India: BMC to build 'Bow-String' bridge to connect coastal road with Bandra Worli sea link

The Brihanmumbai Municipal Corporation (BMC) in the financial capital of India, Mumbai, is planning to construct a "Bow-String" bridge to connect the 10.58-kilometre Mumbai Coastal Road Project (MCRP) with Bandra-Worli Sea Link (BWSL).

To ease vehicular congestion, the BMC has started MCRP to significantly reduce travelling time in Mumbai. The high-speed road project is expected to originate from the Princess Street flyover near Marine Drive and will end at BWSL. 

Notably, the decision to build a "Bow-String" bridge was taken after the local fishing community started a protest. Earlier, an arterial bridge was to be constructed on monopiles (pillars) to connect MCRP with BWSL. However, the fishing community argued that the gap between pillars was not adequate for boats which could be dangerous for boats during strong waves, as well as hamper their livelihood.

They demanded that the gap between pillars be around 200 metres while the BMC suggested 60 metres. As the protests snowballed, Chief Minister Eknath Shinde intervened, earlier this year in January and recommended that the gap be increased to 120 metres. 

After a relative period of back and forth, BMC gave up on the arterial bridge and decided to construct a ‘Bow String’ girder bridge.

“The primary reason why we chose this option is that this bridge doesn’t require additional piling works and the removal of one of the existing monopiles will not pose any threat to the structure. This bridge will be held by high-tension chords and these kind of designs are suitable for smaller bridges built without any strong foundation,” one of the officials was quoted as saying by the Indian Express.

A Bow-String bridge is a type of bridge which is held together using high-tension chords instead of resting on pillars for support. The arch-shaped chords support the end of the bridge tightly with the surface. Due to the shape of the bridges, which resembles that of a 'bow', the name came into being. 

One of the major reasons why such a bridge has been preferred by the BMC is because of safety. After BMC considered the requests of fishermen, the gap between pillars was increased but it proved to be unsafe for the overall structural integrity of the bridge. 

Currently, BMC has set a November 2023 deadline for the project. However, with the change in design, the deadline may very well be pushed beyond May 2024. 

“The work on the other stretches of the coastal road is on schedule. This bridge will come up in the northern fag-end, which is within the last one kilometre. If the remaining stretch is ready before bridge work completes, then the MCRP may be opened for vehicular movement,” added the official.