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Interaction of MSE Abutments with Superstructures under Seismic Loading
The document discusses the seismic performance of Mechanically Stabilized Earth (MSE) bridge abutments as part of research presented by Prof. John S. McCartney and Yewei Zheng from UC San Diego. It covers numerical simulations, physical testing methods, and the introduction of a new Master’s program in Geotechnical Engineering aimed at addressing local engineering challenges and improving geotechnical practices. The study aims to enhance design guidelines for MSE bridge abutments considering both static and seismic load conditions.
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Interaction of MSE Abutments with Superstructures under Seismic Loading
- 1. 2/16/2017 1 Interaction of MSE Abutments with Superstructures under Seismic Loading Prof. John S. McCartney and Yewei Zheng University of California San Diego Department of Structural Engineering Presentation to: GI of ASCE Orange County Section November 3, 2016 Presentation Overview 2 2 • Personal Research Introduction •Geotechnical Engineering at UCSD – Faculty – Facilities – New MS in Geotechnical Engineering • Technical Presentation: MSE Bridge Abutments – Motivation – Numerical Simulations with FLAC – Experimental Shaking Table Testing Program – Unsaturated Soil Aspect: Apparent Cohesion Estimates – Preliminary Results
- 2. 2/16/2017 2 3 Personal Research Introduction University of ColoradoBoulder BS/MS 2002 Faculty 2008-2014 University of Arkansas Faculty 2007-2008 University of California San Diego Faculty 2014-present University of Texas at Austin PhD 2007 Personal Research Focus Material Characterization 1. Unsaturated soil mechanics • Effective stress evaluation • Yielding mechanisms under changes in temperature and suction • Compression behavior of soils to high stresses • Thermal volume change mechanisms • Measurement of hydro/thermal properties (SWRC, HCF, TCF, VHCF) 2. Geosynthetics engineering 3. Shear strength of tire-derived aggregates Foundation Engineering 1. Centrifuge and full-scale modeling 2. Thermally active geotechnical systems (energy piles, geothermal heat storage systems, thermal soil improvement) 3. Offshore foundations Earthquake Engineering and Soil-Structure Interaction 1. Seismic response of unsaturated soils 2. Seismic response of MSE bridge abutments 4 4 Personal Research Introduction
- 3. 2/16/2017 3 Geotechnical Faculty at UCSD Ahmed Elgamal, Professor Enrique Luco, Professor JohnMcCartney, Associate Professor Ingrid Tomac, Asst. Research Scientist Tara Hutchinson, Professor 5 http://nees.ucsd.edu/facilities/shake-table.shtml Large-scale experiments (UC San Diego outdoor shake table) 6
- 4. 2/16/2017 4 Length of 6.7m (22 ft), width of 3 m (9.6 ft) and height of 4.7 m (15.2 ft) Facilities: Large Laminar Container 7 Facilities: Container for Retaining Wall Testing on the Large Shaking Table 8
- 5. 2/16/2017 5 Facilities: Powell LaboratoryShake Table 9 UCSD South Powell Structural Lab Shake Table: • Dimension: 10 ft. x 16 ft. • Shaking DOF: 1D in N‐S direction • Maximum gravity load: 80 kips • Dynamic stroke: ± 6 in. • Dynamic capacity: 90 kips • Large laminar container Facilities: Large Soil Pit for Foundation Testing 9m-deep soil pit and reaction wall for foundation testing Earth moving equipment: Bobcat, compactor, backhoe, crane 10
- 6. 2/16/2017 6 Facilities: Full-Scale Soil-BoreholeThermal Energy Storage System 11 0 5 10 15 20 25 30 35 Thermal energy (GJ) Solar Borehole Array Actidyn Model C61-3 Capacity: 50 g-ton Nominal radius: 1.70m Max. acc.: 130g UCSD Facilties: Geotechnical Centrifuge 12
