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Proceedings ArticleDOI

Pavement thickness evaluation by GPR survey in Idaho

31 Mar 1998-Vol. 3400, pp 236-249
TL;DR: In 1995 and 1996, the Idaho Transportation Department (ITD) conducted a series of ground-penetrating radar (GPR) surveys as a nondestructive testing (NDT) method to evaluate the thickness of asphalt and Portland cement concrete (AC/PCC) pavements in Idaho.
Abstract: In 1995 and 1996, the Idaho Transportation Department (ITD) conducted a series of ground-penetrating radar (GPR) surveys as a nondestructive testing (NDT) method to evaluate the thickness of asphalt and Portland cement concrete (AC/PCC) pavements in Idaho. GPR surveys employed both air-coupled and combination air and ground coupled systems with their associated equipment and software. A total of 30 miles of AC/PCC pavements were evaluated by GPR surveys. The results obtained were correlated with the site-specific ground-truth data from borings. Knowledge of pavement layer thickness is needed to predict pavement performance, establish load carrying capacities and develop maintenance and rehabilitation priorities. In addition, for new construction, it is important to ensure that the thickness of materials being placed by the contractor is acceptably close to specification. Core sampling and test pits are destructive to the pavement system, expensive, time consuming and intrusive to traffic. The objective of the ITD study was to evaluate, compare and assess the ability of these two GPR systems to accurately measure the thickness of multiple pavement layers, and document the data nondestructively. This paper reviews the findings of these surveys and provides statistically based data for both AC and PCC pavements. The overall study has shown that reasonably accurate, dependable determination of pavement thickness can be achieved by using GPR survey for conditions encountered in Idaho.

Summary (2 min read)

1. INTRODUCTION

  • Both GPR ftrms (A-C and A-G-C) were asked to provide the output and documentation of the process involved for statistical and visual validation on the highway network and project level analyses.
  • Both GPR ftrms additionally had to describe their study results on pavement thickness data, and correlate the fmdings with the ground-truth data (GTD) obtained from lTD borings drilled in the designated locations of the GPR test sections.
  • The correlation against the GTD was required to determine the accuracy (including both the network and project level data accuracy analyses) of these NDT devices typically used elsewhere in pavement thickness data collection processes.
  • The focus of the study was centered upon the applicability of the GPR system(s) to conditions encountered in Idaho.

2. GPRlNDT PROCEDURES

  • The development ofGPR began in the late 1960's.
  • GPR, more appropriately called short-pulse radar, is the electromagnetic analog of sonic and ultrasonic pulse-echo methods.
  • The electrical property of interest is the material's dielectric constant.
  • Pavement structures having mUltiple layers with similar dielectric constants are more difftcult to evaluate, and it may not be possible to identify each individual layer and measure its thickness.
  • Immediately following the transmitted pulse is a strong surface reflection, the shape of which is indicative of the shape of the radar pulse transmitted by the antenna.

3. GPR METHODOLOGIES USED IN lTD STUDY

  • ITO required the assessment of newly developed GPR technologies for both project and network level applications, including demonstration of the equipment operations, data analysis procedures, and comparison of the analyzed GPR data with measurements made by more traditional means.
  • Test sections represented a wide spectrum of network and project level applications, including interstate, principal and minor arterial in both urban and rural settings, and consisted of both AC and PCC pavements.
  • LTD required a variety of GTD information for direct comparison between GPR and core measurements which consisted of coring road test sections at designated locations, logging the bore holes (maximum depth of7 ft.) and obtaining samples from the materials encountered.

3.1 Air-Coupled (A-C) GPR System:

  • "All data for this study for the project and network level surveys were collected by setting the hom antenna 18 inches above the pavement surface at normal driving speeds which ranged from 25 mph on urban roads to 55 mph on the interstate highways.
  • No lane closures or traffic control was required.
  • Data collection for the project level survey included one for each wheel path and one at the center of the lane.
  • The results of data analysis were presented as plots, maps and American Standard Code Information Interchange data files.").
  • The data from this sub-sectioning is exported to an analysis program which automatically computes the layer thicknesses at a prescribed interval.

