Seismic Retrofit of the I155 Bridge at Caruthersville, Missouri

1
Seismic Retrofit of the I-155 Bridge at
Caruthersville, Missouri

• Mark R. Capron, P.E.
• Jacobs

2
Presentation Overview

• Project team
• Description of the Bridge
• 1993 - 1994 Study
• Current Study
• Summary

3
Project Team

• MoDOT
• Tennessee DOT
• FHWA
• Jacobs
• Mid-America Earthquake (MAE) Center
• Fuller Mossbarger Scott and May (FMSM)

4
MAE Center Overview

• One of three Centers established by the National
  Science Foundation (NSF)
• Funded by NSF, 8 core universities, and joint
  collaborative projects with industry

Mid-America Earthquake Center
5
Description of the Bridge

• Bridge Structure
• Missouri 1,030 ft concrete approach spans
• Steel girder spans 2,150 ft, 2 girder,
  multi-girder
• Two span truss 920 ft and 520 ft
• Tennessee 2,480 ft concrete approach spans
• Designed and built in 1970s

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Concrete Approach Spans
Multiple Prestressed Concrete Girders
Composite Concrete Deck
Steel Bearings
Cap Beam
Multiple Concrete Columns

• 5 Hoops at 12
• Lap Splices

Tie Beam
Individual Pile Caps
H-Piles
Piers 2-14, 26-59

• 18 Embedment in cap
• No shear connectors
• Driven 40 50 feet

• No top reinforcement

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Steel Approach Spans
Non-Composite Lightweight Concrete Deck
Steel Two-Girder System
Steel Bearings
Multiple Concrete Columns

• 6 Hoops at 12
• Lap Splices

Pile Cap
H-Piles
Piers 15-18
Piers 22-25

• 36 Embedment in cap
• No shear connectors
• Driven 57 - 72 feet

Seal Course
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Truss Spans
Non-Composite Lightweight Concrete Deck
Steel Bearings
Multiple Concrete Columns
Tie Beam

• 6 Hoops at 12
• Lap Splices

Concrete Caisson
Seal Course
Piers 19-21
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Truss Superstructure
Hinge
Wind Transfer Device
Upper Lateral System
Deck Bearing System
Deck
Main Bearings
Lower Lateral System
Important elements of the earthquake resisting
system
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Subsurface Conditions

• River Alluvium
• Loose sand or soft to firm clay
• Upper 30 to 70 feet
• Shear wave velocities 500 to 600 fps
• Mississippi Embayment
• Sand, gravel, and hard clay
• Extends to bed rock at 2700 feet

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Project Location
12
Located 6 Miles From New Madrid Fault
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1993 1994 Seismic Study

• Study phases
• Evaluate existing structure (completed)
• Retrofit feasibility study (completed)
• Evaluation of the retrofitted structure
• Final report and cost estimate
• Criteria documents
• FHWA seismic retrofitting guidelines
  FHWA/RD-83-007
• FHWA seismic retrofitting manual FHWA-RD-94-052
  
• Performance objectives
• Life safety
• No collapse

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1993 1994 Seismic Study (continued)

• Widespread liquefaction to depths of 40 feet
• Dynamic settlement 3 to 17 inches
• Lateral spreading 1 to 13 feet
• Critical structural components have 25 to 60 of
  required capacity
• Conceptual retrofit costs
• 2.2 million restrainers only
• 38.4 million full retrofit
• MoDOT elected to hold project in 1994

Full retrofit of the bridge is a major project
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Current Seismic Study

• MoDOT selected Jacobs for completion of the
  Seismic Study
• Advance the previous study
• Develop alternative seismic retrofit strategies
  and conceptual cost estimates

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Advancing the Previous Study

• Ground motions
• Incorporate peer review comments
• Refine site specific ground motions
• Refine site characterization
• Liquefaction, evaluation and mitigation / ground
  failure
• Incorporate peer review comments
• Obtain additional soil data

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Advancing the Previous Study

• Structural retrofit
• Large capacity isolation bearings and dampers
• Push-over analysis of bents
• State-of-the-art soil structure interaction
• Conceptual cost estimates and constructability

