Indian bridges on their last legs

A recent survey by the Union,ministry of surface transport has revealed the pitiable state of bridges in India

 
By Rahul Shrivastava
Last Updated: Sunday 07 June 2015

Indian bridges on their last legs

-- (Credit: Arvind Yadav / cse)EVEN before the 2 spans of the Songsu bridge over Seoul's Han river collapsed an October 21, leading to 32 deaths, experts in the country had been clamouring to close several of South Korea's brides due to technical reasons.

Closer home, the results of a hurriedly conducted survey of the 5,600 bridges out of a total of 6,500 by the Union ministry of surface transport (MST) during September-October this year, has the alarm bells going wild. The ministry now faces the daunting task of aconstructing over 650 bridges in advanced stages of decay. The survey bas also marked 20 bridges as "highly distressed", 680 in need of major repairs and another 2,000 for routine repairs.

The survey found as many as 50 per cent of the bridges to be precarious to same degree. The accusing finger is aimed directly towards the conceptualisation "on, construction and quality of maintenance, highlighted by the fact that several bridges constructed in the past 5 to 10 years figure high on the list. The surveyors have estimated a massive expenditure of around Rs 400 crore to get the bridges back on their columns.
On the road past recovery According to B P Marwah, deputy secretary, Indian Road Congress (IRC), "The situation is precarious. If something is not done immediately, many bridges might well be past recovery. The government agencies are yet to react, although many such situations have led to disasters in the past. There is also a need to rethink policies because construction methods are strictly jacketed by inadequate conceptual specifications."

Experts claim this to be one of the most crucial factors that lead to the rickety, patchwork performance of Indian bridges. D P Gupta of the department of road development says, "Everywhere except in India, concepts dictate construction methods. Bridges in India have to be built according to geological and hydrological aspects, like environment, humidity and rainfall."

Mandarins in the MST blame floods and high humidity levels for the large-scale deterioration. However, experts at the Indian Association of Bridge Engineers (IABE) hold that adverse or aggressive environmental conditions are just one of the reasons. Says Pratik Sengupta, a civil engineer with the LABE, "Aggressive environmental conditions do take a toll on the health of a bridge, but it is also well known that safeguards for design durability and construction specifications have been grossly neglected. This can be gauged by the fact that bridges in India are designed to withstand 50 floods whereas it is 150 in the developed countries."

A structural engineer with the Indian Institute of Technology in Delhi adds, on condition of anonymity, "In India, the aging period of bridges is 30 to 40 years. The reason behind this premature aging is the high traffic load Down To Earth November 30,1994 that the bridges are subjected to. The ITO bridge in Delhi, for instance, is handling over 10 times the traffic it was designed to withstand."

Again, the MST is blamed. As far back as in 1986, a Rail India Technical and Economic Services Ltd report warned the ministry that bridges are being subjected to higher loads than they were supposed to. The report also held some lightweight, highly-stressed modern designs partially responsible for the rapid deterioration. Says Uma Shankar Dixit of the Public Works Department in Delhi, "A modern structure has only moderate reserve strength and tends to collapse as soon as serviceability is exceeded."

According to Atanu Mukherjee, structural engineer with Engineers Consortium, a consultancy firm, "Bridge-building is not just spanning a river or gully. It's a matter of combining different aspects. The increase in the quantum of traffic, changes in river flow and urbanisation of surrounding areas have to be considered before starting construction. But such things are alien to Indian bridge building. The inadequate detailing before construction, fancy concepts like slender sections m6re vulnerable to vibrations, and lack of strict quality control during construction are some of the reasons why the bridges are so inefficient."
Gnawing at the foundations The shortsightedness of development 'policies are gnawing at the foundations of bridges in the country. A joint secretary with the MST says, "The cost of building a bridge with a long lifespan is phenomenal. Therefore, bridges with shorter lifespans are constructed. But this is based on the assumption that within a certain period another bridge would be constructed to share the load. But it never happens. There is either lack of funds or they are delayed."

Many experts are not happy with the technology used to build the bridges. Kuchhwa, head of standards and research (bridges) in the MST, says, "In India, we have switched over to the prestressed concrete technology. We are at par with international standards as far as the knowhow is concerned. But we fail when it comes to implementing it, mostly because of rampant corruption."

The ministry has done little to remedy the situation. N K Sinha, a chief engineer with the MST, says, "There is no check when the bridge is constructed. The ratios of concrete, steel and other components are changed and the fitting is not done according to specifications. Site selection is sometimes done ignor ing geological conditions. Take, for instance, the Nizamuddin bridge in Delhi: there have been problems with the foundations due to the differential settlement of the strata."

Pramod Bhargava, a bridge expert with Gammon India, which has constructed several bridges in the country, says, "Bridge building involves 2 aspects - conceptual and computational. The first requires considerable application, engineering, judgement and experience. The conceptual design, the materials to be used and the combinations to be chosen to produce an economical structure which will meet,safety standards, have to be considered. Although we are building lots of bridges, there is still a need for combining all these aspects."

Gupta adds, "The trend to construct lightweight bridges with highly stressed designs has not worked well. These include the Mahatma Gandhi Setu over the Ganga near Patna and the new ISBT bridge over the Yamuna in Delhi. The older design structures have larger reserve strength. There is also a need to adopt technology suitable to India, not just ape Western trends in structural design."

New materials and techniques like neoprene expansion joints, pot cantilevers and cable-stayed have been developed in recent years. But according to Sinha, "Modern structures are quite complicated and needy trained technicians for The reliability of concrete, the common material used to construct bridges in India, greatly depends on do method of construction, which is out by untrained persons. A small pocket of un-compacted concrete or a small change in the levels of reinforcements or insufficiently cured conctresults in higher failure risks."

Bridging all aspects
Pratik, however, adds, "Bridge technology should not be considered in isolation. Factors like better weather forecast systems. Drainage management and effluent treatment have to be upgraded as these have direct bearing on the bridge'

The survey has also exposed the lack of maintenance of the bridges on the national highways in all the 6 zones carved out by the MST. Sinha says, "Although there is a paucity of funds, general apathy towards the bridges is one "of the most important reasons why disasters occur or premature aging affects the serviceability. This is also because of poor insp6ction standards." Most experts agree that if inspection is carried out properly and is followed up with proper maintenance, the bridges will survive longer.

Both Sinha and Gupta expressed displeasure over the instructions in the IRC manual for maintenance and inspection. Marwah, however, argues, "The manual is not faulty. The problem is in carrying out inspections, which is cumbersome, as most of the bridges have been designed without providing proper access to various sides of the structure."

The repair and rehabilitation of bridges is yet to come of age in India. There is a dearth of experienced agencies as well as of technical knowhow to carry out detailed investigations, Meanwhile, a draft for the creation of a bridge management system gathers dust in the ministry.

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