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OCR for page 138
138
vironmental, and traffic conditions to which the pavement
is likely to be subjected.
Asphalt concrete construction projects were selected in
Colorado, Michigan, Texas, Virginia, and Wyoming for
participation in Phase II of the project. Field construction
procedures were documented, cores of newly compacted
asphalt concrete obtained, samples of asphalt-aggregate
mixtures actually used in the construction obtained, along
with samples of the aggregates and asphalt binders. Lab-
oratory specimens were prepared by several different
methods to compare with the field cores. The laboratory
specimens were subjected to various conditioning pro-
cedures and tests methods to identify techniques for pre-
dicting traffic loading and environmental foes of distress.
Research has been completed. The final report has been
submitted and is being reviewed.
AREA 10: SPECIFICATIONS,
PROCEDURES, AND PRACTICES
Project 10-1 FY '64
Development of Guidelines for Practical and
Realistic Construction Specifications
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Miller-Warden Associates
W. B. Warden
November 15, 1963
November 14, 1964
$25,000
It is recognized that many existing specifications do
not properly consider variations in work and materials
which are inevitable and characteristic of the best con-
struction possible today. In a development of guidelines
for adequate specifications, this project included such
areas as surface smoothness for subgrades, bases, and
pavements; thickness measurements for bases and pave-
ments; gradation and other requirements for aggregates
and aggregate mixtures; and a summary of selected cur-
rent specifications pertinent to the areas of study. Con-
sideration was given to the validity of specifications with
respect to need in the accomplishment of purpose, eco-
nomic impact inherent in specifications, natural variations
inherent in work and material, and variations inherent in
methods of measurement and control test procedures.
The final report for this project has been published as:
NCHRP Report 17, "Development of Guidelines for
Practical and Realistic Construction Specifications."
Project 10-2 FY '64
Evaluation of Construction Control
Procedures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Miller-Warden Associates
S. B. Hudson
November 4, 1963
February 1, 1966
$59,750
This research was initiated to obtain needed basic in-
formation for the formulation of standards for evaluation
and acceptance of work, materials, and highway con-
struction. Its objectives included a study to determine
variations inherent to measurement methods, testing tech-
niques, and sampling methods and procedures. The scope
of this study was confined to the examination and inves-
tigation of gradation of aggregates. It includes a review
of measurement and test procedures to determine those
not including precision statements and a study involving
statistical techniques for evaluating gradation test pro-
cedures, sampling methods, and variations inherent in
aggregate gradations.
Initial phase research has been completed, and the proj-
ect report has been published as: NCHRP Report 34,
"Evaluation of Construction Control Procedures-In-
terim Report."
Project 10-2A FY,6s
Evaluation of Construction Control
Procedures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Materials Research and Develop-
ment
S. B. Hudson
July 15, 1966
November 14, 1967
$70,945
The continuation phase of Project 10-2 specifically con-
sidered (1) the variations in gradation of aggregates, in-
cluding fine aggregates, drawn from the bins of operating
hot-mix plants, with sampling error, short- and long-term
variations, and the effect of cold-feed variations to be
included; (2) a statistically designed experiment to deter-
mine the effect of variation in gradation of coarse aggre-
gate, within the range found to be inherent under existing
controls, on the strength and workability of laboratory-
prepared concrete; (3) the effect of increment size with
respect to maximum particle size and accuracy of the
results of sampling to provide additional information as
to the shape and minimum capacity of tools to be used
for sampling coarse aggregates; and (4) further study of
the basic pattern of variation of gradation.
OCR for page 139
139
Research has been completed, and the project report
has been published as: NCHRP Report 69, "Evaluation
of Construction Control Procedures- Aggregate Gra-
dation Variations and Effects."
Project 10-3 FY '64 and FY '65
Effects of Different Methods of Stockpiling
and Handling Aggregates
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Miller-Warden Associates
S. B. Hudson
Oct. 22, 1963
Apr. 30, 1964
$25,000
Oct. 15, 1964
Oct. 16, 1965
$30,000
The difficulties associated with producing aggregates
and providing them at the job site within desirable spec-
ification limits have been recognized for many years. To
provide further knowledge for a possible solution to these
difficulties, the over-all objectives of this research were to
(1) find the effects of stockpiling and handling on the
properties of an aggregate, including segregation and deg-
radation, and (2) establish suggested procedures for better
practices in stockpiling and handling.
Initial research was directed principally to the aspects
of stockpiling, and the results have been published as:
NCHRP Report 5, "Erects of Different Methods of
Stockpiling Aggregates."
Continuation of the initial research was authorized to
expand the scope to include, in addition to further stock-
piling investigations, the effects on aggregate properties
of several routine methods for handling, spreading, and
compacting bases. This work has been completed, and
the project report has been published as: NCHRP Report
46, "Effects of Different Methods of Stockpiling and Han-
dling Aggregates."
Project 10-4 FY '64 and FY '65
Rapid Test Methods for Field Control of
Construction
Research Agency: Clemson University
Principal Invest.: Dr. A. E. Schwartz
Elective Date: Feb. 1, 1964
Completion Date: Feb. 28, 1965
Funds: $30,000
May 1, 1965
Feb. 28, 1967
$69,320
It has been recognized that there is a need for improved
methods of sampling and testing to keep pace wth ac-
celerated production rates and increased volumes of ma-
terials being used in highway construction. In an effort
to fulfill this need, this research project proposed to seek
out areas in which rapid test needs are most critical and
to explore and summarize existing knowledge in these
areas with the ultimate aim of accelerating the develop-
ment of new methods of meeting these needs.
Work in the initial phase of this project consisted of a
survey of the state of the art in the development, need,
and use of rapid test methods for field control of con-
struction.
During the continuation phase, emphasis was placed
on further development and evaluation of improved test
procedures in the areas of asphalt content of bituminous
paving mixtures, density of aggregate base courses and
bituminous layers, gradation of aggregates, and soil com-
paction.
Research has been completed, and the project report
has been published as: NCHRP Report 103, "Rapid Test
Methods for Field Control of Highway Construction."
Project 10-5 FY '64 and FY '65
Density and Moisture Content Measurements
by Nuclear Methods
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Research Triangle Institute
Dr. R. P. Gardner
Jan. 15, 1964 Apr. 1, 1965
Jan. 31, 1965 Oct. 7, 1966
$28,801 $59,835
For the past several years, investigators have studied
the application of nuclear devices for determining mois-
ture content and density of subgrade, subbases, and base
components. Some of the researchers have indicated such
devices are applicable for field control, while others are
still evaluating the technique. If these nuclear devices are
capable of accurate and reliable determinations, there is
a possibility that considerable economy may result in
construction and control procedures. The objectives of
the initial research were (1) to review the literature and
other available data to determine what has been done by
others in the evaluation and correlation of nuclear equip-
ment, (2) to evaluate and analyze assembled data consid-
ering such factors as accuracy and precision, and (3) to
make recommendations for the development of needed
equipment.
Research on the initial phase has been completed, and
the project report for this phase has been published as:
NCHRP Report 14, "Density and Moisture Content Mea-
surements by Nuclear Methods Interim Report."
The objective of the continuation phase was to inves-
tigate, in depth, the promising findings from the initial
research. Theoretical investigations were supplemented by
field experiments to establish a technique for calibrating
nuclear gauges to provide improved accuracy in the mea-
surement of soil moisture content and density. In the
pursuit of these objectives, calibration standards were de-
veloped which are applicable to nuclear gauges currently
In use.
OCR for page 140
140
Research on the continuation phase has been com-
pleted, and the project report for this phase has been
published as: NCHRP Report 43, "Density and Moisture
Content Measurements by Nuclear Methods."
Project 10-5A FY,68
Optimization of Nuclear Density and Moisture
Content Measurement Methods
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
North Carolina State University
Dr. R. P. Gardner
February 1, 1968
January 31, 1970
$5 1,214
The essential objective of this study was to optimize
nuclear gauge calibration methods and thus improve op-
erational performance of the gauges for control of mois-
ture and density during construction of highway
subgrade, subbase, and base components. The objectives
of the research have been met. Procedures have been
developed for optimization of nuclear backscatter-type
density gauge calibration, a quantity factor approach has
been developed for evaluating the over-all performance
of density gauges, and a tentative model is available for
improved calibration of nuclear moisture gauges. The
research has also provided a basis for design of even better
nuclear backscatter-type density gauges.
Research has been completed, and the project report
has been published as: NCHRP Report 125, "Optimi-
zation of Density and Moisture Content Measurements
by Nuclear Methods."
Project 10-6 FY '64 and FY '65
Measurement of Pavement Thicknesses by
Rapid and Nondestructive Methods
Research Agency: IIT Research Institute
Principal Invest.: K. E. Feith
Dr. S. D. Howkins
February 1, 1964
October 31, 1966
$108,821
Elective Date:
Completion Date:
Funds:
Present methods of measuring the thicknesses of high-
way pavements are time consuming and generally do not
provide data early enough for the contractor to alter
operations so as to comply. It is recognized that a non-
destructive technique would be advantageous, both cost-
and time-wise, in comparison to present methods. In in-
itiating this research, four objectives were outlined. They
included: (1) a study of all past and present methods of
measuring thicknesses of highway pavements to deter-
mine if any existing method may be suitable; (2) a fea-
sibility study of proposed methods now under
development; (3) proposals for other feasible methods;
and (4) recommendations for promising methods for de-
velopment of instrumentation.
Research has been completed, and the project report
has been published as: NCHRP Report 52, "Measurement
of Pavement Thickness by Rapid and Nondestructive
Methods."
Project 10-7 FY '64
Potential Uses of Sonic and Ultrasonic
Devices in Highway Construction
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
The Ohio State University
Dr. F. Moavenzadeh
Dr. R. C. McMaster
February 1, 1964
March 31, 1965
$24,3 10
The use of sonic and ultrasonic devices is well known
in some fields. Present practical application of sonic and
ultrasonic frequencies and the results of recent experi-
ments indicate a wide range of potential uses of such
devices in highway construction. It is felt that possible
uses may include pile driving, mixing and compaction of
materials, sampling of materials, drilling, cutting, and
many other applications. In an effort to evaluate potential
uses, this research study was initiated with the objectives
of studying available information on present uses of high-
frequency vibrations and making a feasibility study of
possible applications to highway construction.
