MAE CENTER RESEARCH SUCCESS WITH DOTs

Past and Future

Neil M. Hawkins - Professor EmeritusUniversity 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

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

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

FINANCIAL IMPACTS

• REVENUE LOSSES

• FACILITY REPAIR COSTS*

• LIABILITY EXPOSURE

• RESPONSIBILITY TO SOCIETY*

• Road* vs. Rail

THE HIGHWAY SYSTEM LIFELINE

• SPACIALLY DISTRIBUTED COMPONENTSINTERCONNECTED 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

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)

systems integration enabling technologies fundamental knowledgekey:

Deep SoilResponse

Deep SoilResponse

GT-19

SE-3

InventoryTechnologies

InventoryTechnologies

DS-2

ResponseAnalysisTools

ResponseAnalysisTools

DS-3

VulnerabilityFunctions

VulnerabilityFunctions

DS-4

RegionalResponseSimulation

RegionalResponseSimulation

DS-5

NetworkLoss

NetworkLoss

DS-6

NetworkVulnerability

NetworkVulnerability

DS-7a

Damage-Functionality

Damage-Functionality

DS-7b

S-E ImpactAssessment

S-E ImpactAssessment

DS-8

Risk Assessment

Risk Assessment

DS-9

SyntheticEQ Hazards

SyntheticEQ Hazards

HD-1

EQ SourceModeling

EQ SourceModeling

HD-2

Ground Motion Data

Ground Motion Data

HD-3

Gujarat-NMSZRelations

Gujarat-NMSZRelations

HD-4

EQ PathModeling

EQ PathModeling

HD-5

EQ SiteModeling

EQ SiteModeling

HD-6

Ground Deformations

Ground Deformations

HD-7

Decision Support Tools

Decision Support Tools

AcceptableConsequence

AcceptableConsequence

NetworkStrategies

NetworkStrategies Structure

RetrofitStrategies

StructureRetrofitStrategies Multi-Hazard

Application

Multi-HazardApplication

CM-1CM-2

CM-3

CM-4

CM-5

ST-14

Railroad BridgeAssessment

RR-5Fragility of

Transportation NetworksSE-13

Vulnerability of Air/RailNetworks

SE-11NetworkRetrofit

Benefit-Cost

ST-13Retrofit of BridgeColumnsST-12

ResponseModification

of Bridges

FoundationImprovement

FoundationImprovement

GT-5

Inventories ofTransportation

Networks

SE-28Emergency

PriorityRoutes

PartiallyRetrofitted

Bridges

Hazards Definition Thrust Area

Consequence Minimization Thrust Area

Damage Synthesis Thrust Area

ST-63Piers and

Abutments

ElastomericBearings

ST-62

ST-17

I-40 Bridge Instrumentation

ST-19Partially

RetrofittedBridges

Figure 2-4: Integration of Transportation Officials Stakeholder Thrust Area Research with Core Research

HIGHWAY INVENTORYNEW MADRID SEISMIC ZONE

• CHARACTERISTICS OF SYSTEM WITHIN AREA WITH 0.1g ACCELERATION FOR 500 YEAR RETURN PERIOD

• Age for 90% of BridgesInterstate 1966 + - 8 yearsOverpass 1963 + - 8years

• Type of Bridge 2/3rds ContinuousSteel : Concrete

4:1Overpasses1:1 Interstate

NBI Lacks Information on Bearing, Bent, Foundation, and Soil Characteristics

Interstate Bridge Characteristics Different to Secondary Road

HIGHWAY INVENTORYILLINOIS SOUTH OF I-70

Piers

Deck

Elevation of Typical Bridge

B1 B2 B3B4

Pier 1 Pier 2

Rocker BearingExpansion

Deck

Rocker BearingExpansion

Rocker BearingFixed

• 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 ContinuousSupport Type:50% Multi-Col. Pier40% Wall-Pier90% of Foundations

Pile Supported30% on Soil Likely to

Liquefy

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

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

RETROFIT STRATEGIES

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

RESTRAINER CABLES

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.

RESTRAINER CABLES

RESTRAINER CABLES – TEST RESULTS

Over 100 Restrainer Retrofits Modified by TN DOT

Cable Restrainer Load - Displacement

Displacement (in)

0 2 4 6 8 10

Load

(ki

p)0

10

20

30

40

50

60

Displacement (mm)

0 50 100 150 200 250

Load

(kN

)

0

50

100

150

200

250

13

2

Current - pier

Current - girder

Cable Yield Strength

Cable Ultimate Strength

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?

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.

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.

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.

bearings: 252 kips

columns: 360 kips

crashwall: 440 kips

cap beam: 340 kips

pile group: 450kips

pile cap: 380 kips

Base shear capacity in terms of pier elements

bearings: same

Modified & Wrappedcolumns: 220 kips

crashwall: same

cap beam: same

pile group: same

pile cap: same

As-built Retrofitted

COLUMN CAPACITY DESIGN RETROFIT

COLUMN AND BEAM WRAPPING

0

10

20

30

40

50

60

70

80

90

100

Earthquake Intensity

Pro

babi

lity

(%)

major damage

10% EQ 2% EQ

moderate damge

minor damage

Effect of As-Built versus Retrofit

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 Layer While Maintaining Vertical Load Capacity During EQ.

FOUNDATION IMPROVEMENT USING MICROPILES

C L

E x i s t i n g P i l e s

0 . 3 m1 5 m

D i a m e t e rE x i s t i n g P i l e s

L e n g t h

R e t r o f i t P i l e s

S t e e l P i p eC o n c r e t e P i l eR e i n f o r c e m e n t

D i a m e t e r L e n g t h

1 1 m1 5 m1 5 m0 . 0 1 3 m

0 . 1 6 3 m0 . 2 0 3 m

4 S p a c e s @ 1 . 8 m

1 0 . 8 m

9 . 0 m

0.9

m

E x i s t i n g P i l e s

1.8

m1 .

8 m

1 . 3 5 m

P i l e sR e t r o f i t

E x i s t i n g P i l e C a pR e t r o f i t P i l e s

1.35

m0 .

9 m

0 .9

m

1 . 3 5 m

R e t r o f i t P i l e s

0.9

mP L A N V I E W

E L E V A T I O N

E N D V I E W

1 .35

m

C E x i s t i n g P i l e sLE x i s t i n g P i l e s

0 . 3 m1 5 m

D i a m e t e rE x i s t i n g P i l e s

L e n g t h

R e t r o f i t P i l e s

S t e e l P i p eC o n c r e t e P i l eR e i n f o r c e m e n t

D i a m e t e r L e n g t h1 1 m

1 5 & 3 0 m1 5 m0 . 0 1 3 m

0 . 1 6 3 m0 . 2 0 3 m

1 . 8 m

4 . 5 m

2 . 7 m

E x i s t i n g P i l e s

1.8

m1 .

8 m

1 . 3 5 m

P i l e sR e t r o f i t

1.35

m0 .

9 m

0 .9

m1 .

35 m

1 . 3 5 mR e t r o f i t P i l e s

0.9

m

P L A N V I E W

E L E V A T I O N

3 x 10 Retrofitted Pile Group

3x3 Retrofitted Pile Group

Case Study Foundations

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

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)

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.