Analysis

  • Basic Analysis Interval Plotting Interval Reporting Interval Type Pavement thickness was analyzed for all the network surveys and for the right wheelpath data for the project level surveys.
  • The right wheel path was used since it is where the cores were taken.").

3.2 Air-Ground-

  • The 'air-coupled' antenna is mounted on an adjustable boom above the pavement and measures thin pavement layers.
  • The rack mounts include control and timing electronics for each sub-system, digitizing computer and monitor, and video sub-system.
  • A comprehensive radar signal processing hardware and software provides the means to effectively combine the large volumes of raw data and allow automated interpretation to provide continuous mUltiple pavement layer thickness and velocity profiles.
  • The system measures the signal velocity to detennine the thickness at each location by varying the geometry between the transmitter and the receiver.
  • Project level surveys were conducted at approximately 15 mph with a spatial sample interval of approximately 8 inches.

4. SUMMARY OF FINDINGS

  • Additional statistical analyses of the data was done using Pearson's Correlation Coefficient.
  • The evaluation of the data suggests good, dependable relationships between GPR and GTD for measurement of the thickness of the surface course.
  • Base course thickness measurements appears to have only a minimal to moderate relationship between GPR andGTD.

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Pavement %ickness Evaluation by GPR Survey in
Idaho
Joseph C. Sener
Boise State University
Robert M. Smith
Idaho Transportation Department
Michael D. Garz
Idaho Transportation Department
George A. Murgel
Boise State University
Robert W. Hamilton
Boise State University
See next page for additional authors
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Pavement Thickness Evaluation
by GPR Survey in Idaho
Joseph
C.
Sener, Robert
M.
Smith, Michael
D.
Garz
George
A.
Murgel, Robert
W.
Hamilton, David
R.
Haws
ABSTRACT
In
1995
and 1996, the Idaho Transportation Department (lTD) conducted a series
of
ground-penetrating
radar
(GPR) surveys
as
a nondestructive testing (NDT) method to evaluate the thickness
of
asphalt and Portland
cement concrete (ACfPCC) pavements
in
Idaho. GPR surveys employed both air-coupled and combination air and
ground coupled systems with their associated equipment and software. A total
of
30 miles
of
ACIPCC pavements
were evaluated by
GPR surveys. The results obtained were correlated with the site-specific ground-truth data from
borings.
Knowledge
of
pavement layer thickness
is
needed
to
predict pavement performance, establish load carrying
capacities and develop maintenance and rehabilitation priorities.
In
addition, for new construction,
it
is
important
to
ensure that the thickness
of
materials being placed by the contractor
is
acceptably close
to
specification. Core
sampling and test pits are destructive
to
the pavement system, expensive, time consuming and intrusive
to
traffic.
The objective
of
the lTD study was
to
evaluate, compare and assess the ability
of
these two GPR systems
to
accurately measure the thickness
of
multiple pavement layers, and document the data nondestructively. This paper
reviews the findings
of
these surveys and provides statistically based data for both AC and
PCC
pavements.
The overall study has shown that reasonably accurate, dependable determination
of
pavement thickness can
be achieved by using
GPR survey for conditions encountered
in
Idaho.
Key Words:
GPR survey, pavement thickness evaluation, NDT testing.
1.
INTRODUCTION
The research study was performed
as
a part
of
the lTD Research Project No. 119 (GPR Test Sections).
The
study considered network (whole section length) and project (500 foot-long section length) level pavement
applications. The objective was to assess and analyze the ability
of
GPR technology as a NDT method
of
data
collection for
ACIPCC pavement. GPR surveys employed either air-coupled (A-C) or combination air and ground-
coupled (A-G-C) systems, each with associated equipment and component software for interpretation
of
gathered
pavement thickness data (i.e., pavement surface thickness, base thickness and subbase thickness).
lTD provided the descriptions and locations
of
eight state highway test sections by functional class, route
number, beginning and ending mile posts, and whether the pavement type was flexible (AC) or rigid
(PCC)
pavement for the GPR technology application. lTD also provided a plan and procedures guide
for
collection
of
pavement thickness data at normal driving speeds, with no lane closures, for rural and urban highway sections. The
plan addressed the speed limit variation from
35
mph
to
55
mph. The summary
of
roadway test sections
is
provided
in
Table I. The total length
of
network lanes surveyed was 29.269 miles. The total number
of
500-foot long
sections surveyed was
16.
Joseph
C.
Sener, Assistant Professor, Ph.D., P.E., Boise State University, College
of
Engineering, Civil Engineering
Department, Boise, Idaho
Robert
M.
Smith, Research and Assistant Materials Engineer, P.E., Idaho Transportation Department, Boise, Idaho
Michael
D.
Garz, Project Engineer, P.E., Idaho Transportation Department, Boise, Idaho
George A. Murgel, Assistant
Professor, Ph.D., P.E., Boise State University, College
of
Engineering, Civil
Engineering Department, Boise, Idaho
Robert
W.
Hamilton, Assistant Professor, Ph.D., P.E., Boise State University, College
of
Engineering, Civil
Engineering Department, Boise, Idaho
David
R.
Haws, Assistant Professor, Ph.D., P.E., Boise State University, College
of
Engineering, Civil Engineering
Department, Boise, Idaho
236/
SPIE
Vol.
3400
SPIE Vol.
3400.
0277-786XJ98/$10.00

