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OCR for page 164
164
and revise the compensation models on the basis of the
evaluation.
5. Prepare a guide for determining rates of compen-
sation for damages resulting from exposure to highway
traffic noise for practical application in planning and
design of highways.
Research has been completed, and copies of the agen-
cy's final report have been distributed to NCHRP spon-
sors. Microfiche of the agency's final report may be
purchased (see final page of this section for ordering in-
formation).
AREA 12: BRIDGES
Project 12-1 FY '65
Deformation of Steel Beams Related to Per-
mitted Highway Bridge Overloads
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Missouri
Dr. Adrian Pauw
Dr. J. W. Baldwin, Jr.
February 1, 1965
June 30, 1967
$50,000
This research was initiated to study the magnitude and
effect of permanent deformations in simple-span com-
posite and noncomposite steel-stringer highway bridges.
Included in the work was a study of the causes and
magnitudes of stress which, in addition to normal load
stresses, lead to yielding of the steel stringer at load
stresses with calculated magnitudes lower than the yield
point of the material. Such factors as residual stress dis-
tribution due to rolling and welding, effects of thermal
gradients, and the effects of creep and shrinkage of the
slab on the stress in the steel were considered.
The final report has been included in the report for
Project 12-6, which was not published in the NCHRP
report series; however, microfiche of the report may be
purchased (see flea' page of this section for ordering in-
formation).
Project 12-2 FY '66
Distribution of
Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Wheel Loads on Highway
Iowa State University
Dr. W. W. Sanders, Jr.
June 1, 1966
December 31, 1968
$79,512
The current AASHO specifications for the distribution
of wheel loads to highway bridge floor systems are in-
adequate. This study correlated and evaluated the large
amount of research conducted on this problem to date
and made suitable recommendations for changes in the
specifications covering wheel-load distribution factors for
the various types of floor systems used in bridges. The
major emphasis was on short- and medium-span bridges
without skew. Included were floor slabs supported by
steel, reinforced concrete, and prestressed concrete, as
well as floor systems produced by adjacent box beams.
The final report has been published as: NCHRP Report
83, "Distribution of Wheel Loads on Highway Bridges."
Project 12-3 FY,66
Development of Waterproof Roadway Joints
for Bridges
Elective Date:
Completion Date:
Funds:
Research Agency: Southwest Research Institute
Principal Invest.: Dr. E. W. Kiesling
J. E. Minor
December 15, 1965
March 14, 1969
$149,895
The research was directed toward the development of
designs for economically feasible waterproof bridge ex-
pansion joints that adequately provide for thermal ex-
pansion and contraction and remain serviceable when
installed normal or skewed to the line of tragic. Rec-
ommendations were made for the design, installation, and
maintenance of the joints.
The research has been completed. The essential findings
from the study have been reported in NCHRP Research
Results Digest 14 (Oct. 1969~. Because it contains pro-
prietary information, the final report will not be published
in the NCHRP report series and is available only to the
sponsors of the Program.
Project 12-4 FY '66
Thermal Characteristics of Highway Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Southwest Research Institute
Dr. Thein Wah
December 15, 1965
March31,1968
$ 102,400
This study sought to determine the magnitude and
significance of thermal gradients in girder-supported high-
way bridges and to develop an analytical method for
predicting the resulting thermal stresses. Field tests were
conducted to attempt to validate the analytical method.
The final report was not published in the NCHRP
report series; however, microfiche of the report may be
purchased (see final page of this section for ordering in-
formation).
Project 12-5 FY,67
Protection of Steel in Prestressed Concrete
Bridges
Research Agency: University of Denver
Principal Invest.: Dr. W. C. Hagel
OCR for page 165
165
Elective Date:
Completion Date:
Funds:
September 15, 1966
November 15, 1968
$173,255
This project sought to determine environmental con-
ditions under which special protection is required and to
develop effective protective systems under both pre- and
post-tensioning configurations. Specifically, the objectives
were (1) to conduct a thorough survey of available do-
mestic and foreign data on corrosion and prevention of
corrosion of prestressing steel in bridges, buildings, pave-
ments, and other structures; (2) to review present practice
to evaluate the effectiveness of prevention of corrosion
and mechanical damage during manufacturing, shipping,
and placing; (3) to identify the mechanisms of corrosion
which attack prestressing tendons under various condi-
tions, possibly including, but not limited to, the influence
of concrete and grout composition, the presence of free
water, electrolysis, and the presence or absence of crack-
ing; (4) to devise an appropriate accelerated corrosion test
or tests simulating the various service conditions sur-
rounding prestressing tendons; (5) to evaluate various
possible protective systems for prestressing tendons, in-
cluding, but not limited to, metallic, plastic, or inhibitive
coatings, grout substitutes or admixtures, cathodic pro-
tection, etc.; (6) to perform field and laboratory experi-
ments to determine the effectiveness of present grouting
methods for post-tensioned work and to suggest improve-
ments in methods and/or materials; and (7) to evaluate
the effectiveness of concrete cover over tendons.
The final report has been published as: NCHRP Report
90, "Protection of Steel in Prestressed Concrete Bridges."
Project 12-6 FY '67
Prediction of Permanent Camber of Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Missouri
Dr. James W. Baldwin, Jr.
Dr. Adrian Pauw
February 1, 1967
April 30, 1972
$82,253
The primary objective of this research was to recom-
mend a means of predicting the permanent camber in
rolled beams resulting from specific fabrication methods
and to include (1) a thorough survey of available data on
residual stresses in rolled beams; (2) a survey of existing
methods of cambering beams and a classification of meth-
ods into different categories, if possible, with cambering
by both mechanical and thermal means being studied; (3)
the determination of the magnitude and distribution of
residual stresses in beams as rolled and delivered to the
fabricator without camber, with the beams studied being
of sizes representative of typical highway bridges; (4) the
determination of the effect of the cambering methods
investigated on residual stresses; (5) the determination of
permanent deformations in rolled beams without added
camber when subjected to repeated loads at various levels
with loads lower than those causing computed yield-point
stresses (this does not presume to be fatigue loading, but
the number of cycles applied would be equal to six-months
service life of a bridge); (6) the determination of per-
manent deformations in rolled beams cambered by the
methods investigated when subjected to repeated loads at
various levels of loading lower than those causing com-
puted yield-point stresses, the number of cycles applied
being equal to six-months service life of a bridge; and (7)
the formulation of a mathematical model (after the de-
termination of objectives 5 and 6) for predicting the per-
manent camber.
The final report, which includes the findings of Project
12-1, was not published in the NCHRP report series;
however, microfiche of the report may be purchased (see
final page of this section for ordering information).
Project 12-7 FY '67
Effects of Weldments on Fatigue Strength of
Steel Beams
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Lehigh University
Dr. John W. Fisher
Oct. 1, 1966 July 1, 1970
Jan. 31, 1970 Dec. 31, 1972
$ 199,023 $200,000
The principal objective of Phase I of this research was
to develop design relationships that define the basic be-
havior of welded coverplated beams under constant-
amplitude fatigue loading. The results of the Phase I work
have been reported in: NCHRP Report 102, "Effect of
Weldments on the Fatigue Strength of Steel Beams."
The Phase II work had the objective of extending the
basic knowledge obtained under Phase I into important
design considerations, including stiffeners and/or lateral
and transverse connections. Phase II included a contin-
uing review of existing data and mathematical relation-
ships defining the fatigue behavior of various details under
constant-amplitude loading. It also included a statistically
designed and controlled experiment that was intended to
provide new information for the development of suitable
mathematical relationships that can predict the fatigue
behavior of welded beams with stiffeners and/or lateral
and transverse connections. Variables studied included
applied stresses, design details, and type of steel.
Phase II research has been completed, and the final
report has been published as: NCHRP Report 147, "Fa-
tigue Strength of Steel Beams with Welded Stiffeners and
Attachments."
OCR for page 166
166
Project 12-8 FY '66
Bridge Rail Service Requirements as a Basis
for Design Criteria
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Texas A & M University
Research Foundation
Dr. Robert M. Olson
Mar. 1, 1968 Jan. 2, 1970
Feb. 28, 1969 June 30, 1971
$28,793 $69,753
The Phase I research effort had as its objective the
development of tentative service requirements, and the
results have been published as: NCHRP Report 86, "Ten-
tative Service Requirements for Bridge Rail Systems."
The Phase II effort had as its objective the quantifi-
cation of the service requirements to produce design cri-
teria for bridge rail systems. This objective was to be
pursued by further establishing the validity of a simple
mathematical model developed under Phase I; by con-
ducting parameter studies using the mathematical model
to evaluate simulated vehicle-barrier collisions; by devel-
oping tables, curves, or Homographs for use by design
engineers; and by refining the limits of tolerable decel-
eration on the basis of more recent information.
Phase II research has been completed, and the final
report has been published as: NCHRP Report 149,
"Bridge Rail Design-Factors, Trends and Guidelines."
Project 12-9 FY '67
Elastomeric Bearing Research
Research Agency: Battelle Memorial Institute
Principal Invest.: J. C. Minor
Elective Date: September 1, 1967
Completion Date: January 31, 1970
Funds: $84,800
This project contemplated research on elastomeric
bearings and bearing systems using materials as defined
in the AASHTO specifications for elastomeric bearing
pads. The major objectives of the project were to evaluate
(1) erect of geometry on compressive strain, compressive
set, shear modulus, and rotational modulus for hardness
between 50 and 70 durometer and sizes from 50 to 200
sq in., and the effect of lamination on these values; (2)
relative performance of glued laminated pads compared
to fully vulcanized units, including an elective test of the
adhesion between layers; (3) relative performance of
molded pads versus pads sawed from larger sheets with
an evaluation of the sawing process and determination of
an acceptable cut surface; and (4) evaluation of the aging
and low-temperature (to -40 F) characteristics of the
various pads.
The research has been completed, and the final report
has been published as: NCHRP Report 109, "Elastomeric
Bearing Research."
Project 12-10 FY '70
Analysis anti Design of Bridge Bents
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Portland Cement Association
Dr. James E. Carpenter
January 1, 1970
December 31, 1973
$297,900
The present strong emphasis on safe and aesthetic de-
sign of reinforced concrete highway bridges has resulted
in substructure configurations that depart widely from
the traditional footing-column-cap frame design. Aes-
thetic considerations often dictate the concealment of
massive concrete caps and elimination of numerous ver-
tical columns; however, design procedures in current use
are not applicable to these new configurations. There is
a general- feeling that current procedures result in
overdesigned structures containing much more steel than
is necessary. Therefore, an urgent need exists for the
development of appropriate design procedures.
Although the ultimate need is to establish valid design
procedures that are applicable to many configurations of
bridge bents, this project was limited to investigation of
bent caps concealed in straight, continuous, reinforced
concrete bridges.
Design procedures were developed by (1) constructing
and testing adequately scaled reinforced concrete models
of representative bents and (2) developing a mathematical
model to correlate with the experimental results. The
design procedures may be corroborated by data taken
from full-size bridges instrumented during construction
but not as a part of this project.
Research was based on prototypes representative of
popular box-girder designs. The accomplishment of the
research included: (1) reviewing the technical literature;
(2) determining a design procedure for single- and mul-
tiple-column bents; (3) determining the cap design width
by defining the extent of superstructure participating in
supporting the cap loads; and (4) specifying changes re-
quired in the AASHTO specifications to permit use of
the recommended design procedures.
