Tricky Metro ROB At Begumpet In Hyderabad Completed:- The Hyderabad Metro Rail Limited’s (HMRL) work on a Rail Over Bridge (ROB) over the Begumpet Railway lines and the Railway station, said to be a major engineering challenge, has been completed.
In a statement on Saturday, HMRL Managing Director NVS Reddy said the completion of the ROB had closed a critical gap in the Metro Rail Corridor III. Now, once the Oliphenta Bridge near Secunderabad station too was completed in the next few weeks, the extension of the 8km stretch of Nagole – Mettuguda upto Begumpet would become feasible, he said.
The construction of the Begumpet ROB was done in highly challenging conditions.
The Railway lines and the Railway station below are busy round the clock with continuous train movement and large number of passengers using the station, Reddy said, adding that the bridge was in a curve and wedged between the Begumpet flyover on one side and several buildings on the other side.
In view of the curved nature, the long length and height of 60ft, a special method called Bridge Builder was used for the first time in the Hyderabad Metro Rail project, Reddy said.
“Erection and movement of the ‘Bridge Builder’ device, weighing about 100 metric tonnes and heavy duty cranes to lift the precast segments etc., with all safety precautions and without causing disruption to the continuous movement of trains, station operations, passengers and road traffic was an engineering nightmare,” he said.
To meet these multiple technical challenges, the Bridge Builder was specially built and load-tested initially in the Uppal casting yard before bringing it to the Begumpet site and mounting it on the already built Metro via duct from both Varun Motors and Country Club sides.
After erecting the Bridge Builder on both sides, it was anchored safely with proper counter weights and special steel bars to ensure stability. Eighteen segments weighing 50 tonnes each were incrementally launched as a cantilever hanging bridge from both sides. Each precast segment was lifted in tandem by cranes and placed on a trolley on top of the deck slab with temporary tracks for moving the segment forward to the centre of the Bridge Builder.
The segment was then rotated from inside and lowered to its designated position. Once the segment was properly placed in its position, it was glued and attached to the already completed portion of via duct with HTS cables (steel wires) and pre-stressed.
This segment then became the support base for moving the Bridge Builder forward and all the 18 precast segments were thus attached to the earlier portion of the bridge.
Indian Railways could give only ‘three hour blocks’ for launching each segment after stopping trains beyond midnight once a week. After launching all the segments from both sides, in situ concreting was done for casting the middle segment by making use of a special anchoring platform.
Applauding the work of the specialized bridge team of L&T, led by Railway bridge engineer KM. Rao and his assistant MY Kondalu, Reddy said the entire bridge construction was flawless and done with military precision.
Salient Features :
• Length of ROB – 450ft
• Height of ROB – 60ft
• Length of central span – 213ft
• Length of end spans – 130ft and 107ft
• Weight of each segment – 54 tonnes
• Length of Bridge builder – 130ft
• Width of bridge builder – 213 ft