1. Chesapeake City Bridge Crack Study

2. Introduction Adrian Kollias, P.E.
US Army Corps
of Engineers
Philadelphia District
Introduction
Adrian Kollias, P.E.
Philadelphia District Bridge Program Manager

3. Overview Present problem Previous repair attempts Modeling
Final solution

4. 95 1 295 95 40 C&D Canal 13 301 Philadelphia Wilmington DELAWARE
MARYLAND 95
NEW JERSEY 40
C&D Canal 13
Baltimore
DELAWARE
301
Dover
MARYLAND

5. Chesapeake & Delaware Canal CrossingsMD
Rte
DE Rts
806 71 DE
Rte US
Rte
213 9 US
Maryland
Delaware 13
301
Chesapeake
Bay
Delaware
Bay
Conrail
Chesapeake
City Bridge
2 Lanes
Summit
Bridge
4 Lanes
St. Georges
Bridge
4 Lanes
Reedy Point
Bridge
2 Lanes N

6. Terminology
Fracture Critical Members: tension members or tension components of members whose failure would be expected to result in the collapse of partial collapse of a bridge
Fatigue: the tendency of a member to fail at a lower stress when subjected to cyclical loading than when subjected to static loading.
Fatigue crack – any crack caused by repeated cycle loading.
Fatigue life – the length of service of a member.

7. Chesapeake City Bridge
Arch
Pier
Floorbeam
Tie Girder

8. Description Tied-arch structure Two traffic lanes, Maryland Rte. 213
3,954 feet in length
Two-girder, fracture critical structure
ADT = 14,825 (2004)
ADTT = 2,635 (2006)
Constructed
Overall structural condition is fair
Design live load: HS20-44
The bridge is a tied-arch structure located 14 miles west of Reedy Point, Delaware. Consists of the tied-arch main span and 32 simply supported approach spans. The structure was constructed during the period

9. Cracks at 3 Locations: L0, L0’, L1’

11. Bridge Floor System Deck Stringers Tie Girder Sliding Bearings
Cracked Connection Angle Locations
Floorbeam

12. Crack Location
Track Crack Propagation with Bi-weekly Inspections

13. Crack Location
Track Crack Propagation with Bi-weekly Inspections

14. Crack Location
Track Crack Propagation with Bi-weekly Inspections

15. Chesapeake City Bridge
Reason for Concern
Public Safety
Potential for partial bridge failure if corrective measures are not taken
Major traffic thoroughfare connecting both northern and southern Delmarva Peninsula in Maryland
Connects Northern and Southern Chesapeake City

16. Attempt #1 Drilling Holes

17. Replace Top Portion of Cracked Angles
Attempt #2
Replace Top Portion of Cracked Angles
New Angle Section

18. After failed Attempt #2, developed numerical models to investigate the cracking and analyze bridge behavior. Determine that frozen stringer bearings are causing the cracks and must be replaced.

19. Original Bronze Bearings
Stringer
Bronze Plate
Sole Plate
Filler Plate
Bearing Plate
Floorbeam Top Flange

20. Original Bronze Bearings
Crevice Corrosion

21. Attempt #3: Replace “Frozen” Stringer Bearings
Diaphragm
Stringer
Sliding Bearings
Floorbeam

22. New Neoprene Bearings
Sole Plate
Neoprene Bearing Pad
Bearing Plate

23. - Replaced 72 bearings out of 180 total
Repairs performed in 2003
- Replaced 72 bearings out of 180 total
- Repaired connection angles for 6 floorbeams
out of a possible 16 total
Cost: $945,000
Duration: 210 calendar days

24. Cracks reappear at the angle connections 1-year after bearing repair.
Need to re-evaluate numerical models and design a repair retrofit for the angles to prevent future cracking.

25. Global Model

26. Global Modeling: Details and Assumptions
Modeled using STAAD.Pro 2005
Created using beam and shell elements
All members modeled as beam, except deck slab which is modeled using shell elements
Rigid elements and offsets to account for differences in c.g. locations of members
New elastomeric stringer bearings modeled as tri-directional linear springs
Remaining original stringer bearings are modeled as restrained in 3 directions
South main arch bearings free to expand longitudinally and rotate about transverse axis
North main arch bearings fully fixed
Deck is continuous (i.e., can transfer axial force from one panel to another)

27. Calibration of the Global Model
Calibrated to measured global deflection data
Calibrated to measured strains from two previous diagnostic tests
Overall goal of the calibration
Capture the key features of the global response in terms of global deflection and floorbeam stress
Strive for realistic agreement in magnitudes, given very complex behaviors and small magnitudes of measured deflection and stress

28. Initial Findings a. Cracking is Due to Relative Rotation between Tie Girder & Floorbeam b. Cracking is Due to Fatigue not Strength b. Continuous Deck Model Best Predicts Floorbeam Stresses Matching Actual Field Measurements c. Frozen Stringer Bearings and Stiff Deck Joints are both Contributing to the Cracking

29. Deflection Under Test Vehicle

30. Completely Continuous
Model Results
Discontinuous
Slightly Continuous
Completely Continuous

31. Remove Sample of Rubber Deck Joint Material to Test Stiffness

32. Deck Joints

33. Deck Joint

34. Original Deck Joint Design - 1977
Rubber Seal
½” x ¼” Steel Support Bars

35. Deck Joints are Restrained from Movement
Fused Steel Bars

36. Typical Deck Joint
Fused Steel Bars

37. Typical Deck Joint
Fused Steel Bars
Show joint busters video.

38. Double Click to See Video
Joint Busters I
Double Click to See Video
Show Joint Video

39. Double Click to See Video
Joint Busters II
Double Click to See Video

40. High-Pressure Power Washer

41. do not achieve infinite fatigue life even
Models indicate existing FTGC angles
do not achieve infinite fatigue life even
with bearings and deck joints repaired.

42. Retrofit Design Process
Obtain Design Forces – Global Model
Develop Preliminary Retrofit Designs (2 Stiffened + 2 Softened)
Incorporate Retrofit – Local Model
Verify Retrofit Effects - Global Model
Finalize Retrofit Design

43. Local Model

44. Fatigue Analysis Fatigue life is function of stress range
Conducted using actual traffic data (cycles) and vehicle weight crossing bridge
Fatigue category C for out-of-plane displacement behavior
Criteria from AASHTO Guide Specifications and LRFD Specifications

45. Current Repair Contract
Replace top portions of FTGC angles with thicker angle members at L0 to L5 and L1’ to L5’.
Replace all deck joint compression seals
Replace neoprene bearings at exterior stringers at Floorbeams L1 to L3 and L1’ to L3’.
Restore bronze plate bearings at Floorbeams L4 to L7 and L4’ to L7’.
Cost: $1.3 million

46. Questions?