To achieve the objectives of this research, a plan was
developed that includes testing of 75-scale models of two
reinforced concrete box girder bridges. These tests p.o-
vided information on distribution of loads in the vicinity
of the integrated bent cap. Five additional tests on model
bent specimens provided further information on the lo-
cation of critical sections and the effective width of the
bent cap. These 2/-scale specimens were intended to rep-
resent a transverse strip of bridge superstructure that is
parallel to and includes the bent cap and columns. The
reinforcement of the bent cap was varied in these models,
as well as column flare and the thickening of the deck
slab. Analytical studies of load distribution in the entire
bridge and of stress distribution in the bent cap accom-
panied the experimental work.
OCR for page 167
167
Research has been completed, and the project report
has been published as: NCHRP Report 163, "Design of
Bent Caps for Concrete Box Girder Bridges."
Project 12-11 FY '71
Waterproof Membranes for Protection of Con-
crete Bridge Decks
Research Agency: Materials Research and
Development
C. J. Van Til C. J. Van Til
B. J. Carr
Aug. 1, 1970 July 15, 1973
Mar. 31, 1973 Sept. 30, 1978
$206,025 $96,979
Principal Invest.:
Elective Date:
Completion Date:
Funds:
The objective of this research was to develop, or dis-
cover, one or more elective waterproofing membrane sys-
tems for use on concrete bridge decks.
The objective was approached in a two-phase study.
Phase I, now complete, was devoted to preliminary eval-
uation of all available membranes, selection of the most
promising for field evaluation and development of a field
evaluation plan. Phase II was the field evaluation.
The results of Phase I have been reported in: NCHRP
Report 165, "Waterproof Membranes for Protection of
Concrete Bridge Decks Laboratory Phase."
Under Phase II, the five systems selected as most prom-
ising were experimentally installed on new decks at each
of four bridge sites in 1974 and 1975. Semiannual obser-
vations of performance of the installed systems were
made. Research is completed, and the agency's final report
has been distributed to the Program sponsors. Loan copies
are available or microfiche of the report may be purchased
(see final page of this section for ordering information).
Project 12-12 FY '71
Welded Steel Bridge Members Under Variable-
Cycle Fatigue Loadings
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
United States Steel Corporation
C. G. Schilling
K. H. Klippstein
October 1, 1970
October 31, 1975
$3 10,000
The primary objective of this project was to develop
information on the properties of welded steel bridge mem-
bers under variable-cycle fatigue loadings and to develop
a hypothesis for the prediction of life expectancy from
any spectrum of loading.
The agency pursued the project objectives by: a study
of pertinent past work with particular emphasis on field
measurements of stresses in bridges under traffic; a the-
oretical study to predict from existing hypotheses the
fatigue behavior of small specimens and beams that were
tested later in the study; variable-amplitude fatigue tests
of small specimens simulating certain beam details for
the purpose of verifying the variable-amplitude load spec-
tra selected and crack propagation threshold assumptions;
variable-amplitude fatigue tests of relatively large beams
of various steels with typical bridge details similar to those
tested in NCHRP Project 12-7; and complete evaluation
of the experimental results and development of methods
of utilizing the results for design and specification pur-
poses.
Research has been completed, and the final report has
been published as: NCHRP Report 188, "Fatigue of
Welded Steel Bridge Members Under Variable-Amplitude
Loadings."
Project 12-13 FY '73
Cathodic Protection for Reinforced Concrete
Bridge Decks
Research Agency:
Principal -Invest.:
Effective Date:
Completion Date:
Funds:
USS Engineers and Consultants
J. B. Vrable
October 1, 1972
July 31, 1974
$174,601
The objective of this research was to develop a tech-
nically and economically feasible cathodic protection sys-
tem~s) for reinforced concrete bridge decks.
In this study, the two primary approaches to cathodic
protection the impressed current system and the sac-
rificial anode system were investigated. Analog studies
in the laboratory and prototype model studies were main
features of the investigation. The feasibility of applying
either approach to protecting bridge deck steel reinforce-
ment against corrosion was demonstrated. A detailed
work plan for a field evaluation of cathodic protection,
applying the results of the study, was developed.
Research has been completed, and the project report
has been published as: NCHRP Report 180, "Cathodic
Protection for Reinforced Concrete Bridge Decks Lab-
oratory Phase."
Project 12-13A FY '73
Field Evaluation of Galvanic Cathodic Protec-
tion for Reinforced Concrete Bridge
Decks
Research Agency: Portland Cement Association
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Dr. David A. Whiting
August 1, 1975
May 15, 1981
$74,405
Research under a previous NCHRP study, Project 12-
13, had a primary objective of developing technically and
economically feasible cathodic protection systems for the
uppermost reinforcing steel in concrete bridge decks. The
findings, published in NCHRP Report 180, "Cathodic
Protection for Reinforced Concrete Bridge Decks Lab
OCR for page 168
168
oratory Phase," demonstrated the potential of cathodic
protection and recommended field demonstration pro-
grams. These recommendations included both forms of
cathodic protection: impressed current cathodic protec-
tion and galvanic cathodic protection, i.e. the use of sac-
rificial anodes.
On completing Project 12-13, the NCHRP elected to
pursue field evaluations of galvanic cathodic protection
only. Impressed current cathodic protection was already
receiving attention from several states.
The evaluations and related research are now complete.
Absolute judgments on galvanic cathodic protection of
reinforced concrete bridge decks were not possible. How-
ever, the performance of two variations of protective sys-
tems, perforated zinc sheet anodes and closely spaced zinc
ribbon anodes, provides encouragement for further
research and field demonstrations of this relatively simple
method of cathodic protection systems as a possible pres-
ervation technique for reinforced concrete bridge decks.
Research has been completed, and the project report
has been published as: NCHRP Report 234, "Galvanic
Cathodic Protection for Reinforced Concrete Bridge
Decks Field Evaluation."
Project 12-14 FY '73
Subcritical Crack Growth in Steel Bridge Mem-
bers
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
United States Steel Corporation
Dr. John M. Barsom
October 1, 1972
June 30, 1974
$99,923
The long-range objective of this research was to develop
information that would lead to prevention of unstable
crack growth in welded steel bridge members. This ob-
jective included the definition of material requirements
and design specifications to avoid brittle fracture.
The main objectives of this project were:
1. To develop corrosion-fatigue data on bridge steels
in distilled water and 3 percent sodium chloride solution
under stress fluctuations such as occur in actual bridges.
2. To develop an analytical method for predicting the
cyclic life of bridge components in distilled water and 3
percent sodium chloride solution under stress fluctuations
such as occur in actual bridges.
3. To develop methods of utilizing the results for design
and specifications purposes.
The steels studied were A36, A588 grades A and B. Research Agency:
and A514 grades E and F. The test specimens were made Principal Invest:
from base metal of 1-in. plate material and were 1 in. Elective Date
thick. Completion Date:
The longitudinal and transverse tensile properties at
room temperature were established for each grade of steel.
Moreover, energy absorption, lateral expansion, and per
cent shear were determined in the temperature range be-
tween-100°F and room temperature by using standard
impact Charpy V-notch specimens.
Research has been completed, and the project report
has been published as: NCHRP Report 181, "Subcritical
Crack Growth in Steel Bridge Members."
Project 12-15 FY '73
Detection and Repair of Fatigue Cracking in
Highway Bridges
Research Agency: Lehigh University
Principal Invest.: Dr. John W. Fisher
Elective Date: October 1, 1972
Completion Date: April 30, 1975
Funds: $ 100,000
The objectives of the study were to: (1) compile a state-
of-the-art review of existing methods of nondestructive
inspection and evaluate their reliability and adaptability
in the detection of fatigue cracks in welded highway
bridges; (2) compile a state-of-the-art review of typical
existing and currently designed welded bridge details and
evaluate those most susceptible to fatigue crack growth;
(3) review and evaluate methods for improving the fatigue
life and arresting the progress of fatigue damage that
occurs at the weld toes of severe notch-producing details
where the probability of failure is greatest. The methods
were evaluated by tests of "as welded" and of fatigue-
damaged coverplate beam specimens of A36 steel. These
tests were comparable to and correlated with those con-
ducted in NCHRP Project 12-7 and reported in NCHRP
Reports 102 and 147. The experimental variables include
crack size at the time of treatment, methods of improve-
ment, stress range, and minimum stress; and (4) recom-
mend methods for improving the fatigue life of, and
arresting the progress of fatigue damage to, welded high-
way bridges.
Research has been completed, and loan copies of the
agency's final report are available from the NCHRP upon
written request. The findings have been combined with
those from Project 12-15(2) and published as: NCHRP
Report 206, "Detection and Repair of Fatigue Damage
in Welded Highway Bridges."
Project 12-15(2) FY '75
Retrofitting Procedures for Fatigue-Damaged
Full-Scale Welded Bridge Beams
Lehigh University
Dr. John W. Fisher
June 1, 1976
November 30, 1978
$150,000
This study built on research completed earlier under
NCHRP Project 12-15, "Detection and Repair of Fatigue
OCR for page 169
169
Cracking in Highway Bridges." Project 12-15 demon-
strated that peening the weld toe and applying a gas
tungsten arc remelt process were successful in improving
fatigue strength in the laboratory. The current study in-
cluded further work on these methods and was concerned
with three major areas related to the retrofit or repair of
fatigue-damaged members.
Task 1 was intended as a pilot study to demonstrate
the applicability of peening and gas tungsten arc remelting
in the field.
Task 2 was intended to provide supplemental infor-
mation on the low stress range behavior of full-size bridge
beams. These beams were retrofitted and retested after
various levels of fatigue crack growth.
Task 3 was intended to examine the fatigue strength
of beams, with cracks at the ends of transverse stiffeners,
that have subsequently been repaired by drilling holes at
the crack tip. Five existing welded built-up beams were
available for this study from an earlier test program.
Research is completed, and the final report, including
findings from Project 12-15, has been published as:
NCHRP Report 206, "Detection and Repair of Fatigue
Damage in Welded Highway Bridges."
Project 12-15(3) FY'78
Fatigue Behavior of FulI-Scale Welded Bridge
Attachments
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Lehigh University
Dr. John W. Fisher
February 1, 1978
July 31, 1980
$125,000
The objective of this study was to examine the fatigue
strength of beams with web and flange lateral attachment
plates. In addition to providing a more comprehensive
data base for this type of detail, the program was intended
to examine the influence of lateral bracing members on
the out-of-plane distortion of the lateral plate. Further
work was also undertaken during the experimental studies
on the effectiveness of peening and gas tungsten arc re-
melting the fatigue-damaged connections and on the abil-
ity of drilled holes to arrest crack growth.
A total of 18 beams, each with three welded gusset
plate details, were tested in fatigue with stress ranges of
6 to 15 ksi. The results of these tests were used to assess
the adequacy of applicable provisions of the AASHTO
Specification. In addition, the influence of lateral bracing
on the fatigue performance of the attachments was eval-
uated.
Research has been completed, and the final report has
been published as: NCHRP Report 227, "Fatigue Be-
havior of Full-Scale Welded Bridge Attachments."