- 7. 2/16/2017 7 Facilities: Update ofthe Geotechnical Centrifuge New features: • Data acquisition system and actuators • Containers (laminar, 3 clay tanks) • Shaking table • Control room 13 UCSD Element‐Scale Geotechnical Laboratory 14 Stress path triaxial testing setup Standard soil characterization equipment
- 8. 2/16/2017 8 UCSD Element‐Scale Geotechnical Laboratory 15 Geosynthetic pullout box Large-scaledirect shear/simple shear device for shear strength of large particle materials (tire derived aggregates) MS in Geotechnical Engineering at UCSD Goals: • Provide advanced degree option for students seeking to specialize in geotechnical engineering • Meet demand of local employers and interest of current undergraduate students • Build links to practice for students only interested in MS • Provide a recruiting tool for top MS students to continue for a PhD in geotechnical engineering • Facilitate completion of MS coursework in 4 quarters plus a summer • Leverage and build upon existing courses in the department • Build upon existing strengths: earthquake engineering, soil-structure interaction, computational geotechnics, and large-scale evaluation of geotechnical systems Program: • The M.S. degree program includes required core courses and technical electives • M.S. students must complete 48 units of graduate credits for graduation (12 courses) • Suggested focus sequences: • Geotechnical engineering and geomechanics • Geotechnical earthquake engineering • Soil-structure interaction 16
- 9. 2/16/2017 9 MS in Geotechnical Engineering at UCSD Core Courses (Studentsmust take all four): • SE 271 Solid Mechanics for Structural & Aerospace Engineering • SE 241 Advanced Soil Mechanics • SE 242 Advanced Foundation Engineering • SE 250 Stability of Earth Slopes & Retaining Walls Geotechnical electives (students must select at least four): • SE 222 Geotechnical Earthquake Engineering • SE 226 Groundwater Engineering • SE 243 Soil-Structure Interaction • SE 244 Numerical Methods in Geomechanics • SE 247 Ground Improvement • SE 248 Engineering Properties of Soils • SE 207 Rock Mechanics • SE 207 Soil Dynamics • SE 207 Unsaturated Soil Mechanics Other technical electives (choose up to 4): • Students may select from a list of structural, computational mechanics, or geology courses for the remaining 4 technical electives 17 Geotechnical Engineering Graduate Student Organizations CalGeo Student Chapter (Initiated 2015) • Brings in local geotechnical engineers for seminars GeoInstitute Graduate Student Organization (Initiated 2016) • Facilitates engagement of graduate students in international geotechnical conferences 18
- 10. 2/16/2017 10 Technical Presentation: Seismic Response of MSE Bridge Abutments Roadways Slopes Embankments Retaining walls Bridge abutments •General trend is toward the use of GRS‐IBS abutments (close spacing, variable lengths, specific design details from FHWA), but current study is on MSE bridge abutments (length = 0.7H, load applied to bridge seat on reinforced soil mass) • GRS and MSE have many advantages over pile‐supported bridge abutments, including cost savings, easier and faster construction, and smoother transition 19 19 Geosynthetics in transportation applications: Acknowledgements 20 20 • Project sponsors: – Caltrans – Pooled fund members (WashDOT, UDOT, MDOT) • Collaborators – Yewei Zheng, Ph.D. Candidate – Prof. Benson Shing, Chair of SE at UCSD – Prof. Patrick Fox, Head of CEE at Penn State University