This research has been completed, and the project re-
port has been published as: NCHRP Report 25, "Potential
Uses of Sonic and Ultrasonic Devices in Highway Con-
struction."
Project 10-8 FY,70
Evaluating Procedures for Determining
Concrete Pavement Thickness and
Reinforcement Position
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Pennsylvania Dept. of Transporta-
t~on
W. G. Weber
R. L. Grey
March 2, 1970
July 31, 1973
$151,982
The objective of this research was limited to the field
evaluation of available nondestructive systems of inspec-
tion testing for determining pavement thickness and rein-
forcing steel position at the construction site, either before
or soon after the concrete has hardened, to permit the
elimination of, or substantial reduction in, the coring of
pavements.
Research has been completed, and the project report
has been published as: NCHRP Report 168, "Rapid Mea-
surement of Concrete Thickness and Reinforcement Lo-
cation Field Evaluation of Nondestructive Systems."
OCR for page 141
141
Project 10-9 FY '70
Criteria for Need of Seal Coats for Bituminous
Pavements
Research Agency: University of Minnesota
Principal Invest.: E. L. Skok
Elective Date: November 1, 1969
Completion Date: February 28, 1974
Funds: $50,000
The objectives of this project were to develop, and
evaluate in the field, guidelines for the programming of
seal coats on bituminous pavements.
The essential findings of the study have been published
as NCHRP Research Results Digest 48. The agency re-
port has been distributed to the Program sponsors and
other interested persons, and microfiche of the report may
be purchased (see final page of this section for ordering
information).
Project 10-10 FY '74
Acceptance Criteria for Electrostag
Wetdments in Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
United States Steel Corporation
W. P. Benter, Jr.
C. G. Schilling
May 1, 1974
September 30, 1978
$300,000
The over-all objective of this project was to develop
and verify acceptance criteria for the use of electroslag
butt welds in bridges. Research was conducted in two
phases. The specific objective of Phase I was to define
necessary acceptance specifications based on the most
complete study, using laboratory specimens from full-size
welds, that current knowledge and testing equipment
could provide within the allotted funds. The specific ob-
jective of Phase II was to verify the findings of Phase I
by conducting dynamic tests of full-size bridge girders.
Research has been completed, and the project report
has been published as: NCHRP Report 201, "Acceptance
Criteria for Electroslag Weldments in Bridges."
Project 10-11 FY '77
Development of a Performance Specification
For Bridge Deck Joint-Sealing Systems
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Howard Needles Tammen & Ber-
gendoff
Arthur Linfante
December 1, 1976
April 30, 1978
$29,996
The objective of this research was to develop an effective
performance specification for prefabricated, surface
mounted bridge deck joint-sealing systems designed for a
total horizontal movement of4 inches or less.
Research has been completed, and the final report has
been published as: NCHRP Report 204, "Bridge Deck
Joint-Sealing Systems Evaluation and Performance
Specification."
Project 10-12 FY '77
Acceptance of Aggregates Used in Bitumi-
nous Paving Mixtures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Texas A & M University
Research Foundation
Dr. R. L. Lytton
September 1, 1977
June30,1981
$174,41 1
The objective of this study was to evaluate currently
used methods for the acceptance or rejection of aggregates
used in bituminous paving mixtures.
The research was conducted in two phases. Under
Phase 1, four overall schemes for evaluating the quality
of aggregates to be used in bituminous paving mixtures
were formulated, based primarily on various combinations
of current state highway department practices. The four
schemes were evaluated for their relative usefulness (util-
ity) using a utility decision analysis computer program
developed by the researchers. The schemes showing the
most utility were comprised of conventional physical and
chemical tests of aggregate samples.
Consequently, Phase 2 was designed to evaluate various
tests on aggregate samples for their ability to predict
bituminous pavement performance. A decision was also
made to include some bituminous mixture tests and sub-
jective petrographic ratings and to consider climate or
. .
geograp. 11C reglOIlS.
The research has been completed and the agency final
report distributed to all NCHRP sponsors. A limited
number of extra copies of the final report are also available
to NCHRP sponsors. Copies of an agency interim report
documenting Phase 1 and the agency final report, which
concentrates on Phase 2, are also available for loan upon
written request to the NCHRP. In addition, microfiche
of both reports may be purchased (see final page of this
section for ordering information).
Project 10-13 FY '79 and FY '82
Ultrasonic Measurement of Weld Flaw Size
Research Agency: The Welding Institute (England)
Principal Invest.: Timothy J. Jessop Peter J. Mudge
Elective Date: July 1, 1979 October 1, 1982
Completion Date: October 31, 1981 August 31, 1985
Funds: $126,000 $250,000
The overall objective of this study was to identify or
develop, and to validate, ultrasonic testing procedures for
OCR for page 142
142
accurate measurement of flaw dimensions that will allow
fracture-mechanics analysis.
This study was addressed primarily to evaluation of
complete joint penetration groove welds containing
planar-type flaws such as cracks or incomplete fusion.
In the first phase of research, laboratory tests on in-
tentionally flawed specimens were used to determine the
applicability and limitations of AWS D1.1-80 ultrasonic
testing procedures for measuring the dimensions of flaws
in welds. Phase I also included an evaluation of proce-
dures that extend available ultrasonic techniques and have
a potential for accurate measurement of flaws typically
found in structural weldments. The accuracy, precision,
reliability, and reproduceability of the time-of-flight and
probe movement techniques were investigated.
The final report on Phase I has been published as:
NCHRP Report 242, "Ultrasonic Measurement of Weld
Flaw Size."
The specific objectives of Phase II, designated NCHRP
Project 10-13/1, were (1) to develop recommendations
for applications of tandem-probe techniques for the char-
acterization of vertical, planar defects and (2) to refine
the time-of-flight system for sizing through-thickness flaw
. .
dimensions.
The research in this second phase included a review of
all relevant literature and test data in order to develop a
more realistic means of assessing vertical planar defects
within the framework of the currently used AWS Dl.1
code. Time-of-flight equipment was designed and assem-
bled and subsequently evaluated in the laboratory in order
to establish the accuracy of the equipment in measuring
through-thickness dimensions for a variety of weld de-
fects. Finally, a field evaluation of the equipment was
performed in order to establish its accuracy and appli-
cability, as well as to provide recommended procedures
for use.
The research has been completed, and the final report
was submitted at the end of 1988. A decision on publi-
cation of the final report will be made in early 1989.
Project 10-14 FY '79
Locating Voids Beneath Pavement Using
Pulsed Electromagnetic Wave
Techniques
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Georgia Tech Research Corpora-
tion
Dr. J. D. Echard
Dr. W. J. Steinway
April2, 1979
May 1 1981
$99,850
The primary objective of this project was to determine
the practicality of pulsed electromagnetic wave technol-
ogy for locating voids beneath reinforced and nonrein-
forced Portland cement concrete pavements up to 18
inches thick. Another objective was the identification or
development of a data processing technique suitable for
use with the equipment that can be operated by field
personnel and that will provide information on the pa-
rameters of voids beneath pavements. It was further de-
sired that the voids beneath pavements be defined with
an accuracy of at least + I/2 inch in depth and + 6 inches
in horizontal dimension.
Research has been completed with reasonable accom-
plishment of objectives. Theoretical modeling of signal
returns from voids led to suitable techniques for locating
and sizing voids beneath pavements. Very short pulse
radar was connected to a microcomputer to provide real-
time processing of the radar signal return. Measurements
made inside a laboratory-controlled environment verified
the procedure. Additional measurements were made on
specially constructed outdoor pavement sections at 100 F.
70 F. and 32 F. At temperatures of 70 F and below, the
measurements provided excellent estimates of void loca-
tion and size, but at 100 F the measurements were not
as successful.
The project report has been published as: NCHRP
Report 237, "Locating Voids Beneath Pavement Using
Pulsed Electromagnetic Wave Techniques."
Project 10-15 FY'80
Structural Strength Evaluation of Existing
Reinforced Concrete Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Engineering Computer Corporation
Roy A. Imbsen
April 1, 1980 April 1, 1984
Sept. 30, 1982 April 30, 1986
$125,000 $100,000
The objective of this project was to develop improved
methodology for evaluating the structural capacity of ex-
isting reinforced concrete bridge superstructures and to
present it in a specification format suitable for consid-
eration by AASHTO.
The final report on the first Phase I of the research
included findings and recommendations related to meth-
ods of predicting structural capacity for load-rating con-
crete highway bridges. The limit-state approach to bridge
evaluation recommended in this report appeared to be
promising; however, some of the factors included in the
report are not well documented, and the recommended
approach is not yet ready for widespread application.
The Phase I final report will not be published, but copies
of the agency's draft final report were distributed to
NCHRP sponsors early in 1983. Copies are available on
microfiche (see final page of this document for ordering
information).
Phase II of the research had as its objective further
development of the limit-state approach to evaluate the
structural capacity of reinforced concrete bridge super-
structures. The research in the second phase included a
OCR for page 143
143
statistical analysis of information from the FHWA's com-
puterized national bridge inventory system in order to
identify typical reinforced concrete superstructure types
that were applicable to this study. A sensitivity analysis
was conducted to determine the effects of modifications
to the load and resistance factors in the limit-state ap-
proach to evaluation. The factors to be used in the limit-
state approach were identified and evaluated, and a cal-
ibration of the proposed method was performed using
available test data. Finally, the results of the proposed
method were compared with results from the currently
used methods.
The project report has been published as NCHRP Re-
port 292, "Strength Evaluation of Existing Reinforced
Concrete Bridges."
The recommendations and guidelines developed in the
second phases of Project 10-15 were incorporated into
the comprehensive evaluation guidelines developed in
Project 12-28~1~. Refer to Project 12-28~1) writeup for
further discussion.
Project 10-16 FY'81
Assessment of Deficiencies and Preservation
of Bridge Substructures Below the
Waterline
Research Agency:
Principal Invest:
Elective Date:
Completion Date:
Funds:
Byrd, Tallamy, MacDonald &
Lewis
Martin Rissel
February 16, 1981
December 1, 1982
$150,000
This study was intended to use and extend earlier re-
search reported in NCHRP Synthesis of Highway Prac-
tice 88, "Underwater Inspection and Repair of Bridge
Substructures."