Both GPR ftrms (A-C and A-G-C) were asked to provide the output and documentation
of
the process
involved for statistical and visual validation
on
the highway network and project level analyses. Both GPR ftrms
additionally had to describe their study results on pavement thickness data, and correlate the fmdings with the
ground-truth data (GTD) obtained from lTD borings drilled
in
the designated locations
of
the GPR test sections.
The correlation against the GTD was required
to
determine the accuracy (including both the network and project
level data accuracy analyses)
of
these NDT devices typically used elsewhere in pavement thickness data collection
processes. The focus
of
the study was centered upon the applicability
of
the GPR system(s)
to
conditions
encountered in Idaho.
2.
GPRlNDT PROCEDURES
The development
ofGPR
began
in
the late 1960's. The earliest study on the use
ofGPR
in
areas related
to
civil engineering was reported
in
1974. GPR, more appropriately called short-pulse radar,
is
the electromagnetic
analog
of
sonic and ultrasonic pulse-echo methods. GPR
is
governed by a process involving the propagation
of
electromagnetic energy through materials
of
different dielectric constants.· Coetzee, et al 2 provides the following
brief description
of
the procedure:
"GPR directs pulses
of
electromagnetic radiation into the ground or pavement structure. A portion.
of
this energy
is
reflected back
to
the surface, and picked up by the GPR receiver, at each location
in
the pavement structure where a signiftcant difference
in
electrical properties
of
the materials
occur. The electrical property
of
interest
is
the material's dielectric constant. GPR
is
effective for
pavement evaluations
as
long
as
there
is
sufftcient contrast
in
the dielectric constant
of
the paving
materials. Additionally, the dielectric constant
is
frequency dependent. The following dielectric
ranges are typical for paving materials at a frequency of approximately 1 GHz:
Air
Asphalt Surface / Black (asphalt) Base
Concrete / Cement Stabilized Base
Flexible Base
Water
Steel
5
to
6
8 to 9
10
to
11
(highly moisture dependent)
80
81
From the list above,
it
is
evident that pavement layers composed
of
materials having signiftcantly different
dielectric constants can be identified. Pavement structures having mUltiple layers with similar dielectric
constants are more difftcult to evaluate, and it may not be possible to identify each individual layer and
measure its thickness. Additionally, city streets often have utility patches and maintenance practices that
can confuse data reduction.
The wavelength
of
a I-gigahertz GPR system
is
approximately three inches. The thickness
of
layers
approximately one-quarter
of
the radar wavelength or greater can be resolved. Consequently, GPR systems
cannot resolve pavement layers less than I inch
in
thickness. The I-gigahertz system has a depth
of
penetration
of
approximately 24 inches. The penetration depth
is
a function
of
the overall dielectric
constant
of
the pavement structure. Materials possessing a high dielectric constant tend to attenuate the
radar signal, thereby decreasing
its
effective depth
of
penetration.
A
SOO-megahertz GPR system has a wavelength
of
approximately six inches. Since the signal has a longer
wavelength, it can penetrate deeper into the pavement structure. The
500 MHz system
is
capable
of
measuring
to
depths
of
four to five feet, depending
on
the dielectric constant
of
the material. The trade-off
is
less thickness measurement capability with the 500 MHz system when compared
to
the 1 GHz system.,,2
"Assuming that the dielectric constant
of
a given material
is
uniform and known, the two-way
transit time
of
microwave pulses through the material
is
directly proportional to the thickness
of
the
material. The presence
of
observed range
of
errors
in
the results likely reflects the fallacy
of
the
assumption inherent
in
this procedure that the material at all locations has the same relative dielectric
constant and errors exceeding
± 0.25 inches
is
considered acceptable for compliance testing."·
"The
success
of
thickness measurement using GPR depends on a reasonably detectable reflection
from the backside (or the bottom)
of
the member (AC or PCC pavement slab), because this allows for the
SPIE
Vol.
3400/237