Project 12-15~4) FY '79
Steel Bridge Members Under Variable-Ampti-
tude, Long-Life Fatigue Loading
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Lehigh University
Dr. John W. Fisher
April 1, 1980
September 30, 1983
$150,000
The objective of this study was to provide additional
information on fatigue crack growth behavior of steel
bridge members under randomly applied, variable am-
plitude loadings in the fatigue limit, extreme life region.
Testing was carried out on center-crack specimens, cru-
ciform specimens, and full-scale welded beams.
The currently available test data in this region of be-
havior are very sparse and do not provide an adequate
basis on which to assess this problem. The consequences
of triggering fatigue crack growth in existing bridges as
a result of increased loads could have a major impact on
the life expectancy and safety of bridge on high volume
arteries where large numbers of random variable stress
cycles are expected.
Research has been completed, and the final report has
been published as: NCHRP Report 267, "Steel Bridge
Members Under Variable-Amplitude Long-Life Fatigue
Loading."
Project 12-15~5) FY'82
Fatigue Behavior of Variable Loaded Bridge
Details Near the Fatigue Limit
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Lehigh University
Dr. John W. Fisher
September 1, 1983
December 31, 1989
$399,999
Fatigue cracks have developed at the ends of cover-
plates in beams that are only infrequently subjected to
stress ranges exceeding the fatigue limit of AASHTO's
Category E'. For example, in one particular structure,
small cracks have been detected in several beams where
only 0.1 percent of the measured stress cycles exceeded
the estimated fatigue limit. This observed field behavior
suggests that more severe fatigue problems could result
if bridges are subjected to heavier loads in the future, and
the consequences of occasional overloads from permits
and other sources may be more critical than previously
assumed.
The objective of this study is to extend the findings of
Project 12-15(4) by providing additional information on
fatigue crack growth behavior of steel bridge members
under randomly applied, variable-amplitude loadings in
the fatigue limit, extreme life region. Testing will be car-
ried out on eight full-scale welded girders.
OCR for page 170
170
The currently available test data in this region of be-
havior are very sparse and do not provide an adequate
basis on which to assess this problem. The consequences
of triggering fatigue crack growth in existing bridges as
a result of increased loads could have a major impact on
the life expectancy and safety of bridges on high volume
arteries where large numbers of random variable-stress
cycles are expected.
In addition to the test program directed at the primary
objective, a small portion of the total effort was expended
on a reassessment of the fatigue specifications in the
AASHTO Standard Specifications for Highway Bridges.
Minor revisions to the fatigue design provisions were rec-
ommended to, and adopted by, the AASHTO Subcom-
mittee on Bridges and Structures. The evaluation and
recommended specifications were published in: NCHRP
Report 286, "Evaluation of Fatigue Test Data and Design
Criteria on Welded Details."
The fatigue testing has continued through December
31, 1988. One pair of girders was tested for 107 million
cycles with fatigue failures noted in two connection plate
details and three web attachments. A second pair of gir-
ders has received over 50 million fatigue cycles to date,
with no sign of cracking at any detail. Testing on the
remaining two pairs of girders was initiated in late De-
cember 1988.
Project 12-16 FY '75
Influence of Bridge Deck Repairs on Corro-
sion of Reinforcing Steel
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Battelle Columbus Laboratories
Walter K. Boyd
September 1, 1974
November 30, 1977
$214,912
This study was concerned with the problem of corro-
sion of reinforcing steel caused by chloride ions in bridge
deck concrete. The over-all objective of this research was
to determine the relative electiveness of the various repair
methods in arresting corrosion of the reinforcing steel,
both within and outside the repaired areas, and whether
some of these methods actually aggravate the corrosion
problem.
Research has been completed. Copies of the agency
report may be obtained on a loan basis upon written
request to the NCHRP. A limited number of copies is
available to NCHRP sponsors for permanent retention,
and others may purchase microfiche of the report (see
final page of this section for ordering information).
Project 12-17 FY '77
Evaluation of Repair Techniques for Damaged
Steel Bridge Members
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Battelle Columbus Laboratories
H. W. Mishler
November 15, 1976
April 30, 1978
$49,974
The over-all objective of this project was to provide
guidance for the assessment of accidental damage to steel
bridge members and to identify, develop, and evaluate
the effectiveness of repair techniques. The specific objec-
tive of Phase I was to synthesize available information
on the subject and to identify areas in need of investi-
gation. The specific objective of Phase II is to evaluate
the effect of the damage and the repair techniques iden-
tified in Phase I on the behavior of the structure, deter-
mine potential detrimental effects, and define the limits
within which these repair techniques can be used.
Research under Phase I has been completed. The proj-
ect final report has been distributed to state highway
agencies, and copies may be obtained on a loan basis upon
written request to the NCHRP. A limited number of
copies is available to NCHRP sponsors for permanent
retention, and others may purchase microfiche of the
report (see final page of this section for ordering infor-
mation).
Project 12-17A FY '79
Guidelines for Evaluation and Repair of Dam-
aged Steel Bridge Members
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
George O. Shanafelt and Willis B.
Horn
W. B. Horn, G. O. Shanafelt
October 1, 1981
May 31, 1984
$99,950
The overall objective of this two-phase project was to
provide guidance for the assessment of accidental damage
of steel bridge members and to identify, develop, and
evaluate the effectiveness of repair techniques. The specific
objective of Phase I (Project 12-17) was to synthesize
available information on the subject and to identify areas
in need of investigation. The specific objective of the sec-
ond phase of research (Project 12-17A) was to extend the
effort carried out under Project 12-17 and to develop a
manual of recommended practice.
Research under Phase II produced a detailed procedure
of assessment and evaluation of damage. Recommenda-
tions of repair techniques and the effects of those repairs
were detailed to the extent possible using currently avail-
able information. These results were presented in a user's
manual recommending procedures and specifications for
steel bridge repair.
OCR for page 171
171
Research has been completed, and the final report has
been published as: NCHRP Report 271, "Guidelines for
Evaluation and Repair of Damaged Steel Bridge Mem-
bers."
Project 12-18 FY '77
Development of an Integrated Bridge Design
System
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Multisystems Inc.
Dr. Som P. S. Virk
September 6, 1977
December31,1982
$224,985
The objective of this research was to initiate the de-
velopment of an integrated, modular bridge design system
encompassing current bridge design specifications and al-
lowing the engineer a wide range of interaction with the
computer in performing his design functions. Such a sys-
tem should be able to accommodate a variety of typical
bridges.
The project consisted of two phases. Phase I included
a preliminary investigation with the most important prod-
ucts being an inventory of currently used bridge design
software and the definition of a framework for an inte-
grated bridge design system. The actual development of
the system and its functional modules occurred in the
second phase of research.
Research has been completed. The objective of this
research was not fully accomplished. A limited, follow-
up study was carried out under NCHRP Project 12-18A
to evaluate the current status and provide information
for future activity in this area.
Project 12-1 8A FY '81
Assessment of an Integrated Bridge Design
System
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Engineering Computer Corporation
Roy A. Imbsen
February 1, 1984
January 3, 1986
$15,000
The objective of Project 12-18 was to initiate the de-
velopment of an integrated, modular bridge design system
encompassing current bridge design specifications and al-
lowing the engineer a wide range of interaction with the
computer in performing his design functions. Such a sys-
tem should be able to accommodate a variety of typical
bridges.
Project 12-18 did not reach its objective. A module for
computation of bridge geometry was demonstrated to
operate within the integrated system, but, for undeter-
mined reasons, the superstructure design module did not
function properly as part of the system.
Because of the limited success of Project 12-18, an
independent assessment of the status of the integrated
bridge design system was made. This study included an
evaluation of the computer code developed in Project 12-
18 in order to determine if it could be used in future
programs, and a determination of the options available
for additional research.
The project has been completed. The final report pro-
vided the following conclusions:
1. In the development work of NCHRP Project 12-18
for the integrated software system, too much emphasis
was placed on the computer system aspect and not enough
on the end-user needs.
2. The geometry module works well and is quite useful.
3. The superstructure module does not work properly.
4. AASHTO had initiated development of its own
bridge design program (BDS) rendering Project 12-18
obsolete.
The agency final report will not be published in the
regular NCHRP report series. It has been distributed to
Program Sponsors only.
Project 12-19 FY'78
Cathodic Protection of Concrete Bridge Struc-
tures
Research Agency: Corrosion Engineering & Research
Co.
William I. Ellis
January 1, 1978
December 31, 1980
$250,000
Principal Invest.:
Effective Date:
Completion Date:
Funds:
The primary objective of this study was to develop and
evaluate one or more cathodic protection systems to con-
trol corrosion of steel in chloride-contaminated structural
members (excluding top reinforcement in decks and steel
in members below water or soil).
The cathodic protection system developed reflects con-
sideration of: economic feasibility, including design,
installation, operating, and maintenance costs; compati-
bility with the structure, including repaired areas; poten-
tial safety hazards; life expectancy; and resistance to
various environments, such as freeze-thaw and marine
conditions.
A secondary objective was to prepare a state-of-the-art
report based on a thorough survey of methods, materials,
and criteria that have been used to control corrosion in
concrete bridge members other than the top portion of
decks. The report describes both successful and unsuc-
cessful experiences.
Research has been completed. The state-of-the-art re-
port and the final report have been distributed to state
highway agencies. Copies are available for loan upon writ-
ten request to the NCHRP or microfiche of the report
OCR for page 172
172
may be purchased (see final page of this section for or-
dering information).
Project 1 2-19A FY '79
Concrete Sealers for Protection of Bridge
Structures
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Wiss, Janney, Elstner Assoc., Inc.
Donald W. Pfeifer
August 1, 1979
December 1, 1981
$99,190
The objective of this study was to establish the efficacy
of sealers used to protect reinforced concrete bridges ex-
posed to chloride contamination and to provide guidance
for their use on bridge members concentrating on struc-
tural elements other than the top surface of the deck.
Accordingly, a variety of testing procedures were devel-
oped and several candidate sealers were evaluated. The
proprietary labelling of the sealers tested has only been
made available to NCHRP sponsors. Of widespread in-
terest, however, should be the testing procedures used.
The research has been completed, and the project report
has been published as: NCHRP Report 244, "Concrete
Sealers for Protection of Bridge Structures."
Project 12-19B FY'81
Cathodic Protection of Concrete Bridge Struc-
tures
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Wiss, Janney, Elstner Assoc., Inc.
William F. Perenchio
J. Robert Landgren
November 1, 1982
April 30, 1985
$138,900
Although the NCHRP project panel was generally
pleased with the contents and presentation of the final
report for Project 12-19, they agreed that the findings
were not ready for widespread application. Consequently,
a decision was made to pursue further the Project 12-19
objective of developing and evaluating one or more ca-
thodic protection systems to control corrosion of steel in
chloride contaminated structural elements (excluding top
reinforcement in decks and steel in members below water
or soil). Specifically Project 12-19B included: (1) labo-
ratory investigations aimed at further development and
evaluation of cathodic protection systems using conduc-
tive coatings as secondary anodes, and (2) field evaluations
based on actual applications and monitoring.
Laboratory tests were performed on three conductive
coatings. After optimizing the test results for the primary
requirements of conductivity and durability, one coating
was selected for further work. A cathodic protection sys-
tem using the selected coating was applied to a laboratory-
size concrete slab located at the Federal Highway Ad
ministration's Turner-Fairbank Highway Research Cen-
ter and to an actual bridge pier in cooperation with the
Illinois DOT.
