Construction sites : all the lines of Hanshin expressway
Keywords : Steel bridge piers, Concrete bridge piers, Superstructure, Seismic reinforcement
In the south part of Hyogo prefecture, the earthquake occurred early in the morning of the 17th January 1995 and the infrastructures in the area suffered serious damages including the Hanshin Expressway structures. Based on the knowledge and experiences obtained from this disaster, the seismic design standards of the Hanshin Expressway have been reconsidered and reviewed.
In addition, earthquake-resistant countermeasures have being implemented for the existing bridges designed with old standards.
The general classification of the earthquake-resistant countermeasures in the bridge sections can be divided into the following three types:
(1) The earthquake-resistant countermeasures of the steel piers
- Concrete Filled Steel reinforcement method is a construction method that fills concrete inside the bridge piers to a certain height and enhances earthquake resistance (strengthening against bending and collapse).
- Longitudinal rib reinforcement method is a construction method which adds ribs in the longitudinal direction inside the bridge piers, reinforces the existing ribs and increases the earthquake resistance (strengthening against failure ).
- Anchorage reinforcement method is a construction method that reinforces the base's parts of the pier and increases the earthquake resistance (strengthening against collapse).
(2) Anti-earthquake countermeasure of concrete piers
- Steel Jacketing method is a Construction method to increase earthquake resistance (make it strong against failure). In this method the mortar is filled between the steel plate and the pillar.
- Concrete jacketing method is a construction method in which concrete is wound around the pier of concrete (thickness enlargement ), and the earthquake resistance is enhanced (strengthened against failure).
Carbon fiber sheet Jacketing method is a construction method that raises the earthquake resistance (strengthening against breakage) by winding a carbon fiber sheet around the piers of concrete. The carbon fiber sheet penetrates the resin and hardens it.
(3) Anti-earthquake countermeasures for superstructure
- Seismic isolation rubber support : By superimposing rubber and steel plates in a sandwich-like shape, it has the effect of following the movement of the girder and reducing the seismic force.
- Girder Connection : a bridge collapse prevention device,It connects the two consecutive girders with the cable chain and prevents the girder from falling.
- Installation of displacement restricting structure : When the support is damaged, the girder falls onto the beam and prevents a difference in level from being formed on the road. Increase the area of the beam top surface to prevent the girders from falling.
- Securing the girder length : Preventing the girder from falling by rigidly connecting the girders, It connects two girders with the cable chain and prevents the girder from falling.
- Displacement restriction device : When the bearing is damaged, the girder falls onto the beam and prevents it from moving and making a step on the road.