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

BRIDGE PBEE Dr. Jinchi Lu, Prof. Kevin R. Mackie, Prof. Ahmed Elgamal

CASE STUDY

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

2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY SOIL DEFORMABILITY

METHODOLOGY 1.Specification of Ground Motion Input; 2.Bridge-Ground Finite Element Model; 3.Performance-Based Earthquake Engineering Quantities

STEP 1: INPUT GROUND MOTION PEER NGA database 5 bins of 20 motions: Mw= ; R = km Mw= ; R = km Mw= ; R = km Mw= ; R = km Mw= ; R = 0-15 km

STEP 2: F.E. MODEL FIBER SECTIONS ABUTMENT: ELASTIC ELEMENTS DECK: FORCE- BASED ELEMENTS SOIL: 9-NODE BRICK ELEMENTS

STEP 3: PERFORMANCE GROUPS (PGs) TOTAL REPAIR COST RATIO (%) TOTAL REPAIR TIME (CWD)

PILOT INVESTIGATION - BASE ISOLATION TECHNIQUE ASSESSMENT - SOIL DEFORMABILITY RESPONSE

2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY PBEE RESULTS (MODEL COMPARISON)

MODEL 1 – SIMPLE ROLLER ISOLATOR Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3

influence of SOIL STRENGHT (JEN MOTION)

SOFT SOIL STIFF SOIL Deformation for JEN motion at t=10.15 sec SCALE 200 MODEL 1 – influence of SOIL STRENGHT

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 1 – SIMPLE ROLLER ISOLATOR

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 2 – ABUTMENT ISOLATION

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 2 – ABUTMENT ISOLATION

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 3 – COLUMN ISOLATION

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 3 – COLUMN ISOLATION

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MODEL 4 – FULL ISOLATION

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MODEL 4 – FULL ISOLATION

2 HPs: 1. ELASTIC SPRING ELEMENTS; 2. LONGITUDINAL BEHAVIOUR ONLY PBEE RESULTS (SOIL COMPARISON)

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 STIFF CLAY

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) STIFF CLAY

MODEL 4 – Full isolation MODEL 2 – Abutment isolation Deformation for JEN motion at t=10.15 sec SCALE 200 STIFF CLAY

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 MEDIUM CLAY

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) MEDIUM CLAY

Max Long. Drift Ratio (Column) - PG1 Max Long. Relative Deck End Abutment Displacement – PG3 SOFT CLAY

Total Repair Time (Crew Working Days, CWD) Total Repair Cost Ratio (%) SOFT CLAY

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

FURTHER APPLICATIONS - TRANSVERSAL EFFECTS ASSESSMENT - IMPLEMENTATION OF NON LINEAR MODELS FOR ISOLATORS

THANK YOU FOR YOUR ATTENTION!