1. 1
Tushar Kotiya1
, Chandrapal Khasiya2
, Ashish Masani3
, K R. Trivedi4
1
B.E.Student in Civil Engg. A.D.Patel Institute of Technology, New Vidyanagar, Anand, Gujarat, India
2
B.E.Student in Civil Engg. A.D.Patel Institute of Technology, New Vidyanagar, Anand, Gujarat, India
3
B.E.Student in Civil Engg. A.D.Patel Institute of Technology, New Vidyanagar, Anand, Gujarat, India
4
Associate professor, Department of Civil Engineering, A.D.Patel Institute Of Technology, New Vidyanagar,
Anand, Gujarat, India
Email: kumartrivedi@gmail.com4
Abstract- Presently, the need for infrastructure renewal is rapidly growing globally. Highways pavements, bridges,
parking garages and other exposed structures are becoming functionally obsolete or deteriorating. Looking at the increasing
usage of road infrastructure, it is essential to provide durable pavement for uninterrupted travel and low maintenance. The
amount a flexible pavement deflects under load indicates, in part, its adequacy as far as structural capacity is concerned.
Repeated deflection may cause the pavement to crack and distort as a result of fatigue, excessive bending stresses,
accumulated plastic deformation and other factors. Non-destructive structural evaluation of pavements is an important part of
the pavement management process, particularly at the project level. These measured deflection data using Benkelman Beam
are analyzed to determine the tolerability of the pavement. Here is an effort to evaluate few of the pavement characteristics
of an existing National/State highway. This paper describes about the results obtained from various research done on the
flexible pavement.
Key Words–Flexible pavement, Benkelman Beam, Properties of pavement, Deflection.
1. INTRODUCTION
In recent years, with the evolution in engineering and
technology, the usage of road infrastructure has been
exponentially increased. So, it becomes essential to provide
good quality pavements for constant flow of traffic and low
maintenance. The deflection of the pavement depends
majorly on the load of traffic which directly affects its
tolerability. Non-destructive structural evaluation of
pavements is an important part of the pavement
management process, particularly at the project level. These
measured deflection data using Benkelman Beam are
analyzed to determine the adequacy of the pavement.
A road network is a valuable Government asset and failure
to maintain the roads that form the network will lead to their
rapid deterioration which in turn will lead to increases in
road user costs and accidents and the need for expensive re-
construction works. Well-maintained roads make a valuable
contribution towards the country’s economy. Different types
of tests such as the Benkelman Beam Test, Falling Weight
Deflectometer and Dynamic Cone Penetrometer (DCP) test
and the CBR test all provide useful information on
pavement strength. It is obviously essential to select the
right type of test. For strengthening of existing pavements,
the Benkelman Beam test or the Falling Weight
Deflectometer is preferred, since it gives the actual strength
of the pavement directly and quickly.
India has one of the largest highway and road networks on
the planet, third only to the road network of the United
States and China. The road network has expanded from 0.4
million km in 1951 to about 3.32 million kilometers
presently, a sevenfold increase, but traffic has increased 120
times (Department of Road Transport and Highways, Govt.
of India). This leads to the deterioration of the surface of the
asphalt pavements and a need to rehabilitate them before
further damage could occur. Since the use of a concrete
overlay, called as white topping, is a relatively new concept
in Hot Mix Asphalt (HMA) pavement rehabilitation in
India, there is a need to evaluate its performance for Indian
traffic and climatic conditions by conducting Falling Weight
Deflectometer (FWD) and Benkelman Beam Deflection
(BBD)test on conventional white topping overlays
constructed in Pune city (India).
The amount of a flexible pavement deflects under load
indicates, in part, its adequacy insofar as structural capacity
is concerned. Repeated deflection may cause the pavement
to crack and distort as a result of fatigue, excessive bending
stresses, accumulated plastic deformation and other factors.
The performance of the flexible pavement is influenced by
many factors. These include gross load, tire pressure,
repetition of load, thickness and durability of the various
pavement components, and the elastic-plastic properties of
the pavement components, (particularly the sub grade soil).