precise identification
of
the reflection and, therefore, the accurate measurement
of
the transit time.
Conditions that would prevent the reflection from being precisely detected include the presence
of
the
relatively high attenuation
of
the microwave pulses by the pavement materials, insufficient difference
between the relative dielectric constants
of
the pavement materials (surface and base course), and
pavements that are too thick. For some pavements, it
is
likely that there may be only small differences
between the relative dielectric constants
of
the surface course (AC or PCC), base course and the subbase
materials, so that this reflection would be very weak and difficult to identify. Consequently, prior to
an
actual inspection,
it
is
generally difficult
to
predict how precise the GPR measurements will
be
in
measuring the thickness
of
a particular pavement."}
"Short-pulse
radar systems operate by transmitting a single pulse that
is
followed by a "dead time"
in
which reflected signals
are
returned to the receiver. A basic radar system consists
of
a control unit, a
monostatic antenna
(i.e.,
an
antenna that
is
used
for
both transmitting and receiving),
an
oscillographic
recorder, and a power converter for
DC
operation. A multi-channel instrumentation tape recorder
is
recommended due to the relatively fast rate
at
which the inspection has
to
be carried out.
In
operation,
as
the radiated pulses travel through the material, different reflections will occur at interfaces that represent
changing dielectric properties. Each reflected eletromagnetic pulse arrives back at the receiving antenna at
a different time that
is
governed by the depth
of
the corresponding reflecting interface and the dielectric
constant
of
the intervening material. A receiver circuit reconstructs the reflected pulses
at
an
expanded
time scale by a time-domain sampling technique. The resulting replicas
of
the received radar signals are
amplified and further conditioned
in
the control unit before they are
fed
to an output. The analog output
can be displayed on an oscilloscope,
an
oscillographic recorder, or a facsimile gray-scale graphic recorder.
It
can also be recorded on magnetic tape
for
future processing or analysis. On an oscilloscope or
an
oscillographic recorder, the received radar signals may appear similar to the waveform depending on the
radar system used. The received signal consists
of
three basic components. At the top
is
the transmitted
pulse that serves
as
a time reference. Immediately following the transmitted pulse
is
a strong surface
reflection, the shape
of
which
is
indicative
of
the shape
of
the radar pulse transmitted by the antenna. Then,
at a later time equal to the pulse travel time from the surface to an interface and back to the antenna, the
interface reflection appears. The vertical scale
is
the time scale, which can be calibrated by a pulse
generator that produces pulses at equally spaced time durations.
If
the wave speed
in
the material
is
known, the time scale can be converted
to
a corresponding depth scale."}
3.
GPR
METHODOLOGIES USED IN lTD STUDY
The GPR system results provide pavement engineers with subsurface information for "project level"
rehabilitation design or "network level" planning. The degree
of
detail and frequency
of
measurement depend
on
the requirements
of
the user. The research by ITO included both.
At the project level, the objective was
to
gather detailed information for the selected project. The
information included continuous subsurface profiles
of
the thickness
of
layers, including determination
of
base
problems, subgrade anomalies, surface and sub-surface cracks, voids, debonding and weakened or stripped areas.
Rehabilitation design will utilize assigned appropriate layer thicknesses
in
overlay thickness calculations. One
to
three project level sections, 500 feet
in
length, were identified for detailed evaluation and correlation with GTD
within each
of
the overall network level test sections.
At the network level, the objective was
to
locate pavement segment profiles and check expected
performance by gathering sufficient continuous surface and subsurface course thickness information for future
planning purposes and budget estimates.
ITO required the assessment
of
newly developed GPR technologies for both project and network level
applications, including demonstration
of
the equipment operations, data analysis procedures, and comparison
of
the
analyzed GPR data with measurements made by more traditional (destructive) means. A total
of
8 road test sections
were identified and surveyed
as
part
of
this evaluation
by
ITO. Test sections represented a wide spectrum
of
network and project level applications, including interstate, principal and minor arterial in both urban and rural
settings, and consisted
of
both
AC
and
PCC
pavements. lTD required a variety
of
GTD information for direct
comparison between GPR and core measurements which consisted
of
coring road test sections at designated
locations, logging the bore holes (maximum depth
of7
ft.) and obtaining samples from the materials encountered.
238/
SPIE Vol.
3400

