|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 203
203
Many construction projects require the use of traffic
barriers to adequately protect the motoring public and
construction workers. Geometric and operational restric-
tions in these work zones frequently preclude the use of
the same design standards for these barriers and terminals
that normally apply to permanent systems.
One common example involves two-lane, two-way
bridges where one-half of the bridge is repaired while
maintaining alternating one-way traffic in the remaining
lane (usually with temporary traffic control signals). The
most common method of traffic control is to install a
concrete barrier on the bridge approaches and across the
bridge to protect the motorists and workers. While this
practice normally provides an acceptable measure of
safety for motorists and workers, problems occur when
an intersecting highway or driveway that cannot be closed
exists near the end of the bridge. In this example, and in
other restricted situations, there is often inadequate room
to install either the barrier runout at the specified flare
rate, an impact attenuator, or other terminal treatments
meeting the performance standards for permanent barrier
systems.
The objective of this research is to develop improved
and treatments for temporary traffic barriers, traffic con-
trol plans, and user guidelines for restricted work-zone
situations. The following tasks will be conducted:
Phase I
Task 1 Identify types of existing work-zone situations
where standard barrier terminal treatments and traffic
control plans cannot be installed because of restricted
conditions. Examples include bridge ends near an adjacent
intersecting street, temporary traffic barriers with road-
way/driveway openings, end treatments for barriers on
narrow medians, and locations having restricted space for
barrier deflection. Selected highway agencies, manufac-
turers, and other organizations are to be surveyed to
determine common problem situations and current treat-
ments.
Task 2 Classify the specific situations identified in
Task 1 into groups having similar characteristics. Factors
that should be considered include traffic parameters, site
features (highway geometries, terrain), and anticipated
frequency of the problem situations.
Task 3 Develop conceptual designs for barrier ter-
minal and traffic control treatments for the groups iden-
tified in Task 2. Factors to consider include: design
vehicle, approach speed, barrier flare rate, safety, and
roadway geometries. Sloped terminals for concrete bar-
riers under low approach speed conditions will be in-
cluded as one of the end treatments.
Task 4 Evaluate the proposed treatments for typical
situations. Evaluation criteria include safety, traffic ca-
pacity, user delay, costs, and ease of implementation.
Task 5-Prepare a report on the findings of the above
tasks. This report will contain a detailed work plan for
Phase II, including recommendations for the development
and evaluation of the proposed barrier terminal treat-
ments through analysis and crash tests.
Phase II
Task 6 Develop detailed designs for barrier terminal
treatments.
Task 7- Evaluate the terminal treatments developed
in Task 6 through full-scale crash tests.
Task 8 Develop a user's manual including detailed
design drawings for recommended barrier terminal treat-
ments and special traffic control plans, and guidelines for
their use. This manual will be in sufficient detail and in
a format suitable for consideration by AASHTO for in-
corporation into its design criteria.
Task 9 Prepare final research report.
Tasks 1 and 2 have been completed.
AREA 18: CONCRETE MATERIAL
Project 18-1 FY '68
LS
Revibration of Retarded Concrete for Contin-
uous Bridge Decks
Research Agency: University of Illinois
Principal Invest.: Dr. H. K. Hilsdorf
Elective Date: September 1, 1967
Completion Date: December 1, 1969
Funds: $ 103,895
This research had the objectives of (1) conducting a
survey to determine the extent to which either delayed
vibration or revibration has been used in placing bridge
deck concrete, including the purpose, conditions, and re-
sults; (2) determining by laboratory and/or field tests if
transverse and longitudinal cracking can be significantly
reduced by revibration after retarded concrete has been
placed over the entire deck of a continuous bridge or a
complete segment of several spans supported by a con-
sinuous girder system; (3) determining the effect of re-
vibration and subsequent finishing on the durability of
bridge deck surfaces exposed to deicing chemicals; and
(4) determining the most effective and practical means of
revibration in the field.
The research has been completed, and the final report
has been published as: NCHRP Report 106, "Revibration
of Retarded Concrete for Continuous Bridge Decks."
Project 18-2 FY,73
Use of Polymers in Highway Concrete
Research Agency: Lehigh University
Principal Invest.: Dr. John A. Manson
Elective Date: October 1, 1972
OCR for page 204
2W
Completion Date: September 30, 1975
Funds: $300,000
The over-all objective of this project was to develop
the technology for the economical use of polymers to
improve the serviceability of concrete in highways. The
immediate goal concerned economically feasible methods
for polymer impregnation of concrete bridge decks in
place.
