Video summary
The video examines the catastrophic collapse of a newly constructed flyover in Kolkata, India, on March 31, 2016, which resulted in the tragic loss of 27 lives and injured dozens more. Located on the busy Vivekananda Road, this infrastructure project was intended to alleviate severe traffic congestion but instead became a site of disaster after nearly seven years of construction plagued by delays, financial disputes, and regulatory hurdles. The structure, designed with steel plate girders and concrete decks, was meant to be completed in 2010 but faced numerous setbacks, including the contractor's financial difficulties and land acquisition issues, pushing the completion date significantly behind schedule.
The investigation revealed that the collapse occurred during concrete pouring operations on a cantilevered section of the bridge, where the steel superstructure failed under flexural and shear stresses. The primary cause was identified as an inadequate joint design at the connection between the cantilever girder and the central column, which could not support the full dead load once concrete was poured on both sides of the structure. While other sections of the flyover utilized two columns per section to distribute loads evenly, this specific segment relied on a single central column with poor vertical attachment, leaving it vulnerable to failure when the increased weight exceeded its capacity.
Following the disaster, authorities charged several employees of the contracting company with murder, though the firm initially attempted to deflect blame by labeling the event an accident or an act of God. A committee appointed by the state government concluded that the structure was not salvageable and recommended tearing it down entirely, returning the area to its pre-construction state. The incident highlighted severe flaws in the project's execution, including improper design choices, rushed construction amidst budget overruns, and a lack of adequate safety measures, ultimately serving as a stark warning about the dangers of cutting corners on public infrastructure projects.
Read the full video transcript
Managing the flow of traffic must be a
nightmare for city planners.
Even a medium-sized town, keeping
everyone moving has to be a tricky
affair.
But nothing compared to managing the
traffic flow in a country like India.
Famous for its high numbers of vehicular
traffic, one of the worst places in
India is the city of Kolkata, where some
4 million people try and traverse the
city streets and highly dense suburbs
every day.
In a city like this, there's not a
massive amount of easy things you can do
to increase traffic flow.
Widening roads is very unlikely due to
the age of the city.
Instead, you either have to go up
or below the road. And in our story
today is about the building of an
overpass.
After nearly 7 years of construction,
delays, and controversy, it would be the
site of a disaster, where this newly
built overpass would, without warning,
crash on top of the road it was built to
relieve pressure on.
Today, we're looking at the Kolkata
flyover disaster of 2016. My name is
John, and welcome to Plainly Difficult.
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pinned comment below.
Busy, busy roads. This is the
Vivekananda
Road. It is a major east-west
thoroughfare through the Indian city of
Kolkata.
The road intercepts multiple main
avenues in the city. Being the busy city
Kolkata is, this main route connection
is obviously a traffic nightmare. India
as a whole is known for its insane
roads, and Vivekananda Road is no
different.
And it's hardly surprising that the
municipal government sought out a way to
ease the traffic along the route and
tackle congestion in the Buddha Bazaar
area. And like all busy cities, widening
the road was much of a non-starter.
Instead, a flyover was chosen with an
outline being conceived in 2007. A
contract was put out to tender and a
bidding process was run by
Hyderabad-based IV
RCL. The company was a well-established
infrastructure builder and was the
lowest bidder, predicting the cost of
the project would have a 164 crore rupee
cost.
Kind of like 40 to 41 million United
States dollars at the time. Well, that's
what Google says anyway. The contract
was issued in 2008 with the project
slated to be completed in 2010. It was a
2.5 km long roadway and had two
carriages with two lanes in each
direction.
Which were made up of eight asphalt
surface on top of a 100 mm poured
concrete wearing course. That was all on
top of a reinforced concrete deck slab
of 200 mm thick, which was then placed
on steel plate girders supported on box
girder steel columns placed at intervals
along the length of the flyover.
The columns were set on reinforced
cement concrete footings, which were set
at 45 m into the sandy clay substrate.
The roadway section was in some parts
cantilevered with a column running down
the center of the road below. Other
sections had two supporting columns on
either side of the road to allow the
bridge's load to be distributed evenly
across the structure. Now, the use of
the steel basis for the structure
allowed for off-site construction, which
invariably meant that the project would
be quick. But almost straight away, it
would run into issues and slow down.
This was due to financial problems from
the city and the contractor, as well as
getting the appropriate regulatory
clearances. All this pushed back the
completion date from 2010.
By 2013, construction had ground to a
complete halt and the contractor was
demanding more money for completion.