- 11. 2/16/2017 11 Research Motivation GRS bridge abutments have been widely used in US, but has not been adopted in California due to uncertainty about seismic performance: • Geotechnical: backfill settlementand facing displacement • Structural: bridge deck and seat movements, impact force between bridge deck and seat, and interaction between bridge superstructure and GRS abutment, overall philosophy of GRS vs. MSE (concerns with bridge deck being placed directly onto the reinforced soil mass) 21 21 MSE wall performance in Maule Earthquake, Chile Research Motivation GRS bridge abutments have been widely used in US, but has not been adopted in California due to uncertainty about seismic performance: • Geotechnical: backfill settlement and facing displacement • Structural: bridge deck and seat movements, impact force between bridge deck and seat, and interaction between bridge superstructure and GRS abutment, overall philosophy of GRS vs. MSE (concerns with bridge deck being placed directly onto the reinforced soil mass) 22 22 MSE bridge abutment performance in Maule Earthquake, Chile
- 12. 2/16/2017 12 Literature Review – Static Performance • Lee and Wu (2004) reviewed several case studies of in‐ service GRS abutments and reported satisfactory performance under service load conditions •Adams et al. (2011) reported excellent performance for five in‐service GRS‐IBS abutments • Field and laboratory static loading tests indicate that the GRS piers and abutments had satisfactory performance under design loads and relatively high load‐bearing capacity (Adams 1997; Gotteland et al. 1997; Ketchart and Wu 1997; Wu et al. 2001, 2006; Adams et al. 2011; Nicks et al. 2013) 23 23 Literature Review – Seismic Performance • El‐Emam and Bathurst (2004, 2005, 2007) performed a series of shake table tests on reduced‐scale GRS walls with a full‐height rigid facing panel • Ling et al. (2005, 2012) conducted full‐scale shake table tests on GRS walls with modular block facing using fine sand and silty sand as backfill soils • Yen et al. (2011) found that GRS abutments performed well from post‐earthquake reconnaissance for 2010 Maule Earthquake • Helwany et al. (2012) conducted large‐scale shake table tests on a GRS abutment and found that it can sustain sin motion up to 1g without significant distresses 24 24
- 13. 2/16/2017 13 Literature Review – Seismic Performance References Height (m) Facing BackfillReinforcement Input motion Findings El‐Emam and Bathurst (2004, 2005, 2007) 1.0 rigid panel sand polyester geogrid sinusoidal facing lateral displacement could be reduced by using smaller facing panel mass, inclined facing panels, longer reinforcement, stiffer reinforcement, and smaller vertical reinforcement spacing Ling et al. (2005, 2012) 2.8 modular block sand/silty sand polyester geogrid earthquake longer reinforcement at top layer and smaller reinforcement vertical spacing improved seismic performance; vertical acceleration has little influence; apparent cohesion improved seismic performance Helwany et al. (2012) 3.6 modular block sand woven geotextile sinusoidal GRS abutment remained functional under sinusoidal motions up to 1.0 g 25 25 Project Objectives • Investigate performance of MSE abutments for service limit state, strength limit state, and extreme event limit state (seismic loading) • Approaches: • Numerical simulations using FLAC2D and FLAC3D • ½ scale experimental physical modeling • Improve design guidelines for external and internal stability of MSE bridge abutments for static and seismic loading 0 ~ 200 kPa 200 ~ > 1000 kPa extreme loadings service limit strength limit extreme event limit 26 26
- 14. 2/16/2017 14 Validation of FLAC 2D Model for Static Loading Founders/Meadows Parkway Bridge,CO (Abu-Hejleh et al. 2002) Extensive instrumentation 27 27 Instrumented section 800 (after Abu-Hejleh et al. 2002) 28 28 Validation of FLAC 2D Model for Static Loading