The objectives of Project 10-16 were; (1) to develop
improved methodology for evaluating the effects of below-
the-waterline deficiencies on the structural capacity of the
substructure, and (2) to develop solutions to specific de-
terioration problems that are found in bridge substruc-
tures below the water surface and in the splash zone.
Accomplishment of these objectives involved: (1) address-
ing the deficiencies cited in the previously mentioned syn-
thesis report, (a) review and summarize the present state
of the art of structural strength evaluation techniques for
bridge substructures below the water surface, with par-
ticular emphasis on quantifying the consequences of the
deficiencies on the structural integrity of the bridge, and
(b) for these deficiencies, develop guidelines for assessing
the seriousness of the problem, a rating system to identify
the urgency for corrective action, and practical methods
to predict structural capacity. (2) Addressing the second
part of the objective, (a) based on available information,
identify and evaluate methods used to arrest deterioration
below the water surface and in the splash zone, and (b)
develop new or improved methods that may prove effec-
tive in arresting deterioration below the water surface and
in the splash zone; this effort was limited to the following
elements and problem areas:
. Bridge elements concrete piers and footings, pre-
stressed concrete piles, and reinforced concrete piles.
. Problem areas deterioration due to corrosion,
freezing and thawing, chemical attack, and abrasion.
Research has been completed, and the final report has
been published as: NCHRP Report 251, "Assessment of
Deficiencies and Preservation of Bridge Substructures Be-
low the Waterline."
Project 10-17 FY '81 and FY '83
Use of Antistripping Additives in Asphaltic
Concrete Mixtures
Research Agency: David G. Tunnicliff
Principal Invest: David G. Tunnicliff
Elective Date: March 1, 1981
Completion Date: July 1, 1989
Funds: $500,000
There is an increasing awareness of asphaltic concrete
pavement failures caused by stripping of asphalt cements
from the aggregates. Consequently, more highway agen-
cies are requiring the use of antistripping additives. If an
additive is used when it is not needed, the added cost is
an economic waste. If an additive is used ineffectively,
the pavement may require early and costly maintenance
and/or rehabilitation. Highway agencies need informa-
tion on the selection, effectiveness, and use of antistripping
additives.
The long-term general objective of this research is to
provide information on the selection and use of anti-
stripping additives (materials used to improve the asphalt-
aggregate adhesion in asphaltic concretes). The specific
objective of the initial phase was to develop guidelines
for the incorporation of antistripping additives in as-
phallic concrete paving mixtures considering the influence
of such factors as (1) storage and handling of the additives,
and (2) stability and effectiveness of additives during mix-
ing and storage of asphaltic concrete.
Research has been completed on the initial phase with
accomplishment of the objectives. The test method for
measuring the potential for moisture damage in asphalt
concrete pavements described in NCHRP Report 246 was
modified to reduce test time and control the degree of
saturation. The modified test method was used to evaluate
effects of storage and handling of asphalt aggregate mix-
tures on antistripping additives. The project report for
the initial phase has been published as: NCHRP Report
274, "Use of Antistripping Additives in Asphaltic Con-
crete Mixtures." The report contains a state of the art in
use of antistripping additives in asphaltic concrete paving
mixtures and guidelines for use of such additives.
OCR for page 144
144
Research on the field evaluation phase is in progress.
A precision study has been completed for the test method
developed in the initial phase. That test method and pre-
cision study have been approved by ASTM Committee
D-4 and should appear in the 1989 Book of ASTM Stan-
dards as Designation D 4867, "Test Method for Effect
of Moisture on Asphalt Concrete Paving Mixtures."
Project 10-18 FY '81
Specifying and Obtaining Entrained Air in
Concrete
Research Agency:
Principal Invest:
Elective Date:
Completion Date:
Funds:
Construction Technology Labora-
tories/PCA
David C. Stark
Dr. David Whiting
May 4, 1981
June 1, 1983
$73,585
The objective of this research was to develop practical
guidelines for specifying and obtaining the optimum
amount of entrained air in concrete. Consideration was
given to interations between typical concrete ingredients
and various admixtures.
Research has been completed and the project objective
accomplished in the form of guidelines for field control
of air-entrained concrete. A state-of-the-art report on air-
entrained concrete was also prepared and copies printed
for distribution to program sponsors. Loan copies are
available (see final page of this section for ordering in-
formation).
The final report including the guidelines has been pub-
lished as: NCHRP Report 258, "Control of Air Content
in Concrete."
Project 10-19 FY ,81
Adding Dust Collector Fines to Asphalt Paving
Mixtures
Research Agency: The Pennsylvania State University
Principal Invest: Dr. David A. Anderson
Elective Date: March 1, 1981
Completion Date: November 30, 1982
Funds: $49,926
The objectives of this project were: (1) to conduct a
state-of-the-art survey of studies dealing with the effect
of dust collector fines on asphalt concrete and current
practices for specifying and handling these fines, and (2)
to characterize by generic type those dust collector fines
now in use. Of particular concern was the dust collected
in baghouses.
Research has been completed, and the final report has
been published as: NCHRP Report 252, "Adding Dust
Collector Fines to Asphalt Paving Mixtures."
Project 10-20 FY '81, FY '83, and FY '85
Elastomeric Bearings Design, Construction,
and Materials
Research Agency:
Principal Invest:
Elective Date:
Completion Date:
Funds:
University of Washington
Dr. C. W. Roeder
Dr. J. F. Stanton
2/1/8 1 6/1/83 6/1/86
6/30/82 1 1/30/86 5/3 1/89
$74,715 $150,000 $150,000
The objective of the first phase of research was to
develop specifications for unconfined, plain and reinforced
elastomeric bridge bearings.
The findings of Phase I of Project 10-20 were published
as: NCHRP Report 248, "Elastomeric Bearings Design,
Construction, and Materials," and included recommen-
dations for improved specifications for unconfined, plain
and reinforced elastomeric bridge bearings. These rec-
ommendations were based on currently existing infor-
mation. In 1985, AASHTO adopted many of the
recommendations of the Phase I research, substantially
revising the provisions for elastomeric bearings in the
Standards Specifications for Highway Bridges.
The objective of the second phase of research was to
develop a more sophisticated specification for special ap-
plications and to improve the simplified provisions rec-
ommended in Phase I. The Phase II research included
testing and evaluation of bearing compression, rotation,
shear, stability, fatigue, and low temperature behavior.
Recommendations for a more rational bearing specifica-
tion are included in the project report and have been
made to the AASHTO Bridge Committee.
The findings of Phase II of Project 10-20 were published
as NCHRP Report 298, "Performance of Elastomeric
Bearings."
The objectives of the third phase of research are to (1)
resolve design procedures for special applications of un-
confined elastomeric bearings and (2) provide a critical
state-of-the-art review of design and construction pro-
cedures for confined elastomeric bearings. The Phase III
research includes the following tasks:
Unconfined Elastomeric Bearings
1. Further experimental verification of low tempera-
ture behavior including effects on heating and cooling
rates and shear stiffness of elastomers at low temperatures.
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2. Develop guidelines for recommended manufacturing
procedures and tolerances.
3. Develop recommended test procedures to prequalify
the elastomeric material and also for acceptance of the
finished bearings.
4. Preparation of a final report including revisions to
the more sophisticated specification developed in Phase
II.
Pot Bearings and Slide Surfaces
1. Gather data relevant to pot bearings from the lit-
erature and from interviews with manufacturers and en-
gineers.
2. Gather data relevant to PTFE sliding surfaces.
3. Synthesize the information gathered in Tasks 1 and
2.
4. Prepare a final report that includes a summary of
the state-of-the-art in pot bearing design and use, includ-
ing recommendations for further research.
Through December 31, 1988, research on the third
phase has fallen slightly behind schedule. The draft pot
bearing state-of-the-art report was submitted in mid-1988
and was reviewed by the NCHRP project panel. Technical
revisions were suggested for the report, which will be
incorporated in the final report to be submitted by the
agency in early 1989. The low temperature elastomer tests
have also fallen somewhat behind schedule, but should
be completed by April 1989.
Project 10-20A FY'88
High-Load, Muiti-Rotational Bridge Bearings:
Design, Materials, and Construction
Research Agency:
In developmental stage
Principal Invest.:
E ec ive Da e 30 months
Completion Date:
Funds: $250,000
In recent years, specialty bearings have been introduced
for use in highway bridge construction. Prominent among
these are the high-load multi-rotational (HLMR) types
of bearings.
Current specifications for HLMR bearings have been
developed from industry standards and vary widely
throughout the United States. There is a need for a broad
range, generic specification that reflects the best of current
practice and will ensure long life, high quality, reliable
bearings.
Although there is a proliferation of HLMR bearing
specifications, many basic questions remain unanswered.
These include questions related to: (1) the performance
characteristics of such bearings subjected to induced ec-
centric loading while under rotation; (2) the apparent loss
of full performance capabilities; (3) the long-term dura-
bility of certain materials and bearing configurations; and
(4) the disparities between domestic and foreign design
procedures and materials applications.
There is also inadequate information available to the
bridge engineer providing concise guidance on the selec-
tion of an appropriate bearing for a specific design situ-
ation. Therefore, a selection guide is needed which will
inform bridge engineers of the relative performance fea-
tures for HLMR and conventional bearings used in new
bridge designs in the United States.
The objectives of this research are to develop (1) a
bearing selection guide for all bearings currently used in
new bridge designs in the United States and (2) specifi-
cations for high-load multi-rotational bearings that can
be recommended to AASHTO for consideration for adop-
tion. Base-isolation bearings are not intended to be in-
cluded in this research. PTFE slide units associated with
high-load multi-rotational bearings shall be considered.
The research will include the following tasks:
Task 1. Review current domestic and foreign codes of
practice, research findings, and performance data on all
bridge bearings within the scope of the bearings selection
guide that will be developed under Task 2. The emphasis
of this survey, however, should be placed on the HLMR
bearings that will be covered under the specification to
be developed in Task 3.
Task 2. Develop a draft bearing selection guide for all
bearings currently used in new bridge designs in the
United States, with the exception of base-isolation bear-
~ngs.
Task 3. Develop draft specifications for the design,
materials, and construction of HLMR bearings in a for-
mat suitable for consideration by AASHTO.