Land acquisition for the off-ramp area
at the Howrah end ground to a stop. In
addition to this, some columns locations
had to be changed, resulting in various
project redesigns.
Things were clearly not going well. Work
would resume in 2014, but only for a
couple of months.
Again, the project was slowed down.
This time with IVCRL hitting financial
issues. In December 2015, a consortium
of banks that IVCRL owed money to took
the company over. By the time 2016 had
rolled in, the project was whopping 7
years behind schedule.
But, that's hardly surprising
as every public works program runs over
time. Just look at Crossrail here in
London.
The project was announced to be complete
by the end of March 2016, but again this
deadline was also beginning to slip.
Another one was set for August 2016.
On the 30th of March 2016, work to pour
concrete wearing surface was being
undertaken on sections of the flyover.
Around 80% of the project had been
complete by this time.
And the project would be finished and
everyone would be happy, right?
Right?
What is a disaster? Well, sadly not.
The 31st of March 2016 was another day
in the long-awaited, over-budget, and
now looking run-down flyover project.
Casting work is underway between two
piers on a roughly 40-m stretch on the
Howrah bridge-bound section near Girish
Park,
one of Kolkata's most densely populated
neighborhoods.
Traffic continued below along the
Vivekananda Road
with the building works going on above,
the streets are the usual hub of
vehicles, tuk-tuks, scooters, bicycles,
and pedestrians, all funneling along the
road. However, at around 12:40 p.m., the
normal business of the area would be
catastrophically interrupted as a 150-m
or 490-ft section of the overpass
crashed down onto the roadway below.
Splitting in half by the center columns,
this meant that the steel superstructure
had crashed into both
portions of the traffic below.
Hundreds were underneath the structure
when it collapsed. In the immediate
aftermath, nearby witnesses ran in to
try and pull anyone from the rubble.
The National Disaster Response Force
helped in dragging people from the
wreckage. By the next day, on the 1st of
April, the missing list was at roughly
100 people.
Around 80 people had been pulled from
the wreckage at that point. And over the
next few days, more more dead were
found. With by the 2nd of April leading
to a final death toll of 27 and an
official injury toll of 80.
Whilst all this was ongoing, five IVRCL
employees based out of Kolkata were
charged, in addition to two based in
Hyderabad, with murder.
Straight away, the company started to
deflect blame, calling the failure an
accident, and even one official stating
it was an act of God.
But this is where the next part of the
video will try and figure out how much
God's hand was actually in this.
Investigation.
So, in the aftermath, a committee was
set up by the West Bengal Chief
Minister,
Mamata Banerjee, to dig into the cause
of the disaster. This would make use of
the Indian Institutes of Technology, and
its report would be published in August
2016.
Parts of the investigation would look
into the viability of rebuilding the
flyover and salvaging some of the
already constructed structure.
Spoiler alert, it would not be
salvageable, requiring it to be all be
torn down. Leaving street scenes like
this, almost exactly the same as before
the project began.
So, how did the structure fail?
Well, looking at the photographs, it
gives us a good idea. See how both sides
of the bridge's cantilever sections had
failed and were lying on the ground each
side of the column?
Where points to an issue with the steel
girder superstructure not being able to
carry the loads back to the columns.
It was found that on the day of the
collapse, concrete was being poured over
cantilever girder two on column 40.
Previously, concrete had been poured on
girder one and had successfully carried
the load. It was only after the load was
increased on the other side that failure
had occurred via flex and shear
stresses.
This meant that the joint of the
cantilever girder where it met the
column was inadequate for a full dead
load condition of having the concrete
deck slab on either side of the girders.
Now, why did the rest of the bridge not
collapse? Well, this is because the
other parts used two columns per
section. Thus, the roadways load had its
own column to support it.
The design of the cantilever section was
poor with little to no vertical
attachment between the cantilever and
the supporting column, meaning there was
little to no shear resistance.
The project was the definition of a
botched job. Improper design, rushed,
but at the same time bloated, slow, and
overbudget.
Undertaken just to filter money away
from the public purse and into the
pockets of a private company.
I can't remember where I read it now,
but the flyover was meant to be
future-proof for 2040 traffic loads. And
someone said it wasn't ready for 2016
non-traffic loads.
So, that's my video on the 2016 Kolkata
bridge collapse. It's going to be a
three on my scale. This is what I've got
on my root cause analysis card. Do you
agree? Let me know in the comments
below.
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All that I have to say is thank you very
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