RETROFIT OF OTHER STRUCTURES

Although the primary application areas for the use of fabric/tow as external reinforcement are in buildings, bridges, tunnels, chimneys and smokestacks, fabric sheet forms have been successfully used on a variety of other structures for purposes ranging from control of cracks and exfoliation of concrete to strengthening and seismic retrofit. One promising area is the repair and/or strengthening of historic structures where the use of conventional repair/retrofit methods would result in significant changes in appearance. Since the sheet forms are extremely thin and conformable, they can easily be used without fear of causing dramatic aesthetic changes. Figure 4.51 shows an example where Replark was used to repair a 22 m high sacred arch built in 1929 that would otherwise have collapsed from age and deterioration.


(a) application of Replark to the post


(b) retrofitted and repainted arch
Fig. 4.51. Repair of the Sacred Arch in Nakamura Park in Nagoya.

These materials have also been used to repair, strengthen, and upgrade concrete retaining walls (Figure 4.52), concrete water tanks, reinforced concrete sewer pipes, prestressed concrete "hume" pipes (large water supply pipes and pipes used in penstocks), foundations and pedestals. In some cases they have been used for repair, strengthening and/or waterproofing of water channels and box culverts (Fig. 4.53). Due to the ease of application on concrete and wood, sheet type materials have been used extensively for the strengthening of aged and deteriorating wooden and concrete electric poles, especially in their use on railway lines (Fig. 4.54). In order to ward against shocks, an insulating layer of glass fabric is often used in conjunction with the carbon fiber sheets. The FITS system, which uses aramid fibers, is widely touted as more suitable in this application due to its nonconductive characteristics. Because of its resistance to corrosion and its potential for rapid installation, these fabric sheet forms (primarily carbon fiber-based) are increasingly being used for repair and retrofit of marine structures such as dock walls and quays (Fig. 4.55). Glass fiber tow sheet has also been used to repair walls of block balustrades. In this application, a single layer is sufficient to strengthen and renew a badly exfoliated and corroded section (Fig. 4.56).


(a) overall view of the retaining wall


(b) close-up showing application of horizontally aligned shee
Fig. 4.52. Use of Replark sheet for the repair of a railway retaining wall in Sakai, Osaka.


Fig. 4.53. Repair of the inside walls of a box culvert.


Fig. 4.54. Use of FORCA FTS-C-200 carbon and FTS-GE-300 tow sheet for the repair of electric poles.


(a)


(b)
(c)
Fig. 4.55. Use of Replark for repair of a quay in Tokyo Bay. The sheet material enabled retrofit in a confined area.


Fig. 4.56. Schematic details of repair of concrete block balustrade using FORCA glass tow sheet.


Published: November 1998; WTEC Hyper-Librarian