Task 4. Prepare an interim report which includes the
following: (1) a summary of the findings from Task 1; (2)
the draft selection guide and draft specifications; (3) a
prioritized list of laboratory tests, possibly supplemented
by field observations, that may be required to complete
the selection guide and specifications; and (4) a recom-
mended test program of the highest priority research
needs that can be accomplished within a funding level of
$150,000.
Task 5. Perform laboratory tests. As a minimum, these
tests shall examine the moment-rotation characteristics
and lateral load capacity for all types of HLMR bearings,
and sealing requirements and internal lubrication for pot
bearings.
Task 6. Revise the draft selection guide to incorporate
the findings from Task 5.
Task 7. Revise the draft specifications for HLMR bear-
ings to incorporate the findings from Task 5.
Task 8. Submit a final report documenting all research
and presenting the recommended bearing selection guide
and specifications.
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Project 10-21 FY'81
Performance of Bridge Deck Concrete
Subjected to Traffic-lnduced Vibrations
During Placement
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Transportation Research Board
Dr. Paul E. Irick
Mr. T. L. Copas
February 1, 1980
September 30, 1981
$25,000
The objective of this study was to determine the effects
of tra~c-induced vibrations on concrete for various bridge
deck repair and widening procedures and to indentify
criteria for materials, design, construction, and traffic con-
trol procedures to alleviate any negative erects. The re-
search included consideration of the following factors
associated with bridge deck concrete used in overlays, full
and partial-depth restoration, and widening: (1) bonding
to substrate and adjacent concrete: (2) bonding to rein-
forcing steel; (3) differential consolidation; (4) interaction
between concrete properties and differential consolida-
tion; (5) differential deflections; (6) frequency of vibration
(traffic induced); (7) porous planes of weakness; (8) traffic
control criteria; (9) design criteria (including bridge type);
(10) construction practice (including deck preparation);
(11) crack development from all sources; and (12) mix
design effects.
The study included the following tasks:
1. Identification of relevant research and field investi-
gations.
2. A survey of current practice and attitudes on main-
taining traffic during bridge deck restoration or widening.
3. Follow-up contact with a number of highway agen-
cies to gather more detailed information on the field per-
formance of bridge decks that have been restored, patched
or widened in the presence of traffic induced vibrations.
4. A recommendation for additional research to be
directed toward determining the causes and possible so-
lutions for any negative erects determined to be associated
with such vibrations.
NCHRP Project Panel D10-21 decided that a prelim-
inary study should be carried out under NCHRP Project
20-5. "Synthesis of Information Related to Highway
Problems," and $25,000 of the $250,000 that was origi-
nally allocated for this study were reallocated for this
purpose. Research has been completed, and the final re-
port has been published as: NCHRP Synthesis of High-
way Practice 86, "Erects of Traffic-Induced Vibrations
on Bridge-Deck Repairs."
The draft final report included an evaluation of research
needs with recommendations for specific work to meet
these needs. The project panel accepted the synthesis topic
consultant's recommendation to not carry out additional
research on this subject. This recommendation was based
on the fact that no convincing evidence was found in this
study to indicate that the performance of concrete bridge
decks is degraded by traffic-induced vibrations during
placement. The unused portion ($225,000) of the allocated
funds has been returned to the AASHTO Research Com-
mittee for reallocation to other NCHRP projects.
Project 10-22 FY '82
The Performance of Weathering Steel in
Bridges
Research Agency: Sheladia Associates, Inc.
Principal Invest.: Dr. Pedro Albrecht
Elective Date: April 1, 1982 July 23, 1984
Completion Date: February 29, 1984 August 31, 1987
Funds: $74,851 $120,699
The objectives of the first phase of research were (1)
to assemble a systematic body of information on the per-
formance of weathering steel, and (2) to document and
evaluate the current state of practice.
The first phase of research has been completed, and
the final report published as: NCHRP Report 272, "Per-
formance of Weathering Steel in Bridges."
The second phase of research has as its specific objec-
tives (1) to fatigue test 8-year weathered A588 transverse
stiffener specimens under constant loading in air and
aqueous environments, and (2) to develop practical guide-
lines for design, construction, maintenance, and rehabil-
itation of weathering steel bridges.
Research on the second phase is complete. The agency's
revised final report is now under review for possible pub-
lication in the NCHRP report series.
Project 10-23 FY '82
Removal of Lead-Based Bridge Paints
Research Agency: Midwest Research Institute
Principal Invest.: Michael K. Snyder
Effective Date: July 1, 1982
Completion Date: June 30, 1983
Funds: $81,118
The objectives of this research were to: (1) identify the
severity of pollution related to bridge cleaning and
(2) recommend improved techniques for removal and re-
covery of lead-based bridge paints. Environmental pol-
lution and toxicity inflation associated with lead paint
removal and disposal, environmental regulations pertain-
ing to lead paint removal, and environmental test methods
for lead paint residues were reviewed and commented on.
Removal and recovery methods were summarized and
evaluated. Concepts for improving existing technology
and comments on new techniques under development
were generated.
Research has been completed, and the project report
published as: NCHRP Report 265, "Removal of Lead-
Based Bridge Paints."
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147
Project 10-24 FY'82
Rapid Replacement of PCC Pavement
Segments
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Dr. A. H. Meyer
R. F. Carmichael III
MarchlS, 1982
March 14, 1988
$240,000
The objective of this research was to identify, describe,
and evaluate methods that had been and were being used
for rapid replacement of lane-width segments of both
continuously reinforced and jointed PCC pavements rel-
ative to costs, placement conditions, traffic characteristics,
performance and expected service lives. Field sites in six
States: California, Illinois, Minnesota, Michigan, Texas,
and Virginia were identified and monitored over several
years. The field sites represented a variety of environ-
mental regions and PCC pavement types (i.e., jointed
plain, reinforced, and continuously reinforced concrete
pavements).
Findings indicated little variety in materials being used,
but design and replacement techniques vary. Troublesome
issues are determining the limits of segments needing
replacement and determining the number and size of re-
placement segments before a major reconstruction is rec-
ommended.
Research is complete; a summary of findings will be
published in Research Results Digest 169, "Rapid Re-
placement of PCC Pavement Segments." Copies of the
agency final report were distributed to all state highway
departments and are available to others for loan or pur-
chase. (See final page of this document for ordering in-
formation.)
Project 10-25 FY'83
Measurement of Cement and Water Content
of Fresh Concrete
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
U.S. Army Corps of Engineers
Waterways Experiment Station
Richard L. Stowe, Alan D. Buck,
Tony B. Husbands, Joe G. Tom
October 13, 1983
September 5, 1986
$149,995
The objective of this research was to establish the appli-
cability and accuracy of test methods for the determi-
nation of cement and water content of freshly mixed
concrete. The following test methods were investigated:
(1) US Army Construction Engineering Research Labo-
ratory/Kelly-Vail (CERL/K-V), Rapid Analysis Ma-
chine (RAM), FHWA nuclear device, a centrifuge test,
and an x-ray emission spectrometer for determination of
cement content; and (2) CERL/K-V, hot plate and mi-
crowave oven for the determination of water content.
Research is complete. The final report has been pub-
lished as NCHRP Report 284, "Evaluation of Procedures
Used to Measure Cement and Water Content in Fresh
Concrete."
Project 10-25A FY'85
Instantaneous Determination of Water
Cement Ratio in Fresh Concrete
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Wiss, Janney, Elstner Associates,
Inc.
William G. Hime
June 1, 1985
December 31, 1988
$300,000
The objective of this research project is to develop a
method of measuring the water-cement ratio in concrete
that could form the basis of an acceptance test at the job
site. The desirable characteristics of such a method are:
(1) rapidity results should be obtainable within 2 min-
utes or less, (2) accuracy measurement of water-cement
ratio to within 0.02, (3) cost the equipment should be
of such price (under $5,000) that a testing agency might
reasonably be expected to acquire several items, (4) con-
venience the method should consist of a probe to be
inserted directly into a central or truck mixer, (5) ver-
satility the test should be capable of being performed
at any time from first mixing up to the maximum delivery
time allowable (approximately 90 minutes at a concrete
temperature of 70°F), and (6) simplicity the probe
should be easily calibrated so that the erects of changing
concrete material and temperature may be accommo-
dated. It is anticipated that a method based on a direct
determination of the water-cement ratio is most likely to
satisfy all of the above requirements, but an approach
that measures cement and water contents separately can
be pursued if justified. Some methods that may be ap-
propriate are measurement of dissolved ions, radioactive
detection of soluble or insoluble species, and chromato-
graphic analysis of volatile compounds. The following
three tasks shall be addressed to achieve the project ob-
jective.
Task 1 Evaluate and demonstrate in the laboratory
the feasibility of using an elements or compounders) nat-
urally occurring in cement that can be instrumentally
measured to define the water-cement ratio of a concrete
mixture. The elements or compounders) identified should
not occur in typical concrete admixtures or concrete ag-
gregates in sufficient quantity or form to have a significant
effect on instrumental (probe) analysis.
Task 2 Investigate candidate materials to be added
to cement during its manufacture that can be readily
measured and whose concentration will suitably reflect
the water-cement ratio of concrete. The selection of a
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materialist must consider: (a) the cost of the basic pro-
totype material, and of the procedures and equipment
which could be used to add the material to the cement;
(b) the potential availability of analytical equipment of
adequate accuracy of discrimination; and (c) the inter-
ference from usual concrete ingredients including admix-
tures. The first step in this task is to identify candidate
materials and measurement schemes. Based on estimates
of cost and feasibility of additions, one or more materials
should be used in the laboratory to demonstrate perform-
ance in a high pH environment and to determine if mea-
surements can be made with the required accuracy.
Task 3-Having selected the most promising ele-
ment~s) or compounders) whose concentration is to be
measured, demonstrate the feasibility of performing mea-
surements quickly in the field. The demonstration may
consist of using a commercially available probe, if such
exists, or developing a prototype probe for each element
or compound to the point where it is apparent that a
small rugged commercial model is possible.
Research had initially concentrated on the feasibility
of a single electronic probe for directly measuring the
water-cement ratio of fresh concrete. Experiments were
conducted to detect the dispersion of various elements in
cement paste. As a result, the sensitivity of the technique
to measure the water-cement ratio in a concrete matrix,
given its variability, has been questioned.
