mae center research success with dots past and future neil m. hawkins - professor emeritus...
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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.