1

Effect of Confinement on StrengthConcrete Columns

of Reinforced

Chai Jaturapitakkull Kraiwood Kiattikomo12

Somchai Chucheepsaku13 and Anek Siripanichgorn4

King Mongkut’s Institute of Technology Thonburi

Abstract

The objective of this study is to investigate the effect of confinement on the

strength of concrete columns subjected to eccentric load when using different spacing

of tied reinforcement. A total number of 48 reinforced concrete columns was tested.

Each column has a cross sectional area of 20x30 cm with a height of 120 cm and is

reinforced with 6 main bars with a diameter of 12 mm. The samples of columns were

divided into 4 groups and each group had 12 columns. The first group was the columns

without any confinement, the rests were the columns with confinement provided by

tied bars having a diameter of 6 mm. The second, third, and fourth groups were the

columns with a spacing of tied bars of 5 cm, 10 cm, and 20 cm, respectively. Each

group was tested in 4 cases, having load eccentricity of 0, 3, 6, and 9 cm, respectively,

from the centroid of the column. Three columns were tested for each case.

The results showed that the columns with tied bar resisted higher load than

the one without any tied bar. It was found that the columns with heavy confinement

gave higher compressive loads and larger lateral deflections as compared with the

columns of less confinement. For columns without any confinement, the failure

occurred suddenly when the columns reached their ultimate loads. In contrary to the

columns with confinement, cracks were observed at the covering of the columns,

then spalling occured, after that the columns failed slowly.

’ Assistant Professor, Department of Civil Engineering

’ Associafe Professor, Department of Civil Engineering

3 Associate Professor, Department of Civil Engineering

4 Assistant Professor, Department of Civil Engineering

t

-~15815-1 Bi15. i?d 20 au"undl iqWlUU 2540 .

4

115115-l 'di15. i?d 20 iXhihi$JlfJU 2540

Column Size (cmxcm) Height (cm)

20x30 120

20x30 120

20x30 120

20x30 120

Tie Spacing No. of Columns- - 12

06@0.05 m 12

06@0.10 m 12

06@0.20 m 12

6-012

d060 0.05

1158157 Bi)ii. i%? 20 Ql?lJn" 1 i+JltlU 2540 _

a : 6cm

DIAL GAUGE c

DIAL GAUGE dLLchLv&m4L+iIi

1 1 5 8 1 5 7 Gt5. afi 20 Whn” 1 ijtJU1ElI.1 2 5 4 0

8

LRI Tsxkkl 5sl:: Pu Pu "75s"uri;Mw'nLkl hKwJa~

lh=iafl L~aqlJ$ nwma n"lWXU uammJ%ut!uu m51h.l

(au*) (au*) (@% (@% fh Puvmaa~(ch)

AQ - 0 64.78 70.60 -5.82 -8.24

A3 - 3 55.30 57.40 -2.10 -3.66

10 6 1 66.48 1 47.13 ) +19.35 +41.06

9

1151157 iWi5. aii 20 ilihih i+lUW 2540 .

Gnd3 (da)

tin 5zMl~fl 5sl:: Pu Pu "Y+hhlii"AJ GXKK'LIEI~

lhafl tiklqwfi nwm FhW-JfU ?JFl~l~ltG~Ul~ElU fmfiu

(au.1 (flu-1 Gw ({N n'u PU nmw (6~)

c9 10 9 62.54 39.11 +23.43 +59.91DO 5 0 82.73 70.60 +12.13 +17.18

140

130

120

110

100

90

80

7 0

60

50

40

30

20

10

00 4 8 12 16 20 2 4 28

Strain of Column (x0.0001)

140

130

120

110

100

90

60

70

60

50

40

3 0

20

10

O$ 1 I I I I I I I I I 1 I I I

0 4 8 ,12 16 20 2 4 26

Strain of Column (x0.0001)

1 4 0

130

120

110

1 0 0

9 0

8 0

7 0

6 0

5 0

4 0

3 0

2 0

10

0

A6 Column

D6 Column

I I 1 I I 1 I 1 1 I I I I I I0 4 a 12 16 2 0 2 4 2 8

Strain of Column (x0.0001)

110 _I100 -

9 0 -

8 0 -

7 0 -

60 -

5 0 -

4 0 -

3 0

2 0

10

q A9 Column

+ B9 Column

0 C9 C o l u m n

A D9 Column

Strain of Column (x0.0001)

115SI5-I iV5. a$ 20 Qihn" 1 ijt-yUW 2540

90

8 0

7 0

6 0

7.0 505

Bs

4 0

3 0

A DO Column

0 CO Column

+ BO Column

q A0 Column

I I I I

2 4 6

Lateral Deflection (mm)

90

8 0

7 0

6 0

5 0

4 0

3 0

2 0

10

0

A 03 Column

0 C3 Column

+ 83 Column

q A3 Column

0 2 4 6

Lateral Deflection (mm)

8 0

6 0

0 2 4 6

Lateral ,Deflection (mm)

3151151 885. an” 2 0 U?Jn” 1 i@llUU 2 5 4 0 _

7 0

6 0

5 0

4 0

3 0

2 0

10

0

A D9 Column

0 C9 Column

+ B9 Column

0 A9 Column

16

'1l%Wi4 Bi15. id 20 Whndl ijfjUlfJU 2540 _

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

AC1 3 18- 89, 199 2, “Building Code Requirements for Reinforced Concrete,”

AC1 Manual of Concrete Practice Part 3-1992, American Concrete Institute.

Iyengar K. T. S. R., Desayi, P., and Reddy K.N., 1970, “Stress-Strain

Characteristics of Concrete Confined in Steel Binders,” Magazine of Concrete

Research, Vol. 22, No. 72, pp. 173-184.

Soliman, M. T. M. and Yu, C.W., 1967, “The Flexural Stress-Strain Relationship

of Concrete Confined by Rectangular Transverse Reinforcement,” Magazine of

Concrete Research, Vol. 19, No. 61, pp. 223-238.

Yong, Y. K., Nour, M. G., and Navy, E. G., 1988, “Behavior of Laterally

Confined High-Strength Concrete Under Axial Loads,” Journal of Structural

Engineering, Vol. 114, No. 2, pp. 332-351.

Dilger, W.H., Koch, R., and Kowalczyk, R., 1984, “Ductility of Plain and

Confined Concrete Under Different Strain Rates,” Journal of American Concrete

Institute, Vol. 81, No. 1, pp. 73-8.

Sargin, M., Ghosh, S.K., Handa, V.K., 1971, “Effects of Lateral Reinforcement

Upon the Strength and Deformation Properties of Concrete,” Magazine o f

Concrete Research, Vol. 23, No. 75-76, pp. 99-110.

Gangadharam, D. and Reddy K.N., 1980, “Effect of Cover Upon the Stress-

Strain Properties of Concrete Confined in Steel Binders,” Magazine

Research, Vol. 32, No. 112, pp. 147-155.

ASTM C 39, 1990, “Standard Test Method for Compressive

Cylindrical Concrete Specimens,” Annual Book of ASTM

Volume 04.02.

of Concrete

Strength of

Standards,

18