Steel decks fixed for MTHL, India’s longest sea bridge

India's longest sea bridge finally seems to be taking shape as work on erecting the first pair of Orthotropic Steel Decks (OSD) for the Mumbai Trans-Harbour Link project connecting Sewri with Nhava Sheva was successfully completed on Tuesday.

MMRDA shared a photo of the work on Twitter and posted: "This nice picture is real! MTHL Taking Shape!! The 1st pair of Orthotropic Steel Deck (OSD) Spans erection successfully completed yesterday between Pier Location MP124-125 (ID: OSD 4N1 and 4S1)." It may be noted that OSD 4N1 (North Span) was placed on January 14 while OSD 4S1 (South Span) was placed on February 7.

Orthotropic Steel Deck

The erection of the Orthotropic Steel Decks marks a milestone event as it is one of the most complex construction activities of the Phase-I works which is being carried out by the L&T-IHI Consortium. Phase-I Package-1 involves construction of 10.38 kms of long bridge across the Mumbai Bay including Sewri Interchange at Mumbai Side.

OSD is a steel deck superstructure, strengthened or stiffened both transversely and longitudinally, which will carry the vehicular load more efficiently among three planes and improve the load-carrying capacity of the bridge as compared to concrete superstructures.

The decks also weigh less compared to concrete or composite girder ones, and have a longer span of 180 metres. According to a press release, OSD is the ideal solution considering MTHL site conditions such as navigational channels, discharge channels, and longer pier-to-pier distances. It is also more cost-effective compared to the cable stay or suspension bridges.

The steel spans are fabricated in workshops in Japan, Vietnam, Taiwan etc. and then delivered to India to enable faster construction work and lessen deck-related on-site activities. Once assembled, the OSDs are transported to the spot on a barge which was specifically designed and manufactured for the purpose. The flat top ballastable barge weighs 5,359 MT and is 110 metre in length and 64 metre in breadth, which is around the size of a football ground.

Work details

The MTHL, also known as the Sewri Nhava Sheva Harbour Link, is a 22-km long, 6-lane bridge with around 16.5 km over the sea and about 5.5 km long viaduct on land on either side. The link has interchanges at Sewri in Central Mumbai, Shivaji Nagar at Mumbai Bay and NH-4 B at Chirle, Navi Mumbai.

The total length of spans of the OSD superstructure in both carriageways of MTHL is about 6.41 km. The width of the steel superstructure is about 14.92 metre for each carriageway. The total steel quantity to be used for the OSD superstructure in MTHL will be about 87,452 MT.

65% work done

MTHL has been identified as the important infrastructure to improve the connectivity between Mumbai and Navi Mumbai and continue economic development in Mumbai Metropolitan Region. Once complete, it will reduce the travel time between south Mumbai and Navi Mumbai to 20 minutes from around 120 minutes.

The total cost of the project is Rs 17,843 crore and 80 per cent of piers works are completed till now. Of the overall project, about 65 per cent completed. The project is expected to be completed in the year 2023.

It will feature approach sections, interchanges, intelligence transport system and other amenities required for a sea bridge. The traffic conditions on the stretch will be monitored and managed from the traffic control centre with the help of CCTV cameras and related facilities installed on the stretch.