Pavement distress may be influenced by a combination of
the above factors. Pavement failure may result from
excessive shear stresses, consolidation of one or more of the
pavement components, lateral showing, bending or a
combination of these. Historically, pavement design has
been approached from two broad differing points of view.
First, the practicing engineer most often uses concepts of
design based primarily on pavement performance. Second,
the approach used by researches and educators is based
principally upon theoretical concepts. Experienced has
indicates that neither of these concepts by itself gives the
optimum answer. Complete reliance upon pavement
performance represents a static condition where one must
wait a relatively long period of time before new concepts
EVALUATION OF FLEXIBLE PAVEMENT –
A REVIEW

2. 2
can be proven out. On the other hand, theoretical equations
are generally based upon simplified assumptions of
elasticity and many times are still too cumbersome to be
used in practice.
A.C.Benkelman, an employee of the U.S.Bureau of Public
Roads, developed in 1953 the so-called Benkelman beam or
deflection beam. This device was introduced during the
WASHO road test (WASHO: Western Association of State
Highway Officials), which was conducted from 1952-1954
in Idaho in the USA.
The Benkelman beam is a non-destructive portable test
device, which is able to record the pavement surface
deflections occurring under actual truck traffic loading at
different discrete points along a pavement. The results of
these measurements can be used for analyzing the bearing
capacity of an existing pavement structure and to design the
possibly required overlay.
Purpose of measuring deflection:-
The primary purpose of determining the deflection of an
existing pavement, insofar as structural adequacy is
concerned, is to obtain basic data either by inference or by
direct measurement relative to the stress-strain properties of
a pavement structure. Sometimes measurement of gross
deflection at a pavement surface may not yield the desired
results. Such factors as radius of bending and component
deflection have their effect.
The secondary purpose of deflection testing is therefore to
determine pavement strengths in order to decide what
rehabilitation works need to be undertaken and how strong
they need to be.
OBJECTIVES OF RESEARCH
1) To determine the pavement strength.
2) To determine the properties such as cracks,
undulation, temperature, rutting, etc.
3) To determine the deflection property using
non-destructive methods.
4) Comparison of various methods.
2. SUMMARY OF PREVIOUS
RESEARCH
Department of transportation, California [1] has described
five pavement deflection measuring devices in the test
method. Basically, the method consists of measuring the
total deflection resulting from a load applied on the surface
of the pavement. The results say that a comparison of each
deflection measuring device to the California deflectometer
should be performed at least once a year. The results should
be record in an appropriate form that is easy to use.
Ir. A.F.H.M. Visser, ET.AL [2] introduced and described
the Benkelman deflection test. Furthermore Benkelman
beam test are stimulated using two multi-layer programs,
based on an elastic and visco-elastic material model for
asphalt. The results of these two programs are compared
with each other. Finally, using the model based on visco-
elasticity as a benchmark, the limiting conditions for elastic
analysis are indicated.
Murillo Feo C.A, ET.AL [3] correlated between deflection
measurements on flexible pavements under static and
dynamic load techniques. The results of the experiment
depict the deflections under static load are higher than those
generated by dynamic load ; this is due to longer duration of
load application. Therefore, the results obtained from
deflection values under static load do not represent
accurately the effects made by moving loads, so the
structural analysis made using static loading equipment may
generate higher costs in rehabilitation projects.
Gary W. Sharpe, ET.AL [4] compared the road ratter and
Benkelman beam methods and depicted the relationship
between road ratter and Benkelman beam deflections using
elastic theory. The results of experiment will illustrate some
relations between the Benkelman beam and road ratter
deflections.
D.R.Jundhare, ET.AL [5] presented the linear, exponential
and logarithmic relationship between Benkelman beam and
falling weight deflectometer deflections for edge and corner
loading positions of conventional white topping overlay by
using computer.
