Behaviour of Glass Fiber Wrapped Concrete

International Journal of Advanced Engineering Technology

IJAET/Vol. I/ Issue I/April-June, 2010/74-83

Research Paper

BEHAVIOUR OF GLASS FIBER WRAPPED CONCRETE

COLUMNS UNDER UNIAXIAL COMPRESSION

P.Sangeetha1, R.Sumathi

2

Address for Correspondence

1Lecturer, Department of Civil Engineering ,Sri Venkateswara College of

Engineering, Pennalur, Sriperumbudur-602105 Tamilnadu.

Email id: [email protected] 2Assistant Professor, Department of Civil Engineering, Arulmugu Meenakshi

Amman College of Engineering, Thiruvanamalai District. Tamilnadu ===============================================================

ABSTRACT

Fiber – Wrapping using Fibre – Reinforced Plastic (FRP) shells is one of effective methods,

significantly enhances the strength and ductility of concrete columns. The paper reports the

behaviour of the GFRP wrapped concrete columns under uniaxial compression. The cross section

of the concrete columns considered in the work is circular with diameter of 150mm and height

300mm. The Parameters that are varied in the investigation are wrapping shell materials, (which

includes GFRP Materials Surface Mat(SM), Chopped Strand Mat (CSM) and Woven Roving Mat

(WRM)), Number of Plies (1Ply and 3plies) and Period of Curing (7 & 28 Days). Results from a

series of the experimental study were reported and discussed. The study on small – scale

specimens showed that confinement increased the strength of the concrete columns loaded

axially.

KEY WORDS

Fiber Reinforcement, Compressive Strength, Curing, Concrete, Glass Fiber.

==============================================================

INTRODUCTION

In recent years, retrofitting of concrete

columns by wrapping and bonding of

fiber– reinforced plastic (FRP) sheets,

straps, belts, or precured shells around

the columns has become increasingly

popular. Studies of concrete columns

confined with glass, aramid, or carbon

fibers have been used successfully to

retrofit building columns, bridge or

expressway piers, and chimneys. An

incremental finite element approach [4],

are used to evaluate the response of

fiber-wrapped square columns confined

with carbon and aramid fibers. Many

researchers [1-3 & 5], have proposed

models for concrete cylinders and square



columns strengthened with FRP sheets.

The axial load behavior of concrete-

filled tubular (CFT) columns with the

width-to-thickness ratios are studied [6]

and stiffening scheme to enhance the

ultimate strength and ductility of square

CFT columns was proposed. The proper

material constitutive models for concrete

– filled tube (CFT) columns are

proposed [7] and verified by the

nonlinear finite element program

ABAQUS against experimental data.

This paper, investigates the

characteristics behaviour of reinforced

concrete columns. FRP is used to wrap

the columns circumferentially. All

columns were tested to failure by

applying axial concentric loads. Results

of testing the columns showed that FRP

is effective in producing columns with

high compressive strength.

Experimental Study

Specimen preparation and Testing

A total of forty-two cylindrical columns

of size 150 X 300 mm were prepared

and twenty one specimens were cured

for 7 days and remaining specimens

were cured for 28 days. Out of 21

specimens of 7 days cured and 28 days

cured, eighteen columns were wrapped

circumferentially with glass fiber

reinforced polymer of Surface Mat

type, Chopped Strand Mat and Woven

Roving Mat after 7 and 28days curing of

single and triple plies and three columns

without wrapping respectively. All the

specimens were tested in the

Compression testing machine of capacity

50kN. Ultimate load readings were taken

to study the compression behavior of the

specimens. Table 1 shows the

description of various specimens

prepared for testing. Fig.1 shows the

column specimens without wrapping.

Fig.1: Column Specimens before

wrapping

Fig.2-4 shows 28 days cured column

specimens wrapped with SM, CSM and

WRM of single ply. Fig.5 shows the

compression test carried out on Triple

plies chopped Strand Mat wrapped on

columns cured for 28 days



Fig.2:Columns with Single ply Surface Mat

Fig.3: Columns with Single ply of Chopped Strand Mat

Fig.4: Columns with single ply of Woven Roving Mat

Fig.5:Compression testing carried out on 28 days cured Triple Plies Chopped

Strand Mat column.



Fig. 6:Variation in Compressive Strength after 7 and 28 days cured specimens

wrapped with single ply of GFRP.

Fig.7:Variation in Compressive Strength after 7 and 28 days cured specimens

wrapped with Triple plies of GFRP.

0

5

10

15

20

25

30

UC SM CSM WRM

Types of GFRP Material

Compressive Strength in N/mm2

7 days cured Columns

Wrapped with Single Ply


Wrapped with Single Ply

0

5

10

15

20

25

30

35

40

45

50

UC SM CSM WRM




Wrapped with Triple Plies28 days cured Columns Wrapped

with Triple Plies



Fig. 8:(a) and (b)Variation in Compressive Strength of specimens wrapped with

Single and Triple plies of GFRP after 7 and 28 days of curing.

