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MAE CENTER RESEARCH SUCCESS WITH DOTs Past and Future

MAE CENTER RESEARCH SUCCESS WITH DOTs Past and Future. Neil M. Hawkins - Professor Emeritus University of Illinois MAE Center Annual Meeting - 2002.

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MAE CENTER RESEARCH SUCCESS WITH DOTs Past and Future

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  1. MAE CENTER RESEARCH SUCCESS WITH DOTsPast and Future Neil M. Hawkins - Professor Emeritus University of Illinois MAE Center Annual Meeting - 2002 With sincere appreciation of the contributions of Professors DeRoches and French (Georgia Tech), Aschheim, LaFave and Long (Illinois), Hwang (Memphis), and personnel from GaDOT, IDOT and TDOT and Caltrans

  2. ORGANIZATION OF PRESENTATION • BACKGROUND – Lifeline Considerations for Transportation Systems • BACKGROUND – The Highway System Lifeline • OVERVIEW OF MAE TRANSPORTATION RESEARCH ACTIVITIES AND SUCCESSES • VISION FOR FUTURE

  3. THE TRANSPORTATION SYSTEM AS A LIFELINE • DESIGN REQUIRES CONSIDERATION OF FACTORS DIFFERING FROM THOSE FOR BUILDINGS • ACCEPTABLE PERFORMANCE DEPENDS ON: • Functionality of System after Event and Not Life Safety During Event • Financial Impact of Event

  4. FINANCIAL IMPACTS • REVENUE LOSSES • FACILITY REPAIR COSTS* • LIABILITY EXPOSURE • RESPONSIBILITY TO SOCIETY* • Road* vs. Rail

  5. THE HIGHWAY SYSTEM LIFELINE • SPACIALLY DISTRIBUTED COMPONENTS INTERCONNECTED OPERATIONALY AND PHYSICALLY • REDUNDANCY ALLOWS SOME LEVEL OF LOCAL DAMAGE • AGENCY’S JURISDICTION DETERMINES ITS RESPONSIBILITIES • SEISMIC HAZARD DEFINED BETTER BY SCENARIO EVENT THAN PROBABILISTIC GROUND MOTION

  6. HIGHWAY LIFELINE SYSTEM DESIGN • PERFORMANCE GOALS FOR SCENARIO EARTHQUAKE – 2 Rather than 1.5 on Estimated Ground Motions? • IDENTIFICATION AND QUANTIFICATION OF HAZARD – Soil Liquefaction, Permanent Ground Deformations, Structural Movements and Failures, and Importance of EQ Event Relative to Other Hazards. • ASSESS DAMAGE STATE FOR SCENARIO EVENT Functionality of Components, Time and Cost to Repair. • EVALUATE SYSTEM FUNCTIONALITY- IDENTIFY RISK REDUCTION OPTIONS (CBE)

  7. HIGHWAY INVENTORYNEW MADRID SEISMIC ZONE • CHARACTERISTICS OF SYSTEM WITHIN AREA WITH 0.1g ACCELERATION FOR 500 YEAR RETURN PERIOD • Age for 90% of Bridges Interstate 1966 + - 8 years Overpass 1963 + - 8years • Type of Bridge 2/3rds Continuous Steel : Concrete 4:1Overpasses 1:1 Interstate NBI Lacks Information on Bearing, Bent, Foundation, and Soil Characteristics Interstate Bridge Characteristics Different to Secondary Road

  8. HIGHWAY INVENTORYILLINOIS SOUTHOF I-70 • BRIDGE CHARACTERISTICS VERY DIFFERENT TO CALIFORNIA BRIDGES. PIERS NOT INTEGRAL WITH BEAMS OR DECK. • 533 Bridges on Primary Emergency Routes (Interstates) • For 10% Sample: 2/3rds Steel Continuous Support Type: 50% Multi-Col. Pier 40% Wall-Pier 90% of Foundations Pile Supported 30% on Soil Likely to Liquefy

  9. VULNERABILITY-FUNCTIONALITYRELATIONSHIPS • EXPERT OPINION -“EMPIRICAL” RELATIONSHIPS – HAZUS • ANALYTICAL RELATIONSHIPS • Approach Slabs • Major River Crossing • Pavement • “Standard” Bridge • EQ with 10% probability in 50 years causes little structural damage to as-built interstate bridges. • EQ with 2% probability in 50 years causes wide damage to steel bearings, columns and foundations

  10. DAMAGE TYPES BRITTLE • Bearing or Pedestal Failure • Beam or Column Shear Failure • Column Lap Splice • Pile Shear or Pullout DUCTILE • Bearing Overturning • Excessive Pier Drift • Excessive Ground Displ. • Pile Flexure

  11. RETROFITSTRATEGIES • Restrainer Cables • Elastomeric Bearings • Column and Cap Beam Wrapping • Micropile Additions

  12. RESTRAINERCABLES Restrainer Cables are used to ensure that bridge beams movements relative to the bearings are restricted and beams cannot displace off bearings longitudinally or transversally.

