AASHTO STANDING COMMITTEE ON RESEARCH
AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS
NCHRP Problem Statement Outline
I.
PROBLEM NUMBER
To be assigned by NCHRP staff.
II.
PROBLEM TITLE
Process for Evaluating the Impacts of Implements of Husbandry on Pavements
III.
STATEMENT OF THE RESEARCH PROBLEM
The configurations and weights of farm equipment, known as implements of husbandry
(IoH), have changed and increased to meet the needs of the agricultural industry.
Although this equipment has been designed for use primarily in farm fields, travel from
farm to field often occurs on public roadways.
Understanding the impact these vehicles have on public roadways is important for state
agencies. It is equally, if not more, important for local government agencies since this
equipment utilizes local roadways more often and their pavement structures are not
typically built to the load carrying capacity of state highways.
Impacts from conventional trucks can be evaluated using ESALs (equivalent single axle
loads). However, the obvious differences between IoH equipment and conventional
trucks (i.e., size, weight, configuration, tires) are not accommodated in the ESAL
evaluation for pavement impacts. Therefore, there needs to be a method (i.e. calculation,
coefficients or software) by which pavement structure engineers can evaluate these
vehicles for their impacts on the life of pavement structures and their service lives.
Special note to AASHTO committees and subcommittees: Please indicate the relationship
between the suggested problem and the committee’s strategic plan and/or its overall
research agenda. If not related to a planned agenda, explain the urgency of the research
need.
IV.
LITERATURE SEARCH SUMMARY
A literature search on the TRID database produced several documents that addressed the
concerns and investigated the impacts that IoH-type vehicles have on pavements;
however, they do not address how to incorporate this understanding into a usable factor
such as an ESAL.
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The TRID database literature search provided:
STRESSING OUR FUTURE
Iowa Department of Transportation
1997, 6 p
http://trid.trb.org/view/538678
Abstract: This pamphlet discusses the transportation equipment used by agricultural
operations in Iowa, and the dramatic impact on Iowa's road system and its maintenance
from use of the equipment. Stress to pavements is related to a vehicle's axle weight and
Iowa's laws regulate the axle weights of most heavy vehicles using roadways. However,
most vehicles used as "implements of husbandry" are exempt from regulation for weight
limits. Consequently, many vehicles used in farming operations exceed the weight limit.
A chart is displayed communicating the effect of different vehicles on roadway
pavements. The chart lists effects on PCC pavements; however it notes that structurally
equivalent asphalt concrete pavements have similar impacts. Stress on bridges is also
significantly increased by certain vehicle types.
Effects of Implements of Husbandry (Farm Equipment) on Pavement Performance
University of Minnesota, Twin Cities; Minnesota Department of Transportation
2012, 551p
Lim, Jason; Azary, Andrea; Khazanovich, Lev; Wang, Shiyun; Kim, Sunghwan; Ceylan, Halil;
Gopalakrishnan, Kasthurirangan
http://trid.trb.org/view/1141534
Abstract: The effects of farm equipment on the structural behavior of flexible and rigid
pavements were investigated in this study. The project quantified the difference in
pavement behavior caused by heavy farm equipment as compared to a typical 5-axle, 80
kip semi-truck. This research was conducted on full-scale pavement test sections
designed and constructed at the Minnesota Road Research facility (MnROAD). The testing
was conducted in the spring and fall seasons to capture responses when the pavement is
at its weakest state and when agricultural vehicles operate at a higher frequency,
respectively. The flexible pavement sections were heavily instrumented with strain
gauges and earth pressure cells to measure essential pavement responses under heavy
agricultural vehicles, whereas the rigid pavement sections were instrumented with strain
gauges and linear variable differential transducers (LVDTs). The full-scale testing data
collected in this study were used to validate and calibrate analytical models used to
predict relative damage to pavements. The developed procedure uses various inputs
(including axle weight, tire footprint, pavement structure, material characteristics and
climatic information) to determine the critical pavement responses (strains and
deflections). An analysis was performed to determine the damage caused by various
types of vehicles to the roadway when there is a need to move large amounts agricultural
product.
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Response of Iowa Pavements to Heavy Agricultural Loads
Iowa Department of Transportation; Iowa Department of Transportation; Center for
Transportation Research and Education
1999, 38p
Fanous, Fouad; Coree, Brian; Wood, Doug
http://trid.trb.org/view/1311863
Abstract: Iowa's county road system includes several thousands of miles of paved roads
which consist of portland cement concrete (PCC) surfaces, asphalt cement concrete (ACC)
surfaces and combinations of thin surface treatments such as seal coats and slurries.
These pavements are relatively thin pavements when compared to the state road system
and therefore are more susceptible to damage from heavy loads for which they were not
designed. As the size of the average farm in Iowa has increased, so have the size and
weights of implements of husbandry. These implements typically have fewer axles than a
truck hauling the same weight would be required to have; in other words, some farm
implements have significantly higher axle weights than would be legal for semi-trailers.
Since stresses induced in pavements are related to a vehicle's axle weight, concerns have
been raised among county and state engineers regarding the possible damage to
roadway surfaces that could result from some of these large implements of husbandry.
