1. ALMA MATER STUDIORUM - UNIVERSITA’ DI BOLOGNA
FACOLTA’ DI INGEGNERIA
Corso di Laurea in INGEGNERIA CIVILE
D.I.C.A.M.
Dipartimento di Ingegneria Civile, Ambientale e dei Materiali
Tesi di laurea in PROGETTI DI STRUTTURE
SHAKE-TABLE TEST ON A FULL-SCALE BRIDGE
REINFORCED CONCRETE COLUMN
Tesi di laurea di:
FRANCESCO CARREA
Relatore:
Chiar.mo Prof. Ing. MARCO SAVOIA
Correlatori:
Chiar.mo Prof. Ing. CLAUDIO MAZZOTTI
Chiar.mo Prof. Ing. JOSE’ RESTREPO
Dott. Ing. MATTHEW SCHOETTLER
Dott. Ing. GABRIELE GUERRINI

2. INTRODUCTION AND OBJECTIVES
 Validate or improve current analysis methods and design practice
 Assessment of reduced-scale models adequacy
 Full-scale bridge reinforced concrete column
 Unidirectional shake-table test
 Current Caltrans design specification
 Moment-Curvature Analysis
 Pushover Analysis
 Non-linear time history analysis
Experimental test:
Analytical modeling:
Objectives:
Earthquakes whit increasing intensity
Comparison UC-Berkeley
Specimen response prediction
Personal experience at University of California – San Diego

3. TEST SETUP: SPECIMEN
Code references:
Bridge Design Specification, 2004
Seismic Design Criteria, 2006
Column height: 7.31 m
Column diameter: 1.21 m
Longitudinal reinforcement:18 Ф36 bar
Transverse reinforcement:
Butt welded double hoops Ф16 spaced at
152 mm on-center
Concrete cover to hoops: 50 mm
Superstructure
Column
Footing
West East
Snap shoots during construction:

4. TEST SETUP: RESTRAINT DEVICES
Safety Column
Detail
Superstructure
Wood blocks
Steel rod
Steel angle
1.03 m
0.95 m
0.27 m
Energy dissipation
upon impact
Max drift ratio = 10%

5. Restraint Towers
Superstructure
guide
Detail
Transverse and
torsional
displacements
restraint
Restraint tower
Steel tube
TEST SETUP: RESTRAINT DEVICE

6. TEST SETUP: MAIN INSTRUMENTATION
Longitudinal
strain gauges
Strain on
longitudinal bars
Longitudinal
Transverse
Transverse
strain gauges
Strain on hoops

7. TEST SETUP: MAIN INSTRUMENTATION
Linear
potentiometer
(LVDT)
Curvature
Shear deformation
Fixed-end rotation
Wire
potentiometer
Horizontal
displacements
Accelerometer
Inertia
forces
Moment
and
Shear
Curvature
Shear
Fixed-end
rotation
String
Potentiometer
Accelerometer

8. MATERIAL PROPERTIES
Concrete [MPa]
f’c 27.6
F’ce 33.9
f’c,29 40.3
f’c,42** 40.9
f’c,43*** 42.0
Transverse Steel [MPa]
fyh 377.9
fuh 592.2
**First day of testing
***Second day of testing
Longitudinal Steel [MPa]
fy 518.5
fu 706.7
Material strengths
*Tests conducted on bent bars

9. LOADING PROTOCOL
Ground motions selection requirements:
 Representative of the San Francisco Bay Area seismicity (strike-slip faulting);
 Sensitivity to damping in the predicted first mode period range of the structure (0.72 sec undamaged,
1.07 sec fully cracked);
 Determined target displacement ductility demands;
 Scale factor equal to 1.0 to achieve the desired displacement demands.
Loma Prieta, 1989
Kobe, 1995

