Rehabilation work of the Karal Railway Over Bridge (ROB)

JNPT decided to take up the rehabilation work of the Karal Railway Over Bridge (ROB). It got functional in 1991. There are 36 spans of varying lengths having 37 expansion joints in this bridge and the length is 700m. During the heavy rains in july, 2005 the wearing coat and expansion joints were severly damaged. These damaged coats and joints were subsequently
repaired and re-laid. But the bridge was still not working satisfactorily. The vibrations of bridge during the vehicle movement were becoming more and more noticeable. The major observation during the site visit are as follows…

1. Expansion joints were not functioning properly. In the original design there was no provision of appropriate expansion joint.
2. Slab area of expansion joint was found to be damaged severly due to heavy vehicular movement. The gap between two spans has become significant and concrete had deteriorated.
3. The neoprene/elastomeric bearings provided in bridge were inadequate for heavy vehicle movements. They appear to be bulging out and damaged.
4. There was a visible sag in the superstructure in many spans. The typical structural failure cracks in the girders were observed.
5. The new expansion joints could not last long due to excessive vibrations and the poor quality of deck concrete at the end of span.
6. The substructure/piers appeared to be sound.

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