Government of the People’s Republic of Bangladesh [6] has
carried out the surveys from the survey roots Start Node and
to the survey roots End Node. The aim of this section is to
set out, as clearly as possible, a simple description of what
Benkelman beam testing is and how it should be
undertaken. The result says that the survey is always carried
out in the direction of the traffic – never against the traffic
in a lane.
C.J.Kruse, ET.AL [7] determined the relationship between
the plate bearing test and Benkelman beam test for
predicting the allowable spring load, and to determine the
relationship of the two test methods to load carrying
capacity, pavement structure, and performance of country
roads and municipal streets in Minnesota. The experimental
results are a mathematical correlation was developed

3. 3
between the plates bearing test the Benkelman beam test.
However, the data scatter, or variance, is such that it cannot
be recommended for use.
Navneet Garg, ET.AL[8] compared between falling weight
deflectometer and static deflection measurements on
flexible pavements at the national airport pavement test
facility. The results from FWD tests and static load tests
performed on the flexible pavement test items at NAPTF are
presented. The comparison of relative surface deflections
for different flexible pavement structures from FWD tests
and static tests is very different.
J.H.Defoe[9]evaluated the strength and load carrying
capacity of stabilized in-place recycled basis as compared
with conventional hot plant-mixed basis used for
constructing bituminous shoulders and pavements. The
results of the study where expressed as estimated stiffness
modulus values for the two base materials. This general
method of analysis is a recent innovation in pavement
thickness design and is currently being modified and
improved as experienced dictates. And both black base and
stabilized base sections constructed on clay sub grades
experienced greater deflections than those constructed on
sand.
ASTM International (American Society for Testing and
Materials) [10] provided procedural information for
measuring pavement surface deflections, directly under, or
at locations radially outward from a known static, steady
state or impulse load. The paper also includes general
descriptions of the various types of static and semi
continuous deflection testing devices, and procedures for
deflection measurement corresponding to each testing
devices.
3. CONCLUSSIONS
The following are the conclusions from the present study.
 With various methods like static and dynamic the
properties of flexible pavement can be easily
determined.
 Measured data through Benkelman beam can be
compared with other methods to get the accurate
measurements.
 With the help of survey manual the process
becomes ease.
REFERENCES
[1] Department of transportation California, methods
of test to determine flexible pavement habilitation
requirements by pavement deflection
measurements, California test 356, March 2000.
[2] Ir. A.F.H.M. Visser and D.Priambodo
Koesriendartono, towards a mechanistic analysis of
Benkelman beam deflection measurements, Heron,
VOL.45, NO.3 (2000), ISSN 0046-7316.
[3] Murillo Feo C.A and Bejarano Urrego L.E.,
correlation between deflections measurements on
flexible pavements obtained under static and
dynamic load techniques, Proceedings of the 18th
International conference on soil mechanics and geo
technical engineering, Paris 2013.
[4] Gary W. Sharpe and Herbert F. Southgate, Road
ratter and Benkelman beam pavement deflections,
Commonwealth of Kentucky, department of
transportation division of research, June 11-1979.
[5] D.R.Jundhare,Development correlation between
Benkelman beam deflection and falling weight
deflectometer for conventional white topping
overlay, journal of basic and applied scientific
research,2(9)8725-8731,2012, ISSN2090-4304.
[6] Government of the People’s Republic of
Bangladesh, Benkelman beam deflection survey
manual, ministry of communications roads and
highways department, May 2005.
[7] C.J.Kruse and E.L.Skok, Flexible pavement
evaluation with the Benkelman beam, office
of materials, investigation no. 603, summary
report-1968 (1983 Revision).
[8] Navneet Garg and Wayne.H.Marsey, Comparison
between FWD and static deflection measurements
on flexible pavements at the national airport
pavement test facility (NAPTF), Federal aviation
administration airport technology transfer
conference 2002.
[9] J.H.Defoe, Benkelman beam testing shoulder and
pavement recycling projects, research laboratory
section testing and research division, research
project 81TI-727, research report no. are-1217,
November 10,1983.
[10] ASTM International (American Society for Testing
and Materials), standard guide for general
pavement deflection measurements,
Designation:D4695-03