1. Approaches to Historic Bridge Rehabilitation Case Study #2
Holmes Street Bridge, No. 4175
(Deck Truss)
Shakopee, Minnesota
Bob Frame
Mead & Hunt, Inc.

2. Holmes Street Bridge No. 4175
Case study #2
Shakopee, Minnesota
Built to carry MN trunk highway over the Minnesota River, tributary to Mississippi
Pedestrian use since 2005
Deck truss
Built 1927
Structure length: 645 feet
4 main river spans: Warren truss, with 3 truss lines
4 approach spans (2 north, 2 south): cast-in-place concrete beams

3. Bridge 4175 Rehab Case study #2
Project: to restore and convert to pedestrian use
Rehab in process
Client/Owner: Mn/DOT
Engineer: HDR, Inc.
Contractor: Kramer Bros.
Section 106 rehab guidance: Mead & Hunt, Inc.
Before rehab
During rehab

4. Case study #2
Issue 1 - Repair gusset-plate connections & replace lower chord members
Left: Typical gusset plate in good condition, upper and center of trusses.
Right: Typical gusset plate in poor condition, located below drains.

5. Lower chord members & gusset plates in serious-to-critical condition
Case study #2
Lower chord members & gusset plates in serious-to-critical condition
Gusset plate with retrofit; up to 100% section loss in some plates.
Buckled gusset plate between diagonal & vertical members

6. How Significant Issue Was Resolved
Case study #2
First, strong-back system used to relieve stress on truss connections

7. Case study #2
Rivets replaced with bolts
Old bearing pins replaced
Lower chord members replaced.
Rivets were removed.

8. Issue 2 – Repair historic concrete
Case study #2
On concrete approach spans & abutments
Delamination, spalling, graffiti
Beams to be repaired
Sidewalk brackets to be replaced

9. How Significant Issue Was Resolved
Case study #2
Shotcrete used for repair patches and to replicate missing features
Test repairs to check replication of architectural shapes
Test panels to compare color & surface texture treatment

10. How Significant Issue Was Resolved
Case study #2
Sculpting architectural details
Applying shotcrete to repair area

11. Replicating concrete sidewalk brackets
Case study #2
After initial concrete demolition
Building formwork
Removing forms

12. Contractor demonstrating graffiti & paint removal
Case study #2
Contractor demonstrating graffiti & paint removal
Left:
Using water – less effective
Right:
Using micro-abrasive blast – more effective
Black Diamond product used

13. How was Section 106 handled
Case study #2
Issue: all rehab to be compliant with Secretary of the Interior’s Standards
Steel repairs were considered compliant
Concrete repairs considered compliant
Shotcrete use approved by SHPO
Micro-abrasive blast approved by SHPO

14. How was Section 4(f) handled
Case study #2
No 4(f) issues

15. Lessons Learned/Conclusions
Lifting truss allows repair/replacement of gusset plate connections & lower chord members
Shotcrete to repair & match adjacent historic concrete
Sculpted to replicate details
Concrete stain for color
Micro-abrasive blast for texture