The program was conducted jointly by Lehigh Uni-
versity and The Pennsylvania State University.
The study included a state-of-the-art survey, laboratory
development of engineering data on the penetration of
candidate materials, testing of drying techniques and pro-
totype impregnation equipment, durability studies, and
experimental impregnations of two bridge decks. Final
work centered on the use of methyl methacrylate and
trimethylolpropane trimethacrylate (MMA/TMPTMA)
as the monomer system. Two methods of drying (propane-
fired infrared and propane torch units), two methods of
monomer application (soaking and pressure), and two
methods of polymerization (hot water and steam) were
used. Polymer penetration to depths of more than 4 in.
was achieved. Extreme dryness was found to be the key
to deep penetration. This was obtained with temperatures
of about 250 F at 4-in. depths. The first successful pen-
etrations of a bridge deck were achieved with equipment
covering areas of only a few square feet. Field equipment
was enlarged and up-graded, and successful impregna-
tions were achieved over several 36-sq ft areas on two
bridge decks one a test-track deck and the other a deck
in regular service. A field manual describing the tech-
niques that were developed and including suggested safety
precautions and acceptance criteria is included in the final
report.
Research has been completed, and the final report has
been published as: NCHRP Report 190, "Use of Polymers
in Highway Concrete."
Project 18-2(2) FY '78
Polymer Concrete in Highway Bridge Decks
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Lehigh University
Dr. John A. Manson
January 1, 1978
March 15, 1979
$30,000
NCHRP Project 18-2 demonstrated the feasibility of
polymer impregnation of salt-contaminated, but struc-
turally sound, bridge decks to depths sufficient to encase
the upper layer of steel reinforcement (about 4 in.) as a
possible means of arresting or preventing corrosion. It
was concluded that additional research and development
work will be needed to refine the method and to extend
its applicability beyond the range of variables of the com-
pleted investigation. Polymer impregnation includes a
high-temperature drying process whose erects on the du-
rability and structural integrity of the deck concrete are
not now understood. It has been noted that the process
causes fine cracks to appear in the concrete, but little else
is known. The authors of NCHRP Report 190 concluded
that research is needed to (1) measure the extent of this
problem and provide a solution if required; (2) provide
additional information on the long-term effectiveness of
the impregnation process in preventing or arresting cor-
rosion: and (3) determine the economics of the use of
polymer impregnation. Determination of long-term effec-
tiveness and economics will require consideration of the
relative merits of various processes for impregnation as
well as other methods of prevention and repair of bridge
deck corrosion problems. Research is also needed to de-
termine whether corrosion in a contaminated deck can
be controlled by sealing with a shallow polymer impreg-
nation, or complete encapsulation of the top reinforce-
ment is necessary.
NCHRP Project 18-2~2) was not intended to provide
answers to all of these specific questions. Its objective was
more general: to clarify the state of knowledge with regard
to polymer concrete in bridge decks. It did not involve
extensive investigations to develop new research findings
but was intended to outline what is already known, what
additional information is needed, and what new research
needs to be undertaken. The final report provides guidance
for decisions on future research in this area.
Research has been completed. Copies of the agency's
report may be obtained on a loan basis upon written
request to the NCHRP. A limited number of copies are
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 18-2(3) FY,78
Long-Term Rehabilitation of Salt-Contami-
nated Bridge Decks
Research Agency:
Principal Invest.:
Elective Date:
Completion Date:
Funds:
Lehigh University
Dr. John A. Manson
May 1, 1980
April 29, 1983
$199,900
A critical review and experimental work were con-
ducted on methods for the rehabilitation of salt-contam-
inated bridge decks. Emphasis was given to improving
techniques for the impregnation of concrete with
poly~methyl methacrylate) and to the concept of scarifi-
cation to remove the top layer of concrete, followed by
impregnation with a polymer or corrosion inhibitor, and
overlaying with a low-permeability concrete. Exploratory
research with electrochemical removal of salt was also
conducted.
Resistance to freezing and thawing and to corrosion
Representative terms from entire chapter:
terminal treatments
