Indian bridges are crucial components of the transport infrastructure, serving as vital links between cities and enabling smooth mobility. India is home to a network of distinctive bridges, which include river and sea bridges, rail bridges and road bridges. The country also has a robust pipeline of upcoming projects, as a result of growing urbanisation and the ambitious infrastructure initiatives of the government.
Tracking growth
Historically, Indian Railways (IR) has been a front runner in bridge construction. Besides, IR has its own codes and manuals for bridges, which prescribe stringent inspection and maintenance schedules. Some of the notable accomplishments are the construction of India’s longest bridge, the Bogibeel bridge, and its tallest bridge, the Chenab rail bridge. India’s engineering expertise is reflected in these significant projects. Additionally, dedicated freight corridors include a variety of bridges with innovative designs and methods of construction.
The Udhampur-Srinagar-Baramulla Railway Link Project (USBRL), a national project aimed at providing all-weather rail connectivity to the Kashmir Valley, is an ongoing mammoth project. The USBRL involves construction of numerous tunnels (38) and bridges (927) in highly rugged and mountainous terrain. The combined length of these bridges is over 13 km. This includes the construction of the Anji bridge (725 metres), the first cable stayed bridge by IR. Furthermore, the ministry aims to build 1,000 rail overbridges (ROBs)/rail under passes in 2023-24.
Several landmark road bridges have also been constructed in the road sector. For instance, the Ministry of Road Transport and Highways (MoRTH) constructed the 5.56 km-long Mahatma Gandhi Setu in Bihar. The technological research done for this engineering marvel serves as a case study for other upcoming complex bridge projects. Similarly, the construction of ROBs on the Firozabad-Etawah section of the Agra-Lucknow Expressway was challenging. One of the ROBs built along the busy Delhi-Howrah rail line had an abnormal skew of 460 degrees.
Strong backing
Increasingly, new technologies, designs and construction methods are being deployed during the construction and maintenance phases in an effort to mitigate challenges in bridge construction.
The bridge design and construction process has evolved significantly with the introduction of smart digital technologies. Building information modelling is one such technology, which serves the architecture, engineering and construction segments. MoRTH has set up the Indian Bridge Management System (IBMS) to identify distressed bridge assets and inform the concerned implementation agency to take corrective measures. South Central Railway (SCR) has introduced drones for improving the inspection and maintenance of bridges. However, geospatial technology to remotely monitor the condition of bridges is an area that needs focus.
A few of the principal factors considered for the selection of a bridge construction method are regularity of the span lengths, horizontal and vertical profiles of bridge decks, and soil strata. Some of the commonly used construction methods in India are cast in-situ, balanced cantilever, span-by-span, full span and the incremental launching method. Precast segmental construction has also gained popularity and is used to achieve accelerated bridge construction, better quality control and reduced life cycle cost.
After design and engineering, the material plays a critical role in construction. Common construction materials include structural steel, reinforced concrete and pre-stressed and post-tensioned concrete. Additionally, the use of sustainable construction materials, along with other environment-friendly interventions, is an emerging trend within the sector.
Green moves
Several attempts have been made to reduce the environmental effect of concrete, which is used in volumes second only to water. These include the use of industrial by-products called supplementary cementing materials such as fly ash and slag cement. The first geogrid reinforced fly ash approach embankment was constructed for the Okhla flyover bridge in New Delhi.
Further, in order to alleviate the problems of scarcity of natural materials and reduce greenhouse gas emissions, alternative materials such as manufactured sand and iron, steel, and copper slag aggregates are being used. Different types of concrete are being developed, which includes self-compacting concrete, high performance concrete, fibre-reinforced concrete and ultra-high-performance concrete. Fibre-reinforced bridges could practically last for the longest time as they are completely non-corroding in nature, while wooden and steel bridges typically need refurbishment. The use of high-performance concrete with reduced permeability is the topmost mitigation strategy with respect to corrosion management.
Furthermore, the utilisation of tunnel muck, a waste product of tunnel excavation, in the USBRL project has resulted in the reduction of carbon emissions by 80 per cent, while simultaneously decreasing the project cost by 30 per cent.
Improving safety
Over the years, several Indian bridges have been found to be precarious to some degree. More needs to be done to remedy this. There is a scope for improvement in the conceptual specifications governing bridge construction methods. For instance, high levels of engineering diligence could go into detailed project reports. Additionally, it is imperative that the government counterparty’s capacity be enhanced in terms of strict contract enforcement.
The railway sector has been making concerted efforts to uphold safety standards. Several Indian railway bridges date from prior to 1947 and are constantly monitored. As a result of centralised regulatory supervision, feedback is efficiently incorporated at the earliest, as are lessons learned for future safety measures.
However, with a number of government entities and regulators at the national, state and rural levels, the road sector is yet to raise its standards at all safety levels. Nonetheless, the launch of the IBMS by the Indian Academy of Highway Engineers is a positive step forward. Over the past few years, with the help of the IBMS, a multitude of bridges have been identified for renovation and replacement.
Currently, bridges in India necessitate performance-based standards, with the objective of averting failure, irrespective of the size of the structure.
Major upcoming projects
The Mumbai Trans-Harbour Link, the upcoming longest sea bridge in the country, is 21.8 km long and will constitute six lanes with a holding capacity of 70,000-80,000 vehicles. The bridge is scheduled to be completed by December 2023.
The Pamban bridge, a vertical leaf-type bridge, being implemented by Rail Vikas Nigam Limited, involves the construction of a new 2.05 km-long bridge near Pamban in Tamil Nadu in lieu of the existing scherzer rolling lifting bridge on the Mandapam-Pamban rail line at an in-vestment of Rs 2.5 billion. The construction work is expected to be completed by mid-2023.
The Chenab bridge is a 1,315 metre-long railway bridge being constructed in Jammu & Kashmir. It is part of the USBRL project. As of February 2023, IR has commenced the track-laying work. The project is scheduled to be completed by early 2024.
Going forward
Construction of modern structures for bridges is complicated. Thus, there is a need for skilled and trained engineers and experts to plan the construction of these structures using the best methods and equipment. The evolution of bridge engineering is strongly linked to the advancements in materials, construction processes and technology. To this end, around Rs 50 billion will be invested in Uttar Pradesh to introduce new technologies to construct bridges on railway crossings.
Bridges need to focus on the conceptual and computational aspects to construction, along with service life performance. Innovations in design and construction techniques, and adaptation of global best practices to Indian conditions hold great potential. As safety is paramount, more effort to remedy safety-related challenges is needed, keeping in mind that preventive maintenance is always better than post-damage work.
Going forward, bridge construction will provide huge opportunities to contractors, developers, consultants and investors. A few of the announced projects are the Versova-Virar sea link and Kopari-Patni bridge on Thane Creek in Mumbai, the Kushiyara bridge in Assam, Belani bridge in Uttarakhand, Dehra bridge in Himachal Pradesh and Kotlien bridge in Manipur. Additionally, the Uttar Pradesh government recently approved funds worth Rs 1.83 billion to construct three ROBs at the Harauni, Bharwara and Kesarikheda railway crossings in Lucknow.
Ishita Gupta and Harman Mangat
