. Data from each site
will fill half of the design factorial.
- One site in a dry freeze climate
(northwest United States) with a fine-grained subgrade. Data from each site
will fill half of the design factorial.
- Two sites in a dry no-freeze climate
(southwest United States), one on a fine-grained subgrade and the other on a
coarse-grained subgrade. Data from each site will fill half of the design factorial.
Five additional SPS-2 sites (60 sections total) are needed to complete the
design factorial. While it is impossible to determine the exact effects at
this time, the lack of data from these missing sites will limit the results
obtainable from the SPS-2 experiment, as summarized below:
- There will be no performance data
and, thus, no performance findings from the missing sites.
- The missing site corresponding
to the site in Arizona (dry/no-freeze and coarse subgrade) will make it impossible
to determine (without confounding factors) the main effects and interactions
for the dry/no-freeze climate.
- The missing section at the Nevada
site will reduce the findings for that site and corresponding cell (although
the Washington site appears to be a replicate).
- Adequate SPS-2 sites exist in wet-freeze
climates, making a full inference space of performance data available. All
main effects and interactions in this climate should be ascertainable.
- The number of SPS-2 sites in no-freeze
climates, both wet and dry areas, is deficient. There will be difficulties
in determining the main effects and interactions in these climates.
Some of these deficiencies can be overcome through use of mechanistic data
analysis. However, there is no mechanistic analysis method that considers all
factors involved, and the missing data cells will always limit in the verification
and calibration of any performance models.
In addition to the 12 core sections at each site required by the SPS-2 experiment,
SHAs have built a total of 40 supplemental sections with SPS-2 projects. The
main value of the supplemental sections will be as a direct comparison to the
core sections. For example, one supplemental section in Washington did not
have dowels, and this will provide a direct comparison to a similar design with
dowel bars. Various other comparisons are possible, including skewed joints,
base types, subdrainage, slab thickness, asphalt concrete pavement, jointed
reinforced concrete, special dowels, and variable slab thickness. These sections
are valuable to the States, and efforts should be made to ensure that their
construction and monitoring data are collected and stored.
Data Availability and Completeness
The SPS-2 project is an extremely valuable source of performance data for modern
concrete pavements. The performance of these sections will be of great interest
to all highway agencies building concrete pavements, and of course to the concrete
industry as well. This report will be the major reference document for all
future SPS-2 research studies, and will be the major reference document for
the 14 SHAs that have constructed SPS-2 project sites.
Data elements that were considered to be essential to the SPS-2 experiment
analyses have been assessed. The data availability and completeness for the
SPS-2 sites are considered good overall. A high percentage of the SPS-2 data
is at level E-greater than 82 percent for all data types, and greater than 99
percent for many.
However, a significant amount of data is still missing, especially traffic,
distress and faulting surveys, and key materials testing data. These deficiencies
need to be addressed before serious analysis of the SPS-2 experiment can occur.
The SPS-2 data deficiencies are summarized below:
- Wisconsin-newly constructed, data
processing under way and all data expected to be complete.
- Arizona, Arkansas, and North Carolina-late
initial survey for most monitoring types. Backcasting of IRI and distress data
will be required.
- Colorado and North Dakota-late
initial survey for one monitoring collection activity, either longitudinal profile
measurements, deflection testing, faulting, or distress data.
- Kansas SPS-2-very deficient faulting
data. Faulting measurements currently under way.
- Traffic data are very deficient
for 5 of 13 sites (40 percent).
- Joint faulting data are not being
collected as required by LTPP, and this will limit the analyses that can be
conducted.
- Arkansas, Kansas, North Carolina,
and Wisconsin are missing significant PCC materials testing data.
Note that the LTPP program is embarking on a systemwide effort to resolve all
missing data. Some missing data have already been obtained. This effort will
greatly improve the data availability for future analysis.
Experimental Design versus Actual Construction
Required experimental design factors were compared with the actual constructed
values stored in the IMS database. This database includes both the site condition
factors and pavement design features. Most SPS-2 sections follow the experiment
design for the large majority of the design factors. Most deviations from the
experiment design are found in the concrete slab thickness and 14-day flexural
strength. A number of sections were more than 12 mm too thick or too thin,
or were more than 10 percent too high or too low in flexural strength.
