980561 “Corrosion Investigation, Evaluation, and Pier Replacement Scheme for the Long Key Bridge”
980606 “Inelastic Design and Testing of Steel Bridges
Comprising Noncompact Sections”
980788 “Prestressed Concrete Plank Bridges - Diagnosis of
Longitudinal Cracking in Topping Slabs”
980933 “Accounting for the Effects of Corrosion Section Loss
in Steel Bridges”
981038 “The Effect of Corrosion on Crack Development and
Fatigue Life”
981048 “Testing of a High-Performance Concrete, Single-Span
Box Girder”
981302 “Large Studs for Composite Action in Steel Bridge
Girders”
981369 “Seismic Retrofit of the Vincent Thomas Suspension
Bridge, Los Angeles, California”
981495 “Optimization of Structural Design for High Performance
Concrete Bridges"
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981529 “Seismic Strengthening of Column-Pier Cap
Connections”
Abstract: Inelastic design procedures allow the designer flexibility and
the possibility of more economical designs by decreasing member sizes and
eliminating cover plates and flange transitions at negative moment regions.
Previous experimental results show that compact girders meet or exceed design
limits and expectations when subject to design load levels. Current provisions,
however, apply only to compact steel bridges. Expanding inelastic design
provisions to include noncompact sections is desirable because of the wide use
of plate girders with thin webs. General inelastic provisions applicable to
compact and noncompact girders will create designs that are more consistent over
the steel bridge inventory. Conclusions: Although the analytical tools
exist, large-scale testing is necessary to validate theoretical engineering
practice. Inelastic design procedures, currently limited to bridges comprising
compact sections, offer the potential for significant cost savings by accounting
for a better estimate of the true strength and behavior of the bridge. Also,
inelastic techniques permit greater design flexibility such as optimizing
material use by eliminating cover plates and flange transitions, and quantifying
the redistribution characteristics for more consistent safety considerations.
The proposed provisions allow the use of compact and noncompact girder sections,
unlike current procedures that are limited to compact sections. The proposed
LRFD inelastic design provisions are also greatly simplified compared to current
inelastic design methods.
Bryan A. Hartnagel, Michael G. Barker, Department
of Civil Engineering, E2509 EBE, University of Missouri – Columbia, Columbia, MO
65211. Tel: (573) 882-2467.
Abstract: Pre-tensioned concrete planks acting compositely with
reinforced concrete topping slabs have been the standard method of short-span
superstructure construction in New South Wales, Australia for nearly 30 years.
Longitudinal cracking in the deck topping slab has been observed in relatively
new plank bridges. The consequence of this cracking has been an increase in
maintanence expenditure and a concern regarding a reduction in strength due to a
smaller lateral distribution of load. An investigation was developed to study
the cause and effects of the cracking. Conclusions: The study concluded
that the cracking was most likely initiated by a combination of restrained
thermal shrinkage stresses and the stresses induced by the passage of overloaded
vehicles. The growth of heavy vehicle loads and the passage of overloaded
vehicles early in the structure’s life has meant that the laboratory test
program conducted in the 1970’s is no longer representative of current field
conditions. As a consequence, the detailing of future plank bridges is being
modified to cater to the changing traffic conditions. This paper is not included
on the 1998 Preprint CD-ROM. Please contact author for information.
R.J.
Heywood, R.J. Taylor, W.S. Roberts, Infratech Systems & Services P/L,
Queensland University of Technology, P.O. Box 3699, South Brisbane, Queensland
4101, Australia. Tel: +61 7 3237 8100 Fax: +61 7 3237 8188. e-mail: 100242.1527@compuserve.com. D.J.
Carter, Roads and Traffic Authority of NSW, P.O. Box K198, Haymarket, NSW 1238,
Australia. Tel: +61 2 9662 5289 Fax: +61 2 9662 5748. e-mail: don_carter@rta.gov.au.
Abstract: Corrosion is a major cause of deterioration of steel bridges.
In addition to material loss, it can cause unintended fixities, movements,
distortions and fatigue cracks. The consequences of corrosion can range from
progressive weakening of a bridge structure over a period of time, to sudden
failures. The behavior of a structure affected by corrosion may be different
from that assumed in its original design. Also, the capacity of members and
connection details may be governed by failure modes different from those that
controlled their original design. Therefore, the effects of corrosion damage
need to be carefully assessed with respect to all likely failure modes, at the
local, member and structure level. Conclusions: A systematic,
multi-phase, approach for the evaluation of the effects of corrosion section
loss on bridge capacity is presented. The first phase of the evaluation process
is to identify the corrosion mechanisms, determine the extent of corrosion and
estimate the possible consequences. The second phase of the evaluation process
is a quantitative evaluation of corrosion effects. A two-level office evaluation
approach is recommended. To obtain a direct measure of the effects of corrosion
section loss, a residual capacity factor concept is proposed. Provisions for
assessing the effects of uniform and localized corrosion with respect to
strength and stability criteria are presented as an illustration of the proposed
approach.
