ABSTRACT
Japan is one of the world’s most seismically active nations, and damaged by earthquake disasters, the Great Hanshin Awaji Earthquake Disaster on January, 1995 and the Great East Japan Earthquake Disaster on March, 2011.
Seismic retrofit of highway bridges, jacketing piers and adding unseating prevention structures etc. was being developed. In this paper, seismic retrofit works of the bridge on major expressway which is secured in entire bridge system as the seismic isolated bridge, replaced piers and built new piers without traffic restriction is described.
Oiwake bridge is a three span continuous steel box girder, located on Meishin expressway, minimum skew angle is 26 degree, by the crossing conditions. The middle pier is the rocking column with hinges at each top and bottom ends (Figure 1). General view of Oiwake bridge. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig299_1.tif"/>
Plasticization of the superstructure and excessive displacement of the rocking columns, which have been revealed in the seismic performance verification stage, indicated that seismic retrofit design has to be carried out not only for the piers but also for the entire bridge system.
The seismic isolation design was adopted as the seismic retrofit method to both improve damping characteristic of the bridge and to minimize the seismic force by improving the energy dissipation performance. A decision was made to remove the rocking columns replace them by new piers with damping systems in order to achieve seismic isolation design. (Figure 2). Outline figures of seismic retrofit works. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig299_2.tif"/>
The method of retrofit which doesn’t require traffic restriction, this is a very important plan for the promotion of seismic retrofit work for old bridges as well as measures against aging of bridges.
