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