10. LOADING PROTOCOL
Test Earthquake Date
Moment
magnitude
Station Comp.
Target
displacement
ductility
Scale
factor
PGA
[g]
EQ1 Loma Prieta 10/18/1989 6.9
Agnew State
Hospital
090 1.00 1.0 -0.199
EQ2 Loma Prieta 10/18/1989 6.9 Corralitos 090 2.00 1.0 0.409
EQ3 Loma Prieta 10/18/1989 6.9 LGPC 000 4.00 1.0 0.526
EQ4 Loma Prieta 10/18/1989 6.9 Corralitos 090 2.00 1.0 0.454
EQ5 Kobe 01/16/1995 6.9 Takatori 000 8.00 -0.8 -0.533
EQ6 Loma Prieta 10/18/1989 6.9 LGPC 000 4.00 1.0 -0.512
EQ7 Kobe 01/16/1995 6.9 Takatori 000 Not applicable 1.0 0.646
EQ8 Kobe 01/16/1995 6.9 Takatori 000 Not applicable -1.2 -0.829
EQ9 Kobe 01/16/1995 6.9 Takatori 000 Not applicable 1.2 0.819
EQ10 Kobe 01/16/1995 6.9 Takatori 000 Not applicable 1.2 0.851
White-noise and ambient vibration Dynamic properties identifications
Ground motions selection requirements:
 Representative of the San Francisco Bay Area seismicity (strike-slip faulting);
 Sensitivity to damping in the predicted first mode period range of the structure (0.72 sec undamaged,
1.07 sec fully cracked);
 Determined target displacement ductility demands;
 Scale factor equal to 1.0 to achieve the desired displacement demands.

11. LOADING PROTOCOL
Assumption: equal elastic and inelastic displacement demands
Ground motions selection requirements:
 Representative of the San Francisco Bay Area seismicity (strike-slip faulting);
 Sensitivity to damping in the predicted first mode period range of the structure (0.72 sec undamaged,
1.07 sec fully cracked);
 Determined target displacement ductility demands;
 Scale factor equal to 1.0 to achieve the desired displacement demands.

12. TEST RESULTS: EQ1 – AGNEW STATE HOSPITAL
Base moment – base curvature Base shear – top displacement
East viewObservations:
Essentially linear elastic response;
Experimental idealized yield curvature :
Experimental idealized yield displacement:
Global view: Plastic region:
Curvature ductilities
Displacement ductilities

13. TEST RESULTS: EQ3 – LGPC
Base moment – base curvature Base shear – top displacement
East viewObservations:
Ductile response with large hysteresis loops;
Good agreement between experimental and
analytical yield moment;
Displacement ductility of 4.01;
The largest shear force in any tests;
Higher modes effects in shear-displacement
response;
Essentially horizontal cracks and concrete cover
spalling (West); no sign of longitudinal bar buckling.
Global view: Plastic region:

14. TEST RESULTS: EQ5 – TAKATORI 80%
Base moment – base curvature Base shear – top displacement
East view
Observations:
Ductile response with large and hysteresis loops;
Stiffness but not strength degradation;
Displacement ductility of 6.33;
Horizontal, vertical and diagonal cracks, and deep
concrete spalling (East and West);
Visible onset of longitudinal bars buckling (West):
two bars bent between first and second hoops.
Global view: Plastic region:

15. TEST RESULTS: EQ9 – TAKATORI 120%
Base moment – base curvature Base shear – top displacement
East viewObservations:
Ductile response with large hysteresis loops;
Drop in moment capacity due to a longitudinal bar
fracture;
Stiffness degradation but not globally strength
degradation;
Vertical load bearing capacity was preserved;
Displacement ductility of 7.06;
Three longitudinal bars fractured (1-East, 2-West)
Superficial crushing of concrete core.
Global view: Plastic region:

16. TEST RESULTS: FAILURE MECHANISM
Onset
Onset
Straight bar
Buckled bar
Fractured bar
Shaking direction

17. TEST RESULTS: FAILURE MECHANISM
Onset
Onset
Straight bar
Buckled bar
Fractured bar
Shaking direction
Compression
Tension

18. REMARKS AND CONCLUSION
 Under the design earthquake (EQ3), a maximum displacement ductility of 4.01 was reached; aesthetic
damages consisted mainly of concrete cover spalling with no sign of longitudinal bar buckling;
 Before collapsing the specimen sustained a displacement ductility of 7.06, about 75% larger than the
one allowed by the specifications;
 Failure involved buckling and subsequent fracture of longitudinal bars after the hoops had yielded;
 Concrete core suffered only superficial crushing in proximity of the buckled and fractured bars;
 Throughout the test up to EQ9 the vertical load bearing capacity was fully preserved.
Current design practices provided a safe and resilient structure: not only the system performed as desired
under the design earthquake (maintained gravity load bearing capacity), but it was able to sustain a much
larger displacement demands before reaching collapse.

19. THANK YOU