Davide Forcellini, Univ. of San Marino

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SEISMIC ASSESSMENT OF ISOLATED BRIDGE
CONFIGURATIONS ADOPTING A PBEE METHODOLOGY
Davide Forcellini, Univ. of San Marino Prof.
Ahmed Elgamal, Dr. Jinchi Lu, UC San
Diego Prof. Kevin Mackie, Univ. of Central
Florida
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BRIDGE PBEE
Dr. Jinchi Lu, Prof. Kevin R. Mackie, Prof. Ahmed
Elgamal http//peer.berkeley.edu/bridgepbee/
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CASE STUDY
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CONFIGURATIONS
Assumptions 1. Isolators represented by ELASTIC
SPRING ELEMENTS 2. FULL 3D MODEL WITH
LONGITUDINAL SHAKING ONLY
2 HPs 1. ELASTIC SPRING ELEMENTS 2.
LONGITUDINAL BEHAVIOUR ONLY
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SOIL DEFORMABILITY
2 HPs 1. ELASTIC SPRING ELEMENTS 2.
LONGITUDINAL BEHAVIOUR ONLY
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METHODOLOGY

• Specification of Ground Motion Input
• Bridge-Ground Finite Element Model
• Performance-Based Earthquake Engineering
  Quantities

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STEP 1 INPUT GROUND MOTION
PEER NGA database http//peer.berkeley.edu/nga/
5 bins of 20 motions Mw 6.5-7.2 R 15-30 km
Mw 6.5-7.2 R 30-60 km Mw 5.8-6.5 R 15-30
km Mw 5.8-6.5 R 30-60 km Mw 5.8-7.2 R
0-15 km
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STEP 2 F.E. MODEL
DECK FORCE-BASED ELEMENTS
ABUTMENT ELASTIC ELEMENTS
FIBER SECTIONS
SOIL 9-NODE BRICK ELEMENTS
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STEP 3 PERFORMANCE GROUPS (PGs)
TOTAL REPAIR COST RATIO () TOTAL REPAIR TIME
(CWD)
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PILOT INVESTIGATION

• BASE ISOLATION TECHNIQUE ASSESSMENT
• SOIL DEFORMABILITY RESPONSE

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PBEE RESULTS(MODEL COMPARISON)
2 HPs 1. ELASTIC SPRING ELEMENTS 2.
LONGITUDINAL BEHAVIOUR ONLY
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MODEL 1 SIMPLE ROLLER ISOLATOR
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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influence of SOIL STRENGHT (JEN MOTION)
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MODEL 1 influence of SOIL STRENGHT
Deformation for JEN motion at t10.15 sec SCALE
200
STIFF SOIL
SOFT SOIL
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MODEL 1 SIMPLE ROLLER ISOLATOR
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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MODEL 2 ABUTMENT ISOLATION
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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MODEL 2 ABUTMENT ISOLATION
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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MODEL 3 COLUMN ISOLATION
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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MODEL 3 COLUMN ISOLATION
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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MODEL 4 FULL ISOLATION
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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MODEL 4 FULL ISOLATION
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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PBEE RESULTS(SOIL COMPARISON)
2 HPs 1. ELASTIC SPRING ELEMENTS 2.
LONGITUDINAL BEHAVIOUR ONLY
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STIFF CLAY
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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STIFF CLAY
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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STIFF CLAY
Deformation for JEN motion at t10.15 sec SCALE
200
MODEL 2 Abutment isolation
MODEL 4 Full isolation
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MEDIUM CLAY
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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MEDIUM CLAY
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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SOFT CLAY
Max Long. Drift Ratio (Column) - PG1
Max Long. Relative Deck End Abutment
Displacement PG3
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SOFT CLAY
Total Repair Cost Ratio ()
Total Repair Time (Crew Working Days, CWD)
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CONCLUSIONS

• GROUND ISOLATION IS A KEY PARAMETER
• THAT MAY SIGNIFICANTLY AFFECT SSI RESPONSE
• BENEFIT OF THE ISOLATION TECHNIQUE
• SAVE THE COLUMN, POSSIBLY AT THE ABUTMENTS
  EXPENSE
• ROLE OF DEEP FOUNDATIONS UNDER THE ABUTMENT
• PREVENTING SETTLEMENTS (REDUCING REPAIR COSTS)
• TRANSVERSAL EFFECTS

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FURTHER APPLICATIONS

• TRANSVERSAL EFFECTS ASSESSMENT
• IMPLEMENTATION OF NON LINEAR MODELS FOR
  ISOLATORS

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THANK YOU FOR YOUR ATTENTION!