Site: Hanshin Expressway
Kobe, Japan
Dated visited: October 1996
Host/Contact: Masahiko Uemura, Tonen Corporation
Michio Tezuka, General Manager, Sho-Bond Corporation
Summary: Seismic retrofit of rectangular columns using the Sho-Bond method.

ACTIVITIES OF INTEREST

In its efforts to develop a carbon fiber based sheet material for use in seismic retrofit, Toray developed the Torayca cloth, which is flat unidirectional fabric consisting of carbon fiber tows held together by polyester threads in the direction of the fibers (between tows) and normal to them. Nineteen rectangular columns of size 2 m x 3 m x 6 m high were retrofitted using this cloth on the Hanshin expressway. The column retrofit was designed to enhance deformation capacity during seismic events as well as to enhance longitudinal steel which was dropped-off or cut-off over the column height in the original RC design. The procedure for application of the cloth is shown in Figures B.91-B.98, and close-ups of the reinforcement on a column are shown in Figures B.99-B.101. The columns are first sanded or sandblasted to prepare the surface and large holes, cracks, etc., are filled with an epoxy based putty. An epoxy primer is then applied, on top of which a layer of resin is applied (after gelation of the primer). The cloth is then laid on it and is pushed to ensure resin flow using rollers and hands. Once the layup is complete and the component has cured, a finish coating that serves as a color and a protective coating is applied. Details related to materials are given in Table B.11.


Fig. B.91. View of columns before application of Torayca sheet.


Fig. B.92. Surface preparation (sanding).


Fig. B.93. Application of primer.


Fig. B.94. Final surface preparation (application of epoxy based putty).


Fig. B.95. Application of resin layer.


Fig. B.96. Application of Torayca sheet.


Fig. B.97. Application of a finish coat.


Fig. B.98. Columns after application of external reinforcement.


Fig. B.99. Close-up of Torayca sheet after impregnation onto concrete. (Impregnation is facilitated through the application of hand pressure.)


Fig. B.100. Close-up of Torayca sheet on a column showing overlap regions and resin flow.


Fig. B.101. Close-up showing application of the first layer of Toraya sheet (note the lack of overlap around the corner).

Table B.11
Materials Characteristics

Item

Characteristic

Test Method

Value

Carbon Fiber Sheet

Unit Weight (g/m2)

Specific Gravity

Tensile Strength (kgf/mm2)

Tensile Modulus (kgf/mm2)

 

JIS R 7601

JIS 7601

JIS 7601

300 (+/- 25)

1.8 (+/- 0.04)

> 460

23,500 (+/- 1000)

Primer

(Sho-Bond Neoprimer)

Bond Strength (kgf/cm2)

(7 days, ambient cure)

JIS A 6910

> 20

Resin/Epoxy

(Sho-Bond CE)

Flexural Strength (kgf/cm2)

Tensile Strength (kgf/cm2)

Shear Strength (kgf/cm2)

(7 days, ambient cure)

JIS K 7203

JIS K 7113

JIS K 6850

> 400

> 300

> 100

Details related to procedure and usage for a typical application are given in Table B.12.

Table B.12
Details for a Typical Application

Step

Process

Material

Amount (kg/m2)

Time Interval (at 20°C)

1

Application of primer

Sho-Bond Neoprimer

0.10

1 hr. - 7 days

2

Application of the first layer of reinforcement

Resin: Sho-Bond CE

Carbon Fiber Cloth

Resin: Sho-Bond CE

0.40

0.30

0.40

Within 7 days of application of the primer

3

Application of the second layer of reinforcement

Resin: Sho-Bond CE

Carbon Fiber Cloth

Resin: Sho-Bond CE

0.40

0.30

0.40

Within 7 days of application of the first layer of reinforcement

4

Application of the finish coat

Sho-Bond F-2

Sho-Bond F-2

0.15

0.15

Between 1 hr. and 3 days after the application of the final layer of reinforcement


Published: October 1998; WTEC Hyper-Librarian