Citations
More filters
15 Oct 2009
TL;DR: In this paper, an innovative methodology, called SOFTSYS, Soft Computing Based Pavement and Geomaterial System Analyzer, is proposed as an original way of interpreting the results of FWD tests for full-depth and conventional flexible pavements with the purpose of determining pavement layer properties as well as the layer thicknesses from FWD data without the need for pavement coring.
Abstract: Evaluating structural condition of existing, in-service pavements constitutes annually a major part of the maintenance and rehabilitation activities undertaken by State Highway Agencies (SHAs). Accurate estimation of pavement geometry and layer material properties through the use of proper nondestructive testing and sensor technologies is very important for evaluating pavement’s structural condition, its remaining life for maintenance and rehabilitation purposes, and for properly incorporating life cycle cost considerations into an up to date, improved Pavement Management System. For this purpose, pavement deflection basins gathered from the nondestructive Falling Weight Deflectometer (FWD) test data are commonly used to evaluate pavement structural conditions. Development of an innovative methodology, called SOFTSYS, Soft Computing Based Pavement and Geomaterial System Analyzer, is proposed here as an original way of interpreting the results of FWD tests for full-depth and conventional flexible pavements with the purpose of determining pavement layer properties as well as the layer thicknesses from FWD data without the need for pavement coring. Since the layer thickness information plays a crucial role in FWD data back calculation and remaining pavement life estimation, the outstanding contribution of SOFTSYS will be in the reliable estimation of pavement layer thicknesses in addition to their stiffness properties. Using only FWD test results (i.e. deflections) as inputs, SOFTSYS will calculate all the necessary properties for pavement evaluation. This study focused first on the use of ANN pavement structural models developed with the results of the ILLI-PAVE finite element (FE) program to predict pavement deflections under FWD loading. Then an innovative soft computing application, referred to herein as SOFTSYS, was introduced for the hybrid use of Genetic Algorithms (GAs) and artificial neural networks (ANNs) to estimate pavement layer properties including the hot mix asphalt concrete (HMA) thickness from only the FWD test data collected on full-depth asphalt pavements built on both natural and lime modified subgrades. The performances of the developed surrogate ANN structural models (forward models) were well above satisfactory; i.e., these ANN models could be used in lieu of finite element analyses for the quick and accurate predictions of the surface deflections and the critical responses of all types of full-depth flexible pavements found/constructed in Illinois, Indiana and Ohio.

16 citations

Journal ArticleDOI
TL;DR: A novel diagnostic model for evaluating the damage condition of a cement-stabilised base course using a T-S fuzzy neural network (FNN) indicated the effectiveness of the developed FNN method.
Abstract: This paper presents a novel diagnostic model for evaluating the damage condition of a cement-stabilised base course using a T-S fuzzy neural network (FNN). An evaluation criterion for core damage r...

