The damage of Shinkansen viaducts was investigated in the range from the north entrance of Myoken tunnel to Nagaoka station, about 6 kilometers long, including the passing trace of the derailed train. The derailed train stopped at about 1.5 kilometers from the exit of tunnel as shown in Photo 1.
In this section of Shinkansen viaducts, the main structure was the multi-span reinforced concrete rigid-frame structure with reinforced concrete pile foundations of 16 m in length. There were two types of rigid-frame viaduct, including gerber type and divided-pillar type as shown in Fig. 1. The height of columns varies with route elevation and ground level.
The rigid-frame viaducts located between the north entrance of tunnel and the location where derailed train stopped suffered damage. Damage mainly occurred at top of the columns in rigid-frame viaducts, i.e. underneath the rigid-zone of connection of beam and column. The damage included flexural crack, spalling of cover concrete, flexural failure with extensive spalling of cover concrete and exposure of reinforcements as shown in Photos 2, as well as shear cracks at column midheight, which developed from the flexural crack, as shown in Photo 3. |
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