The Alaskan Way Viaduct Steve Kramer University of Washington Seattle, Washington

The Alaskan Way Viaduct Steve Kramer University of Washington Seattle, Washington (The interesting stuff, not the structural stuff)

Alaskan Way Viaduct 2.2 miles long 86,000 vehicles per day North of Yesler Designed by City of Seattle Constructed in 1950 South of Yesler Designed by Washington State DOH Constructed in 1956

Alaskan Way Viaduct

© 1993 DeLorme Mapping Seattle Yesler Terrace Elliott Bay 99 Harborview Hospital U S Marina Hospital Mason Hospital Union Depot King Street Station Seattle University 1ST 4TH ALASKAN WAY BOREN E MADISON RAINIER AVE S S 1ST STEWART YESLER WAY I-5 RAMP I-90 © 1993 DeLorme Mapping Seattle section WSDOT section Alaskan Way Viaduct

Seattle section WSDOT section

Alaskan Way Viaduct Seattle Section

Alaskan Way Viaduct WSDOT Section

Seismic Vulnerability Concerns Loma Prieta earthquake M= km south of Oakland Cypress Structure Highway 17 in Oakland Double-deck reinforced concrete structure Similar age Similar design requirements Pile supported due to soft surficial soils

Cypress Structure

Alaskan Way Viaduct Investigations 1990 WSDOT internal review UW review UW/WSDOT investigation WSDOT seawall investigation

UW / WSDOT Investigation WSDOT Seawall Investigation Structural Engineering Aspects Geotechnical Engineering Aspects Seawall performance Effects on AWV Remediation strategies

Geotechnical Engineering Investigation Site characterization Seismic hazard analysis Ground response analyses Foundation response characteristics Evaluation of liquefaction hazards

Site Characterization Review of historical records Review of previous subsurface investigations Supplemental subsurface investigations ­ ­ SPT ­ ­ CPT ­ ­ Seismic cone ­ ­ Downhole seismic

Seattle, 1888 Historical Records

Seattle, 1884 Historical Records Lake Washington Yesler I-5

Looking NW from Beacon Hill

Looking north along waterfront

Looking east from Elliot Bay

Seattle Regrading Activities

Tideflats, 1896 Tideflat Reclamation

Railroad Avenue s

Seattle Seawall 12,000 lb/ft lateral thrust Four different wall types - - Timber pile-supported relieving platform (2) - - Pile-supported concrete wall - - Fill and rip rap wall Total cost: $1.4 million

Type B Seawall Section

Precast Section Master Pile Timber Relieving Platform Batter Piles (12) Vertical Piles (6)

Pile/Platform Connection

Seawall Construction

Fill and Rip Rap Wall Section

Alaskan Way Viaduct History - - Originally intended as downtown bypass - - Design began in 1948, bids opened Seattle section opened April 4, WSDOT section opened Sept 3, Seneca Street off-ramp opened Columbia Street on-ramp opened 1966 Facts - - 7,600 ft long ,867 yards of concrete, 7,460 tons of rebar ,410 ft of piling

36 ft 22 ft 70 ft Typical Elevation (WSDOT Section) 57 ft

36 ft 22 ft 47 ft Typical Interior Bent (WSDOT Section)

Foundations WSDOT Section Seattle Section

2’ 2.5’ Foundations Seattle Section WSDOT Section 17’ 13.5’ 12’ 3.5’

Seattle Section WSDOT Section Originally intended to use only H-piles Contractor requested change Steel piles - 48 tons All other piles - 40 tons

S. Massachusetts St. Columbia St. University St. Yesler Way S. Royal Brougham Way Blanchard SubsurfaceData Stewart St. 50 shallow borings by SED in deep borings by WSDOH in mid-1950s Various borings by others 8 borings with SPT 16 CPT soundings with seismic cone 2 deep borings with downhole seismic

Elevaion (ft) Elevation (ft) Waterfront Fill Tideflat Deposit Till 1000 ft Blanchard Stewart University Yesler Massachusetts Royal Brougham Subsurface Profile

Standard Penetration Resistance (blows/ft) Depth (ft) Uncorrected SPT Resistance

Uncorrected CPT Tip Resistance Depth (ft) Cone Penetration Tip Resistance (tsf)

Shear Wave Velocity (ft/sec) Depth Below Top of Till (ft) Federal Building B-1 B-2 Till Stiffness Average

Input Motions PSHA (10% in 50 yrs = 475-year return period) - - Peak acceleration - - Spectral velocities - - Bracketed duration Design-level response spectrum Quasi-synthetic time histories Deconvolution to produce 3 “bedrock” motions Acceleration (g) Time (sec)

