Friday , 22 January 2021

Triumph in precision engineering

On precision engineering and technical triumphs…

We have given to the city not only a civil engineering and architectural marvel, but a great traffic solution. That said, having been involved with the project as engineer from day one, the happy conclusion of an year since it was commissioned gives me great personal satisfaction and pride.

The precision engineering statement relates to the accuracy with which we have completed the construction of the structure. In the case of the Bandra cable stayed bridge, the requirement was for the tower construction which had to be completed within three millimeter accuracy. The tower geometry – it is diverging in one plane and converging in the other – was a very difficult exercise. We managed the final construction within one millimeter accuracy. It was the same again in the case of the superstructure on either side of the cable-stayed bridge. It was a big challenge to achieve the desired profile and accuracy. During the execution of the project we had to address engineering challenges like drilling foundations in variable geological conditions across the sea stretch between Bandra and Worli. There was an extensive exploration and drilling programme and complex load design calculations on pier by pier basis. The process involved building the super structure of the approach bridges with the biggest spans in the country, constructing the 128 metre diamond shaped concrete tower with unique leg shape and then the erection of the 2,00,000 MT Bandra cable-stayed deck supported on stay cables.

The project incorporated the most modern technologies and methodologies for the first time in the country. BWSL is the first cable- stayed bridge built in India in open sea conditions. In no other project in the country, including the DMRC, have heavier span segments been lifted. To test the pile load we employed the Osterberg Cell technique within the foundation. The project also made use of the Asian Hercules, among the biggest floating shear leg cranes in the world, to move a 1,260 MT launching truss from Bandra to the Worli end of the main cable stayed bridge.

The delay…

It has not been easy. The delays have purely been on account of external reasons. I have to say the bridge is a remarkable feat in the light of several obstacles like us having to stop work for up to five and a half months in a year due to difficult sea and monsoon conditions, not to mention the objections from the fishing community and various permissions required. The difficulties were also in the form of mobilising construction equipment from various parts of the world for the project. You have to agree that the scale of the project and the logistics involved is staggering.

Environmental practices…

There was constant monitoring of all environmental parameters. We took extreme care to reduce the level of noise. Waste water coming from the batching plants and labour camps were always treated. Some of this was used for curing purpose and the remainder was released into the sea. We were commended with the Golden Peacock Award for outstanding achievement in Occupational Health and Safety for the project.

Project Markers

Designed by Dar Consultants, the UK, the Bandra-Worli Sea Link was commissioned by Maharashtra State Road Development Corporation (MSRDC) and built by Hindustan Construction Company (HCC). The technical consultant for the project was VSL Singapore Pvt Ltd. The Rs 1306 crore bridge was inaugurated on June 30, 2009 by Sonia Gandhi, Chairperson, United Progressive Alliance (UPA) and Member of Parliament.

• First Indian cable-stayed bridge, with largest span, to be constructed in open sea.

• 4.7km, twin, 4-lane independent carriageway bridge across the open sea.

• The length of the bridge is 63 times the height of the Qutub Minar in Delhi.

• Its weight is equivalent to 50,000 African elephants.

• The length of the steel wires used is equivalent to the circumference of the earth.

• The height of the cable-stayed tower is 128m, which is equal to a 43-storey building.

• A total of 424 cables were used for the cable stays at Bandra and Worli.

• 16-lane toll plaza with 20m wide promenade and state-of-the-art traffic monitoring, surveillance, information and control systems.

• 2342 pre-cast segments for total bridge with varied width.

• 40,000mT of reinforcement, 2,30,000 cum of concrete, 5,400mT of post tensioning strands and bars used.

• Bridge consumed nearly 22,235 tonnes of steel.

• Osterberg cell technology used for the first time in India to check pile strength up to 9600mT.

• Asian Hercules, one of the world’s largest floating shear leg cranes, used to shift a 1,260mT launching truss.

• Up to 25m high pier in open sea, giving ample headroom to marine traffic.

• Use of Polytron Disc in bearings on piers for the first time in India.

• Cables sourced from the Shanghai Pujyang Cable Company subjected to a series of quality and engineering tests including fatigue tests of two million cycles.

• Cables made of high tensile steel designed to take the maximum load of 900 tonnes.

• 92,000 tonnes of cement was utilised to make BWSL.

• 3000 workers were employed to work on the sea link project. These included engineers, technicians and consultants from China, Egypt, Canada, Switzerland, Britain, Serbia, Australia, Singapore, Thailand, Hong Kong, Indonesia and the Philippines.

• The total power consumption of the sea link is 1000KW or 1MW per day. The power required for the illumination is being provided by Brihanmumbai Electric Supply and Transport (BEST) and Reliance Power. The bridge also has its own in-house diesel generator to meet critical emergency power requirements.

• The sea link reduces travel time between Bandra-Worli from 60-75minutes to about seven minutes.

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