Out of the 13 SPS-2 project locations, only the recently constructed Wisconsin
site does not have enough data in the IMS database to be evaluated. These data
are currently in the pipeline. Of course, data from the California site under
construction also are not in the database at this time.
Eight projects can be characterized as good to excellent when comparing designed
versus constructed values, while the remaining four projects are considered
poor to fair.
In addition to the comparison of the designed versus constructed values from
the IMS database, construction reports of from all 13 SPS-2 reports sites were
reviewed to identify construction deviations and difficulties. Four projects
were found to have experienced more than minor construction difficulties or
deviations.
The following summarizes significant deviations when comparing the designed
versus constructed factorial factors, and more than minor construction deviations:
- Delaware-significant deviations
in both slab thickness and flexural strength. This project is also considered
to have moderate construction deviations.
- Iowa-significant deviations in
flexural strength, slab thickness, and lane width. The lane width deviation
may be a data entry error. This project is also considered to have moderate
construction deviations.
- Michigan-moderate construction
deviations.
- Nevada-significant deviations in
subgrade type, flexural strength, and slab thickness. This project is also
considered to have moderate construction deviations. Extensive cracking occurred
early, and one section has been taken out of service.
- Washington-significant deviations
in flexural strength and slab thickness. The traffic level for 1997 appears
to be erroneous.
Early Performance Trends
The SPS-2 sections are relatively young, and a large majority show little distress.
As of January 2000, only 43 of 155 sections (28 percent) are showing any noticeable
distresses. Ninety-five percent of the SPS-2 sections have less than 1 mm of
edge joint faulting. Eighty-seven percent of the SPS-2 sections show zero transverse
cracking, and 78 percent of the sections have zero longitudinal cracking.
Based on the initial statistical analyses and comparisons, the following initial
performance trends are noted (note that long-term performance may be different
from short-term performance):
- The initial IRI of SPS-2 sections
after placement ranged from 0.76 to 2.19 m/km with a mean of 1.30 m/km.
- JPCP constructed on coarse-grained
soil were smoother (lower initial IRI) than those constructed on fine-grained
soils.
- JPCP constructed on PATB were smoother
than sections constructed on LCB or untreated aggregate base.
- The IRI trend over time depends
heavily on the initial IRI, the traffic loadings, and the extent of joint faulting.
- Sections with PATB show the lowest
total longitudinal cracking levels, while the sections with LCB show the highest
longitudinal cracking.
- Thinner (203 mm) slabs show more
longitudinal cracks. Sections with a thinner slab and widened slab show the
highest level of longitudinal cracking.
- Sections with PATB show the lowest
percentage of slabs cracked transversely, while the sections with an LCB show
the highest transverse cracking.
- Thinner (203 mm) slabs show more
transverse cracks than thicker slabs. Sections with a thinner slab and a widened
slab show the highest level of transverse cracking.
- Sections with aggregate base show
the highest joint faulting level. Sections with LCB and PATB have the lowest
joint faulting.
- Widened slab sections show less
faulting than conventional width slabs.
States' Expectations from the States for the SPS-2
Experiment
Two national workshops were held where input was received from the States on
the SPS-2 project. The meetings were held on November 2-3, 1999, in Columbus,
OH, and on April 27, 2000, in Newport, RI. The research team made presentations
at both conferences about the status of SPS-2 data collection, analysis, and
availability, and the near- and long-term LTPP products. Several participating
States made presentations on the status and analyses of their SPS-2 projects,
as well as the States' expectations of the SPS-2 experiment. There were many
discussions of the future directions of the SPS-2 experiment and the analyses
of the SPS-2 data at both conferences. Those discussions are summarized below.
In general, the States are satisfied with the SPS-2 experiment and fully expect
to get valuable information about different design features from the project.
Many States have been conducting or planning their own analyses of their SPS-2
projects. Some analyses have already yielded useful results. The States would
like to see a focus on implementation of SPS-2 findings as they evolve over
time.
First and foremost, what the States want to know the effect on pavement performance
and cost-effectiveness of the SPS-2 experimental factors, such as:
- Drainage and base type.
- Widened lanes.