14 citations

Journal Article
TL;DR: In this paper, the authors investigated and developed the potential of ground penetrating radar (GPR) and electrical methods to assess pavement construction; they showed that GPR can detect the defauts and estimer the teneur in eau dans les chaussees mixtes.
Abstract: RESUME Dans le contexte des infrastructures urbaines quebecoises vieillissantes et dans un souci de planification des travaux, il faut pouvoir diagnostiquer de facon rapide, fiable et a moindre cout les chaussees urbaines Ce memoire de maitrise s’interesse a investiguer et a developper le potentiel du georadar et des methodes electriques pour l’auscultation des chaussees urbaines, soumises aux cycles de gel-degel et de saturation et desaturation On souhaite detecter les defauts et estimer la teneur en eau dans les chaussees mixtes Ces dernieres consistent en une couche de surface asphaltee, une dalle de beton de ciment et une fondation Des etudes anterieures basees en grande partie sur des modelisations et des etudes terrain, ont montre un potentiel certain de l’application conjointe du GPR et des methodes electriques pour l’auscultation de ce type de chaussee Toutefois, une meilleure evaluation du potentiel serait obtenue si on pouvait avoir acces aux proprietes physiques des materiaux de la chaussee et a des donnees geotechniques La mise en contexte permet tout d’abord de souligner le lien entre les variations de proprietes physiques des materiaux routiers, l’apparition des defauts structuraux et la teneur en eau Apres une breve etude par modelisation numerique, des mesures radar sont realisees sur une chaussee montrealaise (Canada) avant sa rehabilitation complete Lors de la destruction de la chaussee, on preleve des echantillons de sols dans les tranchees et des blocs de beton et d’asphalte sont recuperes pour etudier ensuite leurs proprietes physiques en laboratoire La permittivite complexe du beton et de l’asphalte est mesuree avec une sonde a terminaison ouverte qui integre sur un volume de 30 cm3 dans la plage de frequence 50 MHz-900 MHz Les mesures de resistivite electrique sont faites sur des carottes extraites des blocs de beton et d’asphalte avec un montage simple Les mesures sont faites sur les echantillons secs et humides, ce qui permet d’obtenir une approximation des valeurs prises en fonction des changements climatiques sur une annee En parallele, on mesure la teneur en eau sur les echantillons de sol Les teneurs en eau sont elevees et le sol a une composition de silt argileux, ce qui justifie la forte conductivite obtenue avec les mesures electriques realisees sur la fondation de la chaussee reconstruite Les donnees geophysiques et geotechniques disponibles sont ensuite compilees Des modelisations dites de verification et de correlation sont realisees pour etre comparees aux mesures realisees sur le terrain Finalement, on observe une bonne concordance Ce travail fournit une base a des travaux futurs plus specifiques----------ABSTRACT Quebec’s infrastructures are ageing A reliable, quick and economical assessment of the state of urban roads would help to plan civil engineering This MSc thesis aims to investigate and develop the potential of Ground Penetrating Radar (GPR) and electrical methods to assess pavement condition subject to wetting, freezing and drying cycles The objectives are to display defects and estimate water content in the materials used for the mixed pavement construction; these consist in layers of asphalt (top), concrete (middle) and grade and sub-grade (bottom) Prior studies showed a valuable potential of joint application of GPR and electrical resistivity to assess mixed pavement condition These studies were mainly based on numerical modeling and some site tests using both methods It was concluded that a better evaluation of the potential of the coupled methods would come from the assessment of physical properties and validation from geotechnical evidences At first, we characterized the context Structural defects and water content implied modification of physical properties of road materials After running numerical modeling, we carried out an experiment in one of the streets in Montreal (Canada) where pavement needed complete rehabilitation GPR surveys were carried out before the pavement was destroyed and removed, and subsequently a resistivity imaging was carried out on the subgrade layer We also sampled blocks of asphalt and concrete along the street from the demolition rubble in order to study their physical properties in the lab Soil samples were taken from trenches to measure water content The grade and sub-grade were mainly a mix of clayey-silt and gravel, as the embedding ground is grey clay We measured the complex dielectric constants of asphalt and concrete in the range 50 MHz-900 MHz with a recently developed dielectric probe sampling a volume of 30 cm3 Resistivity measurements were also performed on large cores of asphalt and concrete using an in-house system Measurements were carried out on dry and wet samples, which provided a range of values encompassing the climatic conditions for the whole year Finally the physical property and geotechnical data were used as input to numerical modeling and the modeled responses compared to the survey data The predicted data fit nicely with the observed data This work aims to provide further information for a better calibration of geophysical devices in pavement condition assessment Moreover, it gives a wide range of information, which could become a base for further and more specific works

