Site: Carbon Fiber and Reinforcement Research Association (CFRRA)
[Workshop at Osaka]
Secretariat - c/o Tonen Corporation
Palace Side Building, 1-1-1 Hitotsubashi
Chiyoda-ku, Tokyo 100, Japan
Date Visited: October 1996
Hosts: M. Uemura, Tonen Corporation & Chief Secretary, CFRRA
M. Okoshi, Deputy Manager, Tonen Corporation
T. Hoshijima, Mitsubishi Chemical
Dr. Koga, Obayashi Construction Company
Summary: The Carbon Fiber Repair and Reinforcement Research Association (CFRRA) was formed with the aim of promoting the use and research of carbon fiber sheet technology in the retrofit and strengthening areas.

BACKGROUND

The CFRRA was formed in July 1994 to promote the use of, and research into, carbon fiber sheet technology in the retrofit and strengthening areas. At the time of the WTEC visit, it had over 250 members, most of which are small construction firms. The association consists of four main classes of membership:

The chairmanship rotates among the large general contractors. At the time of the visit, the chairmanship was held by Shimizu.

The technical committee is chaired by Professor Ikeda of Yokohama National University. The committee is divided by function into four subcommittees: bridge superstructure, bridge substructure, building, and tunnel. The association maintains very close ties to the Public Works Research Institute (PWRI), the Building Research Institute (BRI) and the various expressway and railway corporations, conducting joint research and demonstration projects, and assisting in the preparation of design guidelines.

ACTIVITIES OF INTEREST

CFRRA reported that over 2,000 applications/projects have been completed using carbon fiber sheets as external reinforcement. It was estimated that 25,000 m2 of sheet were used in 1993, 60,000 m2 were used in 1995, and it was expected that 600,000 m2 would be used in 1996. Applications range from the strengthening of columns (Fig. B.2), strengthening of road decks (Fig. B.3), repairs of floors and beams (Fig. B.4) to repairs of retaining walls (Fig. B.5), tunnels, quays (Fig. B.6) and chimneys.

A large variety of structures have been retrofitted. A significant number of the projects have been conducted by the Tonen Corporation. To date over 250 bridge columns have been retrofitted using carbon fiber sheets and another 800 are in various stages of implementation. Seismic column retrofitting is considered mainly for flexural and shear strengthening rather than for the confinement in the plastic hinge region. This is one reason why a number of large rectangular columns have also been retrofitted.


Fig. B.2. Strengthening of columns.


Fig. B.3. Strengthening of a bridge deck slab.


Fig. B.4. Repair of deteriorated floors and beams in buildings.


Fig. B.5. Repair of retaining walls.


Fig. B.6. Repair of a quay.

There appears to be a clear preference for the use of carbon fiber sheets over glass or aramid even though Tonen makes all three varieties and buys fiber externally for all three. Carbon fiber sheets offer greater durability and chemical inertness, coupled with the lack of moisture-induced degradation and the absorbence of UV light by carbon fibers (which protects the resin system from degradation), all of which are important factors influencing their selection.

Currently there is a critical need to strengthen and retrofit bridge deck slabs to increase the load capacity from 20 tons to 25 tons. This is viewed as an excellent application for carbon based sheet materials, and has resulted in a growing interest from the three firms in this area. In addition, this type of retrofit is considered to help correct crack-based deficiencies that might otherwise result in punching failure. In an attempt to tailor materials for applications, Tonen Corporation and Nippon Steel have set up a collaboration for the use of high modulus carbon fibers for this segment of the retrofit market. Draft design guidelines have been prepared for columns, decks and tunnels and are currently under review. Tests are being conducted both under the aegis of the Ministry of Construction and the CFRRA, and at individual companies to assess the durability of the materials and techniques. These tests are expected to continue in the future.

Although over 100 patents have been filed by the member companies in Japan, there is widespread sharing of information and cross-licensing to enable the growth of this market.


Published: October 1998; WTEC Hyper-Librarian