Results

Purpose

Undergraduate Intern: Jose G. Jimenez Jr. (jgjimene@gmail.com), 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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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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L.embed/D.str (-)

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1/2" Black Strand

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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