Research has been completed, and the project report
published as: NCHRP Report 278, "Cathodic Protection
of Concrete Bridge Substructures."
Project 12-20 FY '78 and FY '80
Bridges on Secondary Highways and Local
Roads: Rehabilitation and Replacement
Research Agency: University of Virginia
Principal Invest.: Henry L. Kinnier
Elective Date: March 1, 1978 June 1, 1980
Completion Date: Feb. 29, 1980 Nov. 30, 1981
Funds: $119,923 $49,955
The objective of the first phase of this project was to
develop (1) procedures for accomplishing repair and
strengthening operations for bridges on secondary high-
ways and local roads, (2) standard replacement structures
and components that could be mass produced, and (3)
an economic process for determining the most cost-effec-
tive alternative available in a given situation.
Phase I has been completed, and the final report was
published as: NCHRP Report 222, "Bridges on Second-
ary Highways and Local Roads Rehabilitation and Re-
placement." The primary content of this report consists
of a manual of recommended practice comprising 34 re-
pair procedures for common bridge deficiencies and 27
bridge replacement systems available for use in the United
States.
The objective of the second phase of research was to
expand the effort carried out under Phase I. Additional
procedures for repair of the following types of bridge
damage were studied: fatigue of steel members, scour,
deck deterioration, fire, seismic, and accidental impact.
Replacement systems based on the following concepts
were considered: short-span segmental construction, sec-
tional prestressing, modular construction and precast con-
crete box culverts. These repair procedures and
replacement systems were prepared in the format used in
the manual developed in Phase I. Innovative concepts for
bridge rehabilitation and replacement were also studied.
Phase II has been completed, and the final report has
been published as: NCHRP Report 243, "Rehabilitation
and Replacement of Bridges on Secondary Highways and
Local Roads."
Project 12-21 FY '79 and FY '82
Evaluation of Damage and Methods of Repair
for Prestressed Concrete Bridge Mem-
bers
Research Agency: George O. Shanafelt and Willis B.
Horn
Principal Invest.: W. B. Horn, G. O. Shanafelt
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173
Effective Date: April 15, 1979
Completion Date: Sept. 14, 1980
Funds: $58,520
The over-all objective of this study was to provide
guidance for the assessment of accidental damage to pre-
stressed concrete bridge members and to identify, develop,
and evaluate the effectiveness of repair and replacement
techniques. The research was carried out in two phases.
The specific objective of Phase I was to synthesize
available information on the subject and to identify areas
in need of investigation. The specific objective of Phase
II was to develop and evaluate improved repair proce-
dures for damaged prestressed concrete bridge members
and to prepare a manual of recommended practice.
Phase II included an evaluation of the effect of damage
and the positive and negative aspects of selected repair
techniques on the behavior of the structure and of the
limits within which these repair techniques can be used.
This was being accomplished through application of se-
lected techniques to damaged members and subsequent
laboratory testing. A detailed procedure for assessment
and evaluation of damage was produced. Recommenda-
tions of repair techniques and effects of those repairs were
detailed. These results are presented in a user's manual
recommending procedures and specifications for pre-
stressed concrete bridge repair. Repair methods include:
the metal sleeve (see NCHRP Report 226, Nos. 3 and
5), the internal splice (Nos. 7 and 8), and the external
post-tensioning system (No. 2~.
Research is complete and project reports for Phase I
and Phase II have been published as: NCHRP Report
226, "Damage Evaluation and Repair Methods for Pre-
stressed Concrete Bridge Members," and NCHRP Report
280, "Guidelines for Evaluation and Repair of Damaged
Prestressed Concrete Bridge Members."
Project 12-22 FY'81
Thermal Effects in Concrete Bridge Super-
structure
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Engineering Computer Corporation
Roy A. Isabsen
October 1, 1981
January 31, 1984
$100,000
The objective of this research was to develop recom-
mended specifications and design procedures for consid-
eration of thermally induced stresses and movements in
concrete bridge superstructures.
The research has been completed. The report and rec-
ommended specifications have been published as NCHRP
Report 276, "Thermal Effects in Concrete Bridge Super-
structures."
May 15, 1982 Project 12-23 FY'89
Jul. 8, 1985
$129,934
Recommended Revisions to the AASHTO
Manua/ for Maintenance /nspecVon of
Bridges
Research Agency:
Principal Invest:
Effective Date:
Completion Date:
Funds:
A. G. Lichtenstein & Associates,
Inc.
Abba G. Lichtenstein
January 3, 1989
January 2, 1991
$200,000
The AASHTO Manual for Maintenance Inspection of
Bridges is intended as a guide to provide uniformity in
the inspection procedures and evaluation techniques for
all bridges on public roads. The Manual was initially
adopted by AASHTO in 1970, and since that time only
minor changes and additions have been made. Many sub-
sequent advances in analytical and practical techniques
are being used in bridge design, construction, and eval-
uation, but have not been reflected in the Manual.
Research is needed to update the existing Manual. A
thorough review and revision of the inspection and eval-
uation criteria, on the basis of current technology and
recently completed and on-going research, will result in
better assessment of the condition and load capacity of
existing bridges.
The objective of this report is to develop a revised
Manual for Maintenance Inspection of Bridges that can
be recommended to AASHTO for consideration for adop-
tion.
In developing the revised Manual, consideration shall
be given to current practice, recently completed and on-
going research, and appropriate AASHTO committee and
FHWA activities to provide: (1) guidance for inspection,
evaluation, and load capacity rating of existing bridges;
(2) a recommended method for load capacity rating along
with acceptable alternate methods; (3) appropriate con-
sideration of inspection requirements and preparation of
inspection reports; (4) a methodology for assessing the
safe load capacity from load tests; and (5) consideration
of fatigue and other serviceability requirements. The re-
vised manual shall also include consideration of factors
such as scour, redundancy, and detail criticality and eval-
uation procedures that are applicable to bridge manage-
ment systems.
The revised Manual shall be prepared in a flexible for-
mat that allows for future revisions, and a commentary
shall also be provided.
The project will include the following tasks:
Task 1. Review relevant literature and current do-
mestic and foreign procedures and specifications for in-
spection, evaluation, and load capacity rating of existing
bridges and other structures.
Task 2. After evaluating the information developed in
Task 1, prepare a comprehensive list of, and rationale for,
recommended revisions to the existing Manual.
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174
Task 3. Prepare a detailed outline for a revised Manual.
As a minimum, the outline shall include chapter and
topical headings along with a description of the intent of
each topic.
Task 4. Present the findings of Tasks 1, 2, and 3 in an
interim report to be submitted not later than 8 months
after initiation of the study. NCHRP approval of the
interim report will be required before commencing Task
5.
Task 5. Prepare a revised Manual and commentary in
a format suitable for consideration by the AASHTO
Highway Subcommittee on Bridges and Structures. Both
shall be prepared in a format that can be easily updated
in the future.
Task 6. Prepare a final report.
Project 12-24 FY,83
Design of MuIti-Beam Precast Bridge Super-
structures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
University of Michigan
Dr. A. H. Mattock
Dr. J. F. Stanton
August 1, 1983
May 31, 1986
$149,879
The objectives of this research were to develop criteria
for design of connections between adjacent precast ele-
ments in multi-beam bridge superstructures, and to de-
velop specification provisions for the lateral distribution
of wheel loads in precast multi-beam bridge superstruc-
tures of single-, double-, and multiple-stem tee girders.
The research has been completed. The report and rec-
ommended specifications have been published as NCHRP
Report 287, "Load Distribution and Connection Design
for Precast Stemmed Multibeam Bridge Superstructures."
Project 12-25 FY'83
Fatigue and Fracture Evaluation for Rating
Riveted Steel Bridges
Research Agency: Lehigh University
Principal Invest.: Dr. John W. Fisher
Elective Date: September 1, 1984
Completion Date: September 30, 1987
Funds: $199,957
The objective of this study was to develop a rational
rating plan for riveted bridges based on available infor-
mation on the fatigue and fracture resistance of such
bridges and components. The research included analytical
studies of existing riveted steel fatigue and fracture data
and laboratory tests on riveted girders and components.
Research has been completed and the final report has
been published as: NCHRP Report 302, "Fatigue and
Fracture Evaluation for Rating Riveted Bridges." The
report includes recommendations for revisions to the fa-
tigue and fracture provisions in the AASHTO Manual
for Maintenance Inspection of Bridges. It is expected that
the AASHTO Highway Subcommittee on Bridges and
Structures will consider the recommendations in this re-
port for possible adoption in the near future.
Project 12-26 FY '85 and FY '89
Distribution of Wheel Loads on Highway
Bridges
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Imbsen & Associates, Inc.
Roy A. Imbsen
April 15, 1985 August 22, 1988
December 15, 1987 May 21, 1990
$300,000 $200,000
The objective of this research is to develop compre-
hensive specification provisions for distribution of wheel
loads in highway bridges.
Research under NCHRP Project 12-26 should consider
all variables affecting the distribution of wheel loads. The
recommended provisions shall apply to both the Service
Load and the Strength Design Methods as well as to
structural evaluation of existing bridges.
Load distribution criteria developed in this study are
expected to include: (1) simplified methods of analysis
including code formulas and (2) analytical models that
are more comprehensive and exact and are intended for
computer-based application.
The first phase of the project focused on steel and
concrete beam-and-slab bridges and multi-cell concrete
box girder bridges. The formulas that were developed in
Phase 1 produced accurate and reliable results for mo-
ment and shear wheel load distributions. Correction fac-
tors for skew and continuity were also developed and
presented in the format of an AASHTO specification.
The Phase I final report will not be published, but copies
of the agency draft report were distributed to NCHRP
sponsors in mid-1988. Copies are available on loan or
microfiche (see final page of this document for ordering
information).
The second phase of the project will concentrate on
concrete slab bridges, precast concrete multigirder
bridges, and spread box beam bridges. The results of both
the first and second phases of the project will be combined
into one comprehensive report and recommended speci-
fication at the end of the second phase.
Through December 31, 1988, research on Phase II of
the project is proceeding on schedule. Simple formulas
are being developed for longitudinal moment distribution
in concrete slab, precast concrete multigirder, and spread
box beam bridges. Work has also progressed well on the
development of correction factors for support skew in
such bridges.
OCR for page 177
177
Completion Date: July 31, 1987
Funds: $164,985
About one-half of the approximately 600,000 highway
bridges in the United States were built before 1940, and
many have not been adequately maintained. Most of these
bridges were designed for lower traffic volumes, smaller
vehicles, slower speeds, and lighter loads than are com-
mon today. In addition, deterioration caused by environ-
mental factors is a growing problem. As a result, a high
percentage of the nation's bridges are classified as deficient
and in need of rehabilitation or replacement. Many of
these bridges are deficient because their load carrying
capacity is inadequate to carry today's tragic. Strength-
ening can often be used as a cost-e~ective alternative to
replacement or posting. Therefore, the research objectives
were to evaluate the feasibility and cost-effectiveness of
present strengthening methods as applied to various types
of bridges and to identify cost-e~ective innovative meth-
ods.