  13. RESTRAINER CABLES

  14. RESTRAINER CABLES – TEST RESULTS Over 100 Restrainer Retrofits Modified by TN DOT

  15. ELASTOMERIC BEARINGS • Allows for Temperature Effects. While Bearings Compress Little They Deform Easily in Shear. • Hysteresis Small W/o Slip at Interface and Large with Slip. • Are Hysteresis Characteristics Advantageous for EQ Effects? • Does Stiffening of Elastomer with Decreasing Temperature Obviate Beneficial Effects for EQ?

  16. ELASTOMERIC BEARINGS • Tests Conducted on New and Used Bearings to Find Changes in Slip, Stiffness and Hysteretic Characteristics with Decreasing Temperature and Increasing Cyclic Deformations. • Dynamic Analyses Made For Typical 3 Span Bridge with Fixed Bearing at Central Pier and Elastomeric Type II Bearings at Side Piers and Type I at Abutments.

  17. ELASTOMERIC BEARINGS • Temperature Effect Unpredictable. Vary Widely with Materials Used by Manufacturer • Elastomeric Bearing Use Can Reduce or Increase Pier Forces. Type and Location Must Be Properly Selected.

  18. COLUMN AND BEAM WRAPPING • Prevents Shear and Lap Splice Failures and Increases Flexural Ductility Capacity. • Steel or Composite Placed as Bands or as Encasement. Effectiveness Varies with Form and Quality Control. • Encasement More Aesthetically Pleasing But Results in Accelerated Deterioration if Located Below Deck Joint. • Effective on Deteriorated Members if Member Properly Repaired First.

  19. COLUMN CAPACITY DESIGN RETROFIT bearings: 252 kips bearings: same cap beam: 340 kips cap beam: same Modified & Wrapped columns: 220 kips columns: 360 kips crashwall: 440 kips crashwall: same pile cap: 380 kips pile cap: same pile group: 450kips pile group: same Retrofitted As-built Base shear capacity in terms of pier elements

  20. COLUMN AND BEAM WRAPPING

  21. FOUNDATION IMPROVEMENT WITH MICROPILES • To Increase Foundation Capacity or Stiffness • To Resist Overturning Where Existing Cap to Pile Connections Are Inadequate • To Extend Piles Below Liquefiable LayerWhile Maintaining Vertical Load Capacity During EQ.

  22. FOUNDATION IMPROVEMENT USING MICROPILES Case Study Foundations 3 x 10 Retrofitted Pile Group 3x3 Retrofitted Pile Group

  23. FOUNDATION IMPROVEMENT USING MICROPLIES • Stiffness Increased 50% with 3x3 Pile Addition. • Even With Retrofit Liquefaction Near Surface Substantially Reduced Pier Lateral Stiffness. • Dynamic Rotational Stiffness Increased Regardless of Which Soil Layer Liquefied. • Stiffness in Field Tests Less Than Predicted

  24. VULNERABILITY- FUNCTIONALITY FOR MID-AMERICA BRIDGES • Methodology to Derive Relationships, Repair Costs and Recovery Time Developed By Hwang (Memphis). • Response of Typical Multi-Span Bridge Controlled by Response of Central Pier. • Vulnerability Functions Derived for “Standard” Bridge for Longitudinal (GaTech) and Transverse Directions (UIUC)

  25. VISION FOR FUTURE • Consensus Criteria Developed for CBE and Performance Based Design of EQ Emergency Routes in NMSZ Using FHWA Pooled Funds. - Design All New, and Systematically Upgrade All Existing, Major River Crossings and Their Approaches to AASHTO-LRFD Seismic Criteria. - Identify Life Safety Needs of Communities and Design and Upgrade Routes Consistent with Those Needs. - Design Other New Structures, and Upgrade Other Existing Structures, to EQ with 10 % PE in 50 years. • MAEC Has Developed The Tools and Skilled Personnel to Successfully Complete That Task.

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