Chesapeake City Bridge Crack Study

1. Chesapeake City Bridge Crack Study

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

5. 213 Chesapeake & Delaware Canal Crossings MD Rte DE Rts 806 71 DE Rte US Rte 9 US Maryland Delaware 13 301 Chesapeake Bay Delaware Bay Conrail Reedy Point Bridge 2 Lanes Chesapeake City Bridge 2 Lanes Summit Bridge 4 Lanes St. Georges Bridge 4 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 1947-1948 • Overall structural condition is fair • Design live load: HS20-44

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 #1Drilling Holes

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

18. After failed Attempt #2, developed numerical models to investigate the crackingand 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. 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 & Floorbeamb. 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. 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 Deck Joint Fused Steel Bars

36. Typical Deck Joint Fused Steel Bars

37. Typical Deck Joint Fused Steel Bars

38. Joint Busters I Double Click to See Video

39. Joint Busters II Double Click to See Video

40. High-Pressure Power Washer

41. 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?