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There are some of the significant bridge projects underway in India. Many more such interesting projects are in the pipeline too. All of which will, apart from increasing the country´s large network of existing bridges (estimated to be around 5.5 lakh), will also stand testimony to the giant leap that the Indian bridge engineering and construction has taken, in the last few decades.
India´s increasing population, rapid urbanization, coupled with traffic congestion and the consequent demand for robust infrastructure have been the driving factors behind the growth of roads and bridge infrastructure. The National Highways Development Project (NHDP), the largest highway project being implemented by National Highways Authority of India (NHAI), Jawharlal Nehru Urban Renewal Mission, Bharat Nirman Programme, Indian Railways massive expansion programme, apart from individual State´s own highway and road developments have all contributed to the development of bridge infrastructure.
´The major infrastructure projects initiated and fast tracked by the Indian government in the railway, roadway sectors, NHDP, dedicated freight corridors, high speed passenger corridors, State capital connectivity, port connectivity and border area connectivity programmes and replacement of old bridges on safety issue are all contributing to the growth of bridge infrastructure,´ says Sunder Banerjee, Director (Projects), Braithwaite Burn & Jessop Construction Company Ltd (BBJ). BBJ is currently executing the 4 km long rail-cum-road bridge over river Ganga at Munger, Bihar at an approximate cost of Rs 1,200 crore.
The value of roads and bridges infrastructure in India is projected to grow at a compound annual growth rate (CAGR) of 17.4 per cent over FY12û17. The country´s roads and bridges infrastructure, which was valued at US$ 6.9 billion in 2009, is expected to touch US$ 19.2 billion by 2017.
Evidently, several new opportunities are opening up in bridge infrastructure for developers, contractors, engineering consultants and others. The future looks even more bullish for various reasons. The Indian Railways have ambitious expansion plans for the next five years. About two-thirds of NHDP road projects are yet to be awarded. In fact the Working Group on Road Sector (WGRS) for the 12th Plan (2012-2017) had suggested that all existing railway level crossings on NH Network should be replaced by road over / under bridges.
´The ongoing NHDP and proposed investment of Rs 8.65 lakh crore in railway projects will open up a host of opportunities,´ says Arun Karambelkar, President and Chief Executive Officer, Hindustan Construction Company Limited (HCC). He added: ´The increasing demands on infrastructure will see the implementation of mega and complex bridge projects.´
HCC has built over 350 bridges, including some signature ones like the Mokameh rail-cum-road bridge across river Ganga in Bihar (India´s first rail-cum-road bridge) Godavari Railway Bridge, Rajamundry, Andhra Pradesh (India´s first and only Bow String Arch Girder Bridge) Varanasi Road bridge across river Ganga, Uttar Pradesh, (India´s longest span cantilever bridge with the widest deck) and the iconic Bandra Worli Sea Link, India´s first cable stayed bridge built in open sea.
Meanwhile, there is a huge opportunity for private players in the development of bridges on PPP basis or as EPC contractors. However, large size EPC contractors who can bring in the state-of-the-art construction techniques will have an added advantage.
On the other hand, repair and rehabilitation of old bridges is yet another potential area. Several bridges in India are more than 100 years old, requiring repair and retrofitting. An accelerated program of replacing several semi-permanent timber bridges in the north-eastern sector is also on the cards.
´More than 50,000 bridges are old in India, which require high end rehabilitation,´ reveals Jitendra Kumar Goyal, Chief General Manager (Technical), National Highway Authority of India. He added: ´They are across the country, but largely along the coastal line, where bridges are more prone to corrosion. Many of them are also in high seismic zones, for which they were not originally designed.´ To this, experts suggest that the new technologies will help in rehabilitating such bridges, which no doubt will be challenging as the implementing agencies do not have the design details, drawings, or calculations etc. of these bridges.
In the last few decades remarkable technologies have been adopted in Indian bridge construction including the latest cable stayed technology ´Cable-stayed technology is one of the latest entrants in India, though it was used once in 1992 in Vidyasagar Setu over the river Hooghly in Kolkata,´ reveals ER Madhav Bhide, Founder and Hon. Director General, Indian Institution of Bridge Engineers (IIBE).
In this technology, Bhide says, ´high-tensile steel cables, are fixed to the supporting girders to take the load of the span and these cables are taken over tower and anchored at the other end of the span.´ He further explains, ´The girders and towers can be of either concrete or steel. Bridges built with this technology provides greater stiffness, enable large spans such as 400-500 meter and do not require large ground anchorages.´
To this, NHAI´s Goyal put forth his view. ´These large span bridges also increase the width of the waterway and facilitate movement of large barges underneath. It is generally restricted to major rivers as it is not very cost effective.´
NHAI has constructed several cable-stayed bridges, including the Naini Bridge in Allahabad and the Second Vivekanand Bridge with cable-stayed extra-dosed spans. Meanwhile, several other technologies and new construction techniques too, that have made their way into Indian bridge engineering. Banerjee lists out some of them: ´Apart from cable stayed bridges, there have been cable stayed extra-dosed spans, arch bridge, PSC box girder (segmental construction) etc.´
He goes a little deeper into the technicality as he suggests that in the foundation area, larger diameter piles are used in place of well foundation, several innovative erection methods, including the cantilever method of launching and erection, are being used to speed up the erection. High performance protective coating is now available to guard against environmental degradation of materials.