- Slab thickness.
- Concrete strength.
In addition to the structural design features, the States also would like to
know what major site condition factors influence performance of concrete pavement,
including:
- Climate.
- Traffic volume and loading.
- Subgrade type properties.
- Embankment.
Other specific expectations from the States include:
- Evaluation of existing performance
prediction equations (i.e., AASHTO formulas).
- Validation of pavement analysis
models.
- Mechanistic/empirical calibration
of lab materials properties, backcalculated materials properties, and WIM data.
- Effects of soil type, base type,
drainage, and climate on long-term subgrade moisture gradients.
- Cost-effectiveness of drainable
bases, underdrains, high-strength concrete, different base types, and other
features.
- Dynamic load response of the concrete
pavements (response of PCC to single, tandem, and tridem axles; effect of vehicle
speed on dynamic response of PCC).
- Using stiffness rather than density
for subgrade acceptance.
As to the future analysis of SPS-2 data, the States believe that it is worthwhile
to complete the missing data (backcast if necessary) to obtain traffic and materials
data. Participants believed that many fundamental studies can be conducted
to see how SPS-2 sections are responding to load and environmental stresses.
It was also suggested that an integrated analysis plan is needed for future
research.
Can SPS-2 Meet Expectations?
The specific experiment expectation of the SPS-2 project was to determine the
main effects and interactions of the following key design features:
- Slab thickness.
- Concrete strength (14 day).
- Base type including PATB, LCB, and untreated aggregate base.
- Lane width.
These main effects and interactions were to be determined for each of the following
subgrade and climatic conditions:
- Fine-grained and coarse-grained subgrade soils.
- Wet freeze, wet no-freeze, dry freeze, and dry no-freeze climates.
This evaluation has identified several significant problems that will limit
the results that can be obtained from the SPS-2. Specifically, SPS-2 project
sites are missing for certain subgrade-climate combinations. Some SPS-2 sites
had construction deviations. Significant materials data and traffic data are
missing from some sites or sections. The missing traffic data and key materials
data must be obtained or forecasted before meaningful global analysis can be
performed. The Nevada site has excessive early cracking that will limit its
usefulness.
However, these problems do not mean that many important and useful findings
and results cannot be obtained from SPS-2 experiments. Some interesting and
important early trends have already been identified that will be useful in the
design and construction of JPCP, even though the sections are only a maximum
of 7.5 years old. As time and traffic loadings accumulate on the SPS-2 sites,
additional valuable performance data will be obtained.
Because of FHWA's intense ongoing effort to obtain missing data (construction,
materials, traffic, and monitoring), valuable results can be obtained from the
SPS-2 sites. It is further believed that even more results can be obtained
if a concerted effort is made to perform proper analyses of the data.
Recommendations for the SPS-2 Experiment
Missing SPS-2 Sites. To complete all the SPS-2 factorial cells,
construction of the following sites is recommended:
- Two sites are needed to complete
the factorial in the dry no-freeze climate: one site with a fine-grained subgrade,
and the other site with a coarse-grained subgrade (i.e., Arizona, California
in the southwest United States).
- Two sites are needed to complete
the factorial and match sites in the wet no-freeze climate with a coarse-grained
subgrade (southeast United States).
- One site is needed to complete
the factorial and match a dry freeze climate with a fine-grained subgrade (north
central United States).
Missing SPS-2 Data. Significant effort is recommended to obtain the
following missing data:
- Materials-PCC strength.
- Traffic-5 sites completely missing traffic data, 11 sites missing continuous WIM data.
- Faulting-collect faulting data from several SPS-2 sites immediately.
Expectations from SPS-2.The overall objective is for the SPS-2
project's results to provide SHAs with documented findings to help them improve
their management, design, construction, and materials procedures related to
JPCP. The following specific information is expected to be gained from the SPS-2
project:
Specific design, subgrade, climate, and traffic effects
- Effect of subdrainage on performance
(faulting, transverse cracking, longitudinal cracking, IRI).
- Effect of widened slab on performance
(faulting, transverse cracking, longitudinal cracking, IRI).
- Effect of base type (lean concrete,
permeable asphalt, dense aggregate) on performance (faulting, transverse cracking,
longitudinal cracking, IRI).
