The Sewri-Nhava Mumbai Trans Harbour Link (MTHL) could give the city its third cable-stayed bridge after the Bandra-Worli Sea Link and the under-construction Versova-Andheri-Ghatkopar Metro corridor.
Although costly,a cable-stayed bridge is useful for stretches where the span,or the distance between two piers,is longer than usual.
According to structural specifications by the Mumbai Metropolitan Region Development Authority (MMRDA),there are four stretches on the MTHL that will need longer spans to overcome navigational challenges. The MTHL walkthrough prepared by the MMRDA shows the use of a cable-stayed bridge on these stretches.
The walkthrough is indicative. A cable-stayed bridge can be used for that portion. The other options are using a balanced cantilever bridge or an extradosed bridge. The decision on which bridge to build depends on the consortium constructing the MTHL, an MMRDA engineer said.
A cable-stayed bridge is built with one or more columns called pylons with cables supporting its deck,while a balanced cantilever bridge has two well-anchored arms and one span between the arms,creating an arch-type structure. An extradosed bridge is a combination of a girder-based and cable-stayed bridge.
A balanced cantilever bridge would be more cost-effective compared with the other two types of bridges, the engineer said. The Vashi bridge built over the Thane creek to connect Vashi and Mankhurd uses the balanced cantilever method of construction.
The four stretches on the MTHL in need of longer spans are Pirpau jetty,requiring five spans of 120 metres each; HPCL requiring two spans of 120 metres each; Thane creek with two spans of 170 metres each; and Panvel creek with two spans of 170 metres each. The average span is otherwise about 50 metres.
Mumbais first cable-stayed bridge was a 500-metre-long structure built as part of the Bandra-Worli Sea Link,which was opened in 2009. The Versova-Andheri-Ghatkopar Metro will have the second such bridge a 175-metre long structure across the Jog flyover on the Western Express Highway.
The MMRDA had proposed to build another cable-stayed bridge over the Manori creek but the project is currently on hold due to environmental concerns.
The 22-km MTHL,estimated to cost Rs 8,800 crore,is going through a third round of tendering,having seen a poor response the first two times. This time,six consortia comprising 18 companies have submitted proposals to build the project,which will boast of the longest sea link in India.