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Davide Forcellini, Univ. of San Marino Prof. Ahmed Elgamal, Dr. Jinchi Lu, UC San Diego Prof. Kevin Mackie, Univ. of Central Florida SEISMIC ASSESSMENT OF ISOLATED BRIDGE CONFIGURATIONS ADOPTING A PBEE METHODOLOGY
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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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2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY CONFIGURATIONS Assumptions: 1. Isolators represented by ELASTIC SPRING ELEMENTS 2. FULL 3D MODEL WITH LONGITUDINAL SHAKING ONLY
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2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY SOIL DEFORMABILITY
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METHODOLOGY 1.Specification of Ground Motion Input; 2.Bridge-Ground Finite Element Model; 3.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 FIBER SECTIONS ABUTMENT: ELASTIC ELEMENTS DECK: FORCE- BASED ELEMENTS 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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2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY PBEE RESULTS (MODEL COMPARISON)
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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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SOFT SOIL STIFF SOIL Deformation for JEN motion at t=10.15 sec SCALE 200 MODEL 1 – influence of SOIL STRENGHT
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 1 – SIMPLE ROLLER ISOLATOR
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 2 – ABUTMENT ISOLATION
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 2 – ABUTMENT ISOLATION
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 3 – COLUMN ISOLATION
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 3 – COLUMN ISOLATION
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 4 – FULL ISOLATION
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 4 – FULL ISOLATION
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2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY PBEE RESULTS (SOIL COMPARISON)
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 STIFF CLAY
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) STIFF CLAY
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MODEL 4 – Full isolation MODEL 2 – Abutment isolation Deformation for JEN motion at t=10.15 sec SCALE 200 STIFF CLAY
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MEDIUM CLAY
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MEDIUM CLAY
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Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 SOFT CLAY
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Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) SOFT CLAY
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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 ABUTMENT’S 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!
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