- 15. 2/16/2017 15 Backfill Soil for Founders‐Meadows Backfill treated as an elastic‐plastic material withMohr‐Coulomb failure criterion, and Duncan‐Chang hyperbolic relationship Comparison of measured and simulated triaxial test results 0 200 400 600 800 1000 1200 0 2 4 6 8 10 Simulated Measured (69 kPa) Measured (138 kPa) Measured (207 kPa) DeviatoricStress(kPa) Axial Strain (%) 3' = 207 kPa 3' = 138 kPa 3' = 69 kPa -1.0 -0.5 0 0.5 1.0 1.5 2.0 0 2 4 6 8 10 Simulated Measured (69 kPa) Measured (138 kPa) Measured (207 kPa) VolumetricStrain(%) 3' = 69 kPa 3' = 138 kPa Axial Strain (%) 3' = 207 kPa 29 29 Reinforcement and Interfaces linearly elastic‐plastic cable elements Axial strain Relative displacement Tensile force Shear force Shear strength Normal force interface elements with Coulomb sliding Reinforcement: Interfaces: 30 30
- 16. 2/16/2017 16 Initial Numerical Model Validation In general, simulated results are in good agreement with field measurements, including displacements, lateral and vertical earth pressures, and tensile strains and forces in reinforcement Lower Wall Construction (Stage 1) Bridge/Approach Construction (Stages2-6) Traffic Loading (Stage 7) Incremental Maximum Lateral Facing Displacement (mm) Measured 12 10 5 Simulated HR n/a 9 3 Simulated NHR 11 14 4 Incremental Bridge Footing Settlement (mm) Measured n/a 12 10 Simulated HR n/a 13 5 Simulated NHR n/a 14 7 Incremental displacements for Founders/Meadows GRS bridge abutment (Zheng and Fox 2016 in JGGE) 0 1 2 3 4 5 6 0 2 4 6 8 10 12 14 16 Measured Simulated HR Simulated NHR Elevation(m) Lateral Facing Displacement (mm) Horizontal restraint (HR) from the bridge structure has important effect on abutment deflections 31 31 Shake Table Testing Program UCSD South Powell Structural Lab Shake Table: • Dimension: 10 ft. x 16 ft. • Shaking DOF: 1D in N‐S direction • Maximum gravity load: 80 kips • Dynamic stroke: ± 6 in. • Dynamic capacity: 90 kips Shake table testing has been successfully used to investigate seismic performance of GRS structures (El‐Emam and Bathurst 2004, 2005, 2007; Ling et al. 2005, 2012; Tatsuoka et al. 2009, 2012; Helwany et al. 2012) 32 32
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- 18. 2/16/2017 18 1g Shake Table Similitude Relationships Scaling Factor λ=2 Length λ2 Density 1 1 Strain 1 1 Mass λ3 8 Acceleration 1 1 Velocity λ1/2 1.414 Stress λ 2 Stiffness λ2 4 Force λ3 8 Time λ1/2 1.414 Frequency λ‐1/2 0.707 Similitude relationships for 1 g shake table test (Iai 1989) Stress-strain relationships for model and prototype (Rocha 1957; Roscoe 1968) 35 35 Goal: same strains in model and prototype UCSD Sand Backfill 0 20 40 60 80 100 0.01 0.1 1 10 PercentFiner(%) Particle Size (mm) SW Sand Cu = 6.1, Cz = 0 36 36
- 19. 2/16/2017 19 UCSD Sand Backfill -2 0 2 4 6 8 0 2 46 8 10 VolumetricStrain(%) 3' = 7 kPa 3' = 138 kPa Axial Strain (%) 3' = 207 kPa 3' = 69 kPa 3' = 34 kPa 0 200 400 600 800 1000 1200 0 2 4 6 8 10 DeviatorStress(kPa) Axial Strain (%) 3' = 69 kPa 3' = 34 kPa 3' = 7 kPa 3' = 138 kPa 3' = 207 kPa 37 37 UCSD Sand Backfill 38 38 Properties Value Specific gravity, Gs 2.61 Coefficient of uniformity, Cu 6.1 Coefficient of curvature, Cz 1.0 Maximum void ratio, emax 0.853 Minimum void ratio, emin 0.371 Recompression index, Cr 0.001 Compression index, Cc 0.006 Friction angle, ′ (°) 49.3 van Genuchten (1980) SWRC model parameter, vG (kPa‐1) 0.5 van Genuchten (1980) SWRC model parameter, NvG 2.1 Drying curve volumetric water content at zero suction, d 0.319 Wetting curve volumetric water content at zero suction, w 0.204 Residual volumetric water content, r 0