Research is complete; the final report has been pub-
lished as NCHRP Report 293," Methods of Strengthening
Existing Highway Bridges." The report details various
methods of strengthening highway bridges. An extensive
overview of all applicable methods is presented. The types
of structures most suitable for strengthening are identified,
and the effectiveness of the various methods is discussed
for these structures. A major part of the study was the
development of a strengthening manual (Chapter 3) for
use by practicing engineers. This manual describes the
most effective techniques and indicates how they may be
used in various types of structures to increase or restore
their load carrying capacity.
Project 12-28(5) FY'85
Standard Methodology for Conducting
Condition Surveys of Concrete Bridge
Components
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
New Mexico State University
Dr. John Minor
August 1, 1985
August 31, 1987
$98,338
Although concrete structures have generally demon-
strated good resistance to loss of load capacity and have
only rarely been removed from service for this reason,
determinations of bridge load capacities are often nec-
essary to fully evaluate the erects of deterioration. Cur-
rently, work is progressing to develop methods to permit
more accurate load capacity analysis; however, inspection
and reporting methods need to be enhanced or refined
and then standardized to help support this work.
In addition, more than one level of inspection should
be available for structures with more severe damage. The
current, federally mandated biennial inspections are ex-
pected to be adequate for the majority of structures; how-
ever, refinements and additional guidance would improve
the uniformity of inspection and reporting. Structures
where the initial inspection and available data indicate a
reduced load capacity also should be reinspected using
procedures that provide a higher level and quality of data
of the structure's properties.
Consequently a research project was needed that would
provide a framework for surveying and reporting the con-
dition of reinforced and prestressed concrete structures.
The framework would have to include more than one
inspection level to improve the reliability of data when
conditions warrant.
The objective of this research was to prepare a manual
for conducting inspections of reinforced and prestressed
concrete bridges to assess their condition and obtain ma-
terial and cross-sectional properties needed to determine
load ratings. The manual should provide guidance to
enable field inspectors to recognize various types of dis-
tress and to assess their significance on capacity. Tech-
niques would also be included to evaluate the strength
and other physical properties of component materials. The
manual would describe the techniques used in routine
biennial inspections, and the nondestructive and destruc-
tive testing techniques required to obtain more detailed
information.
Research is complete. The final report will be published
as NCHRP Report 312, "Condition surveys of Concrete
Bridge Components User's Manual."
Project 12-28~6) FY'85
Distortion-Induced Fatigue Cracking in Steel
Bridges
Research Agency:
Principal Invest.:
Affective Date:
Completion Date:
Funds:
Lehigh University
Dr. John W. Fisher
October 1, 1985
June30, 1989
$250,000
Forces in various steel bridge members, such as cross
bracing, can cause lateral (out-of-plane) distortions in
webs and gusset plates that can eventually result in fatigue
cracking. Such cracking is most likely to occur if the
distortions must be accommodated in a short length of
the web or gusset plate, for example, in the gap between
the end of a stiffener and the flange. In fact, most of the
fatigue cracks that have been observed in existing bridges
have resulted from this cause. The distortions that con-
tribute to this type of fatigue cracking are not calculated
in normal design and rating procedures. Therefore, the
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178
usual AASHTO fatigue provisions can not be applied to
this type of cracking. Instead, existing or proposed bridge
designs must be systematically reviewed to identify and
evaluate potential fatigue problems that might result from
out-of-plane distortions. Although some preliminary
guidelines have been developed (AISC Bridge Fatigue
Guide Design and Details) to assist in this type of re-
view, more comprehensive guidelines and more detailed
criteria are needed.
The objectives of this research are: (1) to categorize
the kinds of fatigue cracks that have occurred because of
out-of-plane distortions; (2) to develop comprehensive
guidelines, including quantitative criteria, if possible, that
define the conditions that are likely to cause fatigue crack-
ing related to out-of-plane distortions; and (3) to evaluate
possible retrofitting techniques, such as drilling holes at
the ends of the cracks, modifying attachment details to
minimize lateral distortions, and increasing the gap be-
tween restraints. Laboratory fatigue tests of selected de-
tails that appear to be particularly susceptible to this type
of fatigue cracking will be needed to accomplish these
objectives. This testing should be correlated with an
FHWA Regional Pooled Funds Study to be conducted
at the University of Missouri and also with relevant pres-
ent and planned field studies on actual bridges.
NCHRP Project 12-28~6) is intended to dove-tail with
the Penn DOT-sponsored HP&R study entitled, "The
Causes of Deformation Induced Cracking in Steel Bridges
and Methods to Retrofit the Damage." The two studies
are expected to be carried out concurrently and the re-
search plans must be complementary. It is intended that
the final report on NCHRP Project 12-28~6) should be
self-su~cient.
By way of expanding on the scope of the Penn DOT-
sponsored study, the following items will be considered
under NCHRP Project 12-28~6~.
Fatigue cracking caused by live load-induced sec-
ondary stresses, both in-plane and out-of-plane.
Common structural details not frequently encoun-
tered in Pennsylvania and, therefore, not included in
the Penn DOT research.
Structural details in multi-stringer bridges.
Interaction between roadway-support stringers and
underlying main structural members.
Design guidelines for structural details that are less
susceptible to distortion-induced fatigue cracking
(e.g., NY DOT details for connection plates at cross
frames).
Guidance on retrofit and repair for use on a nation-
wide basis.
Through December 31, 1988, research on the project
has progressed on schedule. The laboratory test pro-
gram is nearing completion, and work has started on
the preparation of specification provisions that can be
recommended to AASHTO for consideration for adop-
tion.
Project 12-28~7) FY '86
Guiclelines for Evaluating Corrosion Effects in
Existing Steel Bridges
Research Agency: Modjeski and Masters
Principal Invest.: Dr. J. M. Kulicki
Elective Date: May 5, 1986
Completion Date: July 31, 1989
Funds: $298,644
Engineers normally assess the detrimental erects of
corrosion on steel bridge components in terms of the
increased static and fatigue stresses caused by the reduc-
tion in cross-sectional area of the components. Limited
studies have shown that stress concentrations caused by
corrosion in steel bridge members can result in fatigue
behavior equivalent to AASHTO Category E details or
worse. However, corrosion can produce other severe ef-
fects such as (1) the "freezing" of pinned joints causing
unintended bending moments; (2) the freezing of bearings
causing unanticipated forces in piers, abutments, and
bridge members; and (3) the build up of corrosion prod-
ucts causing local forces and distortions usually perpen-
dicular to the plane of a plate element. Some of these
detrimental effects are produced by nonuniform patterns
of corrosion. Guidelines do not exist for bridge engineers
to adequately identify and evaluate these erects of cor-
rosion on critical details of steel bridges.
The objective of this research is to develop practical
guidelines that can be used to assess the erects of cor-
rosion on structural details in steel highway bridges. The
guidelines shall apply to all of the steps involved in eval-
uating the erects of corrosion on the performance of
existing bridges, and shall be suitable for incorporation
into AASHTO's Manual for Maintenance Inspection of
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 bridge engi-
neers, consultants, and owners of steel bridges.
Task 2 Analyze and use the information generated
in Task 1 to establish a framework for the development
of procedures to evaluate corrosion effects in steel bridges.
Task 3 Present the findings of Tasks 1 and 2 in an
interim report to be submitted not later than 8 months
after the initiation of the study. The interim report shall
contain a detailed research plan for Task 4 and a frame-
work for the guidelines to be developed under Task 5. It
shall also include examples illustrating application of the
anticipated guidelines.
Task 4 Conduct laboratory tests, field investiga-
tions, and analytical studies in accordance with the de-
tailed plan presented in the interim report. The purpose
of this task is to provide insight for use in developing
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guidelines for evaluating the effects of corrosion on the
structural behavior of steel bridges.
Task 5 Develop the detailed guidelines in a format
suitable for consideration by the AASHTO Subcommittee
on Bridges and Structures. The recommended guidelines
shall be accompanied by a detailed commentary and ex-
amples of specific applications intended to facilitate un-
derstanding and use of the guidelines.
Task 6 Prepare and submit a final report contain-
ing the research findings and proposed guidelines. Further
research necessary for understanding the causes of the
corrosion process on steel bridges and improving the abil-
ity to evaluate their effects should be identified and prior-
itized along with estimated costs.
Research is in progress. An interim report was sub-
mitted and reviewed, and approved after revision. A meet-
ing of the project panel was held in mid-1988 to review
progress and provide direction to the research agency. A
draft corrosion inspection procedure has been reviewed
by the panel, and work is now proceeding on the com-
pletion of the inspection and evaluation guidelines and
manual.
Project 12-28(8) FY '86
Improving Bridge Load Capacity Estimates by
Correlation with Test Data
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Tennessee, Transpor-
tation Center
Dr. E. G. Burdette,
Dr. D. W. Goodpasture
February 1, 1986
February 19, 1988
$199,994
The objective of this study was to assemble domestic
and foreign bridge test data in order to identify, quantify,
and report on significant aspects of observed behavior
that are now not considered during bridge evaluation and
rating. More than 50 years of bridge test data were col-
lected and evaluated in an attempt to isolate specific mech-
anisms through which bridges resist loads in ways other
than those assumed during typical bridge design or eval-
uation.
Research has been completed and the final report pub-
lished as: NCHRP Report 308, "Correlation of Bridge
Load Capacity Estimates with Test Data." Several po-
tential sources of unaccounted for load capacity are iden-
tified and discussed in detail in the report. In order to
quantify the effects of these sources, recommendations are
provided on the need to perform additional analytical
work or bridge load testing.
Project 12-28(9) FY'86
Methods of Flaw Detection in Concrete Bridge
Components
This project overlapped with another FY '86 NCHRP
project, Project 10-30, "Nondestructive Methods for Field
Inspection of Embedded or Encased High Strength Steel
Rods and Cables." The financial resources originally as-
signed this project have been combined with those of
Project 10-30.
Project 12-28(10) FY'86
Guidelines for Determining Redundancy in
Steel Bridges
Research Agency: Lehigh University
Principal Invest.: Dr. J. Hartley Daniels
Elective Date: March 1, 1986
Completion Date: January 31, 1989
Funds: $299,995
Redundancy in a bridge has been generally defined as
the absence of critical components whose failure would
cause collapse of the structure. To minimize the risk of
collapse, fracture-critical members (FCMs) in existing
bridges generally require more frequent and thorough
inspections than other members, and, in new bridges,
special design, fabrication, and material requirements ap-
ply to FCMs. However, there are considerable differences
of opinion about which types of steel bridges can be safely
classified as redundant.
Current AASHTO specifications define an FCM as a
nonredundant tension member or other component whose
failure would be expected to cause collapse of the bridge
because a suitable alternative load path is not present.
Nevertheless, specific criteria are not available to ade-
quately define redundancy. Experience suggests that many
bridge types have viable alternative load paths that are
not easily identified. For example, longitudinal continuity,
bracing, floor systems, and certain other structural con-
ditions might have significant effects. Other considerations
include the effects of failure of various individual com-
ponents of built-up riveted girders and possible Vierendeel
action due to partial joint fixity when diagonal members
fracture in truss bridges.
Therefore, engineers need a better understanding of
alternative load paths and specific criteria for redundancy.
Furthermore, a classification of various types of steel
bridges by degree of redundancy would be very useful in
establishing bridge inspection and replacement priorities
as well as in design of safe and economical bridges for
new construction.
