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Disclaimer — This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on
publicly available information and may not be provide complete analyses of all relevant data. If this paper is used for any
purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at
the University of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk.
UNBOUNDED TENDONS EFFECT ON SEGMENTAL BRIDGE DESIGN
Jordan Walk, jjw83@pitt.edu, Bursic 2pm, Nathaniel King, nrk20@pitt.edu, Bursic 2pm
Revised Proposal —This paper discusses the importance
of the strength of prestressed unbounded tendons in precast
concrete segmental bridges. Segmental bridges, much unlike
monolithic bridges, are built off-site in pieces, which are then
transported to the construction site to be fitting together.
Tendons provide vital support to the stress placed on
segments of bridges. We seek to analyze the unbounded
method of inserting the tendons and their prestressed
characteristics in segmental bridges, and identify what effects
these have on seismic activity. Since segmental bridges are
made in small, thin sections, it is relatively easy for a seismic
occurrence to cause damage to the bridge.
Unbounded prestressed tendons, which are relatively recent
to bridge design, undergo a high tension “stretch” before
being fixed in concrete, or prestress. This reinforces the
concrete (which is under tensile stress) with counteractive
compressive stress. As one can imagine, the ideal bridge
undergoing seismic activity should perform with both firm
strength and slight flexibility. The unbounded characteristic
allows segmental bridges to endure intense shearing, and
have more freedom to move compared to bounded tendons.
While segmental bridges offer a lower load capacity than
monolithic structures, unbounded tendons, in theory,
offer more flexible movement (shearing ability) and a higher
prestressing degree [1]. In addition, the unbounded nature
allows the segments of the bridge to be more accessible. If
there is damage to a segment, it is easy to replace that piece
at low cost. In comparison to bounded tendons, unbounded
tendons offer a few advantages such as substantial economic
savings, simple element assembly, and its ability to be
replaced [1].
Segmental bridge design is the next generation of bridge
construction and repair; however, seismic activity and
otherwise large stresses cannot be controlled by humans,
which is why it is greatly important to innovate the best
solution within bridge design. We will be researching the
effects of unbounded prestressed tendons via online reports,
making sure to properly analyze and discover the best
methods of utilizing unbounded prestressed tendons in
segmental bridge design. In addition to these online reports,
we are consulting various diagrams and tables that aid in the
comparison of different tests, which help identify the many
characteristics of tendons.
University of Pittsburgh Swanson School of Engineering 1
2016/01/29
With these credible sources, we believe we will find reliable
and relevant information that will allow us to deliver an
educated analysis and presentation of this technology at the
Freshman Conference.
REFERENCES
[1] J. Huang. X. L. Liu. (2006). “Modified Skew Bending
Model for Segmental Bridge with Unbounded Tendons.”
Journel of Bridge Engineering. (Online Article).
ANNOTATED BIBLIOGRAPHY
“Civil
Engineering:
Prestressed
Concrete.”
Civil
Engineering.
(video).
https://www.youtube.com/watch?v=2QQsaPYssVU
This video utilizes graphics to simulate the construction of
a segmental bridge by layering each piece separately. It
highlights the prestressed tendons, in which it simulates the
prestressing process before adding the final layer of concrete.
In addition, the video exhibits cutting the tendons between
segments, representing the unbonded feature of our topic. The
video also includes a clip of removing a segment of the bridge,
without hindering the rest of the structure.
“Code of Ethics.” (2006, July 23). ASCE. (Online Article).
http://www.asce.org/code-of-ethics/
The American Society of Civil Engineers developed a
Code of Ethics as a model of conduct for professional ASCE
members. The seven canons detail all ethical dilemmas
possible in the Civil Engineering Environment. We plan to
utilize these ethics as guidelines to spotcheck our own
research, and to keep us on track to hunt down any unethical
aspects to Unbounded Prestressed Joints in segmental bridge
design.
Z. Huang. X.L. Liu. (2006). “Modified Skew Bending Model
for Segmental Bridge with Unbonded Tendons.” Journal of
Bridge
Engineering.
http://ascelibrary.org/doi/abs/10.1061/(ASCE)10840702(2006)11%3A1(59)
This article comes from the American Society for Civil
Engineers. The article weighs the advantages that segmental
Walk
King
bridges with unbonded tendons have over traditional
conventional bridges. The article compares theoretical
research, such as interaction formulae, to the finite element
method (FEM) analysis. Along with the analysis, they display
diagrams of beam deformation, deflection, and torsion. Based
on the investigation, suggestions for design offer insight on
the behavior of unbonded tendons.
evolution and advantages of segmental bridge construction.
Podonly provides examples of American segmental bridges
dating back to 1949, which will allow us to view the progress
and possible mistakes in segmental construction.
A.Yuan. H.Dai. D.Sun. J.Cai. (2013). “Behaviors of
segmental concrete box beams with internal tendons and
external tendons under bending”. Engineering Structures.
http://ac.els-cdn.com/S014102961200483X/1-s2.0S014102961200483X-main.pdf?_tid=9f3c8636-c439-11e59fdb00000aacb361&acdnat=1453818926_bc080c646612281802
d2cd86445f7cc2
The article is from Engineering Structures, which is a
company that receives technical papers to show the ever
changing engineering world. The authors look at segmental
bridges from a different approach, using both internal and
external tendons instead of only one. They experimented
with these to try and develop an idea ratio of internal to
external to figure out which system would be most beneficial.
S.Im. S.Hurlebaus. D.Trejo (2010). “Inspection of Voids in
External Tendons of Posttensioned Bridges”. Transportation
Research
Board.
http://trrjournalonline.trb.org/doi/abs/10.3141/2172-13
The article comes from The Transportation Research
Board, whose mission is to provide innovations to the
transportation engineering through research. This article tests
if sound inspections of corroding tendons can properly and
effectively determine how close these tendons are to failure.
It compares and contrasts visual inspections and sound
inspections effect on analyzing the voids in tendons and
where these voids are located to allow easy replacement of the
tendons.
G.Li. D.Yang. Y.Lei. (2013). “Combined Shear and Bending
Behavior of Joints in Precast Concrete Segmental Beams with
External
Tendons”.
ASCE.
http://ascelibrary.org/doi/abs/10.1061/(ASCE)BE.19435592.0000453
This article comes from the American Society for Civil
Engineers. Here, the article experiments with how seismic
activity will cause the tendons to possibly bend and
deform. However, the tendons are easily replaceable, which
allows for the easy maintenance of any tendons that get
damaged. It will help us in our paper by demonstrating why
tendons play such a pivotal role in segmental bridges.
M.Veletzos. J.Restrepo. (2014). “Equivalent Unbonded
Length for Modeling of Multistrand Tendons in Precast
Segmental
Construction”.
ASCE.
http://ascelibrary.org/doi/abs/10.1061/(ASCE)BE.19435592.0000502
The article also comes from the American Society for Civil
Engineers, their goal is to develop better infrastructure for the
public. It experiments with how the length and number of
strands in the tendons affect its strength. They explain
different characteristics of the tendons and how they change
in the different scenarios of the experiment. The article will
help our paper by showing how tendons have different
characteristics and attributes.
P. Walter. (1979). “An Overview of Precast Prestressed
Segmental Bridges.” PCI Journal. (Online Article).
http://www.pci.org/pci_journal-1979-january-february-4/
This article comes from the PCI Journal, credited to Walter
Podolny Jr. of the Federal Highway Administration of the
U.S. Department of Transportation. This article provides a
general knowledge base of segmental bridges, including the
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