- Effect of concrete slab thickness
on performance (faulting, transverse cracking, longitudinal cracking, IRI).
- Effect of 14-day concrete strength
on performance (faulting, transverse cracking, longitudinal cracking, IRI).
- Effect of climatic region on performance
(precipitation, temperature).
- Effect of subgrade soil on performance
(fine-grained, coarse-grained).
- Interactive effect of subdrainage, widened slab, base type, slab thickness, concrete strength, climatic region,
and subgrade soil on performance.
- Effect of traffic loading on performance of various design treatments.
Data for use in calibration of mechanistic-empirical distress models
- 2002 Design Guide distress
models.
- Subsequent improvement in future
versions of the guide over time.
Data for use in empirical performance modeling (for pavement management)
Data for use in a variety of mechanistic modeling (backcalculation,
structural analysis)
Data for use in a variety of cost/benefit analyses
- SPS-2 performance data are ideally
suited for use in cost and benefit studies to determine the relative cost-effectiveness
of each design feature in various climates and subgrades.
Future Data Ccollection.It is recommended that the following
areas receive special emphasis in SPS-2 data collection:
- Routine data collection.
- WIM and AVC traffic monitoring:
ensure that LTPP guidelines are followed.
- Joint faulting: follow LTPP guidelines
closely.
- Resolve irregular distress measurements
over time for each SPS-2 section (variations of distress quantities over time).
- Thermal coefficient of expansion
of concrete: ensure that all SPS-2 sites are tested in 2000.
- Collect new data required for 2002 Design Guide calibration.
- Slab curvature measurements: measure
slab curvature when the thermal gradients are zero. Measure this during two
seasons of year, wet and dry.
- Conduct video surveys of edge drains
to ensure they are working, and schedule maintenance if needed.
- Cores along the cracks in JPCP
to determine the initiation of the crack and the direction of its propagation.
In other words, where did the crack initiate: top-down or bottom-up?
Recommended Future Analyses for SPS-2 Experiment
As stated previously, a very small percentage of the SPS-2 test sections currently
have significant levels of distress, and only a few have been taken out service.
The real benefit from this experiment will occur over the next 15 years, as
more and more test sections exhibit higher levels of distress, magnifying the
effect of the experimental and other structural factors on performance.
This report focuses on the quality and completeness of the SPS-2 construction
and monitoring data and on the adequacy of the experiment to achieve the original
expectations and objectives. Detailed analysis of the effect of different design
factors on performance was outside the scope of work for this study. Thus,
future studies using the SPS-2 experimental data should be planned and prioritized
so they can be initiated as the SPS-2 projects exhibit higher levels of distress.
These future studies should be planned for in two stages that focus on local
and national expectations from the experiment. The first stage is to conduct
a detailed assessment or case study on each experimental cell in the project
(companion SPS-2 sites that define a full factorial experiment) to ensure data
adequacy, assess construction deficiencies, and support local interests and
expectations. The second stage evaluates the effect of different structural
features across the entire national experiment. Both analysis stages are briefly
discussed in the following sections. After the sections are 15 to 20 years
of age, a third-stage analysis will ultimately be needed to fully reap the benefits
of the SPS-2 experiment.
Initial Stage-Analysis of Individual Factorial Cells
Each major cell in the SPS-2 experiment consists of at least two companion
projects. One of these companion projects contains experimental sections 1
through 12, and the other contains sections 13 through 24. These companion
SPS-2 sites constitute a full factorial of design factors and make it possible
to evaluate the main effects and interactions of each experimental factor for
those site conditions. A detailed evaluation of the companion projects within
each major cell should be completed as soon as possible to ensure that all of
the data exist and are acceptable. The purposes of the case studies in the
first stage are listed below:
- Resolve construction and monitoring
data anomalies and experimental cell differences for those projects that changed
cell locations from the original experiment design, as they relate to the specific
cell in the experiment.
- Conduct comparative analyses of the individual test sections
at each site, including the supplemental test sections, to identify
differences in pavement performance and response. These comparative studies
should include performance measures, material properties, and as-built conditions.
- Determine the effect of any construction difficulties and
problems and material noncompliance issues with the SPS-2 project specifications,
if any, on pavement performance and response at each site.
