Post on 10-Dec-2021
Seismic Design of Adjacent Rail Bridges in Deep Liquefiable Soils
Kelly Burnell, PE, Kleinfelder, San Diego, CAEbrahim Amirihormozaki, PhD, PE, Kleinfelder, San Diego, CA
Project Purposes
Carries Commuter, Amtrak and BNSF Freight rail linesConstruct 0.9-mile segment of second main track
-LOSSAN Project-
Project Purposes
11 mile Extension9 new stations
-Mid-Coast LightrailExtension Project-
San Diego River Bridge
200 ft
Proposed Mid-Coast LRT Bridge
Existing LOSSAN BR 263.8
Existing LRT Bridge
N
Proposed LOSSAN Bridge Double Track
Ocean Beach Bike Path
Typical SectionMid-Coast Lightrail BridgeNew LOSSAN Bridge
Design Criteria for Different Structures
AREMA– 3 Level Seismic Performance
Criteria– Site Specific RSA
PGA (g)
Return Period(years)
Performance
Serviceability 0.13 100 Minor Damage, Structure useable
Ultimate 0.27 500 Inspectable Damage
Survivability 0.53 2400 Collapse Prevention
Design Criteria for Different Structures
AREMA– 3 Level Seismic Performance
Criteria– Site Specific RSA
Mid-Coast Lightrail– Caltrans Seismic Design
Criteria• 1000-yr Return Period• PGA – 0.42g• Collapse PreventionPGA
(g)Return Period(years)
Performance
Serviceability 0.13 100 Minor Damage, Structure useable
Ultimate 0.27 500 Inspectable Damage
Survivability 0.53 2400 Collapse Prevention
Response Spectra
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 1 2 3 4 5 6
PGA
(g)
Period (sec)
ARS Curves
Lightrail
AREMA - Level 1
AREMA - Level 2
AREMA- Level 3
River Soil Conditions During Earthquake
Ultimate and Survivability Events – Liquefaction up to 80’ deepScour is up to 20 feetSlope Stability and Lateral Spreading
50
0
-50
-100
Original Approach – Ground Improvement
Original Approach – Ground Improvement
Ground improvement 90 feet deepConflicts with existing foundationsStaging of ground improvement
Existing Trolley Bridge Approach– Ground Improvement
Ground Improvement around Shafts
Alternative Approach – Permanent Steel Casings
LiquifiableAlluviam
Dense Gravels
11’
9’
San Diego River
Approx. $4M Cost Savings
Alternative Approach
Why not just use larger diameter conventional shafts?
Seismic Design of Superstructure
EQ EQ
Column Column
Bent Cap
Bearing
Deck
Girder
Floor Beam
Seismic Design of Superstructure
Bent Elevation
Seismic Design of Superstructure
Local Seismic Design
Global Seismic Design
Bridge Plan
Seismic Force
Seismic Design of Superstructure
Resisting Cross Section
Seismic Force
Seismic Design of Superstructure
Resisting Cross Section
Seismic Force
Seismic Design of Superstructure
Resisting Cross Section
Seismic Force
Seismic Design of Superstructure
Finite Element Model (SAP 2000)
Seismic Design of Superstructure
Bridge Plan
Seismic Force
Shear Flow
Seismic Design of Superstructure
1. Simplified Resisting Cross Section
2. Pay Attention to Shear Flow actions at ends of floor beams
Seismic Design of Superstructure – Key Points