Metro Rail ROB Over Malakpet Station Took Just 25 Days

The main span of the Metro Rail Over Bridge (ROB) at Malakpet, of a length of 164 ft, was constructed in just 25 days during this month, which is a new record in India in ROB construction, said MD, HMRL, N V S Reddy.

With a total length of 394 ft (120 mts), the Malakpet Metro ROB was on a curve, and it had to be built at a height of about 58 ft over the narrow portion of NH 65 and over an already existing railway bridge adjacent to Malakpet railway station.

As in the case of the recently completed Begumpet ROB, here also the "Bridge Builder" method of construction was used, with two huge 100-ton bridge builders mounted on to the already built Metro viaduct on both sides of the ROB - i. e. on the Dilsukhnagar side and the Nampally side. The total bridge was built in three portions with the main span length being 164 ft and the two ends on the Dilsukhnagar and Nampally sides being 98 ft and 131 ft respectively.

The bridge conditions were simulated in the Uppal casting yard and the segments were pre-cast in a "match casting" mode, and these precast segments were brought to Malakpet and launched one after the other with the help of a heavy duty crane and the bridge builders in a sequential manner from both sides.

The main portion of the Metro ROB over the existing Malakpet railway bridge was constructed with 12 precast segments. Each precast segment was lifted by heavy duty cranes and placed on the previously laid trolley on top of the deck slab and held by the bridge builder with the help of a winch of 80-ton capacity. The segment was then rotated, manoeuvred and lowered into its specific slot in front of the already erected viaduct and aligned, using temporary beams, stuck with special glue, and stung with special metallic cables.

Once the segment was made an integral part of the viaduct, the segment itself became the base to move the bridge builder forward to launch the next segment in a similar fashion.

The launching of these segments could be done only after midnight in a 3-hour block period given by the railways during which the train operations were suspended each time.

Appreciating the engineering design and execution skills, and the dedication with which the L&T bridge engineering team led by two railway bridge engineers K M Rao and M Y Kondalu, Reddy stated that it was a remarkable engineering achievement in Metro Rail construction in the country.