- Develop findings regarding comparisons made between the
companion projects and test sections and prepare a case study report that
will be useful for the SHAs involved. Such information will also be useful
for the national studies.
This first-stage analysis is considered absolutely essential prior to initiation
of the second-stage analyses.
Second Stage-Analysis of Experimental Findings
The second-stage analyses should not be pursued until the first-stage analysis
has been completed. It is expected that the analyses performed at this stage
will be coordinated with the Strategic Plan for LTPP Data Analysis.
The SPS-2 experiment can contribute to the following specific analyses outlined
in the strategic plan:
- Develop relationships to enable
interchangeable use of laboratory- and field-derived material parameters (Strategic
Plan No. 2B).
- Establish procedures for determining
as-built material properties (2C).
- Identify quantitative information
on the performance impact of different levels of material variability and quality
(2D).
- Estimate material design parameters
from other materials data (2E).
- Quantify information as to the
relationship between as-designed and as-built material characteristics (2F).
- Develop recommendations for climatic
data collection to adequately predict pavement performance (3D).
- Develop models relating functional
and structural performance (4C).
- Calibrate relationships (transfer
functions) between pavement response and individual distress types (5C).
- Identify quantitative information
on the impact of design features on measured pavement responses (deflections,
load-transfer, strains, etc.) (7A).
- Identify quantitative information
on the impact of design features on pavement distress (7B).
- Develop guidelines for the selection
of pavement design features (7C).
In summary, the following future analysis objectives are recommended for the
SPS-2 experiment. These analysis topics are discussed in more detail in figures
25 through 31.
- Perform site-by-site analyses of SPS-2 projects to resolve data problems and gain understanding of performance of individual
test sections (figure 25).
- Determine the effect of the SPS-2 experimental factors on the performance of the jointed plain concrete pavements (figure 26).
- Determine the optimum JPCP design features for specific site conditions and traffic loading (figure 27).
- Determine the effect of concrete slab thickness variations on LTPP and initial ride quality (figure 28).
- Calibrate and validate relationships (transfer functions) between pavement structural response and individual distress types
(figure 29).
- Conduct mechanistic analyses of SPS-2 sites (particularly Ohio and North Carolina) to gain knowledge of critical stresses and deflections to explain their performance in terms of joint faulting and slab transverse and longitudinal cracking (figure 30).
- Conduct cost-benefit analyses of SPS-2 data to determine the cost-effectiveness of various design features (figure 31).
The full results from the SPS-2 experiment will require 20 years of monitoring
for the majority of sections. Additional studies beyond these proposed will
be required.
Objective no. 1
Perform site-by-site analyses of SPS-2 projects to gain understanding
of performance of individual test sections. (Initial stage, expected timeframe
2001 to 2002) |
TOPIC AREA
Pavement design. |
PROBABILITY OF SUCCESS
High. |
LTPP STRATEGIC PLAN
7A, 7B, and 7C.
(Study of the Experimental Factors) |
SUPPLEMENTAL XPERIMENTS
None. |
END PRODUCT
- Identification of test sections that perform well and poorly
at each SPS-2 site, including supplementals.
- Determination of the effect of any construction difficulties and
material noncompliance issues on pavement performance and response.
|
POTENTIAL PRODUCT USE
Design of new or reconstructed cost effective and reliable jointed
plain concrete pavements. |
GENERAL TASKS
- Conduct evaluation of permeable base and edge drains
and outlets to determine their proper construction performance, and
maintenance.
- Resolve construction and monitoring data anomalies
and experimental cell differences for those projects that changed cell
locations from the original experiment design, as they relate to the
specific cell in the experiment.
- Conduct comparative analyses of the individual test
sections at each site, including the supplemental test sections,
to identify differences in pavement performance and response.
- Determine the effect of any construction difficulties,
problems, and material noncompliance issues with the SPS-2 project specifications,
if any, on pavement performance and response.
- Develop findings regarding comparisons made
between the companion projects and test sections and prepare a case
study report that will be useful for the State highway agencies involved
and also will be useful for the national studies.
|
Figure 25. Recommended future analyses for SPS-2-Site-by-site analyses
of SPS-2 projects to gain understanding of performance of individual test sections
(initial stage).