The objectives of this research are: (1) to develop a
better understanding and definition of redundancy in var-
ious types of steel bridges; (2) to establish specific criteria
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for redundancy in such bridges, and (3) to develop guide-
lines for establishing redundancy classifications for var-
ious types of steel 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 bridge engineers
and owners of steel bridges. Emphasis shall be placed on
the performance of steel bridges in which failures of FCMs
were observed.
Task 2-Analyze and evaluate the information gen-
erated in Task 1 and establish a general definition of
redundancy in steel bridges. Consideration shall be given
to load levels. New and innovative ideas as well as es-
tablished practice shall be considered.
Task 3 Using the definition adopted in Task 2,
develop a methodology for applying specific criteria for
redundancy to various types of steel bridges.
Task 4 Present the findings of Tasks 1, 2, and 3
in an interim report to be submitted not later than 12
months after the initiation of the study. The interim report
shall contain a detailed, updated working plan for Task
5 and shall describe the framework for the guidelines to
be developed under Task 6. The report shall include ex-
amples illustrating the application of the methodology
developed in Task 3 and comparisons between results
produced by existing and proposed methods. NCHRP
approval of the interim report will be required before
commencing the remaining tasks.
Task 5 Verify the methodology developed in Task
3 for selected types of steel bridges such as two-girder,
simple- and continuous-span bridges, and other types of
bridges that would be classified as nonredundant by the
present AASHTO criteria. Implementation of this task
may include analytical and experimental methods.
Task 6 Develop guidelines for establishing redun-
dancy classifications for various types of steel bridges.
These guidelines should be particularly useful in estab-
lishing bridge inspection and replacement priorities as
well as in the design of safe and economical bridges for
new construction. The recommended guidelines shall be
in a format suitable for consideration by the AASHTO
Subcommittee on Bridges and Structures. These guide-
lines shall be accompanied by a detailed commentary and
examples of specific applications intended to facilitate the
understanding and use of the methodology.
Task 7 Prepare a final report.
The agency's preliminary draft final report has been
submitted and is now being reviewed by the NCHRP.
The research results are based on detailed evaluations of
2-girder type bridges. However, methods used to evaluate
redundant load paths and shared loading can be translated
to the extent possible to other bridge types.
Project 12-28~11) FY '87
Development of Site-Specific Load Models for
Bridge Rating
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Imbsen & Associates, Inc.
W. David Liu and
C. Allin Cornell
February 9, 1987
February 8, 1989
$200,000
Throughout the United States bridges are evaluated for
their capacity using standard design loads and truck con-
figurations. In some cases bridges are judged to be struc-
turally deficient for the current design loadings and
therefore require load posting. The public pays a high
price when bridges are posted, either in increased travel
time or in costs associated with bridge rehabilitation and
replacement. Bridge design loads and design load fre-
quencies are typically used as inputs to the rating process.
However, the bridge location determines the actual loads,
load frequencies, and truck configurations that an existing
bridge will experience. These factors may differ substan-
tially from the current design loadings for which the
bridge is presently rated. Data on truck traffic show con-
siderable variation with respect to the functional highway
classifications and locations on which they had been col-
lected. More realistic evaluations of bridges may be pos-
sible by developing site-specific loading models.
The bridge rating process must give due consideration
to both safety and serviceability, and it should be highly
dependent on the site-specific loadings. An estimate of
the maximum bridge loading is needed to evaluate the
safe upper limit strength. Loading histograms are required
to determine a bridge's susceptibility to fatigue and for
estimates of remaining life. Realistic loading data would
allow the rating engineer to make a better assessment of
a bridge. Such data would result in improved strategies
for bridge posting, rehabilitation, replacement, and man-
agement.
Research is needed to enable engineers to take advan-
tage of the variations in bridge loadings that can be related
to bridge site characteristics. Substantial improvements
in bridge rating and associated economic benefits could
be realized by using site-specific load data.
The objective of this research is to develop rational site-
specific live-load models for bridge rating that accurately
reflect bridge site characteristics.
In developing these models the following factors, as a
minimum, should be considered: location of bridge, func-
tional classification of highway system, expected vehicle
types and configurations, multiple presence of vehicles,
peak load spectra, and degree of enforcement of legal load
limits.
The research will include the following tasks:
Task 1 Review relevant domestic and foreign prac-
tice and research findings. This information shall be as
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sembled from both technical literature and unpublished
experience of bridge owners and consultants. This infor-
mation shall include both loading histograms and load
models that have been and are presently being developed.
Task 2 Analyze and evaluate the Task 1 data and
determine its applicability. Identify and evaluate the
shortcomings of using current design loadings for bridge
rating. Assess the opportunities for, and the benefits from,
the use of a site-specific load model in bridge rating.
Task 3 Define the specific factors that must be
considered and their anticipated erects on the develop-
ment of the loading models.
Task 4 Prepare an interim report presenting the
findings of the first three tasks and proposing a detailed
working plan for the remainder of the study. The interim
report shall be submitted within 8 months after the re-
search begins. Research on the remaining tasks shall not
be initiated until the proposed working plan has been
approved by the NCHRP.
Task 5 Develop the loading models that account
for bridge site characteristics.
Task 6 Demonstrate the validity of the models de-
veloped in Task 5 by applying them to a number of typical
bridges and sites. Define the limitations for application
of the live-load models.
Task 7 Prepare a final report documenting the re-
search findings.
Research on the project is nearing completion. The
draft final report was expected near the end of December.
A decision on the publication of the report will be made
after the project panel review has been completed in early
1989.
Project 12-28(12) FY '87
inelastic Rating Procedures for Steel Beam
and Girder Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Minnesota
Dr. Theodore V. Galambos
September 1, 1987
November 30, 1989
$199,898
In the United States there are a large number of older
steel beam and girder bridges. Many of them have been
evaluated by elastic analytical methods and judged to be
structurally deficient for current tragic. In some cases
these bridges were not designed for current legal loadings.
In other cases deterioration has reduced their load-car-
rying capacity. The public pays a high price for deficient
bridges both in increased travel time required when
bridges are posted and in the cost of bridge rehabilitation
and replacement. Full-scale tests show that bridges some-
times possess considerably greater load-carrying capacity
than predicted by current evaluation methods. Improved
methods of structural evaluation can produce more re
alistic estimates of load-carrying capacity and might re-
duce the number of bridges classified as structurally
deficient. More realistic evaluation of steel bridges might
be possible by taking inelastic flexural behavior into ac-
count.
Procedures incorporating inelastic flexural behavior are
used to design buildings and bridges. However, these de-
sign procedures can not always be applied directly to the
evaluation of existing bridges. This may be because of
constraints such as high slenderness ratios or inadequate
lateral support. Additionally, present procedures do not
account for changes in lateral load distribution when
stresses are in the inelastic range.
For continuous bridges, the application of such pro-
cedures may permit a higher rating without structural
modification. On the other hand, by providing minor
modifications and applying inelastic rating procedures,
some steel bridge ratings may be further improved. The
load-carrying capacity of a continuous bridge may be
further increased if the unsupported length of the
compression flange at intermediate supports is reduced
by the addition of intermediate diaphragms. The load-
carrying capacity of multi-span bridges with simply sup-
ported spans or with suspended spans may be increased
by modifications which provide partial or full continuity.
A realistic assessment of the benefits of such modifications
can be made by use of practical inelastic rating techniques.
Research is needed to enable engineers to take advan-
tage of inelastic behavior in rating the structural capacity
of typical fully or partially continuous steel beam and
girder bridges.
The overall objective of this research is to develop
practical methodologies for rating existing steel bridges
based on inelastic analysis. The specific objective of the
first phase of research is to determine whether those meth-
ods that account for inelastic action can be applied to
improve the rating of steel bridges.
In the development of inelastic rating procedures the
following factors, as a minimum, should be considered:
plastic-moment and shear capacity criteria; permissible
permanent deflections; and serviceability of the bridge.
Conditions for use of the procedures shall be defined in
terms of the frequency and form of inspections, material
characteristics, state of deterioration, and other relevant
factors.
The research will include the following tasks:
Task 1 Review relevant domestic and foreign prac-
tice and research findings. This information shall be as-
sembled from both technical literature and unpublished
experience of bridge owners and consultants. Recent un-
published data on the inelastic behavior of beams and
girders are available from the American Iron and Steel
Institute.
Task 2- Analyze and evaluate the Task 1 results to
identify opportunities for beneficial application of inelastic
methods to steel bridge rating.
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182
Task 3-Identify bridge types, conditions, and an-
alytical concepts that show promise for inelastic rating
procedures.
Task 4 Prepare an interim report presenting the
findings of the first three tasks and proposing a detailed
working plan for the remainder of the study. (The interim
report shall be submitted within 9 months after the re-
search begins. Research on the second phase shall not be
initiated until the proposed Phase II working plan has
been approved by the NCHRP.)
Task 5 Using available test results, develop ana-
lytical procedures to account for inelastic action in eval-
uating the structural capacity of steel bridges.
Task 6 Develop methods for modifying existing
structures to take advantage of the analytical procedures
developed in Task 5.
Task 7 Apply the developed procedures to selected
examples of various steel bridge types and compare the
results with those from current rating methods.
Task 8- Present the proposed methodology, its ra-
tionale, and the justification for its adoption at the regional
meetings of the AASHTO Subcommittee on Bridges and
Structures.
Task 9 Identify needed research to extend the ap-
plication of the proposed methodology.
Task 10 Prepare a final report documenting the
research findings and presenting the recommendations in
a format suitable for adoption by AASHTO.
Through December 31, 1988, research on the project
is progressing on schedule. The interim report was sub-
mitted in mid-1988 and reviewed at a meeting of the
project panel in September 1988. Since then, work has
progressed on the development of analytical models and
procedures under Task 5.
Project 12-28(13) FY'87
Nondestructive Load Testing for Bridge EvaI
uation and Rating
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Raths, Raths & Johnson, Inc.,
Dr. Suresh G. Pinjarkar
October 4, 1987
April 3, 1989
$150,000
In recent years, bridge engineers have been faced with
an increasing need to reevaluate a growing number of
older, sometimes deteriorated, bridges. These bridges are
expected to carry higher volumes and heavier traffic than
anticipated when they were originally designed. In the
evaluation of these bridges, attempts are made to com-
pensate for uncertainties by using conservative analysis
techniques and idealized mathematical models to assess
load-carrying capacity. This approach results in posting
or removal of adequate structures. Substantial benefits
would be realized if bridges could be evaluated through
nondestructive load testing. Nondestructive load testing
of bridges might be used as an alternative bridge evalu-
ation procedure, and it may reduce the degree of uncer-
tainty by validating assumptions inherent in analytical
rating processes.
Bridge testing is used as a research tool and, to a limited
extent, for determining load-carrying capacity. These tests
require costly equipment and expertise normally not avail-
able to bridge owners. There is evidence that many struc-
tures possess greater load-carrying capacity than can be
predicted by conventional analytical load rating proce-
dures. Load testing methods that can be used reliably by
agencies not specialized in physical bridge testing will
improve the rating process. The primary use of such meth-
ods would be for structures that are found to require
posting based on analysis. It is conceivable that load test-
ing methods can be developed which permit estimates of
load capacity at lower cost than analytical procedures.
