1. Shake Table Testing of a Large Scale Two Span R-C Bridge Univ. of Washington *PI: Marc Eberhard Co-PI: Pedro Arduino Co-PI: Steven Kramer RA: Tyler Ranf Univ. of Nevada, Reno *PI: M. “Saiid” Saiidi Co-PI: David Sanders RA: Nathan Johnson Overall project PI: Sharon Wood, Univ. Texas, Austin

2. Outline Background information Basics of the design Construction and assembly Instrumentation and test schedule Experimental observations/results Analytical modeling Future work

3. Prototype Bridge Frame Continuous CIP post-tensioned RC box girder. 120 ft span lengths. 4 ft circular columns, fixed-fixed. Varied column heights. Drilled shafts (pile extension as opposed to pile cap). Axial load index = 0.08.

4. Shake Table Tests 0.25 linear scale (12in dia. Columns) Columns fixed at pile point of maximum curvature Column heights of 5ft, 8ft & 6ft Input motions: soil motion at pile immediately below plastic hinge Concentrate on column response and interaction in global system

5. Basics of the Design –Columns: NCHRP 12-49 / Caltrans Long. steel ratio = 1.56% Lateral steel ratio = 0.86% –Joints not modeled in detail –Superstructure not modeled in detail Convert prototype into equivalent specimen solid section

6. Inertial/Axial Masses 46.5 kip required per column Weight Scaled by length 3, pressure only by length 2 –Concrete Blocks = 120 kip –Lead = 58 kip

7. Superstructure Design 2 sets - three 331in x 30in x 14in beams Dapped ends DL SF = 2 (ignore post-tensioning)

8. Post-Tensioning Longitudinal System –Prevent cracking in superstructure Transverse System –Maintain beam continuity (90in x 14in) –Clamping force to prevent beam separation caused by transverse lateral moment Mass to deck Footings to tables

9. Construction A BC DEF

10. Assembly 11 pieces cast separately on and off-site Grouted / Post tensioned together Imposed mass added ABC DEF

11. Instrumentation 298 channels @ 100Hz Column lat./long. strain gauges Shear transducers Curvature transducers

12. Accelerometers Transducers

13. Earthquake Motions 1994 Northridge Century City –UC Davis and U. Washington –90deg and 180deg components –Motion transmitted down to bedrock using Proshake (83ft) –Propagated up through medium-dense sand to 2D pile depth (equivalent depth of fixity) Low amplitude testing (pre-yield) (14 tests) –Transverse incoherent motions –Biaxial motions –Centrifuge motions High amplitude testing (to failure) (9 tests) –From 0.075g to 1.66g PGA

14. Transverse modes of bridge Translation (mode 2) 81.9% Rotation (mode 3) 18% Superstructure Bending (mode 6) 0.1%

15. High Amplitude Spectra

16. Damage Progression 0.5g: Significant Flexural Cracks in B1 & B3 1.0g: Concrete Spalling and first lateral steel exposure in B1 & B3 1.33g: long bar exposure in B3

17. Damage Progression 1.33g: First lateral steel exposure in B2 1.66g (failure): four spirals fractured, 36 buckled long. bars

18. Failure test (1.66 PGA)

19. Failure Test Bent 3

20. Acceleration-Disp. Hysteresis Tests 12-20 (cumulative) Bent 1 (6 ft columns) Bent 2 (8 ft columns) Bent 3 (5ft columns)

21. Displacement Ductility

22. Test 19 animation 2.5-17.5sec 1x timescale

23. Test 19 animation 5-7.5sec 0.2x timescale

24. Test 14 Achieved Table Motions

25. Test 19 Achieved Table Motions

26. Data Processing Structural data: displacement, acceleration, strain, curvature, shear Shake table motions –Accelerations, displacements, spectra Videos, photos Correlation of force with acceleration Extract force from shake tables for select runs

27. SAP 2000 Modeling (work in progress) Expansion of model used for design / pre-analysis –Moment-rotation hinges  Nonlinear fiber hinges Model efficiency –Study the effect of fiber and element configurations Model parameters –Material models –Input motions –Time-step / integration Verification/calibration of model –Compare accelerations and displacements from shake table tests –Compare with Drain-3DX Utilize model to focus on system response

28. Test 15 Displacement Predictions m D = 1.5~2.5

29. Test 18 Displacement Predictions m D = 4.1~5.5

30. Test 18 Accel-Disp Predictions

31. Future Work Complete calibration and verification of analytical model Investigation of system response utilizing experimental data and analytical model Expansions of computer model –More complete system –Earthquake loading including biaxial motions