3 citations

References
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Book
01 Jan 1982
TL;DR: In this article, Cox et al. present a survey of the history of statistical methods and their applications in the field of statistics, including the use of the Normal Curve and z scores.
Abstract: Preface I. DESCRIPTIVE STATISTICS 1. Introduction to Statistics Stumbling Blocks to Statistics A Brief Look at the History of Statistics Gertrude Cox (1900-1978) Benefits of a Course in Statistics General Fields of Statistics Summary Key Terms and Names Problems 2. Percentages, Graphs and Measures of Central Tendency Percentage Changes-Comparing Increases with Decreases Graphs Measures of Central Tendency Appropriate Use of the Mean the Median and the Mode Summary Key Terms Problems Computer Problems 3. Variability Measures of Variability Graphs and Variability Questionnaire Percentages Key Terms Computer Problems 4. The Normal Curve and z Scores The Normal Curve z Scores Carl Friedrich Gauss (1777-1855) Translating Raw Scores into z Scores z Score Translation in Practice Fun with your Calculator Summary Key Terms and Names Problems 5. z Scores Revisited: T Scores and Other Normal Curve Transformations Other Applications of the z Score The Percentile Table T Scores Normal Cure Equivalents Stanines Grade-Equivalent Scores: A Note of Caution The Importance of the z Score Summary Key Terms Problems 6. Probability The Definition of Probability Blaise Pascal (1623-1662) Probability and Percentage Areas of the Normal Curve Combining Probabilities for Independent Events A Reminder about Logic Summary Key Terms Problems II. INFERENTIAL STATISTICS 7. Statistics and Parameters Generalizing from the Few to the Many Key Concepts of Inferential Statistics Techniques of Sampling Sampling Distributions Infinite versus Finite Sampling Galton and the Concept of Error Back to z Some Words of Encouragement Summary Key Terms Problems 8. Parameter Estimates and Hypothesis Testing Estimating the Population Standard Deviation Estimating the Standard Error of the Mean Estimating the Population of the Mean: Interval Estimates and Hypothesis Testing The t Ratio The Type 1 Error Alpha Levels Effect Size Interval Estimates: No Hypothesis Test Needed Summary Key Terms Problems Computer Problems 9. The Fundamentals of Research Methodology Research Strategies Independent and Dependent Variables The Cause-and-Effect Trap Theory of Measurement Research: Experimental versus Post Facto The Experimental Method: The Case of Cause and Effect Creating Equivalent Groups: The True Experiment Designing the True Experiment The Hawthorne Effect Repeated-Measures Designs with Separate Control Groups Requirements for the True Experiment Post Facto-Research Combination Research Research Errors Experimental Errors Meta-Analysis Methodology as a Basis for More Sophisticated Techniques Summary Key Terms Problems 10. The Hypothesis of Difference Sampling Distribution of Differences Estimated Standard Error of Difference Two-Sample t Test for Independent Samples Significance William Sealy Gossett (1876-1937) Two-Tailed t Table Alpha Levels and Confidence Level The Minimum Difference Outliner One-Tail t Test Importance of Having at Least Two Samples Power Effect Size Summary Key Terms Problems Computer Problems 11. The Hypothesis of Association: Correlation Cause and Effect The Pearson r Interclass versus Intraclass Karl Pearon (1857-1936) Missing Data Correlation Matrix The Spearman r s' 293 An Important Difference between the Correlation Correlation Coefficient and t Test Summary Key Terms and Names Problems Computer Problems 12. Analysis of Variance Advantages of ANOVA The Bonferroni Test Ronald Aylmer, Fisher (1890-1962) Analyzing the Variance Applications of ANOVA The Factorial ANOVA Eta Square and d Graphing the Interaction Summary Key Terms and Names Problems Computer Problems 13. Nominal Data and the Chi Square Chi Square and Independent Samples Locating the Difference Chi Square Percentages Square and z Scores Chi Square and Dependent Samples Requirements for Using Chi Square Summary Key Terms Problems Computer Problems III. ADVANCED TOPICS IN INFERENTIAL STATISTICS 14. Regression Analysis Regression of Y on X Sir Francis Galton (1822-1911) Standard Error of Estimate Multiple R (Linear Regression with More Than Two Variables) Path Analysis The Multiple Rand Causation Partial Correlation Summary Key Terms and Names Computer Problems 15. Repeated-Measures and Matched-Subjects Designs With Interval Data Problem of Correlated or Dependent Samples Repeated Measures, Paired t Ratio Confidence Interval for Paired Differences Within-Subjects Effect Size Testing Correlated Experimental Data Summary Key Terms Problems Computer Problems 16. Nonparametrics Revisited: The Ordinal Case Mann-Whitney U Test for Two Ordinal Distributions with Independent Selection Kruskal-Wallis H Test for Three or More Ordinal Distributions with Independent Selection Wicoxon T Test for Two Ordinal Distributions with Correlated Selection Friedman ANOVA By Ranks for Three or More Ordinal Distributions with Correlated Selection Advantages and Disadvantages of Nonparametric Tests Summary Key Terms Problems 17. Tests and Measurements Norm and Criterion Referencing: Relative Versus Absolute Performance Measure The Problem of Bias Test Reliability Validityand Measurement Theory Test Validity Item Analysis Summary Key Terms Problems Computer Problems 18. Computers and Statistical Analysis Computer Literacy The Statistical Programs Ada Lovelace (nee Byron, 1815-1852) Logic Checkpoints Answers Recommended Reading 19. Research Simulations: Choosing the Correct Statistical Test Methodology: Research's Bottom Line Checklist Questions Critical Decision Points Research Simulations: From A to Z The Research Enterprise A Final Thought: The Burden of Proof Special Unit: The Binomial Case Appendix A Appendix B Glossary References Answers to Odd-Numbered Items (and Within-Chapter Exercises) Index Statistical Hall of Fame Biographies Gertrude Cox-Chapter 1 Carl Gauss-Chapter 4 Blaise Pascal-Chapter 6 William Gossett-Chapter 10 Karl Pearson-Chapter 11 Ronald Fisher-Chapter 12 Sir Francis Galton-Chapter 14 Ada Lovelace-Chapter 18