There are no clearcut guidelines that help bridge owners
to determine when load testing is an appropriate method
for use in the bridge rating process. An analysis must be
made of the possible benefits, risks, and costs that would
be involved in deciding to load test a bridge. The appli-
cation of a load produces responses in bridges including
strains, deflections, dynamic effects, fatigue crack growth,
and load distribution. The extent and nature of the testing
needed are dependent on the responses which control the
load capacity of the bridge.
Research is needed so that bridge owners can take
advantage of the benefits that may be obtained by per-
forming nondestructive load testing on highway bridges.
The objective of this project is to develop guidelines
for nondestructive load testing of highway bridges that
may augment or enhance the analytical rating process.
The research will include the following tasks:
Task 1 Review domestic and foreign practice and
research findings on physical testing for the purpose of
establishing load-carrying capacity. This information
shall be assembled from both technical literature and
unpublished experience of bridge and building owners and
consultants.
Task 2-Identify typical nondestructive tests that
can be performed on the structure as a whole and on
individual bridge components. Identify the limits of ap-
plicability of these tests. In particular, distinguish between
tests that are diagnostic (e.g., producing input to the usual
analytical rating techniques) and tests that are compre-
hensive (e.g., used in lieu of usual analytical rating tech-
niques).
Task 3 Identify bridge types and structural con-
ditions that are unsuitable for physical testing of load
capacity.
Task 4 Develop a strategy for load rating through
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physical testing. In the development of this strategy, con-
sideration shall be given to cost and risk assessment. Risk
assessment shall include, as a minimum, considerations
of damaging a structure, safety of personnel, loss of equip-
ment, and acceptance of an unsafe structure.
Task 5 Present the findings of Tasks 1 through 4
in an interim report to be submitted not later than 8
months after initiation of the study. NCHRP approval of
the interim report will be required before commencing
the remaining tasks.
Task 6 Develop detailed and specific testing pro-
cedures. Each procedure shall include, but not be limited
to, criteria for establishing test load levels, type and lo-
cation of monitoring, loading methods, types of equip-
ment required for monitoring and loading, and criteria
for evaluation of test results.
Task 7 Identify the technical and nontechnical fac-
tors that must be considered when screening candidate
bridges. Provide examples to show how field testing would
be beneficial to the rating process.
Task 8 Develop guidelines for nondestructive load
testing of bridges.
Task 9 Prepare a final report documenting the re-
search findings and presenting the recommended guide-
lines.
Through December 31, 1988, research on the project
Is progressing on schedule. The interim report was re-
viewed and approved during a meeting of the project panel
at the end of October 1988. It appears that there can be
substantial benefits that can be gained from the successful
completion of this project.
Project 12-29 FY,85
Design of Simple-Span Precast Prestressed
Bridge Girders Made Continuous
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Construction Technology Corpora-
tion
R. G. Oesterle
August 26, 1985
May 31, 1988
$241,993
The design and construction of bridges composed of
simple-span, pre-tensioned girders made continuous for
composite dead loads and for live loads has become wide-
spread. In general, the design of these structures has been
based on the procedure outlined in "Design of Continuous
Highway Bridges with Precast, Prestressed Concrete Gir-
ders," published by the Portland Cement Association in
1969. Although existing bridges designed by this proce-
dure are generally performing well, it is believed that this
method may not accurately predict the true behavior of
these structures in light of new knowledge regarding ma-
terial properties and behavior, new methods of analysis,
and expansion of this concept to longer spans and wider
. .
girder spacings.
One of the major uncertainties in the design of these
structures is the prediction of the positive and negative
moments at the cast-in-place connections at the piers.
This uncertainty is due to the different loading and con-
struction stages, time-dependent effects, and the details
used to make the connections. Because of these uncer-
tainties and the lack of guidance in the AASHTO spec-
ification, widespread differences exist in applying the
results of the PCA procedure for selecting the actual
continuity moments used for the connections at the piers.
Research is needed to resolve these uncertainties and to
develop guidelines for more rational design and to take
advantage of opportunities for more economical construc-
tion.
The objectives of this research are: (1) to investigate
the behavior of precast prestressed bridge girders made
continuous by connections using cast-in-place slabs and
diaphragms at the piers, and (2) to develop design pro-
cedures and guide specifications that can be used to com-
pute elastic, inelastic, time-dependent, and ultimate
moments commensurate with the degree of continuity
developed by the connections at the piers.
The research will include the following tasks:
Task 1 Review relevant current practice, perform-
ance data, and research findings. This information shall
be assembled from both technical literature and unpub-
lished experiences of designers and owners of structures
of this type.
Task 2 Based on available information and the ap-
plication of analytical techniques, develop improved pro-
cedures to determine the degree of continuity and the
moments resulting from dead loads, live loads, and time-
dependent effects.
Task 3 Based on available information and the ap-
plication of analytical techniques, develop improved pro-
cedures to predict the inelastic redistribution of moments
and the ultimate strength of the structure at all critical
stages.
Task 4 Based on available information and the ap-
plication of analytical techniques, develop improved pro-
cedures to determine the strength and serviceability
requirements for the positive and negative moment con-
nections at the piers, allowing for the use of either mild
steel or prestressing steel for positive moment and mild
steel for negative moment. The consequences of providing
no positive moment connection shall also be investigated.
Task 5 The analytical portion of this study shall
be verified by correlation with available experimental data
that are relevant.
Task 6 Present the findings of Tasks 1 through 5
in an interim report to be submitted not later than 18
months after the initiation of the study. The interim report
shall outline the framework of the specifications to be
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developed under Task 7 and shall include examples il-
lustrating the application of the recommended proce-
dures. The report shall also include comparisons between
results produced by existing and proposed methods.
NCHRP approval of the interim report will be required
before commencing Task 7.
Task 7 Prepare detailed specifications in a format
suitable for consideration by the AASHTO Subcommittee
on Bridges and Structures. The recommended specifica-
tions shall be accompanied by a detailed commentary and
selected design examples intended to facilitate their un-
derstanding and use.
Task 8 Identify areas in need of further investi-
gation. Recommend priorities and estimate the time and
costs for the additional research.
Task 9- Prepare a final report.
Research has been completed. The draft final report
was submitted and approved by the project panel near
the end of 1988. The report included recommendations
for changes to the design requirements in the AASHTO
Standard Specifications for Highway Bridges, which will
likely be considered by the AASHTO Highway Subcom-
mittee on Bridges and Structures in 1989. It is expected
that the report will be published in the regular NCHRP
report series in early 1989.
Project 12-30 FY '86
Fatigue of Cables in Cable-Stayed Bridges
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
ACER/Freeman Fox
Jolyon A. Gill
January 13, 1986
February 12, 1989
$124,975
Cable-stayed bridges have become an advantageous and
economical type of structure for medium- and long-span
crossings in the United States. As of 1985, five cable-
stayed bridges are in service, seven are under construction,
and seven are in the design stage. The cable stays are vital
components, and, because they are subjected to repeated
loads, fatigue is an important design consideration.
AASHTO Bridge Specifications do not include design or
material requirements for cable stays; criteria and guide-
lines are needed. Information on fatigue design criteria
for cable-stayed bridges is available in certain foreign
codes, such as the German Specifications DIN-1073 and
subsequent revisions. Those foreign codes presently in use,
together with data available in the United States, should
serve as a basis to develop design criteria and material
requirements suited to American practice.
The objectives of this project are (1) to develop criteria
and guidelines for fatigue design of cable stays and (2) to
develop practical guidelines for material requirements and
for testing wires, strands, and cable-stays.
The project will include the following tasks:
Task 1. Review performance history and data, cur-
rent domestic and foreign codes of practice, and research
findings. This information shall be assembled from both
technical literature and unpublished experiences of de-
signers and owners of cable-stayed bridges. Although this
review shall emphasize fatigue behavior in cables of cable-
stayed bridges, care should be taken to include all relevant
aspects of fatigue in other structural systems.
Task 2. Analyze and evaluate the information gen-
erated in Task 1 to establish rationales for alternative
approaches to the development of design criteria and test-
ing requirements for fatigue effects in cables. This eval-
uation will include consideration of the following: (1)
intensity and frequency of fatigue loading; (2) number
and position of lane loadings including their relationship
to the number and location of stay planes; (3) multiple
lane reduction factors; (4) spacing of cable stays; (5) local
stresses in stay cables at saddles and anchorages; (6) as-
sessment of fatigue strength of cables from tests on short
lengths of individual wires or strands; (7) length similitude
factors to relate tests of short cable specimens to full-
length cables; and (8) quality control and quality assur-
ance of wire and strand to maximize fatigue resistance.
Task 3. Present the findings of Tasks 1 and 2 in an
interim report to be submitted not later than 12 months
after initiation of the study. The interim report shall in-
clude design examples illustrating the alternative ap-
proaches. NCHRP approval of the interim report will be
required before commencing Task 4.
Task 4. Prepare cable fatigue design provisions in a
format suitable for consideration by the AASHTO Sub-
committee on Bridges and Structures. The recommended
provisions shall be accompanied by a commentary and
design examples intended to facilitate their understanding
and use.
Task 5. Prepare materials and testing requirements
to supplement existing provisions in a format suitable for
consideration by appropriate authorities.
Task 6. Identify additional research that is needed
for further development and refinement of the recom-
mended design criteria and materials requirements. Rec-
ommend priorities and estimate time and costs for the needed
research.
Task 7. Prepare a final report.
Research has been completed. The draft final report
was submitted at the end of 1988, and is being reviewed
by the project panel for acceptability. If the report is
approved, it will be published in the regular NCHRP
report series probably in mid-1989.
Project 12-31 FY '86
Notch Toughness Variability in Bridge Steel
Plates
Research Agency: University of Texas at Austin
Principal Invest.: Dr. Karl H. Frank
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185
Effective Date: September 1, 1987
Completion Date: February 28, 1990
Funds: $355,000
In 1979, the American Iron and Steel Institute (AISI)
published a report of a test program that demonstrated
the variability in the impact properties within steel plates
based on tests of plates up to 172 inches in thickness.
These data, plus a concern about variability in thick plates
of A588 steel, prompted AASHTO to publish an interim
specification that resulted in more conservative notch
toughness requirements for steel plates that were to be
used in Fracture Critical Members (FCM's). Because the
toughness requirements in these interim specifications
were not based on any test results, AISI began a second
study to develop data on plates of larger thicknesses and
of grades commonly used as bridge steels.
The second study was recently completed and the re-
sults were presented to the AASHTO Subcommittee on
Bridges and Structures. The recommendation from the
study was to replace the AASHTO interim specification
requirements with the previous specification requirements
for temperature Zones 1 and 2 (P-frequency testing with
removal of the 20°F temperature shift), but to leave the
interim Zone 3 requirement as is, because not enough
Zone 3 test data were generated to enable a sound con-
clusion to be drawn. Accordingly, removal of the interim
AASHTO notch toughness requirements for Zones 1 and
2 was approved in 1986.
The objective of this project is to establish the vari-
ability of CVN impact notch toughness within plates of
A572 Grade 50 and A588 steels for plate thicknesses up
to 4 inches meeting AASHTO Zone 3 fracture notch
toughness requirements. The research will include the
following tasks:
Task 1-Review relevant research findings and per-
formance data in the literature on notch toughness var-
iability within steel plates. In particular, meet with
representatives of AISI to review the information devel-
oped by AISI on such variability of steel plates meeting
Zones 1 and 2 notch toughness requirements.
