Site: Tokyo Shiodome
Tokyo, Japan
Date Visited: October 1996
Host: Masayoshi Okoshi, Deputy Manager, Tonen Corporation
Summary: Retrofit of a bay in a parking garage owned by the Tokyo Metropolitan Highway Corporation through the application of tow sheet.


The project was conducted on an old parking structure in the Ginza area of Tokyo as a demonstration to the Tokyo Metropolitan Highway Corp. of the viability of slab strengthening through the use of externally applied carbon fiber tow sheet, and was one the of first applications demonstrated by the Tonen Corporation in 1992.

The slab of the parking structure showed extreme deterioration and loss of cover as seen in Figures B.114 and B.115. One bay of approximate size 22.5 ft. x 15 ft. was retrofitted using two layers of tow sheet in a grid pattern (Figs. B.116 and B.117). The grid/lattice pattern was used to reinforce the two way slab in both directions, and to provide areas for the visual monitoring of cracking and degradation. An adjacent bay was retrofitted using the technique of bolting stiff steel plates. A comparison of the external reinforcement in both cases can be seen from Figures B.118 and B.119. The carbon fiber retrofit was shown to be faster than the conventional method and has proven to be durable over the interval of time (March 1993 until the time of this WTEC visit).

Fig. B.114. Example of deteriorated slab region.

Fig. B.115. Loss of cover and spalling of concrete due to surface degradation.

Fig. B.116. Application of the tow sheet to the soffit of the slab.

Fig. B.117. Use of rollers for impregnation, and finishing of the surface showing a lattice pattern.

Fig. B.118. Overall view of the completed retrofit (1996) showing the lattice pattern with no cracks.

Fig. B.119. Overall view of the alternate retrofit strategy using stiffened steel plates.

Published: October 1998; WTEC Hyper-Librarian