The 90-metre-long balanced cantilever span of the Kochi metro’s viaduct that hovers over rail tracks at the Ernakulam Junction railway station is set to become an iconic landmark in Kerala.
The curved structure is one of its kind along any metro corridor in the country and will be ready by November 4, officials of DMRC and Haryana-based S.P. Singla Constructions (contractor for the pillar-less span), told the media.
The span will be painted aquamarine-blue (epoxy paint) that will enliven the structure for up to 20 years. The structure is ready, except for a three-metre portion at the centre of the span which will be readied in a week. It will be followed by laying of tracks and other equipment for the metro’s extension up to Thykoodam.
The span towers over the ground at 16 metres, which is more than the height of a five-storey building. Tunnel-like box segments, which are about the height of a room, support the massive span whose weight is balanced by two 65-metre-long fixed spans on either side. Each segment is three metres long. The total cost of the cantilever span and supporting girders, totalling 220 metres, is ₹58 crore.
A total of 120 pre-stressed steel cables, which will be 110 km long if put together, link the cantilever span with the girders.
“It is more or less like a hanging bridge supported by steel cables — only that the cables are concealed here beneath huge chunks of concrete. Two tower cranes, each with a capacity of five and six tonnes and capable of reaching up to a distance of 50 metres, were deployed to put the segments in place.
The structure, whose work began in January 2016, took 34 months to complete. It was mainly due to the delay in acquiring land from the Southern Railway, and the delay in getting clearance from the Commissioner for Railway Safety.
Workers had to be doubly cautious since a few hundred passenger and goods trains criss-cross the rail lines beneath. The presence of 25-kV overhead electric lines too was considered. DMRC engineers were posted all through to ensure quality of work and work-site safety, sources said.
The precast girders beyond the 220-m structure, on the railway station side and beside Karshaka Road, will be in place by December. Unlike in the rest of the metro viaduct, the cantilever structure will have steel parapets on the side, flanked by polycarbonate sheets.
“Readying the lengthy span was the most complicated task along the metro-rail corridor. Both the ends had to meet at the centre of the alignment. The quality of high-strength concrete and pre-stressing was of utmost importance,” said DMRC sources.
Source: The Hindu