Tilted bearing of Saraighat Bridge fixed in three hours

NF Railway engineering feat

GUWAHATI, Jan 16: Just a three-hour traffic block and scripting of an engineering feat! It sounds not in sync with each other. This is a feat scripted by NF Railway engineers.

In just three hours the team of NF Railway engineers rectified the bearing arrangements of Saraighat Bridge on January 12, 2018. Bearing are the arrangement by which the bridge rests on the piers (pillars). The engineers not only link the bridge girders to the pillars but also facilitate the lateral movement of the bridge as a result of expansion etc.

It was probably during the 6.1 Richter scale earthquake of September 21, 2009 that the bearings under two end girders got tilted. While this was not considered unsafe, the bearings in fact needed proper rectifications. The bridge was kept under observation and speed of trains was kept at 45 kmph. Rectification of the bearings was indeed a herculean task as the ends of the bridge girders were to be lifted by about 10 centimetres. Such work was never taken up earlier. The team of Railway Engineers of NF Railway accepted this challenge. After thorough research and design, the engineers decided that the tilted bearings of this bridge would be rectified. Accordingly, necessary preparations were made to deal with all kinds of possible adverse situations that could occur so as to avoid disruption to this vital connectivity. Requisite bearing members were arranged and heavy duty lifting jacks of 500 tonne capacity apart from other machinery were mobilized. To rectify the bearings without any hazard, the rail and road traffic on the bridge was suspended temporarily for three hours, a press release said. Two separate teams of engineers and skilled workers were deployed on both sides for rectification of bearings. Hydraulic and mechanical jacks were installed under the railway girders. With the help of these jacks, the railway girders were lifted as required. The bearings were removed from their place and installed back to correct inclition after cleaning etc. After ensuring correct position of the bearings, the bridge girders were lowered back to origil position. Road surface was brought back to origil level. Rail track was also re-fixed and regular rail and road traffic movement was permitted within three hours, the release said.

As a matter of abundant precaution, in addition to the active hydraulic jacks, two additiol hydraulic jacks of 500 tonne capacity and two mechanical jacks of 100 tonne capacity were kept ready as back-up arrangement. To prepare for the worst scerio of an earthquake occurring during the work execution i.e. when the bridge would be in lifted condition, the girders were tied with cables with fixed structures.

The speed restriction of 45 kmph is planned to be relaxed now which would have far-reaching implication on smoothening railway connectivity to Northeast India, the release added.