Zolan Prucz, Modjeski and Masters, Inc., 1055 St. Charles Ave., New
Orleans, LA 70130. Tel: (504) 524-4354 Fax: (504) 561-1229. John, M. Kulicki,
President and Chief Engineer, Modjeski and Masters, Inc., P. O. Box 2345,
Harrisburg, PA 17105. Tel: (717) 790-9565 Fax: (717) 790-9564.
Abstract: Fatigue and fracture as well as loss of section due to
corrosion are time-dependent performance characteristics that have the potential
to jeopardize the integrity pof bridge structures. During the past 25 years
these conditions have developed in a number of bridges reulting in a loss of
service, costly repairs, and concern with the safety of these structures. The
paper reviews experience with such time-dependent damage since 1970.
Conclusions: Proper inspection, cleaning debris from corners and crevices
and avoiding design features that promote corrosion grooving are all important
steps to eliminating or reducung corrosion problems. The possibility of stress
corrosion cracking in higher strength steels, including wires in cables and
hangers merit special consideration. Very extensive corrosion, such as
encountered on the Mianus River Bridge or the Williamsburg Bridge can create
serious problems with the integrity of the structure, however, in most cases the
general corrosion of bridge structures, if monitored at reasonable intervals and
corrected as necessary should be considered a normal part of bridge service.
This paper is not included on the 1998 Preprint CD-ROM. Please contact author
for information.
John W. Fisher, Ph.D., P.E., Eric J. Kaufmann, Ph.D., Alan
W. Pense, Ph.D., Lehigh University, ATLSS Engineering Research Center, 117 ATLSS
Drive, Bethlehem, PA 18015-4729. Tel: (610) 758-3535.
Abstract: As part of a multi-state research program on use of
high-performance concrete (HPC) in highway bridges, a bridge originally designed
as a three-span adjacent box girder bridge was converted to a single-span bridge
by using 70 Mpa HPC and 15mm strands. As part of the research, a test beam was
constructed and tested. Conclusions: Instruments placed in the beam prior
to casting were used to measure transfer legnth, which was found to be
approximately 1.22 m; larger than the 50 bar diameters usually found in the
AASHTO code, but consistent with recent studies. After the beam concrete reached
the required compressive strength, it was subjected to 1,000,000 cycled of
fatigue at design load. The static and dynamic response of the beam did not
change as a result of the fatigue loading. Finally, the beam was able to resist
the required AASHTO ultimate moment without failure. It was found that the
AASHTO cracking load was conservative for this beam, mostly because the measured
modulus of rupture greatly exceeded the value assumed in the code. The behavior
of the beam was successfully predicted using basic section analysis. This paper
is not included on the 1998 Preprint CD-ROM. Please contact author for
information.
R. Miller, B. Shahrooz, T.M. Baseheart, E. Eberenz, J. Jones, R.
Knarr, R. Sprague, University of Cincinnati, Department of Civil and
Environmental Engineering, P.O. Box 210071, Cincinnati, OH 45221-0017. Tel:
(513) 556-3744 Fax: (513) 556-2599. e-mail: rmiller@boss.ecc.uc.edu.
Abstract: The increasing traffic demand on U.S. bridges and the
continuing use of deicing salts have caused increasing bridge deck deterioration
which, in turn, raises the need for deck replacement. In areas of heavy traffic
volume, deck replacement is often needed in a short period of time. Bridge deck
removal can often be slowed due to the effort needed to remove the deteriorated
concrete from around the connection mechanism required for composite action
between the concrete deck and the girder top flange. A girder-to-deck-
connection which facilitates rapid deck replacement is, therefore, a high
priority. Conclusions: The tests confirmed that the proposed 31.8 mm
diameter studs are an efficient replacement for the conventional 22.2 mm studs.
The strength of the 31.8 mm studs is about twice that of the 22.2 mm studs. This
would allow for fewer studs along the length of the steel girder which would
decrease the effort of deck removal from around these studs, and the probability
of damage to these large studs and to the girder top flange. Using alternate
headed and headless studs may further facilitate deck removal. This paper is not
included on the 1998 Preprint CD-ROM. Please contact author for
information.
Hussam F. Kakish, Mantu C. Baishya, Maher K. Tadros, Civil
Engineering Department, University of Nebraska - Lincoln. Tel: (402) 554-2820
Fax: (402) 554-3288. Darin L Splittgerber, HDR Engineering, Inc.. Tel: (816)
421-5070 Fax: (816) 421-5211.