Ground Response Analysis Equivalent linear analyses (SHAKE) Nonlinear, effective stress analyses (TESS, DESRA) Numerous soil profiles

Time (sec) Acceleration (g) 10 ft soft soil 50 ft soft soil 100 ft soft soil Ground Surface Motions

0.0 Period (sec) S (g) a Ground Surface Response Spectra 10 ft soft soil 50 ft soft soil 100 ft soft soil

Waterfront Fill Tideflat Deposit Till a max Peak Accelerations

Liquefaction Susceptibility Historical evidence - - Sand boils in 1949 and Broken pipes in 1949 and Lateral movements in 1965 Construction techniques - - Hydraulic filling - - Dumping through water Previous investigations - - Mabey and Youd (1991) - - Grant et al. (1992)

Scenario Earthquake #1 Scenario Earthquake #2 M 7.5 a max 0.30 g 0.15 g Displacement (in.) > Little liquefaction susceptibility but in areas with steep slopes. Liquefaction is unlikely, but if it were to occur, large displacements are possible. No displacement likely due to liquefaction. Mabey and Youd (1991)

Depth (ft) (N ) 1 60 (N ) 1 60 required to prevent liquefaction Liquefaction Evaluation Standard Penetration Test

(N ) 1 60 Depth (ft) (N ) 1 60 required to prevent liquefaction Liquefaction Evaluation Standard Penetration Test

FS L Depth (ft) SPT-Based Factor of Safety

Depth (ft) (q ) c 1 (q ) c 1 required to prevent liquefaction (tsf) Liquefaction Evaluation Cone Penetration Test

Depth (ft) (q ) c 1 (tsf) Liquefaction Evaluation Cone Penetration Test (q ) c 1 required to prevent liquefaction

Depth (ft) (N ) 1 60 Design-level ground motion Liquefaction Evaluation Comparison with 1965 observations

Depth (ft) (N ) 1 60 Design-level ground motion 1965 ground motion Liquefaction Evaluation Comparison with 1965 observations

(N ) 1 60 Depth (ft) Design-level ground motion Liquefaction Evaluation Comparison with 1965 observations

(N ) 1 60 Depth (ft) Design-level ground motion 1965 ground motion Liquefaction Evaluation Comparison with 1965 observations

FS L Depth (ft) SPT-Based Factor of Safety 1965 ground motion

Effects of Liquefaction Sand boils - expected over most of length Post-earthquake settlement - - Up to 1” in fill above water table - - Up to 25” in soft, saturated soils Vertical pile movement - - Tip capacity reached at r = Tips of southernmost piles in liquefiable soil Lateral pile movement - - Depends on lateral soil movement ”-12” expected to cause bending failure - - Lateral soil movement depends on seawall movement u All movements variable due to variability of soil profile

Seawall Investigation Transverse profile characterization additional borings (2 offshore) additional CPT soundings Seawall structure characterization - - Member sizes - - Member properties - - Connection strengths Computational model - - Soil - - Seawall - - Soil-seawall interaction Estimation of permanent deformations due to liquefaction FLAC

FLAC Fast Lagrangian Analysis of Continua Explicit finite difference code Large-strain capabilities Several soil constitutive models Structural elements (beams, piles, cables) Interface elements (normal and shear) Coupled stress-deformation and flow capabilities Incremental construction modeling Graphical display of results Dynamic option Creep option FISH programming language

Alaskan Way Viaduct Type B Wall Model Entire Section

Alaskan Way Viaduct Type B Wall Model Entire Section 3400 soil elements 610 structural elements

Type B Wall Model

Precast Section Master Pile Timber Relieving Platform Batter Piles (12) Vertical Piles (6) Type B Wall Model

Modeling Approach Strain Stress G G f i Strain due to softening Primary effects of liquefaction - - Reduction of soil strength - - Reduction of soil stiffness Stiffness reduction approach 1. Analyze with pre- liquefaction properties 2. Analyze with post- liquefaction properties 3. Subtract pre- liquefaction displacements from post- liquefaction displacements

Displacements Maximum Displ = 0.71 ft

Deformed Shape Deformations magnified by factor of 5

Bending Moments

Type B Wall Before liquefaction

Type B Wall During liquefaction

Type B Wall After liquefaction

Fill and Rip Rap Wall Before liquefaction

Fill and Rip Rap Wall During liquefaction

Fill and Rip Rap Wall After liquefaction

Columbia St. Madison St. University St. S. Washington St. Zones of Large Lateral Movements