The purpose of this study was to investigate the inelastic behavior of hollow reinforced concrete bridge columns, and to provide data for developing improved seismic design criteria. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach was incorporated. The proposed numerical method gives a realistic prediction of inelastic behavior throughout the loading cycles for several test specimens investigated. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of hollow reinforced concrete bridge columns.

1. Inelastic Behavior of Hollow
Reinforced Concrete Bridge Columns
T.-H. Kim
Construction Product Technology Research Institute,
Samsung Construction & Trading Corporation, Korea
15 WCEE, 24 September 2012
Lisboa Congress Centre
Lisbon, Portugal

2. CONTENTS
 Introduction
 Objectives
 Experimental Program
 Analytical Study
 Assessment of Performance
 Conclusions

3. INTRODUCTION
 Increasing use of
hollow section columns
• Saving of dead load
• Reduced material and
foundation costs
 Some disadvantages
• No specific criterion
• Not fully understood
Disadvantage

4. OBJECTIVES
 Knowledge on the inelastic behavior of hollow
reinforced concrete bridge columns
• Effect of the configuration of lateral reinforcement
• Effect of the quantity of cross tie
• Based on the experimental and analytical results
 Analytical evaluation method for the performance
of hollow reinforced concrete bridge columns
• Application of developed method
• Circular-cross-section, Ductile flexural response

5. EXPERIMENTAL PROGRAM

6. Test specimens
Korea Roadway Bridge
Design Code (2005)
3 hollow circular
column specimens
Transverse reinforcement
= Outer, Outer & Inner
Cross tie
= 5ea@200,270
10ea@90
P/fck = 0.1

7. Details of Load Frame and Test Setup
Structural Testing Laboratory

8. Load-displacement relationship
HC-O-100 HC-IO-90-L

9. Load-displacement relationship
HC-IO-90-H

10. Hysteretic energy dissipiation

11. ANALYTICAL STUDY

12. RCAHEST
2D or 3D
Flexibility-
based fiber
beam-column
element
4 nodes Elastic
shell element
4 nodes RC
shell element
2D
Elasto-plastic
plane stress
element
RC
plane stress
element
Interface
element
Reinforcing or
Prestressing
bar element
Joint element
2D or 3D
Spring element
4 nodes PSC
shell element
FEAP

13. Construction of cracked concrete model
Crack Reinforcement
Tension stiffening model
Compression stiffness model
Crack
Shear
Shear transfer model
Tension stiffening model
Compression stiffness model
Shear transfer model

14. Model for reinforcing bar in concrete
bare bar
AverageStress
Average Strain
sh
Es
Esh
y
reinforced concrete
average stress of bar
crack
bar
s
av
s
av

15. Confinement model for hollow section [ Mander et al. 1988 ]
Cf
Compressive Strain , C
CE
secE
co co2 sp cc cu
Confined
concrete
First
hoop
fracture
'
ccf
'
cof
t
'
tf
Unconfined
concrete
Assumed for
cover concrete
CompressiveStress,
21 eee KKK 
5.00 
o
i
D
D
12 eK
15.0 
o
i
D
D







o
i
e
D
D
K 122

16. Finite Element Mesh for Analysis

17. Comparison of results
HC-O-100 HC-IO-90-L

18. HC-IO-90-H
Comparison of results

19. ASSESSMENT OF PERFORMANCE

20. General
 Links between Performance Level, Damage State, and
Engineering Limit State (Kim et al. 2007)
Performance Level
(e.g., Stability)
Damage State
Engineering Limit State
Damage Indices
Compressive D.I.
Tensile D.I.

21. Damage Index of Concrete
Where,
2
)
2
2
(1..
cu
cscu
cecompressiv ftgID

 

cc ADftg 3.01

fc
c
N
AD
2
1
'
4.1
004.0
cc
smyhs
cu
f
f 
 

22. Damage Index of Reinforcing Bars
Where,
67.0
)
2
(20.1..
tur
ts
tensile
ftg
ID



rr ADftg 3.01

fr
r
N
AD
2
1
bar)mild(for10.0tu

23. Assessment Procedure
 Description of Performance Levels
Performance
level
Service Repair
Damage
State Index
Fully
operational
Fully
service
Limited epoxy
injection
Hairline cracks 0.1
Delayed
operational
Limited
service
Epoxy injection
Concrete patching
Open cracks
Concrete spalling
0.4
Stability
Not
useable
Replacement of
damaged section
Bar buckling/Fracture
Core crushing
0.75

24. Assessment of performance level

25. Damage during Test
(Specimen HC-O-100)
Drift 0.25% Drift 1.00%

26. Damage during Test
(Specimen HC-O-100)
Drift 4.00% Drift 6.00%

27. Comparative Evaluation for
Specimen HC-O-100
Drift (%)
Experiment Analysis
Note
Damage
Index
Performance Level
0.25 First Cracking 0.05 Fully Operational
1.00 Open Cracks 0.19 Delayed Operational
4.00 Buckling 0.70 Stability
6.00 Fracture 1.00 -

28. Comparative Evaluation for
Specimen HC-IO-90-L
Drift (%)
Experiment Analysis
Note
Damage
Index
Performance Level
0.25 First Cracking 0.05 Fully Operational
1.00 Open Cracks 0.21 Delayed Operational
4.00 Buckling 0.66 Stability
6.00
7.00 Fracture 1.00 -

29. Comparative Evaluation for
Specimen HC-IO-90-H
Drift (%)
Experiment Analysis
Note
Damage
Index
Performance Level
0.25 First Cracking 0.05 Fully Operational
1.00 Open Cracks 0.20 Delayed Operational
4.00 Buckling 0.62 Stability
6.00
7.00 Fracture 1.00 -

30. CONCLUSIONS
 An experimental and analytical study was conducted
to quantify performance measures and examine one
aspect of detailing for hollow RC bridge columns.
 The proposed performance assessment procedure for
hollow RC bridge columns is verified.
 Completion of this work could generate substantial
economic benefits for bridge construction in moderate
or low seismic zones.

31. Thank you