Japanese State of the Art on Seismic Retrofit by Fiber Wrapping for Building Structures: Technologies and Research and Development Activities

Since the 1995 Hansin Earthquake, need of seismic retrofitting of existing structures has been strongly understood. Being expected to reduce inconvenience in retrofit work of buildings, some techniques using carbon and/or aramid fibers have been widely employed in Japan due to lightweight, flexibility, non-welding, and easy handling. Many of these techniques aim to improve shear capacity and ductility of existing reinforced concrete columns and may be called "Standard Method" due to the almost common working procedure. The procedure includes (1) wrapping columns in the transverse direction using continuous fiber sheets, (2) impregnating epoxy resin into the sheets to make FRP composite, and (3) doing surface treatment or arrangement of concrete to prevent voids or wrinkles. This "Standard Method" of fiber wrapping has induced development of other methods that improve a working process or can be applied for other structural members. In the future, the fiber wrapping technique will be more spread, however, it requires an approved and common quality control method. An education program for retrofit engineers and craftsmen should be also established.