- 20. 2/16/2017 20 0 250 500 750 1000 1 10 100 TensileStiffness(kN/m) StrainRate (%/min) Geogrid Reinforcement 0 200 400 600 800 1000 1200 1400 0 5 10 15 20 TensileLoad(N) Strain (%) 10%/min - 1 10%/min - 2 10%/min - 3 0 200 400 600 800 1000 1200 1400 0 5 10 15 20TensileLoad(N) Strain (%) 1%/min 5%/min 10%/min 50%/min 100%/min J = 580 kN/m 2% Typical range J = 378 kN/m <1% 39 39 Prototype (target) Model (used in tests) Manufacturer Model ‐ Tensar LH800 Materials HDPE HDPE Aperture Size (MD x TD) 9 in x 2.4 in 4.5 in x 1.2 in Stiffness (kip/ft) 104 kip/ft 26 kip/ft Length – 0.7H (ft) 9.8 4.9 Shaking Table Testing Plan 40 40 Focus of this presentation Test 1 2 3 4 5 6 7 Purpose Reduced Bridge Load Reinf. spacing Reinf. stiffness Baseline Baseline Steel mesh Reduced Bridge Load (repeat) Shaking Direction Long. Long. Long. Long. Transverse Long. Long. Reinf. spacing (in) 6 12 6 6 6 6 6 Reinf. stiffness (kip/ft) 25.9 25.9 12.9 25.9 25.9 327.6 25.9 Average bridge surcharge (psf) 940 1340 1340 1340 1340 1340 940
- 21. 2/16/2017 21 Experimental/Numerical Design • Bridge deck: 6.4 m long, 0.9 m wide, and 0.45 m deep, 2.3 m clearance •Bridge load: 7 kN + 65 kN + 33 kN (vertical stress = 63 kPa) • MSE abutment: 2.15 m high lower wall and 0.6 m high upper wall • Reinforcement: 0.15 m spacing and 1.5 m (0.7H) long GRS abutment Bridge seat Bridge deck Support wall Sliding platform Upper wall Shake table Steel beam Reaction wall 41 41 Additional Schematics 42 42
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- 24. 2/16/2017 24 Instrumentation Strain gages String potentiometers Linearpotentiometers Pressure cells Load cells Accelerometers Dielectric sensors 47 47 Instrumentation Plan Longitudinal Section L1 Longitudinal Section L2 Transverse Section T1 48 48 L1 T1
- 25. 2/16/2017 25 Estimates of Apparent Cohesion in Backfill 49 49 0 0.5 1.0 1.5 2.0 2.5 0 2 46 8 10 Elevation,z(m) Gravimetric Water Content (%) S = wGs/e 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.1 1.0 10.0 100.0 1000.0 Degree of saturation, S Suction, ψ (kPa) Drying Wetting e = 0.50 n = 0.33 p = 0 relative density = 60% α = 0.85 N = 1.80 α = 0.65 N = 1.80 res res e S SS S 1 vG vG NN vGeS 1 1 1 Apparent Cohesion 50 50 0 0.5 1.0 1.5 2.0 2.5 0 2 4 6 8 10 12 14 Drying Wetting Elevation,z(m) Apparent Cohesion (kPa) f = ’tan’ = (Se)tan’ ’ = (-ua)+s ’ = (-ua)+ ’ = (-ua)+Se ’ = (Se) SWRC is needed for to estimate the apparent cohesion, but otherwise the material properties for saturated/dry soil can be used Apparent cohesion changes with wetting/drying: Effective stress:
- 26. 2/16/2017 26 Concept of Applied Shaking Motions 51 51 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0 5 1015 20 25 30 35 40 Original Scaled Acceleration(g) Time (s) -150 -100 -50 0 50 100 150 0 5 10 15 20 25 30 35 40 Original Scaled Displacement(mm) Time (s) • Frequency of motion is reduced by √2, which shortens the duration • Acceleration amplitude stays the same • Displacement amplitude is scaled by half Typical Response Spectrum of Applied Motion 52 52 0 0.2 0.4 0.6 0.8 1.0 1.2 0.1 1 10 Target input Shaking table PsuedoSpectralAcceleration(g) Frequency (Hz) 1940 Imperial Valley Motion (El Centro Station): 5% damping
- 27. 2/16/2017 27 Applied Shaking Motions Shaking Number Motion Maximum Acceleration (g) Maximum Displacement (mm) Control Mode 1 White Noise 0.126.1 Acceleration 2 1940 Imperial Valley 0.31 66 Displacement 3 White Noise 0.1 26.1 Acceleration 4 2010 Maule 0.40 109 Displacement 5 White Noise 0.1 26.1 Acceleration 6 1994 Northridge 0.58 88.7 Displacement 7 White Noise 0.1 26.1 Acceleration 8 Sin @ 0.5 Hz 0.05 50 Displacement 9 Sin @ 1 Hz 0.1 25 Displacement 10 Sin @ 2 Hz 0.2 12.5 Displacement 11 Sin @ 5 Hz 0.25 2.5 Displacement 12 White Noise 0.1 26.1 Acceleration 53 53 Applied Shaking Motions • White noise – characterize frequencies • Earthquake motions (frequencies scaled) 1. 