Objective
no.2
Determine the effect of the SPS-2 experimental factors on the performance
of the jointed plain concrete pavements. (Expected timeframe 2003 to
2006) |
TOPIC AREA
Pavement design. |
PROBABILITY OF SUCCESS
High (assuming that subdrainage was evaluated in Objective No.
1). |
LTPP STRATEGIC PLAN
7A, 7B, and 7C. |
SUPPLEMENTAL EXPERIMENTS
None. |
END PRODUCT
- Effect of a permeable base drainage system on the performance
of the jointed plain concrete pavements.
- Effect of different base types on the performance of the jointed
plain concrete pavements.
- Effect of widened lane on the performance of the jointed plain
concrete pavements.
- Identification of site conditions where thicker concrete slab
will and will not contribute to improved performance.
- Effect of thicker slabs on the performance of the jointed plain
concrete pavements.
- Effect of higher strength concrete on the performance of the
jointed plain concrete pavements.
- Identification of site conditions where these design features
will contribute to improved performance of the jointed plain concrete
pavements.
|
POTENTIAL PRODUCT USE
Design of new or reconstructed cost effective and reliable jointed
plain concrete pavements. |
GENERAL TASKS
- Review results and findings from each SPS-2 site.
- Conduct statistical analysis to determine significant factors
and interactions on performance.
- Conduct mechanistic-empirical analyses for cracking, joint faulting,
and IRI.
- Based on statistical and mechanistic analyses, determine the
effect of different experimental factors or design features and interaction
on pavement performance and response.
- Prepare practical presentations of the results, including software,
decision trees, etc., for use by practicing engineers, that aid them in
determining the end products above.
|
Figure 26. Recommended future analyses for SPS-2 experiment-study of
the effect of the experimental factors on rigid pavement performance.
Objective
no. 3
Determine the optimum design features for specific site conditions and
traffic loading for JPCP. (Expected timeframe 2003 to 2005) |
TOPIC AREA
Pavement design. |
PROBABILITY OF SUCCESS
High. |
LTPP STRATEGIC PLAN
7A, 7B, and 7C.
(Study of the Experimental Factors) |
SUPPLEMENTAL EXPERIMENTS
GPS-3 and SPS-8. |
END PRODUCT
A guideline, catalog, or a design tool for selecting optimum
combinations of design features for specific site conditions and traffic
level. |
POTENTIAL PRODUCT USE
Design new cost effective and reliable jointed plain concrete
pavements. |
GENERAL TASKS
- Review results from each SPS-2 site.
- Conduct statistical analyses to determine significant factors and
interactions.
- Conduct mechanistic-empirical analyses for transverse cracking, joint
faulting, and IRI for JPCP.
- Obtain representative construction cost data for all needed features
of JPCP over selected regions that include an SPS-2 experiment.
- Based on statistical and mechanistic analyses, identify the optimum
combination of pavement design features to be used for various site
conditions to provide cost effective and reliable JPCP.
- Prepare practical presentations of the results, including software,
guidelines, catalogs, and other tools that aids practicing engineers
in determining the end products above.
|
Figure 27. Recommended future analyses for SPS-2 experiment-determination
of the optimum pavement design features.
Objective no. 4
Determine the effect of concrete slab thickness variations on long-term
pavement performance and initial ride quality. (Expected timeframe 2005
to 2007) |
TOPIC AREA
Pavement design and construction. |
PROBABILITY OF SUCCESS
High. |
LTPP STRATEGIC PLAN
2C and 2F. |
SUPPLEMENTAL EXPERIMENTS
GPS-3 and SPS-8. |
END PRODUCT
A relationship between increased thickness variations and reduced
pavement service life or reduced initial ride quality. |
POTENTIAL PRODUCT USE
Develop pay reduction factors based on concrete slab thickness variation. |
GENERAL TASKS
- Review results from each SPS-2 site.
- Establish the variation in the concrete slab thickness for each of
the SPS-2 test sections.
- Conduct statistical analyses to determine the effect of the slab thickness
variation on pavement performance and response.