Although the future of a probe is likely, current tech-
nology is too limiting. The agency suggested pursuing
other methods such as: a colormetric procedure for iden-
tifying soluble silica in concrete to determine cement con-
tent; and a trained ion-specific electrode, microwave oven
technique, and an infrared method to determine water
content.
Research is complete; the agency preliminary draft final
-
.
report is now under review.
Project 10-26 FY'83
Data Bases for Performance-Related
Specification for Highway Construction
Research Agency: ARE, Inc.
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Dr. W. Ronald Hudson, Dr. Alvin
H. Meyer
June 15, 1983
September 14, 1984
$60,000
The objective of this study was to establish the state
of test records on construction and materials control for
pavement structures and foundations. The primary aim
was to establish which, if any, of the available records
were useful for development of performance-related spec-
ifications.
Assessments of various sources of data and statistical
techniques for use in developing performance-related
specifications resulted. Guidance for future endeavors was
given.
Research is complete; copies of the agency final report,
"Data Bases for Performance-Related Specifications for
Highway Construction," were distributed to all state high-
way departments. Copies are available to others for loan
or purchase. (See final page of this document for ordering
information.)
Project 10-26A FY,84
Performance-Related Specifications for Hot-
Mix Asphaltic Concrete
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
The Pennsylvania State University
Dr. David A. Anderson
and Dr. David R. Luhr
January 6, 1986
June 6, 1988
$250,000
Perfo~ance-related specifications are those that re-
quire tests or other control measures on materials and
construction, the results of which correlate to a known
degree with performance of the completed highway fa-
cility. It can be argued that using control measures that
cannot be related to performance wastes staff time and
increases costs without benefit. The need to use staff ef-
fectively and to reduce sampling and testing costs has
required a continuing examination of specifications by the
states and the Federal Highway Administration. These
examinations have convinced many of the need to identify
effective performance predictors and their variability lim-
its, to develop specifications based on these predictors,
and to apply cost-effective sampling and testing plans to
assure compliance.
One of several ways of establishing performance pre-
dictors is to correlate the results of condition surveys on
pavements directly with original materials and construc-
tion test data. However, previous research has demon-
strafed the difficulty of establishing these direct
relationships, especially when they are attempted nation-
wide with existing data from in-place facilities. A more
promising approach may be to recognize the establish-
ment of design factors as predictors of ultimate perform-
ance and then to use materials and construction testing
as a means to ensure adequate compliance with or achieve-
ment of the design factors. As an example, for asphaltic
concrete construction, stiffness (elastic modulus) and ten-
sile strain would be possible design factors, while asphalt
content and percent air voids would be possible materials
and construction test data.
Although the relationships among materials and con-
struction tests, design factors, and performance are of
primary interest, the relative impact of other factors can-
not be ignored. Factors such as quality of construction,
environment, and reliability of testing techniques are
among many that can have significant effects.
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149
Establishing or verifying the causal relationships and
the sensitivity of these relationships among performance,
design factors, and test data requires first the development
of an overall conceptual model or framework. This con-
ceptual model should make use of established relation-
ships already identified in the literature. Once the concept
has been formulated, the variables and data needs must
be identified. Existing, suitable data should be used to the
extent possible; however, it is unlikely such data will be
available or meet the needs of all data requirements.
Therefore, laboratory and field experiments will have to
be defined to generate supplemental data. With the iden-
tification or generation of data, previously established or
conceptual relationships can be verified and further ana-
lyzed for the predictive sensitivity of each variable and
its reliability. The ultimate purpose will be to develop
materials and construction specifications that relate to the
actual performance of the facility. This process will be
an iterative one, but careful planning will produce mean-
ingful results promptly and with minimum waste.
To limit the problem to a manageable undertaking, and
to mesh with ongoing and upcoming research by the
Federal Highway Administration, the scope of NCHRP
Project 10-26A is confined to performance-related spec-
ifications for hot-mix asphaltic concrete.
The objective of this study is to identify the relation-
ships between materials and construction test data and
the performance of hot-mix asphaltic concrete. Causal
relationships among performance, design factors, and test
data should be verified or established with the ultimate
aim of formulating specifications that directly (or through
identifiable indirect means) relate, within acceptable tol-
erances, to the performance of hot-mix asphaltic concrete
in a pavement cross-section. In some cases, this will re-
quire establishing design factors that relate to perform-
ance and then establishing the materials and construction
tests that will control those design factors. It is noted that
all existing materials or construction tests may not be
related to performance, and, conversely, the present study
may identify the need for tests not currently in use.
Research has been completed. A conceptual frame
work for performance-related specifications for hot-mix
asphaltic concrete was developed, and the laboratory
study providing data to models which indicated relation-
ships between materials and construction variables and
pavement performance has been concluded. The project
final report has been submitted and is being reviewed.
Project 10-27 FY '84
Effective Date:
Completion Date:
Funds:
September 17, 1984
August 31, 1989
$450,000
An increasing responsibility of highway and transpor-
tation agencies is the maintenance, rehabilitation, and
management of highways that have been built. Particu-
larly with regard to asphaltic concrete pavements, this
requires the use of efficient and economical methods for
determining the structural properties of existing pave-
ments. Use of nondestructive testing (NDT) data with
associated analysis methods appears to have potential for
determining these pavement structural properties. Several
types of NDT equipment and analysis procedures are
currently available for providing the desired information.
Analysis procedures utilizing NDT data vary substan-
tially in complexity, accuracy, and availability making
the selection of appropriate equipment and analysis meth-
ods for an individual agency's pavement management
needs difficult.
Up-to-date information on the application and limi-
tations of available analysis procedures for determining
asphaltic concrete pavement structural properties using
NDT data is urgently needed.
The objectives of this research are: (1) to provide meth-
ods and guidelines for calculating the structural properties
of asphaltic concrete pavements, using nondestructive test
data, for use in pavement analysis, design, rehabilitation,
and other pavement management activities; and (2) to
develop detailed procedures to verify the methods and to
adjust the results for local conditions.
Research nears completion. Computer programs have
been developed and demonstrated to use NDT/deflection
basin) data for analyzing up to 4 layers of the existing
asphaltic concrete pavement structure and for designing
resurfacing layers. Verification of these programs is being
provided with field evaluation of in-service pavement sec-
tions selected and instrumented for this purpose. Five
sections are in Texas and three are in Minnesota. Asphalt
concrete-thicknesses and base types are varied) Core sam-
ples of the different pavement layers have been obtained
to determine actual material characteristics. Deflection
data are being collected using various NDT devices.
It is anticipated the computer program and users guide
will be distributed in early 1989 and the project final
report will be available soon thereafter.
Project 10-28 FY'85
A Method to Determine Deteriorated Areas in
Portland Cement Concrete Pavement
Determination of Asphaltic Concrete Research Agency: Gulf Applied Research
Pavement Structural Properties by Principal Invest.: Lucien C. Bomar
Nondestructive Testing Walter F. Horne
Elective Date: November 1, 1985
Research Agency: Texas A & M Research Foundation Completion Date: December 31, 1987
Principal Invest.: Dr. Robert Lytton Funds: $199,784
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The need for maintenance and repair of Portland ce-
ment concrete pavements has increased over the years as
these facilities have deteriorated from the effects of age
and accumulated traffic loads. This has produced a need
for a method to accurately and rapidly determine the
location and extent of deteriorated concrete.
An accurate method would enhance the preparation of
project plans for needed repairs by permitting more pre-
cise calculations of quantities and boundary conditions.
And, a rapid method would be desirable for surveying
long lengths of pavements minimizing the interference
with traffic on heavily traveled roads. To further increase
its utility, the method should be suitable for reinforced
and nonreinforced concrete pavements with and without
overlays.
Various technologies, such as radar, sonics, infrared,
and others, have demonstrated to some degree the fea-
sibility of rapid and accurate detection of deteriorated
areas; but, data reduction and interpretation are slow and
require expertise not generally available in most state
highway agencies. Furthermore, the data may not always
be sufficient for determining quantities and exact locations
and boundaries of the needed repairs at the project level.
Recognizing that existing technologies showed promise,
the NCHRP solicited research proposals to improve ac-
curacy and speed of operation in one or more technologies
of the proposer's choosing and to produce results more
simply displayed and understandable. As a consequence,
improvements to the application of ground penetrating
radar and high resolution video to detect deteriorated
areas of Portland cement concrete pavements were re-
searched. Developments in radar technology and the
interpretation of radar signals were studied as a means
of detecting subsurface deterioration, while studies on
video imaging were intended to provide a method for
recording and cataloging surface deterioration or distress.
Advances in both technologies have made it possible to
apply them as practical tools for sampling purposes. The
research also provides a basis for further study to enhance
the capabilities of both technologies and make them more
suitable for project level decisions.
Research is complete, and the agency final report has
been published as NCHRP Report 304, "Determining
Deteriorated Areas in Portland Cement Concrete Pave-
ments Using Radar and Video Imaging."
Project 10-29 FY '86 and FY '87
Anchorage Zone Reinforcement for Post-Ten-
sioned Concrete Girders
Research Agency: University of Texas at Austin
Principal Invest.: Dr. John E. Breen
Elective Date: October 1, 1986
Completion Date: September 30, 1991
Funds: $490,000
The AASHTO Standard Specifications for Highway
Bridges do not provide adequate guidance for designing
reinforcement for tendon anchorage zones of post-ten-
sioned concrete girders and slabs. Current designs can
result in excessive cracking or congested reinforcing de-
tails. The wide variation of design practices currently in
use suggests the need for research in this area.
Recent investigations at the University of Texas at Aus-
tin have developed design procedures for single tendons
anchored in the webs of girders. However, additional
information is needed for multiple tendons and other
problems such as: influence of additional shear in support
regions, bearing stresses for different types of anchorage
systems, and the influence of diaphragms. Design criteria
are needed for reinforcement details for inclined, sharply
curved, and/or highly eccentric tendons, and for inter-
mediate anchorages and coupling joints of tendons.
