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Results
Purpose
Undergraduate Intern: Jose G. Jimenez Jr. ([email protected]), UC Irvine Intern Faculty Mentors: Dr. John F. Stanton & Dr. Marc O. Eberhard, University of Washington
Intern Graduate Mentor: Olafur S. Haraldsson, University of Washington University of Washington
Background Precast Bridge Bent System
The University of Washington is developing a bridge bent system that will
accelerate bridge construction, extend the bridge’s life-span, and increase
the bridge’s earthquake resiliency. One of the column’s key components is its
unbonded, corrosion resistant epoxy-coated strands that are designed to re-
center the column after a seismic event. It is vital to understand how the
strand’s bonding characteristics change as a result of its epoxy coating.
Research Questions 1. Does an epoxy coated strand bond better with grout than normal black
(carbon) strand?
2. How does the strand’s diameter affect its bond stress capacity?
3. How does the strand’s embedded length in grout affect its bond stress
capacity?
4. How does the grout’s compressive strength greatly alter the strand bond
test’s results?
Re-centering Concept
Acknowledgements
• 3/8” Black strand L.embed = 3”, 9”, & 12”
• 1/2” Black strand L.embed = 4” & 12”
Figure 4 Baldwin 120 kip hydraulic testing machine
Figure 3 Behavior of precast (left) and cast-in-place (right) bridge bents Pang et al., 2008
Figure 2 Precast bridge bent system with unbonded epoxy coated strands and stainless steel reinforcement
Figure 1 Sumiden Wire Products Corp.’s uncoated and
epoxy coated strands
Sumiden Wire Products. Advertisement. SWPC, n.d.
Web. <http://www.sumidenwire.com/prod/pc/index.html>.
Figure 5 Strand bond test specimen and set-up
Black Strand vs. Epoxy Strand
Pang, B.K. Jason, Kyle P. Steuck, Laila Cohagen, John F. Stanton, and Marc O. Eberhard. Rapidly
Constructible Large-Bar Precast Bridge-Bent Seismic Connection. Olympia: Washington State Department
of Transportation, 2008. Print.
I would like to thank Professors Marc O. Eberhard and John F. Stanton as well as my graduate student
mentor Olafur S. Haraldsson for the tremendous amount of help and support they gave me in completing
this project. I would also like to thank Heidi Tremayne for her help in organizing the PEER internship
program and the National Science Foundation whose generous funding made it possible for me to conduct
research at the University of Washington.
References
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Epoxy Strand
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Critical Point (-)
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Epoxy Strand
Figure 6 Average bond stresses at the two slip displacements
and peak load: Black Strand vs. Epoxy Strand
Figure 7 Normalized Average bond stresses at the two slip
displacements and peak load: Black Strand vs.
Epoxy Strand
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lip (
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L.embed/D.str (-)
3/8" Black Strand
1/2" Black Strand
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2 in
. Slip
(ks
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L.embed/D.str (-)
3/8" Epoxy Strand
1/2" Epoxy Strand
Average Bond Stress: 0.66 ksi
Coefficient of Variation: 0.1422
Average Bond Stress: 0.49 ksi
Coefficient of Variation: 0.1403
Figure 8 Bond Stresses at 0.02 in. slip: 3/8” Black vs. 1/2” Black
Strand Figure 9 Bond Stresses at 0.02 in. slip: 3/8” Epoxy vs. 1/2”
Epoxy Strand
1) Although the black strand has a smaller peak bond stress, at small slip
displacements such as 0.02 in. and 0.1 in. the black strand has a larger bond
stress than the epoxy strand.
2) Average bond stress along the strand’s embedded length does not change
significantly with an increase in its embedded length.
3) The average bond stress is not significantly affected by the strand’s diameter.
4) The normalization of the bond stress by dividing the grout strength by its
square root did not affect conclusions 1, 2 and 3. However, since a limited
amount of tests were conducted these conclusions may need to be revised.
Black and Epoxy Strand Pull-Out Tests
• 3/8” Epoxy strand L.embed = 3”, 9”, & 12”
• 1/2” Epoxy strand L.embed = 4”, 12”, & 16”
Conducted 62 strand bond tests
Conclusions
D.str Type L.embed/D.str Non-Norm. Tau ST.DEV Coeff. Non-Norm. Tau ST.DEV Coeff. Max Non-Norm. ST.DEV Coeff. Avg. Coeff.
(in.) Str. (-) At Slip 1 (ksi) (ksi) VAR. At Slip 2 (ksi) (ksi) VAR. Tau (ksi) (ksi) VAR. VAR.
3/8 bl. 8 0.655 0.096 0.146 0.586 0.074 0.126 0.725 0.096 0.132 0.135
3/8 bl. 24 0.712 0.082 0.116 0.696 0.112 0.161 0.762 0.083 0.109 0.128
3/8 bl. 32 0.681 0.231 0.339 0.799 0.091 0.114 0.886 0.054 0.061 0.171
1/2 bl. 8 0.509 0.102 0.202 0.686 0.079 0.115 0.775 0.114 0.148 0.155
1/2 bl. 24 0.757 0.051 0.067 0.826 0.051 0.062 0.862 0.063 0.073 0.067
3/8 ep. 8 0.445 0.127 0.285 0.647 0.094 0.145 1.469 0.152 0.104 0.178
3/8 ep. 24 0.412 0.111 0.269 0.492 0.200 0.408 1.065 0.338 0.317 0.331
3/8 ep. 32 0.438 0.079 0.182 0.574 0.110 0.192 1.208 0.092 0.076 0.150
1/2 ep. 8 0.558 0.226 0.404 0.554 0.162 0.293 0.959 0.220 0.230 0.309
1/2 ep. 24 0.557 0.128 0.230 0.516 0.124 0.241 0.731 0.120 0.165 0.212
Table 1 Average calculated from the profile summary for each strand at its different embedment lengths
Effects of a Strand’s Embedment Length and Diameter