459 citations

Book
30 Jun 1952

454 citations

01 Jan 1996
TL;DR: An overview of the state-of-the-art of ground penetrating radar (GPR) technology as applied to the measurement of as-built conditions, with specific application examples and supporting research study results, is provided in this article.
Abstract: This paper provides an overview of the state-of-the-art of Ground Penetrating Radar (GPR) technology as applied to the measurement of as-built conditions, with specific application examples and supporting research study results. Knowledge of the as-built conditions is an essential part of any non-destructive evaluation program. Existing records and drawings often do not represent what actually took place during construction, nor do they represent changes and repairs that have taken place after initial construction. Ground penetrating radar is a powerful NDE tool for the measurement of the internal dimensions of constructed materials. Existing capabilities include the determination of the thickness of asphalt, concrete, and granular material layers, and measurement of the depth and location of reinforcing steel. The equipment technology has been developed for data collection at up to normal traffic speeds (on pavements and bridge decks), and analytic techniques have been developed to automate the data processing. This paper describes the status of GPR equipment technology that is available for this application, including equipment features, data acquisition methodologies, and data samples for different applications. It also describes the basic principles for GPR data interpretation.

14 citations

Book ChapterDOI
01 Jan 1996
TL;DR: In this paper, the authors provide an overview of typical non-destructive test (NDT) procedures currently used for pavement structural evaluation applications, including surface deflection measurements, spectral analysis of surface waves (SASW), and ground penetrating radar (GPR) approaches.
Abstract: This paper provides an overview of typical non-destructive test (NDT) procedures currently used for pavement structural evaluation applications. In particular, surface deflection measurements, spectral analysis of surface waves (SASW), and ground penetrating radar (GPR) approaches are described and discussed. Data interpretation and application, including problems encountered with each type of measurement, are also covered. Potential future developments in this field are discussed.

2 citations