The objective of this research is to develop design pro-
cedures for end and intermediate anchorage zones for
post-tensioned concrete girders and slabs. The research
will include the following tasks:
Task 1-Review of relevant domestic and foreign
research findings, available performance data, current do-
mestic and foreign practice, and tendon-supplier recom-
mendations. This information would be assembled from
technical literature, unpublished experiences of engineers
and tendon suppliers, insurance company records, and
surveys of bridge and containment vessel owners, fabri-
cators and designers. This review would include but not
be limited to:
a. Procedures used for selecting and designing the dif-
ferent types of tendon anchorage systems and the factors
affecting the reliability of these systems.
b. Procedures used for determining the placement and
alignment of tendons, for proportioning the reinforcement
surrounding the tendon anchorage, and for considering
interaction effects for multiple tendons.
c. Procedures adopted for matching reinforcement re-
quirements for anchorage zones with reinforcement re-
quirements for shear, torsion, and continuity.
d. Procedures adopted for considering bearing effect
and tendon curvature at anchorages.
e. Procedures to consider erects from factors such as
highly skewed structures, diaphragms, and end blocks.
f. Procedures to determine serviceability and failure
behavior.
Task 2 On the basis of the information assembled
in Task 1, evaluate the available design concepts for pro-
portioning end and intermediate anchorage zone rein-
forcement. Identify the limitations to existing knowledge
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151
and design concepts. Determine factors in need of detailed
evaluation. Conduct preliminary analytical studies to
evaluate the relative importance of these factors and to
assist in the development of a detailed research plan,
including laboratory and analytical studies, needed to
accomplish the project objective.
Task 3-Within 12 months of contract initiation,
submit the proposed research plan for NCHRP approval
in the form of an interim report.
Task 4A After NCHRP review, modification, and
approval of the detailed research plan developed under
Task 2, conduct the laboratory tests and analytical stud-
ies.
Task 4B The analytical approaches will be ex-
tended to include some nonlinear finite element modeling
which will track the possible cracking of anchorage zones
and study the effect of nonlinear compression constitutive
relations. The applications to be studied include: multiple
anchorages along slab edges; end anchors; end anchorages
in wider diaphragm type applications; and intermediate
anchorages.
Task SA On the basis of the available information,
experimental data, and analytical results, develop pro-
cedures to determine end and intermediate anchorage
zone reinforcement for post-tensioned concrete girders.
Task 5B The criteria will be extended to develop
analysis and proportioning criteria for: anchorages in dia-
phragms and for the erects of local concentrated loads
and reactions; distribution of load transfer reinforcement
in front of and behind intermediate anchorages; and for
intermediate anchorage zones such as slab, flange, and
corner blisters including out-of-plane deviation erects.
Task 6 Prepare specification provisions to reflect
accomplishment of the objectives in a format suitable for
consideration for adoption by AASHTO. The recom-
mended specifications shall be accompanied by a detailed
commentary and design examples intended to facilitate
their understanding and use.
Task 7 Identify areas in need of further investi-
gation. Recommend priorities and estimate time and costs
for needed research.
Task 8 Prepare a final report containing the re-
search findings and proposed design procedures.
The research has validated the effectiveness of the use
of strut-and-tie models. On the basis of that validation,
Tasks 4B and 5B were added to the research plan in mid-
1988 to extend the applicability of the criteria developed
in the project.
Through December 31, 1988, research has been com-
pleted on Tasks 1 through 4, and is progressing on sched-
ule on Tasks 4A, 4B, 5A and 5B. A detailed progress
report is expected to be submitted in late 1989 providing
an update on the results of the test program and analytical
studies.
Project 10-30~1) FY'86
Nondestructive Methods for Field Inspection
of Embedded or Encased High Strength
Steel Rods and Cables
Research Agency:
Principal Invest.:
University of Manchester Institute
of Science and Technology
Prof. F. M. Burdekin and
Dr. D. G. John
Elective Date: January 6, 1986
Completion Date: September 29, 1986
Funds: $25,000
During review of proposals for Project 10-30, two agen-
cies were selected to conduct a Phase I study. After com-
pletion of Phase I remaining funds from Project 10-30
and funds from Project 12-28~9) would be combined to
pursue an experimental Phase II study, subsequently de-
scribed under Project 10-30~3~. The Phase I research un-
der Project 10-30~1) is described below.
The objective of this Phase I project was to select the
most promising NDI methods for determining corrosion
activity and structural integrity of high strength steel rods
and cables embedded in concrete or encased in ducts. The
agency submitted a report to support the selection and
pursuit of ultrasonic and acoustic emissions. To enhance
the technique, the agency suggested the development of
remote transducers to excite the steel of interest without
direct physical contact. Copies of the agency's report on
Phase I are available for loan upon written request to the
NCHRP. In addition, microfiche may be purchased (see
final page of this section for ordering information).
Project 10-30~2) FY'86
Nondestructive Methods for Field Inspection
of Embedded or Encased High Strength
Steel Rods and Cables
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Southwest Research Institute
Dr. R. E. Beissner
January 20, 1986
October 3, 1986
$25,000
During review of proposals for Project 10-30, two agen-
cies were selected to conduct a Phase I study. After com-
pletion of Phase ~ remaining funds from Project 10-30
and funds from Project 12-28~9) would be combined to
pursue an experimental Phase II study, subsequently de-
scribed under Project 10-30~3~. The Phase I research un-
der Project 10-30~1) is described below.
The objective of this project was to select the most
promising NDI methods for determining corrosion activ-
ity and structural integrity of high strength steel rods and
cables embedded in concrete or encased in ducts. The
agency submitted a report to support the use of magnetic
field disturbance technology and a.c. magnetometry. The
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152
magnetic field disturbance equipment would be used to
detect defects in embedded steel and a.c. magnetometry
for determining corrosion rates. Copies of the agency's
report on Phase I are available for loan upon written
request to the NCHRP. In addition, microfiche may be
purchased (see final page of this section for ordering in-
formation).
Project 10-30(3) FY'86
Nondestructive Methods for Field Inspection
of Embedded or Encased High Strength
Steel Rods and Cables
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Manchester
Gareth John and
F. M. Burdekin
July 1, 1987
September 30, 1989
$400,000
There is growing concern about corrosion, deteriora-
tion, and structural integrity of steel components used in
cable-stayed bridges and segmentally constructed con-
crete bridges when these components are placed in ducts
or embedded in concrete and thereby not accessible for
visual inspection and evaluation. To make informed de-
cisions on maintenance and rehabilitation of bridge mem-
bers, engineers need to know the rate at which
deterioration or distress is occurring and the extent of
damage that has already taken place. Various nonde-
structive inspection (NDI) methods that could be used
to evaluate the condition of these steel components should
be assessed, and one or more practical systems for on-
site inspection and evaluation of steel components in
bridge members should be developed for field use.
After reviewing the results of Projects 10-30~1) and 10-
30~2), the University of Manchester Institute of Science
and Technology's proposed plan for a Phase II was chosen
by the NCHRP. Accordingly, the objective of Phase II
is to experimentally evaluate the chosen methods using
realistic bridge components. The Phase II objective will
be accomplished as follows:
Task 1 Assemble laboratory NDI equipment con-
sisting basically of readily available components and con-
duct sufficient laboratory tests to establish a data base for
determining optimum design concepts for prototype in-
spection systems. The NDI methods included in the in-
spection systems should be capable of determining section
loss, defects, and corrosion activity of steel components
embedded in concrete or encased in ducts. The test spec-
imens shall include lengths of rods and of cables encased
in ducts or embedded in concrete. Specimens taken from
bridges shall be included.
Task 2 Prepare a final report documenting the find-
ings of the research, including recommendations for the
development of systems for the on-site inspection and
evaluation of steel components used in cable stayed
bridges and segmentally constructed concrete bridges.
Research is focusing on the development of ultrasonic
techniques to interrogate the condition of prestressing
steel in concrete. A prototype device is expected with
actual field demonstrations performed. Investigations of
ultrasonic techniques for evaluating cables in suspension
and cable stayed bridges are now intended to be confined
to the laboratory.
Project 10-31 FY ,86
Acceptance Criteria for Steel Bridge Welds
Research Agency: Materials Research Laboratory,
Inc.
Dr. P. B. Crosley
Dr. E. J. Ripling
January 1, 1986
December 31, 1989
$348,350
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Use of inaccurate methods of nondestructive evaluation
and empirical acceptance criteria for bridge welds has
resulted in unnecessary repair of welds and has permitted
unsound welds to be incorporated in some bridges. Failure
to apply accurate bridge weld quality acceptance criteria
can significantly increase construction and maintenance
costs or can lead to structural failures. Unnecessary weld
repairs can generate harmful residual stresses and dis-
tortion and can often create new and more serious dis-
continuities.
Current empirical radiographic and ultrasonic weld
quality acceptance standards had their origin in the boiler
and pressure vessel industry. Use of these empirical stan-
dards has been justified by the inherent inaccuracy of
nondestructive test methods. With improvements in the
ability of nondestructive tests to accurately measure and
characterize weld flaws, it is timely and appropriate to
develop better weld quality acceptance criteria. The de-
velopment of new criteria based on appropriate analytical
methods and verification procedures will produce realistic
bases for design and inspection decisions. New weld qual-
ity criteria will produce safer bridge welds while reducing
unnecessary repairs.
The objective of this research is to develop improved
acceptance criteria for bridge welds.
The research will include the following tasks:
Task 1 Review relevant current domestic and for-
eign codes of practice, performance data, and research
findings. This information shall be assembled from both
technical literature and unpublished experience of de-
signers, fabricators, and owners of steel bridges.
Task 2 Based on currently available information
and the application of appropriate analytical techniques,
develop rational, practical acceptance criteria for welds
in steel bridges.
Task 3 Present the findings of Tasks 1 and 2 in an
interim report to be submitted not later than 12 months
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153
after the initiation of the study. The interim report shall
present the criteria developed under Task 2 and the ra-
tionale for these criteria along with examples illustrating
their application. The report shall also include compar-
isons between results produced by existing and proposed
criteria. Finally, a detailed work plan for Task 4 shall be
proposed in the interim report. NCHRP authorization
will be required before commencing Task 4.
Task 4 Conduct additional analytical studies and
laboratory tests for the purpose of further development
and validation of proposed acceptance criteria for bridge
welds.
Task 5 Revise the acceptance criteria, as necessary,
based on the NCHRP review of the interim report and
in consideration of additional insight gained from the
findings of Task 4.
Task 6 Present the acceptance criteria in a format
suitable for consideration by appropriate code-writing au-
thorities. The recommended criteria shall be accompanied
by a detailed commentary and examples of specific ap-
plications intended to facilitate understanding and use of
the criteria.