- Develop reductions in service life based on these increased variations
in concrete slab thickness.
|
Figure 28. Recommended future analyses for SPS-2 experiment-quantify
the relationships between as-designed and as-built concrete slab thickness and
strength.
Objective no. 5
Calibrate and validate relationships (transfer functions) between pavement
response and individual distress types. (Expected timeframe 2005 to
2007) |
TOPIC AREA
Pavement design. |
PROBABILITY OF SUCCESS
High. |
LTPP STRATEGIC PLAN
7A, 7B, and 7C. |
SUPPLEMENTAL EXPERIMENTS
GPS-3 and SPS-8. |
END PRODUCT
A calibrated and/or validated relationship between pavement structural
responses (stress) and individual distresses. |
POTENTIAL PRODUCT USE
Design of new cost effective and reliable jointed concrete pavements
(would contribute to upgrading of 2002 Design Guide). |
GENERAL TASKS
- Establish a comprehensive input database that includes design, construction,
materials testing, traffic, climatic, and monitoring data, for the response
model.
- Perform mechanistic analysis to determine the critical response stress
and cumulative fatigue damage for the traffic loading applied until
the time of the distress measurement (utilize the relationships in the
2002 Design Guide as well as others).
- Establish the relationships between the cumulative fatigue damage
and the measured distress.
- Perform model assessment and develop calibration coefficients.
|
Figure 29. Recommended future analyses for SPS-2 experiment-calibration
and validation of the pavement transfer functions.
Objective no. 6
Conduct mechanistic analyses of SPS-2 sites (particularly Ohio and North
Carolina) to gain knowledge of critical stresses and deflections to
explain their performance in terms of joint faulting and slab transverse
and longitudinal cracking. (Expected time frame 2005 to 2007) |
TOPIC AREA
Pavement design and construction. |
PROBABILITY OF SUCCESS
Moderate to high. |
LTPP STRATEGIC PLAN
2D and 7B. |
SUPPLEMENTAL EXPERIMENTS
None. |
END PRODUCT
In-depth, field-verified knowledge as to the effects of critical
measured structural responses and curling that will be useful in pavement
design, evaluation, and rehabilitation. |
POTENTIAL PRODUCT USE
Knowledge gained from this experiment will be useful to researchers
and others for improving design procedures to make JPCP a more cost effective
and reliable pavement (upgrade 2002 Design Guide). |
GENERAL TASKS
- Establish a comprehensive input database that includes design, construction,
materials testing, traffic, climatic, monitoring data, and structural
monitoring data (deflections, strains, stresses, others).
- Analyze slab curling at all sites using longitudinal profile data or
other slab curling measurements available (Note: if insufficient data
are available, measure curling at several sites in different climates).
- Perform mechanistic analysis to determine the critical response stress
and cumulative fatigue damage for the traffic loading and slab curling.
- Analyze results and develop findings and recommendations as to impacts
of loading and curling on JPCP performance (cracking and faulting).
|
Figure 30. Recommended future analyses for SPS-2 experiment-mechanistic analyses
of JPCP.
Objective no. 7
Conduct cost/benefit analyses of SPS-2 sites to gain knowledge of the
cost-effectiveness of design features in different site conditions.
(Expected timeframe 2005 to 2007) |
TOPIC AREA
Pavement design and construction. |
PROBABILITY OF SUCCESS
High. |
LTPP STRATEGIC PLAN
7B and 7C. |
SUPPLEMENTAL EXPERIMENTS
None |
END PRODUCT
In-depth, field-verified knowledge as to the cost-effectiveness
of key design features including slab thickness, widened slab, base type,
concrete strength, and a permeable base layer. |
POTENTIAL PRODUCT USE
Knowledge gained from this experiment will be directly useful
to pavement designers in improving the cost-effectiveness of their designs. |
GENERAL TASKS
- Establish a comprehensive input database that includes design, construction,
materials testing, traffic, climatic, and monitoring data.
- Establish typical costs of various design features from the State
highway agencies in the States where SPS-2 sites are located.
- Analyze results and develop findings and recommendations as to the
cost-effectiveness of each design feature in each of the main climatic
zones covered by the SPS-2 experiment.
|
Figure 31. Recommended future analyses for SPS-2 experiment-cost/benefit
analyses of JPCP.
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