This study investigated the effects of variously configured grain carts, tank wagons, and
fence-line feeders on Iowa's roadways, as well as the possible mitigating effects of
flotation tires and tracks on the transfer of axle weights to the roadway.
Impacts of Overweight Implements of Husbandry on Minnesota Roads and Bridges
Iowa State University, Ames; Minnesota Department of Transportation
2004, 13p
Phares, Brent M; Wipf, Terry; Ceylan, Halil
http://trid.trb.org/view/767769
Abstract: Over the past few decades, the national industry has seen the number of farms
decrease with a simultaneous increase in the average farm size. With larger farms and
continuously improving farming techniques, the need to increase production and
efficiency has affected equipment carrying capacity and completely changed the tools
being used. During select seasons, it is common to have single-axle loads on secondary
roads and bridges that exceed normal load limits (typical examples are grain carts and
manure wagons). Even though these load levels occur only during a short period of time
of the year (fall for grain carts and spring for manure wagons), there is concern that they
can do significant damage to pavements and bridges. Currently, the only limitation placed
upon farm implements is a metric based upon the load per unit width of tire. This metric
does not appear to be consistent with the metrics commonly used during design of
infrastructure. The objective of the work presented in this report was to perform a
synthesis study related to the impacts of heavy agriculture vehicles on Minnesota
pavements and bridges and to identify those impacts. The synthesis and associated
analyses were completed using metrics that are consistent with engineering design and
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evaluation concepts. The conclusion of this study validates the years of close observation
of highway and bridge engineers that the heavy agricultural loads can cause potential
problems in terms of both safety to the traveling public and added costs to the
maintenance of the local system of highway infrastructure.
V.
RESEARCH OBJECTIVE
The objective of this research is to define the key differences between IoH equipment
and conventional trucks in order to develop a method for analyzing the impacts of IoH
equipment on pavement structures and their service lives. Specifically, the method
must be one that is readily relatable to pavement design engineers and utilizes readily
available vehicle information.
Pavement design engineers are familiar with the concept of ESALs. Development of
ESAL factors for implements of husbandry would be very relatable and straightforward.
Alternatively, simplified software could be used. Such software would have to produce
results based on some basic, readily available inputs such as gross vehicle weight, axle
weights and spacings, and tire type and pressure.
VI.
ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD
PROPOSED RESEARCH APPROACH
Though various studies have produced an understanding that the impacts IoH vehicles
have on pavements, there has not been advancement in creating an analysis tool.
Because the concept of an analysis tool is new research to the industry, it is expected
that RFP responses to this problem statement would include a thorough discussion of a
proposed research approach.
Any proposed approach for this research should be structured such that it produces a
method or device which can be used by pavement professionals to analyze the impacts
of IoH equipment on pavement structures and their service lives. This method could
include creating an equivalent ESAL factor (if possible), creating a tool such as 3D Move
Analysis that has been simplified, creating a simple software tool or spreadsheet, or
other methods that are as relatable (as ESALs would be) to the general industry.
It is anticipated that a thorough literature search would be conducted and potentially
any available data from previous research projects would be augmented. There may
also be a need for gathering or fresh data (which might have had to be done in order
for the researcher to develop proposed alternatives).
Another phase could include sharing the proposed direction (i.e., equivalent ESALs,
software) with the NCHRP panel so the panel can evaluate the proposed direction.
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Finally, there should be a phase to evaluate the proposed route that clearly shows how
it compares to ESALs or the development of the software or other tool (i.e., what inputs
will be required, what sort of sensitivity is there since basic inputs are what will work
best for pavement design engineers).
In all, it is estimated that this research would cost approximately $250,000 depending
on the solution provided.
RESEARCH PERIOD:
Depending on the solution provided, it is estimated that this project would take 18
months to complete.
VII.
PERSON(S) DEVELOPING THE PROBLEM
Peter Kemp, P.E.
Pavement Supervisor
Wisconsin Department of Transportation
3502 Kinsman Blvd
Madison WI 53704-2507
(608) 246-5393
peter.kemp@dot.wi.gov
Laura Fenley, P.E.
Pavement Structure Engineer
Pavement & Subsurface Exploration Unit
Wisconsin Department of Transportation
3502 Kinsman Blvd
Madison WI 53704-2507
(608) 246-5455
laura.fenley@dot.wi.gov
VIII.
PROBLEM MONITOR
Laura Fenley, P.E.
Pavement Structure Engineer
Pavement & Subsurface Exploration Unit
Wisconsin Department of Transportation
3502 Kinsman Blvd
Madison WI 53704-2507
(608) 246-5455
laura.fenley@dot.wi.gov
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IX.
DATE AND SUBMITTED BY
Show date of submission and by whom problem is submitted.
Advice to State Departments of Transportation and the Federal Highway
Administration: Submitters are encouraged, but certainly not required, to vet or submit
problem statements through an appropriate AASHTO committee or subcommittee.
----------------------------------------------------------------------Please submit completed problem statement online at this link or as a Word file attached to the
following e-mail address:
nchrp@nas.edu
Questions on the process can be directed to the same address or chedges@nas.edu.
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