Task 7 Identify areas in need of further investi-
gation. Recommend priorities and estimate the time and
costs for the additional research.
Task 8 Prepare a final report.
Through December 31, 1988, research on the project
is progressing on schedule. Tasks 1 through 3 have been
completed, and work is progressing satisfactorily on Tasks
4 through 7. Task 4 was modified by the panel and the
research team to include an investigation of the fatigue
behavior of sharp cracks as well as the fatigue behavior
of naturally occurring discontinuities.
Project 10-32 FY'86
Durability of ~n-Place Concrete Containing
High-Range Water-Reducing Admixtures
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Construction Technology Labora-
tories
Dr. David Whiting
January 6, 1986
July 5, 1987
$99,8 1 1
High-range water-reducing admixtures for concrete,
also known as superplasticizers, were first introduced in
Japan and West Germany in the 1960's, and more recently
they were introduced in the United States. These admix-
tures can markedly increase the workability of concrete
mixtures. They also have the potential for producing very
high strength, durable Portland cement concrete by re-
ducing the amount of water used while still allowing
conventional placement methods.
Research indicates that these admixtures may affect
entrained air void systems. Air void spacing factors below
0.008 in. seem to correlate with expected satisfactory lab-
oratory "freeze-thaw" resistance. However, higher spac-
ing factors often found in the concrete containing high-
range water-reducing admixtures may or may not result
in poor durability based on laboratory tests. Because the
correlation between air void characteristics and durability
as measured in the laboratory under freeze-thaw condi-
tions has not been well defined for concretes containing
high-range water-reducing admixtures, further study is
needed. There is also a perception that regardless of lab-
oratory freeze-thaw testing, good field performance can
be expected. Therefore, field performance should be stud-
ied to evaluate the relevance of the relationship between
in-place durability and air void characteristics.
The objective of this research was to assess the rela-
tionship between the durability and the air void charac-
teristics of concrete placed with high-range water-
reducing admixtures. Existing structures subjected to
freezing and thawing were used for this assessment.
Research is complete; the final report has been pub-
lished as: NCHRP Report 296, "Durability of In-Place
Concrete Containing High-Range Water-Reducing Ad-
mixtures."
Project 10-32A FY,87
Durability Testing of High-Strength Concrete
Containing High-Range Water-Reducing
Admixtures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Utah State University
J. Derle Thorpe
October, 1, 1987
March 31, 1990
$249,238
Interest in the use of high-range water-reducing
(HRWR) admixtures, also known as superplasticizers, for
concrete is increasing. These admixtures can markedly
improve the workability of concrete mixtures. They also
have the potential for producing very high strength, du-
fable Portland cement concrete by reducing the amount
of water used while still allowing conventional placement
methods.
Research indicates that these admixtures may affect
entrained-air void systems. Air void spacing factors below
0.008 in. seem to correlate with expected satisfactory
"freeze-thaw" resistance as predicted by laboratory tests.
However, higher spacing factors often found in concrete
placed using HRWR admixtures may or may not produce
laboratory results predicting poor durability. Because of
the poor correlation between air void characteristics of
concretes containing HRWR admixtures and laboratory
durability test results, a question arises concerning the
relationship of air void characteristics and durability.
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154
There are also concerns about the influence of other con-
crete properties on durability and the ability of current
freeze-thaw testing procedures to adequately measure du-
rability in the laboratory as a predictor of field perform
ance.
Therefore, research should be conducted to improve
laboratory testing procedures for evaluating freeze-thaw
durability and to better understand the parameters that
influence the durability of concretes containing HRWR
admixtures. The major concern is the testing of concretes
with low water-cement ratios containing HRWR admix-
tures so that the benefits of high strength and decreased
permeability can be realized.
The objectives of this research are to: (1) investigate
the significance of various concrete properties, such as
air-void characteristics, on the durability of high strength
concretes (compressive strength greater than 4,000 psi)
containing high-range water-reducing (HRWR) admix-
tures, and (2) compare and assess the variability of du-
rability factors calculated from various methods of testing
concretes for freezing and thawing durability. To accom-
plish these objectives, the following tasks shall be per-
formed:
Task 1- Conduct a survey of state highway agency
practices for performing and applying the results of lab-
oratory freeze-thaw tests.
Task 2 Design a partial factorial testing program
to compare and evaluate laboratory methods of freeze-
thaw testing considering the effects of various character-
istics of the concretes. The test program shall include
procedures defined in ASTM C671, ASTM C666 Pro-
cedure A (2 hr/cycle), and ASTM C666 Procedure A (5
hr/cycle), and the most common procedure used by states
based on Task 1. Details of the measurements and the
analyses to be performed on specimens shall be included.
Specimens shall be cured as prescribed by the ASTM
procedures except that one set of specimens in each test
group shall be tested after 2 additional weeks of air drying.
The concrete mixtures shall include 3 generic types of
HRWR admixtures, multiple cement factors, and a range
of air void characteristics. (The recommended testing pro-
gram must be submitted to the NCHRP for approval
prior to conducting subsequent tasks. Two months are
expected to be required for review by the NCHRP.)
Task 3 Conduct test program as approved in
Task 2.
Task 4 Analyze the data and develop relationships.
Task 5 Prepare the final report including conclu-
sions and recommendations on factors that affect the du-
rability of concretes containing HRWR admixtures,
appropriate laboratory testing procedures that produce
realistic results, and acceptable air void characteristics of
high-strength concrete.
Tasks 1 and 2 are complete. Testing has begun under
Task 3.
Project 10-33 FY,86
Potential Benefits of Geosynthetics in Flexible
Pavement Systems
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Georgia Tech Research Corpora-
tion
Dr. Richard D. Barksdale
January 6, 1986
December 15, 1988
$100,000
Test results indicate that the tensile forces that can be
developed in geotextiles and other geosynthetics, such as
geomembranes and geogrids, hereinafter referred to col-
lectively as geosynthetics, will increase the structural
capacity and improve the performance potential of ag-
gregate-surfaced roads placed over very weak subgrades
(i.e., CBR less than 2~. Techniques have been demon-
strated whereby geosynthetics can be tensioned either by
Restretching the geosynthetic or by loading and devel-
oping ruts in the geosynthetic-aggregate system, before
placing additional (leveling) aggregate base.
The applicability of geosynthetics to higher type pave-
ment systems incorporating unbound granular pavement
layers) with an asphalt surface (flexible pavement sys-
tems) needs to be studied to determine whether the struc-
tural capacity and performance potential can be
improved. Although geosynthetics have been used to some
extent in the unbound granular layers of higher type
pavements, their behavior and influence on pavement per-
formance are not well understood. Consequently, a num-
ber of questions must be answered before the feasibility
of widespread use of geosynthetics in flexible pavement
systems can be determined, for example: (1) What types
of geosynthetics should be used and what properties of
these geosynthetics must be specified? (2) Is prestressing
geosynthetics necessary and practical? (3) Under what
conditions do geosynthetics influence flexible pavement
systems? (4) Can the benefits of geosynthetics be docu-
mented?
The objective of this study is to determine the feasibility
of including geosynthetics on the subgrade or in the un-
bound layers to improve the performance of flexible pave-
ment systems or to provide alternative designs for equal
performance. To accomplish this objective, the following
tasks are required:
Task 1 Select and/or develop analytical models or
procedures to evaluate the behavior of flexible pavement
systems incorporating geosynthetics.
Task 2 Analyze and identify the parameters that
influence the behavior of the flexible pavement systems
incorporating geosynthetics. The parameters to be ex-
amined should include but not be limited to: (a) properties
of the geosynthetics, (b) location of the geosynthetics in
the flexible pavement system, (c) installation methods for
geosynthetics including prestressing and the removal of
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155
wrinkles, (d) properties of the aggregate, (e) character-
istics of the subgrade, (f) environmental effects such as
moisture and temperature, and (g) load magnitude and
frequency. Appropriate ranges for significant parameters
should be identified and the relative importance of these
parameters established using theoretical models or pro-
cedures recommended by the investigators.
Task 3 Using a laboratory testing program, vali-
date the model(s) and the appropriateness of the selected
parameters. The laboratory testing program should be
such that the geosynthetics and aggregate materials can
be placed in a manner similar to normal roadway con-
struction. It is anticipated that the validation testing will
be done using an appropriate range of the most significant
parameters. Relevant properties of each material incor-
porated in the laboratory test program should be deter-
mined using tests selected by the investigators and
performed as part of this project.
Task 4 Establish the engineering feasibility of using
geosynthetics in flexible pavement systems based on the
findings from Tasks 1, 2, and 3. Properties of geosyn-
thetics necessary for installation as well as long-term per-
formance must be considered when establishing this
feasibility. Potential benefits to be realized by incorpo-
rating geosynthetics in flexible pavement systems, such
as improved performance or possible tradeoffs among
components of flexible pavement systems, should be pre-
sented.
Task 5-Develop a framework for the design, im-
plementation, and evaluation appropriate for full-scale
field tests to validate the feasibility established in Task 4.
Research is complete; the agency final report is under
review. Research was successfully performed, but indi-
cates that the use of geosynthetics in the unbound layers
of high type flexible pavement systems is not economically
justified at the present time. Given these circumstances,
the most appropriate distribution of the final report is
being evaluated.
Project 10-34 FY'86
Transient Protection, Grounding, and Shield-
ing of Electronic Traffic Control Equip
ment
Research Agency: Georgia Tech Research Corp.
Principal Invest.: Hugh W. Denny
Elective Date: March 1, 1986
Completion Date: January 31, 1989
Funds: $ 179,992
Electronic traffic control equipment is highly suscep-
tible to disrupted operation and even permanent damage
caused by electrical noise and transients (voltage spikes
and surges) associated with connected service and signal
lines. Lines providing electrical power and cables inter-
connecting equipment to sensors, communications sys
tems, or peripheral hardware provide a direct path for
the conduction of disruptive and damaging electrical tran-
sients from externally generated electrical noise. Light-
ning, switching transients, and other electromagnetic
interference (EMI), including radio frequency interfer-
ence (RFI), may be conducted on electrical and signal
lines connected to traffic control equipment. Some dis-
ruptive noise may even originate from companion equip-
ment located within the traffic control cabinet.
