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Chesapeake City Bridge Crack Study

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

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Overview Present problem Previous repair attempts Modeling Final solution

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

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

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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.

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Chesapeake City Bridge Tie Girder Floorbeam Arch Pier

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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

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Cracks at 3 Locations: L0, L0, L1

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

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Crack Location Track Crack Propagation with Bi-weekly Inspections

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Crack Location Track Crack Propagation with Bi-weekly Inspections

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Crack Location Track Crack Propagation with Bi-weekly Inspections

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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

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Attempt #1 Drilling Holes

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

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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.

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

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Original Bronze Bearings Crevice Corrosion

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Attempt #3: Replace Frozen Stringer Bearings Stringer Sliding Bearings Floorbeam Diaphragm

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New Neoprene Bearings Sole Plate Bearing Plate Neoprene Bearing Pad

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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

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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.

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Global Model

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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)

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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

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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

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Deflection Under Test Vehicle

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Model Results DiscontinuousSlightly Continuous Completely Continuous

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Remove Sample of Rubber Deck Joint Material to Test Stiffness

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Deck Joints

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Deck Joint

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Original Deck Joint Design - 1977 Rubber Seal x Steel Support Bars

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Fused Steel Bars Deck Joint Deck Joints are Restrained from Movement

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Fused Steel Bars Typical Deck Joint

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Fused Steel Bars Typical Deck Joint

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Joint Busters I Double Click to See Video

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Joint Busters II Double Click to See Video

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High-Pressure Power Washer

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

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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

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Local Model

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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

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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

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Questions?