This document summarizes research on extending the life of steel girder bridges through the use of post-installed shear connectors. Key findings include: 1) Moment redistribution is possible for partially composite girder bridges, allowing yielding in negative moment regions. 2) Adhesive anchor shear connectors demonstrated much better fatigue performance than welded studs through exhaustive testing. 3) Large-scale bridge testing showed strengthened bridges exceeded strength predictions and had excellent fatigue performance. 4) A recommended design procedure was developed based on the research findings.

1. Graduate Students: Kerry Kreitman, Hemal Patel,
Amir Ghiami Azad
TxDOT Project 0-6719
FERGUSON STRUCTURAL ENGINEERING LABORATORY
Faculty: Michael Engelhardt, Todd Helwig, Rich
Klingner, Eric Williamson
Extending the Life of Steel Girder Bridges
through the Use of Post-Installed Shear
Connectors
TxDOT:
Darrin Jensen, Yuan Zhao, Dingyi Yang, Jamie Farris, Manuel Padron,
Michelle Romage-Chambers, Paul Rollins, Leon Flourney

2. Develop technique to strengthen existing continuous
multi-span non-composite steel girder bridges
Project Objective

4. Older Non-composite Bridge
steel girder
concrete deckPost-installed
shear connector

5. Critical Issue for Practical Application
Minimize number of post-
installed shear
connectors.
Need to employ partial
composite design.

6. Bridge Deck
Girder Flange
Post-Installed Shear Connector:
Adhesive Anchor

7. Strengthening Concept
Partially composite Partially compositeNon-composite
Positive moment Positive momentNegative moment
Increased strength Increased strength
Continuous, non-composite girder

8. YIELD
YIELD
Strengthening Concept:
- Allow yielding in negative moment region / redistribute moment
to positive moment regions
- Strengthen positive moment regions with post-installed shear
connectors using partially composite design

9. Research Questions
• Is moment redistribution possible for partially composite
girders (i.e., can we develop “shakedown”) ?
• What is the fatigue strength of the adhesive anchor shear
connector ?
• How do we compute the shear connector fatigue
demands for a partially composite girder?
• Can we demonstrate good performance in large-scale
tests?
• Can we develop a straightforward design procedure?

10. Bridge Survey
7-8’ 7-8’ 7-8’
Compact
W30-W36
shape
6.5” deck
50-100’ 50-100’ 50-100’
Cover plates top and
bottom over piers
2-6 lanes
Typically no skew
or curvature
2-5 span unit
No shear connectors
Constructed 1950-1970
H15 or H20 design loads

11. 0
2
4
6
8
10
12
14
NumberofBridgeUnits
Inventory HS Load Rating
Initial Concept Studies
Existing
Strengthened (30%)
Bridges can be
significantly
strengthened:
Achieve HS 20 rating with
low composite ratios and
minimal redistribution
Exceeds
current
standardsDeficient compared to
current standards
Conduct load rating for 13 bridges

12. Fatigue Testing

13. Fatigue Testing
0
10
20
30
40
50
60
1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
StressRange,σr(ksi)
Number of Cycles at Failure, N
0
0.01
0.02
0.03
0.04
1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Avg.SlipRange,sr(in)
Number of Cycles at Failure, N
= 0.66
= 0.86
Stress Range:
Slip Range:
= 101 − 13.6 log ≥ 15
= 0.0537 − 0.00725 log ≥ 0.008

14. Fatigue Testing
Key Results:
• Adhesive anchor shear connector has much
better fatigue performance than welded shear
studs.
• Developed fatigue performance predictions
based on both stress-range and on slip-range.

15. Large-Scale Testing
Girder 1: 84’ long; 30% composite; 56 connectors
Girder 2: 104’ long; 20% composite; 40 connectors

16. 16

17. 17

18. Testing Program
• Elastic testing
– Before and after installing connectors
• Fatigue and shakedown testing
– In various orders for each span
• Ultimate strength testing

19. Typical Shakedown Results
Loading Pattern:
0
0.02
0.04
0.06
2 3 4 5 6 7 8
ChangeinDefl.(in)
Cycle Number
Shakedown
criterion

20. Typical Ultimate Strength Results
0
50
100
150
200
250
0 3 6 9 12 15
Load(k)
Total Deflection at Load Point (in)
Predicted partially
composite limit load
Predicted non-
composite limit
load
Connector
failure
Maximum load
applied in
shakedown
test

21. Summary of Large-Scale Test Results
Exceeded predicted strengths at all limit states
– Shakedown was observed to occur in partially
composite strengthened girders
– Excellent high cycle fatigue performance
– Fatigue loading did not adversely affect strength
– Ultimate strength developed at predicted levels
with significant ductility

22. Finite Element Modeling
• ANSYS software
• Extend experimental results
• Evaluate fatigue demands on shear connectors
using slip based approach
Cross section
view
Isometric view
(underside)
Concrete deck
Steel beam

23. -0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0 8 16 24 32 40 48 56 64 72 80
SlipUnder~50kipP2Load(in)
Distance Along Beam (ft)
Slip Profiles
50 kips 50 kips
ANSYS

24. Parametric Studies
• Recommendations for connector layout:
– Location of connector groups is most influential
– Consider constructability
15% of span length
12” spacing (approx.)

25. Recommended Design Procedure
Evaluate strength
of existing bridge
Set strengthening
targets
Check negative moment
regions and redistribute
moments as necessary
Design connectors for
positive moment regions
Locate connectors and
check fatigue strength

26. Research Questions / Answers
• Is moment redistribution possible for partially
composite girders (i.e., can we develop
“shakedown”) ?
YES – Shakedown in possible and predictable
• What is the fatigue strength of the adhesive anchor
shear connector ?
Equations developed (based on exhaustive testing)
to predict fatigue life of shear connectors, based
both on stress-range and slip-range.

27. Research Questions / Answers
• How do we compute the shear connector fatigue demands for
a partially composite girder?
Compute slip demands on shear connectors under fatigue
truck (can use commercial FEA software or “UT-SLIP.”)
• Can we demonstrate good performance in large-scale tests?
Large-scale specimens showed excellent performance under
all loading conditions.
• Can we develop a straightforward design procedure?
Yes.

28. Conclusions of Research Study
Efficient strengthening solution
– Avoid load-posting or costly deck replacements
– Significant increase in load rating (up to 90%)
– Excellent structural behavior
– Simple and quick installation process
– Straightforward design process

29. Implementation
Strengthening technique currently being
implemented on bridge in Lakeport, Texas