Seismic reinforcement, shopping center, carbon fiber sheet

The Hyogo prefecture earthquake that occurred early in the morning of January 17, 1995 caused enormous damage mainly in the Osaka and Kobe region. Also, on the Hanshin Expressway, especially, the Hanshin expressway No. 3 Kobe Line suffered major damage such as on a bridge at 5 places. In order to prevent the same damage again, from 1997, Hanshin Expressway has been strengthening the seismic reinforcement using the concrete filled steel reinforcement method and concrete jacketing method, especially in the pillar of the concrete pier.

Steel Jacketing and concrete jacketing method are construction methods of reinforcing the pier part by seismic reinforcement of a steel plate or concrete on the concrete pier. In the case of the steel jacketing method , the mortar is injected into the interior as it is assumed to be one structure

Photo: Noda Hanshin site
Photo: Noda Hanshin site

However, in the bridge piers (about 35 piers ) in Noda Hanshin Ekimae shopping street, Himejima station front, Tsukamoto shopping street, construction work space is narrow (it is necessary to minimize the removal restoration range), the carbon fiber sheet jacketing method construction method was adopted from perspective that there are many stores (shortening of the construction period is necessary).

Unlike steel sheet, carbon fiber sheet is lightweight, soft, can be cut and applied in a small range of construction and it is characterized by high applicability in the field. In addition, the carbon fiber sheet can be cured by overlaying the sheets in several layers, penetrating the resin, and within a certain range, it can obtain an effect comparable to steel plate reinforcement. In addition, since the resin can be cured in a short time, it also shortens the construction period.

On the other hand, as compared with the ordinary steel plate jacketing method and concrete jacketing construction method, there are some disadvantages such as difficulty in obtaining a reinforcing effect integrated with the pier base and being vulnerable to fire.
So at Hanshin Expressway, regarding concrete pier seismic retrofit reinforcement by the carbon fiber sheet jacketing method, it is currently applied only when restrictions are imposed on supporting bridge pier forms in the field.