The problem of electrical transient damage to electronic
control equipment may be minimized and in most cases
eliminated by proper application of existing technology,
i.e., currently available devices may be able to provide
sufficient protection against equipment malfunction and
deter damage. However, there are no widely accepted
specifications or procedures for application of such de-
vices to the control equipment cabinet, terminal blocks,
and associated wiring. There is a need to develop such
specifications and procedures and to make them available
to operating agencies to obtain maximum benefit from
the protection devices.
The objectives of this research are to: (1) review current
practice and develop recommended procedures for the
transient protection, grounding, shielding, and filtering of
power and signal conductors, cabinets, and equipment
associated with traffic control to assure the proper op-
eration and extended life of the electronic equipment; (2)
develop recommended performance specifications and test
methods for protective devices; and (3) develop a user's
handbook and a video-training tape. To achieve these
objectives, the following tasks will be accomplished:
Task 1-Review all available research and technical
literature to characterize the magnitude and waveform of
transients on all input and output lines of equipment
cabinets and to obtain related information for use in sub-
sequent tasks.
Task 2 Identify and summarize current practice
(performance specifications, test methods, and installation
and maintenance procedures) of the traffic signal com-
munity.
Task 3 Develop preliminary draft procedures for
providing transient protection of electronic traffic control
equipment.
The procedures will address:
a. Ground rods and grounding networks.
b. Bonding and shielding of cabinets, equipment, wir-
ing, and conduit.
c. Protection of cabinet power and signal circuits, in-
cluding dress and respective location of all wires and
harnesses.
d. Fuses and circuit breakers.
e. EMI/RFI filters.
f. Transient protection devices.
g. Test methods and procedures to verify the above.
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156
Describe how the procedures can be applied to both
new and existing installations. Also describe how they
can be used to mitigate line transients from direct, near,
and distant lightning strikes and from conducted and
radiated EMI and RFI.
Task 4- Prepare and submit an interim report pre-
senting the findings from Tasks 1 through 3 and also
include a preliminary table of contents for the final report
and user's handbook.
Task 5 Prepare final recommended procedures,
performance specifications, test methods, and estimated
hardware costs for transient protective devices for AC
service and signal conductors, detector inputs, and com-
munication lines (AC and DC).
Task 6 Prepare a final report and a user's hand-
book documenting the recommendations and specifica-
tions developed in Task 5. Include in the final report
discussion of the rationale and implications of each rec-
ommendation along with applicable cautions. Describe in
the user's handbook representative components, materials
and assemblies, specifications, and procedures.
Task 7 Prepare a reproducible video-training tape
in 72-inch VHS format in 30-minute segments keyed to
the sections of the user's handbook. Prepare an instruc-
tor's guide to supplement the user's handbook and train-
ing tapes.
Tasks 1 through 6 have been completed and the project
panel has reviewed the draft final report. The research
agency is revising the final report and completing work
on the Task 7 videotapes. The completion date was ex-
tended to October 30, 1988 and may have to be extended
into early 1989 in order to complete all remaining work.
Project 10-35 FY'87
Fatigue Behavior of Welded and Mechanical
Splices in Reinforcing Steel
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Wiss, Janney, Elstner Assoc., Inc.
Conrad Paulson and John M. Han-
sen
November 1, 1987
April 30, 1990
$300,000
Many existing bridges cannot accommodate the in-
creasing traffic volumes and loads that are required for
new bridge designs; therefore, highway agencies are
spending large sums of money in rehabilitating, widening,
and repairing these structures. Designs in some cases rely
on the capacity of welded and mechanical reinforcing steel
splices to transfer loads from the new steel reinforcement
to the existing reinforcement. It is often necessary to place
these splices in regions of high stress range. The behavior
under cyclic stress conditions of many currently used
splice configurations has never been adequately deter-
mined.
AASHTO specifications are available for consideration
of fatigue strength in the design of welded details in
structural steel members. Similar guidelines are not avail-
able for welded details in reinforcing steel. The American
Welding Society's AWS-D1.4 provides standards for fab-
ricating welded reinforcing splices, but provides no in-
formation on their fatigue performance. Additionally, the
AASHTO Standard Specification for Highway Bridges
limits the stress range for reinforcing steel, but provides
no guidance on the allowable stresses in welded or me-
chanical splices.
Some fatigue testing of reinforcing steel splices has been
performed. Many of these tests were performed for the
nuclear power industry and concentrated on low cycle/
high stress range tests on large diameter bars. The results
from these tests may be applicable to the development of
guidelines for the design of bridge components subject to
seismic loadings. It is uncertain, however, whether data
exist for the fatigue behavior of reinforcing steel splices
under high cycle/low stress range effects.
Research is needed to assess the fatigue behavior of
welded and mechanical reinforcing steel splices. On the
basis of this assessment, guidelines will be formulated for
use by the designer involved in the rehabilitation and
design of highway bridges. Better understanding of the
fatigue behavior of welded and mechanical splices in rein-
forcing steel will provide for more cost-effective design,
preventive maintenance, and assurance of public safety.
The objective of this research is to-evaluate the fatigue
behavior of, and develop practical fatigue design guide-
lines for, welded and mechanical splices for reinforcing
steel in bridges.
The research will include the following tasks:
Task 1-Review relevant current domestic and for-
eign practice, performance data, and research findings.
This information shall be assembled from both technical
literature and unpublished experiences of engineers, con-
sultants, and owners of concrete structures.
Task 2 Summarize and evaluate the information
generated in Task 1 on the design, application, and fatigue
behavior of welded and mechanical splices in reinforcing
steel.
Task 3-Present the findings of Tasks 1 and 2 in an
interim report to be submitted not later than 8 months
after initiation of the study. The interim report shall con-
tain a detailed research plan for Task 4 and a framework
for the design guidelines to be developed under Task 6.
Task 4- Conduct laboratory tests in accordance
with the detailed research plan presented in the interim
report. The testing shall consist of constant amplitude
fatigue tests in stress ranges realistic for highway struc-
tures.
Task 5 Analyze and evaluate all relevant fatigue
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157
test results from Tasks 2 and 4, and summarize the find-
~ngs.
Task 6-Develop recommended design guidelines in
a format suitable for consideration by the AASHTO Sub-
committee on Bridges and Structures. The recommended
guidelines shall be accompanied by a detailed commentary
and examples of specific bridge applications intended to
facilitate understanding and use of the guidelines.
Task 7 Prepare and submit a final report containing
the research findings, proposed guidelines, and recom-
mendations for further research.
Through December 31, 1988, research has fallen about
4 months behind schedule. The interim report was sub-
mitted in mid-October and reviewed by the project panel
late in the year. The Task 4 laboratory tests were just
starting at the end of 1988.
Project 10-36 FY'88
Evaluation of Weldments Incorporating Back-
ing Materials
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Fleet Technology Limited
Michael J. Pates
May 2, 1988
May 1, 1991
$259,503
In current steel bridge fabrication the material most
commonly used as a backing for groove welds consists of
a continuous steel bar placed against the backside of the
groove. This permits complete joint penetration groove
welding from one side only. Codes require the weld metal
to be thoroughly fused with the steel backing. This fab-
rication technique is widely accepted, particularly when
access to the far side of the joint being fabricated is
restricted. Typical applications where access may be re-
stricted are in welded box girders and columns. In some
cases, the backing bar is removed after the groove weld
has been completed. However, this is not always possible
or necessary.
Fused weld backing becomes an integral part of the
structure and must be continuous, otherwise sharp, lo-
calized discontinuities will concentrate stresses and cause
weld cracking. Additionally, the orientation of the back-
ing relative to the direction of the applied stress is crit-
ically important. While careful adherence to existing
codes regarding design, assembly, welding procedure,
workmanship, and testing should lead to acceptable per-
formance, the essentials of good practice are not widely
understood. Guidance is required for bridge designers,
fabricators, and inspectors on the proper detailing and
fabrication procedures for complete joint penetration
groove welds incorporating fused steel backing bars.
The geometry of restricted access, complete joint pen-
etration groove welds precludes the use of through-thick-
ness nondestructive evaluation procedures other than
ultrasonic testing. However, the presence of the fused steel
backing compromises the accuracy of such tests. Addi-
tionally, precise measurements of the elective weld throat
are often impossible. These problems may be alleviated
by the use of other backing materials and designs. How-
ever, little information is available for the designer, fab-
ricator, and inspector on the performance of such
alternative backing materials in steel bridge applications.
Research is needed to identify suitable alternative backing
materials and designs appropriate for bridge applications.
The objective of this research is to develop a better
understanding of the performance characteristics of fused
steel bars and alternative weld backing materials, and to
determine their potential benefits and limitations in bridge
design and fabrication.
The research will include the following tasks:
Task 1 Review relevant current domestic and foreign
codes of practice, performance data, and research findings
related to typical bridge framing connections using fused
steel backing bars. This information shall be assembled
from both technical literature and unpublished experience
of designers, fabricators, inspectors, and owners of steel
bridges.
Task 2- From the Task 1 findings, develop a user's
guide for designers, fabricators, and inspectors providing
specific recommendations for the use of fused steel back-
ing bars. The guide should identify critical details and
provide appropriate cautions and limitations.
Task 3-Review relevant current domestic and foreign
codes of practice, performance data, and research findings
related to the use of nonmetallic, nonfused backing ma-
terials. Materials such as carbon, which may adversely
interact with molten metal or the welding arc, should not
be considered.
Task 4 Select a limited number of nonmetallic, non-
fused backing materials that may be appropriate for steel
bridge applications. Determine if the details of welded
joints shown in Chapter 2 of the AWS Dl.1 Structural
Welding Code Steel, are appropriate for use with these
selected backing materials. (The selected backing mate-
rials will be used in laboratory studies to be conducted
in Tasks 6 through 9.)
Task 5 Present the findings of the first four tasks in
an interim report to be submitted not later than 9 months
after initiation of this study. The interim report shall
present a detailed research plan for the remainder of the
study. NCHRP approval of the detailed research plan
will be required before commencing Task 6.
Task 6 Conduct laboratory tests on weldments made
with the selected nonmetallic, nonfused backing materials.
Tests should include metal chemistry, metallurgical stud-
ies, and mechanical tests to ensure that there are no
adverse effects on the weld or base material.
Task 7 Fabricate representative T-, corner-, and butt
Representative terms from entire chapter:
principal invest