0

5

10

15

20

25

30

35

40

45

50

UC SM CSM WRM



7 days Cured columns Wrapped

with Single Ply7 days cured columns Wrapped

with Triple pliesSeries3

0

5

10

15

20

25

30

35

40

45

50

UC SM CSM WRM



28 days cured Columns Wrapped

with Single Ply28 days cured Columns Wrapped

with Triple PliesLinear (28 days cured Columns



Fig. 9:Shows the comparison between the compressive strength of 7 & 28 days cured

specimens.

0

5

10

15

20

25

30

35

40

45

Single Ply Triple Plies

No. of Plies


Un Confined Columns

Columns Wrapped with SM

Columns Wrapped with CSM

Columns Wrapped with WRM

0

5

10

15

20

25

30

35

40

45

50

Single Ply Triple Plies

No. of Plies


Un Confined Column

Columns Wrapped with SM

Columns Wrapped with CSM

Column Wrapped with WRM



EXPERIMENTAL RESULTS AND

DISCUSSION

Table 2 shows the results of tested

column specimens. The columns

wrapped with Woven Roving Mat of

Glass fiber exhibited better results than

other type of Glass fiber columns. The

compressive strength of the GFRP

wrapped concrete columns shows better

results when columns are wrapped with

3 plies than single ply.

Effect of FRP Wrapping Materials

The Percentage increase in the

Compressive Strength for change in Ply

from 0 to 1 for specimens wrapped with

Surface Mat, Chopped Strand Mat and

Woven Roving Mat after 7 days curing

were 3.6, 21.46 and 28.97% respectively

and after 28 days curing were 10, 27.17

and 31.46 %. Fig.6. Show the variation

in compressive strength after 7 and 28

days cured specimens wrapped with

single ply of GFRP. The Percentage

increases in the Compressive Strength

for change in Ply from 0 to 3 for

specimen wrapped with Surface Mat,

Chopped Strand Mat and Woven Roving

Mat after 7 days curing were 50, 135.79

and 167.93% respectively and after 28

days curing were 10, 27.17 and 31.46%.

Fig.7. Show the variation in compressive

strength after 7 and 28 days cured

specimens wrapped with Triple plies of

GFRP.

Effect of Plies

The percentage increase in the

Compressive Strength for 7 days & 28

days cured column wrapped with

Surface Mat for Single Ply and Triple

Plies is 3.6 and 50% respectively. The

percentage increase in the Compressive

Strength for column wrapped with

Chopped Strand Mat for Single Ply and

Triple Plies is 21.46 and 136%

respectively. The percentage increase in

the Compressive Strength for column

wrapped with Woven Roving Mat for

Single Ply and Triple Plies is 29 and

168% respectively .Fig. 8 (a) and (b)

show the variation in compressive

strength of specimens wrapped with

Single and Triple plies of GFRP after 7

and 28 days of curing.

Effect of Curing

The percentage increases in the

Compressive Strength for column

wrapped with Single ply of Surface Mat,

Chopped Strand Mat and Woven Roving

Mat from 7 to 28 days cured are 32.72,

30.87 and 27.4% respectively and with

Triple Plies are 21.46, 6.05 and 6.66%

respectively.



Table.1:.Descripition of various specimens prepared for testing

S. No. Specimen Descriptions No. of

Casted

columns

taken

Period

of curing

(days)

Number

of plies

3 7 0 1 Unconfined Column (UC)

3 28 0

3 7 1

3 28 1

3 7 3

2 Surface Mat Column (SMC)

3 28 3

3 7 1

3 28 3

3 7 3

3 Chopped Strand Mat Column (CSMC)

3 28 3

3 7 1

3 28 1

3 7 1

4 Woven Roving Mat Column (WRMC)

3 28 1

Table.2.Results of tested column specimens under Compressive loading condition

S.

No.

Specimen Descriptions Period

of curing

(days)

Number of

plies

Compressive

Strength

(N/mm2)

7 0 15.84 1 Unconfined Column (UC)

28 0 19.81

7 1 16.41

28 1 21.78

7 3 23.76

2 Surface Mat Column (SMC)

28 3 28.86

7 1 19.24

28 1 25.18

7 3 37.35

3 Chopped Strand Mat Column (CSMC)

28 3 39.61

7 1 20.43

28 1 26.03

7 3 42.44

4 Woven Roving Mat Column (WRMC)

28 3 45.27



The over all Percentage increase in

Compressive Strength for different

materials is 30% for single ply from 7

days to 28days of curing and 20% for

Triple Plies .

.

Fig.10.Tested Columns

CONCLUSIONS

The present study used forty-two

columns, wrapped with GFRP of types

Surface Mat(SM), Chopped Strand Mat

(CSM) and Woven Roving Mat (WRM).

Based on the results from a series of the

experimental work the following

Conclusions are made.

• The confinement of columns

with GFRP wrap increased the

strength and ductility of the

concrete Column.

• Different types of glass fiber are

Surface Mat, Chopped Stand Mat

and Woven Roving Mat also

increasing the compressive

strength of the columns.

• Compressive Strength of the

Concrete Columns increases with

increase in the number of plies of

GFRP.

• Period of Curing also increases

the load carrying capacity of

columns.

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Documents

Behaviour of Glass Fiber Wrapped Concrete