1940 Imperial Valley (El Centro) – PGA = 0.31 g/ PGD = 66 mm 2. 2010 Maule (Concepcion) – PGA = 0.40 g/ PGD = 109 mm 3. 1994 Northridge (Newhall) – PGA = 0.58 g/ PGD = 89 mm • Sinusoidal motions (0.5, 1, 2, and 5 Hz) -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0 4 8 12 16 20 24 28 Acceleration(g) Time (s) -100 -50 0 50 100 0 4 8 12 16 20 24 28 Displacement(mm) Time (s) -60 -40 -20 0 20 40 60 0 5 10 15 20 25 30 35 40 Displacement(mm) Time (s) -3 -2 -1 0 1 2 3 0 5 10 15 20 25 30 35 40 Displacement(mm) Time (s) 0.5 Hz 5 Hz Imperial Valley ‐ AccelerationImperial Valley ‐ Displacement 54 54
- 28. 2/16/2017 28 Bridge Seat Settlements Test 4, MauleEarthquake SE SW NE NW Bridge Seat Instrumentation 55 55 Confinement of the soil at the back of the wall (south) leads to less variable strains during shaking -2 0 2 4 6 8 10 0 20 40 60 80 100 NW NE SW SE Settlement(mm) Time (s) -2 0 2 4 6 8 10 0 20 40 60 80 100 Settlement(mm) Time (s) Bridge Seat Settlements Test Vertical Stress (kPa) Residual Bridge Seat Settlements (mm) Bridge Deck Placement Imperial Valley Motion Maule Motion Northridge Motion Test 1 (reduced load) 44 1.4 2.7 2.5 ‐ Test 4 (baseline) 63 2.1 1.5 1.5 2.1 Note: Values are incremental for each testing stage, and are the average of the settlements of the four corners 56 56
- 29. 2/16/2017 29 Lateral Facing Displacements • Lateral face displacements generally increase with elevation • Residual displacements are incremental for each shaking event •Maximum dynamic lateral facing displacements are greater than residual values 57 57 0 0.5 1.0 1.5 2.0 0 1 2 3 4 5 6 EOC - Abutment Imperial Valley - Residual Imperial Valley - Max Maule - Residual Maule - Max Elevation,z(m) Lateral Facing Displacement (mm) Lateral Facing Displacements • Displacements for L1 are larger than L2 despite greater confinement in L1 • Displacements are larger for the Northridge Earthquake, which has larger PGA • Displacements for T1 are larger than L1 and L2 0 0.5 1.0 1.5 2.0 0 0.5 1.0 1.5 2.0 L1 L2 T1 Elevation(m) Lateral Facing Displacement (mm) 0 0.5 1.0 1.5 2.0 0 1 2 3 4 5 L1 L2 T1 Elevation(m) Lateral Facing Displacement (mm) Test 4 - Imperial Valley Motion Test 4 - Northridge Motion 58 58
- 30. 2/16/2017 30 Relative Movements of Bridge Seat and Top of the Wall Test Vertical Stress (kPa) Relative Bridge Seat Lateral Movements (mm) Imperial Valley Motion Maule Motion Northridge Motion Test 1 44 2.46.4 ‐ Test 4 63 ‐0.2 0.4 0 Note: Incremental average values, (‐) is toward the back of the wall 59 59 Fundamental Frequency from White Noise Motions 60 60 0 5 10 15 20 25 0 5 10 15 20 25 Shaking event 1 Shaking event 3 Shaking event 5 FourierAmplitude Frequency (Hz)
- 31. 2/16/2017 31 Acceleration Amplification • Acceleration amplification increases with elevation • Amplification ratios increase from retained soil zone to reinforced soil zone to wall facing •Amplification ratios are larger for L1 than L2 Imperial Valley Earthquake 0 0.5 1.0 1.5 2.0 0.8 1.0 1.2 1.4 1.6 1.8 L1 - Wall Facing L1 - Reinforced Soil Zone L1 - Retained Soil Zone L2 - Reinforced Soil Zone L2 - Retained Soil Zone Elevation(m) Acceleration Amplification Ratio 61 61 Bridge Seat and Deck Accelerations -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0 4 8 12 16 20 24 28 Bridge Seat Bridge Deck Acceleration(g) Time (s) Imperial Valley Earthquake Bridge deck: Max acceleration = 0.53 g Amplification ratio = 1.29 Bridge seat: Max acceleration = 0.64 g Amplification ratio = 1.56 62 62