Abstract: Seismic events release vast amounts of energy. To reduce damage
during a seismic event, directing the earthquake forces away from the most
vulnerable structural elements, through isolation and ductility provisions may
be a more successful strategy than reinforcement for those forces. In places
reinforcement would have been expensive or impossible. The retrofit of the
Vincent Thomas Bridge illustrates methods to modify the bridge’s response
behavior to reduce damage. The most critical elements are the cable bent and
towers, as they support all the weight of the bridge. The cable bent was
retrofitted by isolation and reinforcement, while the tower was made more
ductile by eliminating local buckling. Viscous dampers were added to reduce the
amplitude of motion of the suspended trusses, and clearances were given to
accommodate the remaining motions without collision with the tower legs and
cable bents. The suspended structure side spans were given hinges and friction
connections that allow controlled damage while continuing to provide vertical
continuity. The deck slab motion is limited to several inches relative to the
trusses. Conclusions: ADINA proved to be an efficient tool for the
nonlinear time history analysis. The simplified model proved ideal for
parametric studies and the optimization of designs, whereas the detailed model
most faithfully reproduced the behavior of the structure. There is uncertainty
in predicting the behavior of a large and complex structure during a major
earthquake. By improving the fundamental behavior of the structure there is
greater confidence that the predicted response should be conserved through a
broad range of seismic events. George Baker, Weidlinger Associates, 375 Hudson
Street, New York NY 10014-3656. Tel: (212) 367-2850 Fax: (212) 367-3030. e-mail:
gbaker@wai.com. Tim Ingham, TY Lin
International, 825 Battery Street, San Francisco CA 94111. Tel: (415) 291-3700
Fax: (415) 433-0807. e-mail: tylin1@ix.netcom.com. Dan Heathcote,
California Dept. of Transportation, 1801 30 th Street, Sacramento CA 95816. Tel:
(916) 227-8242 Fax (916) 227-8381.
Abstract: For high performance concrete (HPC) bridge implementation to be
successful nationally, the State DOT’s must see a benefit to its use. One of the
significant benefits of HPC is its improved long-term performance. Although
State DOTs are beginning to look at life-cycle costs, initial costs are still
the basis for evaluation of cost-effectiveness. Because of this and the need to
build and maintain more with less, HPC bridges must be designed and constructed
such that initial costs are comparable or less than conventional concrete
bridges. This can be achieved, even with the potentially higher unit costs of
HPC, through optimization of the design and construction of HPC bridges.
Conclusions: Optimization of a bridge means designing and building for
the requirements of the specific bridge component (deck, beams, substructure) in
its environment (moist, freeze-thaw, sulfate, etc.). HPC bridges should be
designed and constructed using the improved performance characteristics of HPC.
By doing this, initial costs can be comparable or less than conventional
concrete bridges, even with the potentially higher unit costs of HPC. Updating
of the American Association of State Highway and Transportation Officials
(AASHTO) materials and structural specifications to incorporate the improved
performance characteristics of HPC will facilitate the optimization of HPC
designs and result in more cost-effective HPC bridges. Also addressed are issues
of permeability, deck thickness, compressive strength, reduced number of
required beams in design, manufacturer’s rules of thumb for increasing
compressive strength, flexural strength, modulus of elasticity, shrinkage and
creep, use of straight strands, variable camber, and site logistics.
Mary Lou
Ralls, P.E., Texas Department of Transportation, Materials & Tests Division,
125 E. 11 th St., Austin, TX 78701. Tel: (512)465-7963 Fax: (512) 465-7999.
e-mail: mralls@mailgw.dot.state.tx.us.
Ramon L. Carrasquillo, Ph.D., P.E., Construction Materials Research Group,
Center for Transportation Research, University of Texas at Austin, 10100 Burnet
Road, Bldg. 18-B, Austin, TX 78758. Tel: (512) 471-4585 Fax: (512) 471-4555.
e-mail: ramonc@mail.utexas.edu. Ned
H. Burns, Ph.D., P.E., University of Texas at Austin, (see above). Tel: (512)
471-1619 Fax: (512) 471-1944.
Abstract: Many bridges constructed in the 1960's in regions of high
seismic risk have column-pier cap connections with inadequate column bar
development and no shear reinforcement in the joint region. The study described
in this paper focuses on highway bridges built on Interstate 80 in the Reno
area, during the 1960's. Two 0.4-scale specimens representing the essential
features of the column-pier cap connections in these bridges were constructed
and tested. One specimen showed that the as-built specimen had little energy
dissipation capacity and failed at less than 1 percent drift. A second specimen
was used to test a potential strengthening technique. The technique included
increasing pier cap depth, adding a concrete bolster to the joint, and placing a
steel jacket around the column. Conclusions: After strengthening, a
plastic hinge formed in the column, the joint damage was minimized, and the
energy dissipation capacity increased by a factor of five. A conservative design
approach was used to ensure success, but to remain cost effective and maintain
ductility the strengthening scheme did not have large safety factors. The
strengthening methods corrected problems with joint shear, column bar
development, and low pier cap flexural strength. The methods are expected to
work well on similar bridges with only changes in sizes and ratios. In some
cases the as-built conditions may not require all aspects of the strengthening
scheme. Not including part of the strengthening scheme could have large cost
savings, especially in the case of the joint bolster, but it is difficult to
know the entire effect on the system since only one strengthened test was
performed.
David H. Sanders, M. Saiid Saiidi, Troy Martin, University of
Nevada-Reno. Tel: (702) 784-4288 Fax: (702) 784-1390. e-mail: sanders@unr.edu.
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