BBJ has constructed numerous bridges right from the famous Howrah Bridge (Rabindra Setu) over river Ganga. The list includes Vidyasagar Setu, India´s first long span cable-stayed bridge, some steel bridges for Delhi Metro and several rails and rail-cum-road bridges over rivers Ganga (Mokamah, Bihar) Godavari (Rajamundry, Andhra Pradesh) Bramhaputra (Jogigopa, Assam) Mahanadi (Cuttuck, Odisha) and Gandak (Bihar).
Naturally, all major bridge building contractors have been adopting modern technologies, construction methods and innovative practices in the bridges for over two decades in India.
For instance, in the late 80s and early 90s HCC had extensively used balanced cantilever segmental construction method in several bridge construction. Two major bridges across river Ganga near Varanasi and the river Godavari in Andhra Pradesh were built by HCC using this technique. ´The Varanasi Road Bridge had 8 spans each of 131.5 m length and was the longest cantilever span bridge at that time´ reveals Karambelkar.
While elaborating, he explains that the balanced cantilever segmental method is used in projects where the bridge spans are long and where the height, topography or geotechnical conditions render the use of conventional formwork uneconomical. In the pre-stressed concrete road bridge built across the Arabian Sea backwaters near Cochin, HCC used precast span by span construction method, which is used in bridges that have many spans of the same length and need to be built for high speed. It is most often used in conjunction with an erection truss under the bridge segments or an overhead erection truss under the bridge segments or an overhead erection gantry to guide the precast elements into position.
HCC is currently constructing a double deck rail-cum-road bridge over the Brahmapura river at Bogibeel in Assam, India´s first totally welded steel bridge designed as a series of composite truss girder.
Evidently, various technologies, construction techniques and new materials et al have opened up a whole new world of bridge structures that were not even dreamt of earlier. The limit of technology and innovation has by no means been reached. There is scope and need for much more aver industry experts as several issues in bridge construction in India are yet to be tackled.
Bridge construction has always posed several challenges to the bridge engineers and contractors. More so, with changing client specifications and community requirements, it has added up stringent environmental, and safety rules. In addition, there are several other issues too.
According to M Murali, Director General, National Highways Builders Federation (NHBF) late commissioning of projects, limited working period, lack of trained manpower, lack of essential bridging stores and adequate machineries are the major constraints.
However, bridges over rivers pose an altogether different set of challenges, says Murali. ´Unexpected flash floods causing meandering of the river, excess discharge, difficulty in accessing the bridge site, administrative and security concerns are the major challenges here,´ he says.
That said, selection of the bridge site in meandering channels has a greater influence on the bridge cost as the additional bridge length increases the expense. The concept of least bridge length with river training works is the most economical solution for the rivers flowing in alluvial plains. However, the time gap between the conceptual stage and its actual execution on ground can rarely be synchronized. Changes in the river course before, during and even after the construction of bridge are common. This can be attributed to the flash floods in the upper reaches of the catchment area. This phenomenon has not only caused far reaching damages resulting, in time and cost overruns, but also put the credibility and esteem of the engineering fraternity at stake. For example, the permanent bridge constructed over river Gai on NH-52 in Assam is in a redundant state now, as the course of the river has changed completely and the bridge is outflanked´ reveals Murali.
Yet another challenge is repairing and retrofitting of old bridges, many of which were designed for less traffic volume, slower speed and lighter loads, far behind the present day needs. Further, these bridges are deteriorating due to various reasons and the need for their maintenance, rehabilitation or replacement has increased manifold. Maintenance of new bridges is also equally vital. However, it is a neglected exercise in India with no adequate budget provisions.
´Unfortunately, in India there is very little awareness about maintenance. Bridges have to be inspected periodically and very closely and it can be done only by specially trained personnel. Earlier we did not have even bridge inspection units in our country. Now of course it is available but not many use it. Corrosion is another major issue which is of course being addressed now by painting the reverse, metalised coating and by using high strength concrete to minimize permeability of moisture, water etc.´ avers Goyal.
The WGRS has recommended the setting up of Bridge Management System for maintaining a database on bridges and their conditions so that timely decision can be taken regarding their repair and maintenance. Evidently several measures are required to place the bridge infrastructure segment on a higher plane. Speeding up the clearances, faster allocation and implementation of projects, attractive funding systems etc. are some of the suggestions put forward by industry professionals.