Task 2-Review the various methods available for
analyzing variability in notch toughness data within steel
plates.
Task 3-Based on the results of Tasks 1 and 2, select
a method of analysis of test results and develop a system
for reporting test results that will be useful to bridge
engineers. Present the findings of Tasks 1, 2, and 3 in an
interim report to be submitted not later than 9 months
after initiation of the study
Task 4 Concurrently with Task 1, obtain plates of
A572 Grade 50 and A588 to meet AASHTO Zone 3
toughness requirements, as specified in the 1978
AASHTO Guide Specifications for Fracture Critical Non-
Redundant Steel Bridge Members.
Task 5 Develop a specific test matrix to study the
variability of CVN impact notch toughness within each
plate. As a minimum, nine locations per plate shall be
studied.
Task 6 Perform chemical analyses and tensile tests
for each plate. Three longitudinal CVN specimens shall
be machined from the plate blank at each location and
impact tested at + 10°F, i.e., the AASHTO Zone 3 test
temperature. In addition, full transition curves shall be
obtained for longitudinal CVN specimens at 3 locations.
Specific requirements regarding the Charpy V-Notch im-
pact testing shall be as follows:
a. The position of the test specimens within the sam-
pling locations shall be at the 74 thickness as de-
scribed in ASTM A673 (AASHTO T243~.
b. The material blanks at each location shall be large
enough to provide material for retests or tensile tests,
if necessary. All test specimens shall be at least 1
thickness away from any flame cut edge.
c. Only full-size test specimens shall be used (10 mm
X 10 mm).
d. Tests are to be conducted according to ASTM A370
(AASHTO T244~.
.. Absorbed energy in foot-pounds, lateral expansion
in mile, and percent shear shall be reported for each
individual test specimen.
Task ~ Analyze the test results using the meth-
odology developed in Task 3. Only values which are the
average of three specimens shall be analyzed. Variability
within each plate shall be determined and compared with
the average results from the mill report and compared
with the 1978 AASHTO Guide Specification require-
ments.
Task 8 Should there be any unusually low notch
toughness values at any location, an investigation shall
be made to establish the reason.
Task 9-Prepare a final report documenting the find-
ings of the research including recommendations for
needed specification revisions.
Through December 31, 1988, research is progressing
on schedule on the project. The interim report was sub-
mitted in October 1988. A meeting of the project panel
will be held in early 1989 to review the report and approve
the recommended laboratory test program.
Project 12-32 FY'86
Evaluation of Bridge Deck Protective Strat-
egies
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
University of Washington
Dr. N. M. Hawkins
Mr. K. Babaei
April 1, 1986
May 15, 1987
$92,515
During the 1960's and early 1970's, corrosion of steel
reinforcement embedded in concrete contaminated by
chloride deicing chemicals was determined to be a major
OCR for page 186
186
cause of concrete bridge deck deterioration. As a result,
various bridge deck protective strategies were developed
such as epoxy-coated steel reinforcement, latex-modified
concrete overlays, high density concrete overlays, inter-
layer membranes, and thicker concrete cover over steel
reinforcement. Laboratory studies and early experience
indicate that these strategies are effective in improving
the performance of bridge decks. However, because of
the large national investment in bridges and their im-
portance in the efficient operation of highways, it is ap-
propriate to examine the performance of these bridge deck
protection strategies to see if original expectations are
being attained and to determine whether unforeseen prob-
lems may occur.
The specific objectives of this project were to compile
information on currently used bridge deck protective
strategies and evaluate the performance of bridge decks
with more commonly used protective strategies.
The research is complete. The final report has been
published as NCHRP Report 297, "Evaluation of Bridge
Deck Protective Strategies."
Project 12-33
FY '88 and FY '89
Development of a Comprehensive Bridge
Specification and Commentary
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Modjeski and Masters
Dr. John M. Kulicki
July 1, 1988
December 31, 1991
$295,000
Since initial adoption more than 50 years ago, the
AASHTO Standard Specifications for Highway Bridges
have been modified annually by the AASHTO Subcom-
mittee on Bridges and Structures. These specifications are
relied on by engineers in state highway agencies, con-
sulting firms, and other organizations responsible for de-
sign, construction, and maintenance of bridges. Because
of the piecemeal development of the current specifications,
extra care is required to avoid inconsistencies, fragmen-
tation, and internal conflicts as individual sections of the
specifications are revised each year. This problem is com-
pounded by the fact that a comprehensive commentary
is not available to clarify the intent and record the origin
of key provision. Some of the specification's shortcom-
mings were corrected by complete editorial revision of
the specification in 1984.
The AASHTO Subcommittee on Bridges and Struc-
tures recognizes the need for clear, practical specifications
based on the best current technology, and state bridge
engineers and others devote a substantial amount of time
and attention to this end. In recent years, some bridge
engineers have called attention to the potential advantages
of developing a completely new comprehensive specifi-
cation and an accompanying commentary.
In response to a high level of interest among state bridge
engineers, the AASHTO Subcommittee on Bridges and
Structures requested the NCHRP to conduct a study to
recommend an outline for an updated AASHTO bridge
specification. The scope of the study required an identi-
fication of the gaps and inconsistencies in the present
specifications and an assessment of the feasibility of basing
the revised specifications on a probabilistic load and re-
sistance factor design (LRFD) philosophy.
The study has been completed. It identified many areas
where current bridge design technology and design prac-
tice are not reflected in the existing AASHTO specifi-
cations. Additionally, it recommended that new
specifications be developed based on LRFD concepts. The
study also recommended that a comprehensive compan-
ion commentary be developed.
NCHRP Project 12-33 was initiated in mid-1988 with
the objective of developing recommended LRFD-based
bridge design specifications and commentary for consid-
eration by the AASHTO Subcommittee on Bridges and
Structures. The new specifications are expected to draw
heavily from recent developments in bridge design prac-
tice throughout the world as well as from recently com-
pleted and current bridge research.
It is estimated that a completely new LRFD-based
bridge specification will be developed in 42 months at a
cost of approximately $1.6 million.
Thirteen task groups will be responsible for developing
the recommended specifications. The task groups are: gen-
eral features; loads; analysis and evaluation; deck systems;
concrete structures; metal structures; timber structures;
joints, bearings, and accessories; foundations; soil-struc-
ture interaction systems; moveable bridges; bridge rail;
and specification calibration.
Through December 31, 1988, work on the project is
proceeding on schedule. A number of contractors and
consultants have been hired to work with the Principal
Investigator and overall project manager, Dr. John Ku-
licki of Modjeski and Masters, on the development of the
specification philosophy and draft "strawman" specifi-
cation. It is expected that a first draft of the complete
specification will be available for review by AASHTO in
mid-l990.
To date, $396,000 has been obligated on the project.
Included in this amount is $280,000 for Projects 12-33,
12-33A, and 12-33B. The remainder of the obligated
amount covers consultant fees and expenses.
Project 12-33A
FY '88 and '89
Development of a Comprehensive Bridge
Specification and Commentary- Timber
Structures and Code Calibration
Research Agency:
Principal Invest.:
Elective Date:
Sensei Engineers
Dr. Andrzej Nowak
September 16, 1988
OCR for page 187
187
Completion Date: December 31, 1991
Funds: $20,000
NCHRP Project 12-33 was initiated in mid-1988 with
the objective of developing specifications for bridge design
based on the load and resistance factor design philosophy
that can be recommended to AASHTO for consideration
for adoption. (See Project 12-33 writeup for more detail.)
A number of agencies and individuals will be employed
during the course of the project for various tasks and
responsibilities.
The agency employed on Project 12-33A will act under
the direction of the Principal Investigator on Project 12-
33, Dr. John Kulicki. Sensei Engineers will be responsible
for coordinating the activities of the task groups on timber
design and specification calibration.
Project 1 2-33B FY '88 and '89
Development of a Comprehensive Bridge
Specification and Commentary Con-
crete Structures
Research Agency:
Principal Invest.:
Effective Date:
Completion Date:
Funds:
Imbsen ~ Associates, Inc.
Mr. Robert C. Cassano
September 16, 1988
December 31, 1991
$20,000
NCHRP Project 12-33 was initiated in mid-1988 with
the objective of developing specifications for bridge design
based on the load and resistance factor design philosophy
that can be recommended to AASHTO for consideration
for adoption. (See Project 12-33 writeup for more detail.)
A number of agencies and individuals will be employed
during the course of the project for various tasks and
responsibilities.
The agency employed on Project 12-33B will act under
the direction of the Principal Investigator on Project 12-
33, Dr. John Kulicki. Imbsen & Associates, Inc., will be
responsible for coordinating the activities of the task
group on concrete structures design.
Project 12-34 FY '88 and FY '89
Update of AASHTO Standard Specifications
for Highway Bridges: Division Il' Con-
struction
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Imbsen & Associates, Inc.
Robert C. Cassano
October 19, 1987
October 18, 1989
$200,000
The AASHTO Standard Specifications for Highway
Bridges consists of two sections: Division I Design, and
Division II- Construction. Both sections should play an
important role in bridge design and construction. These
sections, along with additional guide and material spec-
ifications, aid public agencies in the preparation and use
of their standard specifications and contract documents.
It is imperative that both sections reflect the latest state
of the art in proven bridge design and construction prac-
tices. As technology changes, it is important to have these
changes reflected in the specifications. Although Division
I has been periodically updated, changes that have oc-
curred in Division II have been made on a piecemeal basis
and do not reflect current practice in bridge construction.
Therefore, the content of Division II is incomplete and
the format is inconsistent. As a result, less than one-half
of the states presently use the current Division II speci-
fication.
The current Division II-Construction specification is
in need of revision and updating. Research should be
undertaken to provide the basis for such a revision fol-
lowed by the preparation of a revised Division II Con-
struction specification.
The objective of this project is to revise the Division
II Construction specification to reflect current practice
in highway bridge construction. This will then provide a
more useful document to public agencies.
The project will include the following tasks:
Task 1. Review current domestic and foreign con-
struction practices and specifications for highway bridges
and similar structures. At a minimum, this should include
representative AASHTO and state construction docu-
ments.
Task 2. Develop a strategy for evaluating the infor-
mation developed in Task 1 in order to identify the fol-
lowing: articles no longer needed in the current Division
II specification; articles requiring revision; and new ar-
ticles which should be added.
Task 3. Using the strategy developed in Task 2,
prepare a comprehensive list of, and the reasons for, rec-
ommended deletions, modifications, and additions to the
current Division II Construction specification.
Task 4. Present the findings of Tasks 1, 2, and 3 in
an interim report to be submitted not later than 6 months
after initiation of the study. The interim report shall also
include a suggested format for the recommended revisions
and new additions. NCHRP approval of the interim re-
port will be required before commencing Task 5.
Task 5. Prepare a revised Division II Construction
specification and comprehensive companion commentary
in a format suitable for consideration by the AASHTO
Subcommittee on Bridges and Structures.
Task 6. Prepare a final report.
Through December 31, 1988, research on the project
is progressing on schedule. The interim report was re-
viewed and approved by the project panel in September
1988. Work is underway on the completion of the rec-
ommended specification and commentary.
Representative terms from entire chapter:
nchrp report
