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Mumbai CST bridge collapse: An engineering failure coupled with irresponsible audit led to the tragedy
One more 'foot over bridge' near CST Railway station in Mumbai collapsed on 14th March 2019 taking six lives and injuring 32 people. It was said that the traffic signal had turned red just before the collapse. That's a coincidence else the fatalities could have been extremely high.

Why a RCC slab/girder collapses? I had written about it in detail in my article 'Mumbai Foot-over Bridge Collapse-The concerned engineers must be booked for gross negligence' published in this platform on 03.07.2018 post the partial collapse of the Andheri FOB. In the conclusion too, I had mentioned that 'The government must set up independent engineering bodies to inspect all such bridges and identify those in need of immediate repairs. IRC (Indian Road Congress) or IEI (Institution of Engineers, India) should be given this responsibility or else there's every chance that bridges constructed 60-70 years ago may continue to collapse causing loss to life and property'.

The present FOB is known to have been constructed forty years ago. But the reason remains the same. I have seen some of the photographs. They clearly show that its reinforcements were exposed which were hidden by applying a plastering coat. When reinforcements get exposed to the atmosphere, they get corroded. Mumbai is situated beside the sea. Thus, its climate is a 'severe' zone for corrosion. Once corroded, it goes on corroding even if you hide it with plastering, concrete or by whatever means. Corrosion means that the reinforcements lose their property to take care of tensile load. In the effect of corrosion it swells and thus creates cracks (micro) in the surrounding concrete. Concrete is very week in taking care of tensile load. A slab or a girder essential a tension member, thus whenever it is exposed to the atmosphere it starts weakening leading up to failure irrespective of its age.

I heard that there was audit and the report said that this particular bridge required minor repairs. Let me reiterate that there is nothing called minor or major repair. It requires replacement only. The basic structure of the FOB is made of steel structures. Thus, the concrete slab needs to be replaced. That's the only viable option. I don't question the wisdom of the auditor, but my experience says that if an auditor says that such bridges can be rectified through minor repairs, I completely disagree.

Such bridges need to be blocked for passenger movement. If passenger movement is very urgent then necessary support below the slabs (to reduce the span) should be provided to increase the life before replacement work begins. This can be considered as a repair just for some time period. Providing support is very easy in such FOBs. Just weld some steel members below the slab joining it with the main steel truss.

I once again recommend that audits must be carried out by reputed institutions like 'Institution of Engineers' or 'Indian Road Congress' or else such incidents shall keep on occurring. Politics will always be there. But the Maharashtra CM must refer this matter to such institutions to avoid more mishaps. This is an engineering failure and engineers of the respective departments are fully responsible.

Note: The author has more than 30 years of experience in the construction sector especially in execution and rehabilitation of bridges.

Editorial NOTE: This article is categorized under Opinion Section. The views expressed in this article are solely those of the author and do not necessarily represent the views of merinews.com. In case you have a opposing view, please click here to share the same in the comments section.
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