Photo from Earthquake Protection Systems Inc.
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Organization of the Current Study
Task A Geotechnical Hazard Assessment Studies
FMSM
Task B Evaluation of the Retrofitted Structure
Task C Non-Linear Analysis with Retrofit and SSI
Task D Quantities and Cost Estimates
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Task A Geotechnical and Hazard Assessment Studies

• Supplement 1993-1994 borings and construction
  records
• Land borings SPT and CPT
• Laboratory testing
• Refraction/Reflection survey
• Spectral Analysis of Surface Waves (SASW)

Photo from FMSM
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Site Characterization

• Six soil profiles selected along alignment

Vs (ft/sec)
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Site Characterization

• Small-aperture seismic array
• Direct observation of spatial coherency from
  earthquake ground motions at small strains

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Site-Specific Seismic Hazard Assessment

• Earthquake sources
• Updated Central US recurrence relations
• Refined NMSZ characteristic earthquake models
• Finite-source and rupture directivity effects
• Seismic wave propagation
• Constrained attenuation relations
• Site effects
• Detailed site characterization
• Site response including effectsof deep, soft
  sediments
• Liquefaction-relatedground failures

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Site-Specific Design Spectra and Time Histories

• Uniform hazard response spectra
• 475, 1000 and 2,475-year return periods

Current Rock Spectra
Current Surface Spectra
Previous Rock Spectra
Previous Surface Spectra
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Site-Specific Design Spectra and Time Histories

• Time histories
• Modified recorded time histories from other
  seismic zones
• Two-component ground motions accounting for
  spatial coherency

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Liquefaction Evaluation

• Liquefaction initiation
• Simplified method using detailed SPCPT profiles
  to evaluation liquefaction susceptibility
• Shear wave velocity profiles
• Permanent ground deformations
• Empirical methods
• MAE-developed models
• Residual shear strength
• Empirical methods based on SPT
• Method based on critical state soil mechanics
• Mitigation Alternatives

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Task B Structural Evaluation

• Linear multi-mode analysis
• Existing structure with new site-specific ground
  motions
• Existing structure with ground motions updated
  for soil modifications
• Retrofitted Structure
• Pseudo static push-over analysis
• Large capacity isolation bearings in main span
• C/D ratios for critical components

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SAP2000 Model
4,245 Frame Elements 17,910 DOF
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Task C Non-Linear Analysis with SSI
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Structural Model SAP2000 and ZeusNL
Gap opening due to transverse rotation
Gap opening due to vertical rotation
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Soil and Foundation Modeling
Soil Profile
5
10
15
20
25
30
35
40
45
50
55
59
Bent No.
270
1
3
250
Mississippi River
1
2
5
5
4
6
6
200
Elevation in feet
7
5
150
8
7
100
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Foundation Types by Geometry
Soil Foundation Modeling
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
Type 8
Type 9
Type 10
Type 7
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3-D Foundation Model

• Foundation class 05 (Bent 10)

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Foundation Property Evaluation
Soil Foundation Modeling

• Lumped springs based on sophisticated soil model
• Better approximation than closed-form spring
  derivation
• Ignore interaction between different DOFs

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Task D Quantities and Cost Estimates

• Develop conceptual cost estimates for retrofit
  alternatives
• Design Risks
• Performance Objectives
• Retrofit Levels
• Constructability review

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Alternative Retrofit Levels

• Full retrofit
• Ground improvement
• Main spans
• High capacity isolation bearings
• Member and connection strengthening
• Foundation modifications
• Approach spans
• Ductility enhancement
• Foundation strengthening
• Bearing replacement
• Restrainers
• Partial Retrofit
• Retrofit to initiation of significant
  liquefaction and ground failures
• Retrofit to initiation of significant foundation
  failures
• Main spans only

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Summary

• Seismic retrofit of this bridge presents a
  challenging project
• Seismic evaluation advances the previous study
  and combines state-of-the practice with
  state-of-the art
• Study designed to develop retrofit alternatives

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Acknowledgments

• MoDOT
• MAE Center
• Amr Elnashai
• Youssef Hashash
• Aman Mwafy
• Glenn Rix
• Paul Bodin
• FMSM

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