Failure Reason of Kolkata Bridge

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On 31st March 2016, The Vivekananda Road Flyover shrunken at 12.25 pm, killing minimum 24 and wounding 80 in north Kolkata’s Girish Park area.  Eye-witnesses fear at least hundreds are still stuck. The flyover is situated in a heavily occupied wholesale marketplace, Barrabazaar, with a full traffic passing all day under it.

Since 2009, the flyover has been under construction and has wasted 9 closing dates until now.

 

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Cause of failure: The great structure is a compound design. RCC deck is stayed over steel girder. Such planning is very costly but most harmless structure. The previous day there was concreting. At times a portion of deck mainly cantilever portion falls due to failure of provisional backing such as brackets etc. But such downfall occurs when concreting work is in advancement because wet concrete weigh up more than set-concrete. (Wet concrete is 3000 Kg per Cum whereas set concrete is 2400 kg/cum). From photographs it’s clear that the pier cap botched thus bringing down two spans maintained over it. Failure of pier has numerous causes.

Design aspect: It was well-known from the start that in line for traffic load and space constraint, the fly over had to be built not limiting the traffic movement. Therefore design has taken care of this part giving all steel structure. Although very expensive, steel structure is the safest structure. Standard design is checked with STAAD.PRO and therefore it can be determined that there was no defective design. Additional all other spans were alright proving that this pier/pier cap had some problems.

Execution aspect: Standard Operating Procedure (SOP) of such execution always necessities to confirm approved material sourcing, fabrication by expert workforce, pre-inspection and post inspection after assembling, detailed scrutiny of the whole thing in the list before any more load is applied. IVRCL is a reputed organization and the concerned government department too is likely to be non-compromising on quality matters mainly when it is being implemented while traffic is permitted to move beneath it.

I consider that there must be some fault of omission, which might have occurred. After doing positively most of spans sometimes mid-level & junior level engineers becomes bit satisfied. Thus inspection might be done calmly neglecting serious flaws either in joints of pier cap/pier or by mistake some surplus eccentric loading being done due to piling up construction materials. These are called human errors.

Who should be held accountable: While executing such workings, as a senior person I use to check the lot personally in spite of declaration from mid-level engineers that they have tested thoroughly. There is nothing wrong if expert and senior people check it once again as even a slight overlook may cause a serious disaster like this. Thus I think the project manager in Kolkata flyover incident was maybe over reliant on on his/her mid-level engineers missing his responsibility.

The supervising agency (in this case the concerned government department) has the duty to cross check the whole thing despite the agency is contract bound for structure and public safety. The concern engineers of supervising department must be held liable.

Third department to be held responsible is traffic police department. When such work is being fulfilled traffic division has mandatory responsibility of public safety. They may not be engineers but they could take essential safety necessities as commonsense.

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