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Chesapeake City Bridge Crack Study. US Army Corps of Engineers Philadelphia District. Introduction. Adrian Kollias, P.E. Philadelphia District Bridge Program Manager. Overview. Present problem Previous repair attempts Modeling Final solution. Philadelphia. 95. 1. 295. Wilmington. - PowerPoint PPT Presentation
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Chesapeake City Bridge Crack Study
• Adrian Kollias, P.E.• Philadelphia District Bridge Program
Manager
US Army Corpsof EngineersPhiladelphia District
Introduction
Overview
• Present problem• Previous repair attempts• Modeling • Final solution
MARYLAND
DELAWARE
NEW JERSEY
301
13
40
1
95
95
295
Baltimore
Philadelphia
Wilmington
C&D Canal
DoverD
EL
AWA
RE
MA
RY
LA
ND
ChesapeakeBay
DelawareBay
Chesapeake & Delaware Canal Crossings
Maryland Delaware
ChesapeakeCity Bridge
2 Lanes
SummitBridge4 Lanes
St. GeorgesBridge4 Lanes
Reedy PointBridge2 Lanes N
Conrail
DERteUS
Rte
MDRte
DE Rts80671US 9
13213
301
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.
Chesapeake City Bridge
Tie GirderFloorbeam
Arch
Pier
– 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
Description
Cracks at 3 Locations: L0, L0’, L1’
Bridge Floor System
Sliding Bearings
Cracked Connection Angle Locations
Stringers
Floorbeam
Deck
Tie Girder
Crack Location
Track Crack Propagation with Bi-weekly Inspections
Crack Location
Track Crack Propagation with Bi-weekly Inspections
Crack Location
Track Crack Propagation with Bi-weekly Inspections
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
Attempt #1Drilling Holes
Attempt #2Replace Top Portion of Cracked Angles
New Angle Section
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.
Original Bronze Bearings
Stringer
Floorbeam Top Flange
Sole Plate
Bearing Plate
Bronze Plate
Filler Plate
Original Bronze Bearings
Crevice Corrosion
Attempt #3: Replace “Frozen” Stringer Bearings
StringerSliding Bearings
Floorbeam
Diaphragm
New Neoprene BearingsSole Plate
Bearing PlateNeoprene Bearing Pad
• 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
• 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.
Global Model
Load 1X
Y
Z
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)
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
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
Deflection Under Test Vehicle
Model Results Measured Stress in Top Flange - Floorbeam L1'
-3.0
-2.0
-1.0
0.0
1.0
2.0
0 100 200 300 400 500
Load Position (ft)
Stre
ss (k
si)
Gage 13 MeasuredGage 16 MeasuredGage 16 Model 6Gage 13 Model 6
Measured Stress in Top Flange - Floorbeam L1'
-3.0
-2.0
-1.0
0.0
1.0
2.0
0 100 200 300 400 500
Load Position (ft)
Stre
ss (k
si)
Gage 13 MeasuredGage 16 MeasuredGage 13 Model 8Gage 16 Model 8
Discontinuous Slightly ContinuousMeasured vs. Predicted Stress in Top Flange - Floorbeam L3'
-3.0
-2.0
-1.0
0.0
1.0
2.0
0 100 200 300 400 500
Load (Rear Axle) Position (ft)
Stre
ss (k
si)
Gage 28 MeasuredGage 27 MeasuredGage 28 Model 18Gage 27 Model 18
Completely Continuous
Remove Sample of Rubber Deck Joint Material to Test
Stiffness
Deck Joints
Deck Joint
Original Deck Joint Design - 1977
Rubber Seal
½” x ¼” Steel Support Bars
Fused Steel Bars
Deck Joint
Deck Joints are Restrained from Movement
Fused Steel Bars
Typical Deck Joint
Fused Steel Bars
Typical Deck Joint
Joint Busters IDouble Click to See Video
Joint Busters IIDouble Click to See Video
Models indicate existing FTGC anglesdo not achieve infinite fatigue life even with bearings and deck joints repaired.
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
Local Model
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
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
Questions?