Iconic Structure: India’s first asymmetric cable-stayed bridge inaugurated

India’s first asymmetric cable-stayed bridge inaugurated

With the inauguration of the much-awaited Signature Bridge on November 4, 2018, India completed its first asymmetric cable-stayed bridge. Since its conceptualisation in 2004, the project’s journey had been marred by several challenges, both administrative and technical. Despite the delay, the bridge boasts of several unique features and has seen the involvement of various companies across the globe. With the commencement of public operations, work for enhancing the aesthetics of the bridge has started and is expected to transform it into a tourist landmark.

“Bridging” the gap

Implemented by the Delhi Tourism and Transportation Development Corporation (DTTDC), the 575 metre Signature Bridge links National Highway-1 near the existing T-point at Wazirabad on the western bank of the Yamuna river to the Marginal Bund road at Khajuri Khas on its eastern bank. The main span of the bridge is spread over 251 metres, while the side spans have a total length of 324 metres. The bridge’s composite deck has eight lanes, four in each direction. It is 35.2 metres wide and is supported by lateral cables – 30 on the front and 8 at the back – placed at 13.5 metre intervals.

One of the most striking features of the bridge is its inclined pylon. The height of the steel pylon is 154 metres, twice that of the Qutub Minar. The top of the pylon is formed by a steel-glass structure which includes an inspection platform. Around 14,500 tonnes of structured steel and 6,300 tonnes of reinforced steel has been used in construction. For the first time in the country, E355 grade steel has been used for the pylon work of a bridge.

The journey to reality

The first announcement for the construction of the bridge was made in 1997. Initially, the plan was to construct a simple span bridge which envisaged an investment of Rs 4.59 billion. Following the announcement, an MoU for the implementation of the project was signed between DTTDC and Delhi’s public works department (PWD) on August 27, 2004. Once the project was taken over by DTTDC, the construction of a cable-stayed bridge was planned. It was decided to implement the project through a single package, involving the construction of both the main bridge as well as the eastern and western approaches. This was estimated to cost Rs 8.87 billion. However, the plan of executing the project as a single package failed to take off even after the award of the contract.

Finally, in 2009, the decision to split the project into two packages was taken and a project cost of Rs 11.31 billion was finalised. The first package entailed the construction of the western and eastern approaches while the second package involved the construction of the cable-stayed bridge. In February 2010, the project was awarded to a joint venture (JV) of Gammon India, Brazil’s Construtora Cidade and Italy’s Tensacciai. Following the project award, construction commenced in March 2010.

Challenges on the way

The journey of the project, right from conceptualisation to construction, was fraught with several challenges. One of the major issues faced in the initial stage was that of obtaining the forest clearance. While DTTDC had applied for the clearance in 2007, it was only granted after a five-year period in 2012. “Geological surprises and the consequent need to redesign and execute foundation P-23 of the bridge proved to be a major challenge,” says Shishir Bansal, chief project manager, Wazirabad Bridge Project, DTTDC. After carrying out the soil investigation, it was revealed that the rock profile of the area was sloping, thereby warranting a change in the design of the foundation P-23.

In August 2012, a proposal for an integrated well-pile foundation was approved. In December 2014, Gammon India acquired two new reverse circulation drilling rigs from Korean firm Buma CE, each costing Rs 700,000-Rs 800,000. These rigs were used for undertaking piling work on the sloping rock terrain at the offshore and onshore level of the river. The piling work was completed within a span of 45 months, in April 2016. With this, the Signature Bridge project became the second bridge project in the country to feature a combination of well and pile foundations. This extensive piling and well foundation supports P-23 and carries most of the 6,600 tonne tensile load exerted by the cable-stressed pylon for the main bridge.

Another major challenge was the identification of a workshop for pylon fabrication. After extensive research, the decision to procure steel from China was taken and the pylon base of the bridge weighing 450 tonnes was fabricated at Jiangsu province near Shanghai. The base was transported from Shanghai to Kandla port in Gujarat. It was then transported from Kandla to Wazirabad in Delhi to the bridge site, covering a distance of 1,640 km by road. The base was transported in modular trailers with 12 axles and 168 wheels with each axle having independent hydraulic arrangement. Transportation of the shipment was done mainly at night. A separate bypass had to be set up en route besides bridges, roads and toll plazas for facilitating the movement of over-dimensional cargo.

“The welding of the first segment (L0) with the base of the pylon posed another major challenge as it required the welding to be done at a very sharp acute angle,” explains Bansal. “As welding plays a major role in the overall stability of the structure, no shortcomings in the quality were acceptable,” he adds. However, this issue was overcome with the assistance of several Chinese and German experts.

Given the solutions adopted to overcome several unexpected challenges experienced during construction, the cost of the bridge escalated from the initial estimate of Rs 11.31 billion to Rs 15.18 billion. Receiving a sanction for the revised project cost proved to be another hassle for DTTDC. Further, the invocation of the corporate debt restructuring and strategic debt restructuring schemes for the debt-laden contractor further threatened project execution. Inadequacy of engineering staff was another major issue which plagued the project.

Lessons learnt and the way forward

Despite all the challenges – lack of funds, difficulty in getting environmental clearance, geological surprises, bureaucratic and administrative hassles – the project has finally been opened for public use. DTTDC has already commenced work for constructing an observation deck atop the 154 metre pylon, which is likely to be completed by February 2019. Further, the installation of high speed lifts, pylon maintenance units and flooring, roof and glass facade of the observation deck will take about two months to complete. Once completed, the bridge will be handed over to the PWD for maintenance. Special machines have been procured from Korea for maintenance purposes. These are expected to arrive in January 2019. The government has also laid out plans of developing the landmark bridge into a prominent tourist destination by enhancing its aesthetic features. Though the iconic structure has opened only recently, issues of vandalism, stealing of nuts and bolts and rash driving on the bridge have come to the fore. To address these concerns, several suggestions such as fixing a speed limit and installing speed breakers on the bridge have been mooted.

Several key lessons can be learnt from the delayed execution of this iconic project. It highlights the need to deploy a dedicated team for project execution, greater cooperation among different stakeholders involved as well as simpler and faster processes for granting approvals and clearances. Improvements in all these areas are definitely needed for execution of similar projects in the future.

(Liya Rashid with inputs from Shishir Bansal, Chief Project Manager, Engineering, Signature Bridge, DTTDC