Seismic Retrofit of the Aurora Avenue Bridge

Transcription

1 Seismic Retrofit of the Aurora Avenue Bridge Tim Ingham Aurora Avenue Bridge 1

2 Aurora Avenue Bridge Aurora Avenue Bridge Also know as the George Washington Bridge Caries SR99 over the Lake Washington Ship Canal adjacent to Lake Union, near Seattle, Washington Built between 1929 and 1931 Has been designated a critical emergency route by the Seattle Engineering Department Traffic Section Is considered a critical bridge 2

3 General Arrangement General Arrangement South approach 3-spans of continuous reinforced concrete construction, 148-ft 3 spans of simply-supported steel truss, 225-ft 5-span steel deck truss main span 200-ft simply supported backspan, S-3 to S ft anchor span, S-2 to S ft main span, S-1 to N-1; includes 150-ft suspended span 350-ft anchor span, N-1 to N ft simply supported backspan, N-2 to N-3 North approach 12-spans of continuous reinforced concrete construction, 694-ft 3

4 Piers Piers Tapered cruciform sections Legs connected by arched portals Very lightly reinforced % vertical ¾ 3 ft centers Spliced to footing Founded on spread footings Buried in contaminated soil 4

5 Seismic Retrofit History 1995 Seismic evaluation and retrofit strategy developed by another consultant PS&E completed by TYLI Stage 1 Retrofit main truss bearings (S-3 to N-3) Restrainers at simple spans S-3, S-2, N-2, & N-3; and suspended span Main span shock-transmission units at S-2 and N-2 Stage 2 Strengthening of piers (S-3 to N-3) Strengthening of some main span truss members Stage 1 & 2 Work Costs and disruption of excavation to retrofit piers larger than anticipated Hazardous materials discovered at the site Stage 1 & 2 work terminated Only the restrainers at S-3 and N-3 installed Base isolation proposed 5

6 Base Isolation Retrofit Analysis Translate model from STRUDL to ADINA Implement seismic isolation bearings Retrofit strategy Constructibility review Cost estimate PS&E Construction support ADINA Model 6

7 ADINA Model Dead Load Strudl Adina Foundation Node Reaction Total Node Total Difference Percentage S3W % S3E % S2W S2E % S1W S1E % N1W N1E % N2W N2E % N3W % N3E % Total % 7

8 Model Modifications Hanging span Deck expansion joints Portal modeling Foundation modeling Ground motion input Friction pendulum bearings Hanging Span Span has only vertical support Longitudinal position solved by nonlinear geometry 8

9 Deck Expansion Joints Contact Element Portal Modeling Inelastic Moment- Curvature Elements 9

10 Moment-Curvature Relationship Moment, ft-kip XSection ADINA Curvature, /ft Foundation Modeling Foundation Element Rigid Links Independent Springs 10

11 Ground Motion Input A c c e l e r a t i o n, i n / s ^ Response Spectra - PanGeo vs. Tacoma Narrows scaled to S&W os4blc.dis Tacoma Narrows Bridge Set 1 / East Anchorage / Longitudinal Tacoma Narrows Bridge Set 3 / East Anchorage / Longitudinal 3ow4blc.dis Period, s Overturning of Structure 11

12 Friction Pendulum Bearing Friction Pendulum Bearings Mechanically simple Mathematically complex µw 12

13 Force-Deformation Relationship One-dimensional behavior N F = D + µ N(sgn D ) where N = vertical force R Common simplification W F = D + µ W (sgn D ) where W = dead weight R Contact Surface Model Slider - Contact Surface Solid Element Slider - Contact Point Dish - Contact Surface Rigid Link, typ. 13

14 ADINA Input File Use ADINA geometric modeling to create dish Define arc Sweep arc around bearing axis of symmetry Use automatic meshing Bearing parameters appear in only a few places in the input file ADINA Code * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * dish - target surface * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * coordinates point system=905 entries name xl yl zl * * line arc name=925 mode=1 p1=25005 p2=25006 center=25007 surface revolved name=911 mode=points line=925 angle=360 ap1=25005 ap2=25007 subdivide surface name=911 mode=divisions ndiv1=05 ndiv2=36 14

15 Mesh Refinement Time History Trace ,72 05,36 05, Y-Displacement, ft X-Displacement, ft Period of Vibration Test Give the slider an initial velocity Radius = 20 feet Coefficient of friction = 1% Video Clip 15

16 Period of Vibration Result R 20ft T = 2 π = 2π = 4.96sec g 32. 2ft/sec Friction Test Analyze slider on a flat, frictional surface Apply both horizontal and vertical motions µ=

17 Motions Acceleration, ft/sec^2 Acceleration, ft/sec^ Horizontal Motion Time, s Vertical Motion Time, s ADINA Solution Video Clip 17

18 Solution using Newmark Method 3 2 Ground Slider 1 Velocity, ft/sec Time, s Comparison Newmark ADINA Displacement, feet Time, s 18

19 Model Comparison Force, kips Deformation, ft Bilinear Model Contact Surface Model Implementation 19

20 Bearing Results (N-2E) Displacement time histories Two-dimensional response Force time histories Hyteresis loops Energy dissipation time history Time history animation Longitudinal Displacement 20

21 Transverse Displacement Two-dimensional Response 21

22 Longitudinal Force Transverse Force 22

23 Longitudinal Hysteresis Loop Transverse Hysteresis Loop 23

24 Energy Dissipation Energy, ft-kips Time, s Time History Animation Video Clip Video Clip 24

25 Column Shear Demand/Capacity Ratios Pier S-3 lower S-3 backwall S-2 S-1 N-1 N-2 N-3 full N-3 split N-3 upper Isolated >2 Original >2 Column Flexure Demand/Capacity Ratios Pier S-3 lower S-3 backwall S-2 S-1 N-1 N-2 N-3 full N-3 split N-3 upper Isolated Original >

26 Pier Drift Pier S-3 S-2 S-1 N-1 N-2 N-3 Isolated Long., ft Tran., ft Original Long., ft Tran., ft Superstructure Demand/Capacity Ratios Member Type BC H K V D Shock Transmission Units STU Isolated Isolated 417 kip Original Peak Force, kip Original 1174 kip 26

27 Friction Pendulum Bearing Demands Force, kip Pier R. Disp. ft. Vertical Long. Tran. S / S / S / N / N / N / Note: Vertical forces are minimum / maximum Fixed Bearings at Piers S-1 and N-1 27

28 New Bearings at Piers S-1 and N-1 Temporary Support at Piers S-1 and N-1 28

29 Temporary Support at Piers S-1 and N-1 Temporary Support at Piers S-1 and N-1 29

30 Temporary Support at Piers S-1 and N-1 New Bearings at Piers S-1 and N-1 30

31 Bearing Testing at EPS Shock Transmission Units 31

32 Shock Transmission Units Replace member with STU 32