Bridge the Gap!

CW lays emphasis on the need to audit old bridges and offers solutions to avoid mishaps like the recent Mumbai-Goa highway bridge collapse.

In a recent tragedy, about 80 per cent of the 70-year-old, British-era Mumbai-Goa highway bridge collapsed. It was, indeed, a red alert on the condition of bridges in India.

One reason stated for the collapse was heavy rainfall, which led to the river swelling; the increase in flow and speed is likely to have caused the collapse. On the day of the mishap, the water level crossed the danger mark - its arch collapsed first, followed by the bridge. However, a PWD official, on request of anonymity, cited ´corrosion of the bridge over the years´ as a primary reason.

Need for maintenance
While India is proud of its British-era bridges, there is a dire need to check and audit the exact number of bridges that are actually fit for use. According to experts, every bridge has a design life, after which it can technically be called ´old´ and deemed unfit for use. Unfortunately, though the records may have a list of more than a lakh bridges, there are no health reports for them.

Meanwhile, Prof Dr Kirty Dave, chartered engineer, adjunct professor at IIT-Mumbai and techno-legal consultant), says, ´Old´ refers to age and it is an irrelevant concept in context of serviceability of the bridge. ´Good´, ´fair´ and ´poor´ should be the prefixes to describe the condition of a bridge depending on the degree of maintenance called for after assessment by bridge auditors. The older they grow in terms of maintenance, standard checks of foundations, supports, bearings and deck status need be carried out with follow-up of recommended maintenance.

The health must be ascertained by non destrictive testing (NDT). A panel of expert bridge auditors needs to be drawn up for various regions and assigned a manageable number of bridges depending upon their resources.´

Getting on the job
For his part, Prashant Fedge, Project Manager, National Highways Authority of India (NHAI), says, ´There is a proper system as per the Indian Roads Congress (IRC) guidelines, based on which NHAI and PWD department engineers regularly check all the bridges.´

However, after the Mumbai-Goa highway bridge tragedy, all PWD department engineers have been tasked on priority to undertake a health checkup for all the British-era bridges. After the monsoon, the engineers will also conduct a check to ensure that the foundation of the bridges is strong.

As most British bridges were constructed with stone considering the traffic then, if required, these would be repaired with concrete.

It´s unfortunate that it took a collapse for action to be taken - but better now than never.

Building Right
Using stainless steel instead of concrete while constructing bridges can be a way to reduce instances of collapse. While the initial cost of using steel would be high, the payoff is a greater lifespan.

A promoter of the use of corrosion-resistant stainless steel reinforcement while constructing bridges, Yatinder Pal Singh Suri, Managing Director and India Head, Outokumpu India, and former President, IIT Kharagpur Alumni Association, explains, ´Be it a steel-fabricated bridge or a concrete one, the reinforcing bar gets destroyed over a period of time owing to humidity and temperature fluctuations in India. This is difficult to repair after a certain time span.´

He also emphasises that when a bridge is designed or being erected, erosion mitigation must be looked into. And, as stainless steel does not corrode, the concrete continues to offer a maintenance-free life of over a hundred years. He concludes by listing the benefits of stainless steel reinforcement: ´Significant increase in durability, reduction in repair and maintenance costs, elimination of concrete sealants, and reduction in thickness of the concrete cover.´

To share your views on this report, write in at feedback@ConstructionWorld.in