- 32. 2/16/2017 32 Bridge Seat and Deck Accelerations 63 63 0 5 10 15 20 25 0 5 1015 20 25 Bridge deck/shaking table Bridge seat/shaking table FourierAmplitude Frequency (Hz) Bridge Seat and Deck Movements 64 64 -16 -12 -8 -4 0 4 8 12 16 0 20 40 60 80 100 East West HorizontalDisplacement(mm) Time (s) -16 -12 -8 -4 0 4 8 12 16 0 20 40 60 80 100 HorizontalDisplacement(mm) Time (s) Test 4 – Maule Motion
- 33. 2/16/2017 33 Bridge Seat and Deck Movements 65 65 -16 -12 -8 -4 0 4 8 12 16 0 20 4060 80 100 RelativeHorizontalDisplacement(mm) Time (s) Test 4 – Maule Motion Bridge Seat and Deck Movements -30 -20 -10 0 10 20 30 0 4 8 12 16 20 24 28 RelativeDisplacement(mm) Time (s) Relative Displacement (mm) 1940 Imperial Valley 2010 Maule 1994 Northridge Residual 2.1 1.4 ‐4.3 Maximum ‐ 6.8/8.3 ‐9.7/9.8 ‐30/20.6 Test 4 Bridge deck sliding relative to bridge seat (relative displacement) Northridge Earthquake seismic joint closed moving away from bridge seat moving towards bridge seat seismic joint remained open 66 66
- 34. 2/16/2017 34 Seismic Joint Closure 0 10 20 30 40 50 60 0 4 812 16 20 24 28 SeismicJointSize(mm) Time (s) Northridge Earthquake closed remained open 67 67 Horizontal Contact Forces: Earthquake -100 -50 0 50 100 0 4 8 12 16 20 24 28 Load Cell - East Load Cell - West HorizontalContactForce(kN) Time (s) Horizontal contact forces for the Northridge Earthquake, Test 4 68 68
- 35. 2/16/2017 35 Reinforcement Strains 69 69 0 0.05 0.10 0.15 0.20 Top Bottom x = 0.46m, z = 1.875 m 0 0.05 0.10 0.15 0.20 Top Bottom ReinforcementStrain(%) x = 0.46 m, z = 0.975 m 0 0.05 0.10 0.15 0.20 0 4 8 12 16 20 24 28 Top Bottom Time (s) x = 0.46 m, z = 0.075 m Test 4 1940 Imperial Valley Motion Reinforcement Strains 70 70 Test 4 1940 Imperial Valley Motion bridge load 0 0.1 0.2 0.3 Initial Maximum Minimum Residual z = 1.95 m layer 13 0 0.1 0.2 0.3 z = 1.50 m layer 10 0 0.1 0.2 0.3 ReinforcementStrain(%) z = 1.05 m layer 7 0 0.1 0.2 0.3 z = 0.60 m layer 4 0 0.1 0.2 0.3 0 0.5 1.0 1.5 2.0 z = 0.15 m layer 1 Distance from Facing, x (m)
- 36. 2/16/2017 36 Reinforcement Strains (Max.) Longitudinal Section L1 bridgeload ReinforcementStrain(%) 0 0.1 0.2 0.3 0.4 0.5 EOC Imperial Valley Maule Northridge z = 1.95 m layer 13 0 0.1 0.2 0.3 0.4 0.5 z = 1.05 m layer 7 0 0.1 0.2 0.3 0.4 0.5 0 0.5 1.0 1.5 2.0 z = 0.15 m layer 1 Distance from Facing (m) bridge load -0.1 0 0.1 0.2 0.3 0.4 EOC Imperial Valley Maule Northridge z = 1.95 m layer 13 -0.1 0 0.1 0.2 0.3 0.4 z = 1.5 m layer 10 -0.1 0 0.1 0.2 0.3 0.4 ReinforcementStrain(%) z = 1.05 m layer 7 -0.1 0 0.1 0.2 0.3 0.4 z = 0.6 m layer 4 -0.1 0 0.1 0.2 0.3 0.4 0 0.5 1.0 1.5 2.0 z = 0.15 m layer 1 Distance from Facing (m) bridge load ReinforcementStrain(%) 0 0.1 0.2 0.3 0.4 0.5 z = 1.95 m layer 13 0 0.1 0.2 0.3 0.4 0.5 z = 1.05 m layer 7 0 0.1 0.2 0.3 0.4 0.5 0 0.2 0.4 0.6 0.8 1.0 z = 0.15 m layer 1 Distance from Facing (m) Longitudinal Section L2 Transverse Section T1 max strain 71 71 Preliminary Findings • The bridge deck load was observed to lead to more static deformations (lateral and vertical), but less dynamic deformations due to the greater geosynthetic confinement • Lateral displacements are greater near the top of the wall but are not large enough to cause geotechnical concerns • Lateral displacements and acceleration responses for section L1 are larger than L2 • Acceleration amplifies with elevation, and amplification ratios increase from retained soil zone to reinforced soil zone to wall facing • Seismic‐induced reinforcement strains are largest near the wall face due to the inertia of the facing blocks • Seismic joint might close during shaking and result in impact force on the bridge seat, but only during high frequency sinusoidal movements or Northridge EQ • Overall, MSE abutments show good seismic performance in terms of lateral facing displacements and bridge seat movements 72 72