Banerjee states that to make bridge construction sector more attractive to private players government must take some measures like additional allocation of funds for infrastructure, speedier decision on awarding jobs, providing clearances and availability of financing and easier terms of payment to the contractors. Adds Karambelkar, ´Most of the projects in the past few years have either been stalled or slowed down due to land acquisition problems, delay in environmental clearances and in settlement of claims, etc. The new NDA government has taken some good steps in the regulatory framework and the scenario seems to be improving. Government needs to make the PPP (Public Private Partnership) contracts more viable and attractive and step up its efforts in removing the policy paralysis and speeding up project implementation.´
Evidently, there are some gaps that need to be bridged in the bridge infrastructure segment. However, there is no doubt that the sector has more exciting and challenging times ahead.
´Use of welded steel for large span railway bridges is yet another development´
What factors are driving the growth of bridge infrastructure in India?
India is a developing country and the development of a country cannot take place without the expansion of its infrastructure which in other words means the construction of new roads, highways, railways, metros, ports, waterways etc. In addition there are widening and expansion of existing infrastructure to cope with the growing needs. Bridges from an integral part of all these developments, as bridges are required to cross highways, arterial roads, railway tracks, rivers, creeks, hills, rivers and sea.
Several projects like the Golden Quadrilateral, North-South and East-West Corridors, Delhi-Mumbai Industrial Corridor, development of state highways, rural roads, and expansion of rail network, metro rail projects, trans-harbour links and sea links have all contributed to the growth of bridge infrastructure. In addition, military bridges are constructed at strategically important locations in north eastern states, Jammu & Kashmir, in the Himalayan region and border areas adjoining our neighbouring countries.
What is latest bridge technology that has entered in India?
Cable-stayed technology is one of the latest entrants in India, though it has been widely used for many decades in developed countries. Even in India the technology was used in 1992 in Vidyasagar Setu (also known as Ravindra Setu) over the river Hooghly in Kolkata. In this technology, high-tensile steel cables are fixed to the supporting girders to take the load of the span and these cables are taken over tower and anchored at the other end of the span. The girders and towers can be of either concrete or steel. Bridges built with this technology provides greater stiffness, enable large spans such as 400-500 meter and do not require large ground anchorages. These bridges also look beautiful.
Some of the bridges built with this technology in the recent past include the Naini Bridge over the Yamuna River in Alahabad , Nivedita Setu over the Hooghly River, Kolkata; Bandra-Worli Sea Link Mumbai and Aldona - Corjuem bridge across river Mapusa in Goa . There are several under construction too, like the Signature Bridge over River Yamuna in Delhi, Pandit Dindayal Upadhyay bridge over river Tapi near Surat and Kota Bridge in Kota, Rajasthan.
What other technological developments have taken place in bridge construction?
Use of welded steel for large span railway bridges is yet another development. Earlier all railway steel girder bridges were made using rivets, which took longer in shop fabrication as each rivet had to be made on site after heating. Though Indian Railways were initially reluctant to use this technology due to safety considerations, they began using it later for smaller spans of plate girders. Now it is effectively used in very large trussed steel - girder bridges too.
Today, techniques ranging from simple pre-casting to segmental construction, innovative methods of launching rigs, using percussion methods for piling, use of additives in concrete, which increases the strength and density of concrete, have all opened up new doors and new challenges to Indian bridge engineers. For instance, the world´s highest rail bridge, and world´s longest steel arch bridge under construction across Chenab river in Jammu and Kashmir is a very challenging project and will bring kudos to Indian bridge engineers when completed.
What are the reasons behind corrosion of bridges? What measures have been taken?
Whenever steel comes in contact with water and air it corrodes. Steel bridges are painted regularly to prevent corrosion. In the last decade, various types of modern paints including epoxy are being used. Research, Design & Standards Organization (RDSO) of Indian Railways at Lucknow has updated specifications so that frequency of painting can be reduced. Metallising, which is coated by sprayed aluminum or zinc, is one of the superior methods of corrosion protection.
In RCC bridges normally steel bars are used and in pre-stressed concrete high tensile steel wires are used to take up the tension in the structural members. Here corrosion occurs, whenever water and air come in contact with these steel parts. Often steel bars are rolled in local rolling mills, where quality control is not maintained, making the bars prone to corrosion. The best way to prevent / minimize corrosion is to ensure that concrete produced on site or in plants is of higher strengths and compacted to reduce permeability. Various types of coatings are also applied to concrete to make it impermeable.
What are the challenges faced by bridge engineers in constructing bridges in India?
One of the major challenges for engineers is to make the bridges corrosion free, more so since their expected life span is 100 years and they are constructed in hilly areas, over rivers and sea. Non-availability of trained supervisors and skilled staff with requisite experience is another problem. There is also a reduction in the number of large bridge companies carrying out fabrication, erection and launching of large-span steel girders. Further, young engineers accustomed to city life comforts and working in air-conditioned environment are reluctant to work at site, more so if they are miles away from city centres. One redeeming factor however is modern communication like internet, mobile and improved road network.
What has been the objective behind setting up IIBE? What have been its achieve¡ments?
IIBE was set up in 1989 to promote and facilitate exchange of information, ideas, understanding and cooperation among bridge engineers in India and outside. It has 169 institutional members and 6,500 individual.