[destinykid]

Originally Posted by Porsche306

The primary reason for failure of bridge is certainly a combination of the resonance effect, overloading and defects in renovation.

Very well summarized. Resonance in itself will not collapse the structure. But due to resonance the amplitude of displacement increases (here sway). The amplitude of sway magnifies the forces in the cables for which they are not designed for. Moreover, this sway creates slack in one side of the cables which are supposed to be in tension. Due to slack their load carrying capacity drops to zero and entire load is transferred to other side of the cables. Which doubles the forces and that too with an impact which increases it by another 50%.

Overall, this structure was overloaded and entire load with impact may have been transferred to one side of cables leading them to snap off. Generally, structures have alternate load paths, but suspension bridges don't have any. The real use case for this structure is a pedestrian crossing bridge. If the bridges are overloaded and then are subjected these types of unanticipated loads, engineers have to relook at the basic design conditions. This is like expecting the car to survive the crash when driven at above 200 kmph. It CAN be done, but is it viable?

[akg7091]

Originally Posted by Gildarts

Well the bridge was being managed and tickets issued by the same OREVA group after renovation. They should have exercised caution in crowd control, knowing the design limitations. Also, It is hard to belive the local authorities which deny any accountability did not come to know about the bridge being open to the public, since it was drawing so much crowd during the festival weekend.
So, the idiots who were recorded swaying the bridge for fun can be scapegoated since they are likely dead already and arrest a couple of low level managers in the OREVA group and close the case.

This is exactly what's gonna happen imo. They will blame the dead, arrest the "manager" and we will forget about this incident in a month

[Mr.Ogre]

I think catastrophes like this are waiting to happen in every nook and corner of our country. Has anyone been to Bhet Dwarka - apologies if I spelt it incorrectly. A few years ago I had visited Dwarka with my wife and parents and my kid. A few kilometers from Dwarka is Bhet Dwarka. You drive to a jetty and from there get on to one of those steamers - boats - to get to Bhet Dwarka. On reaching the jetty I was astonished to see the number of passengers being ferried on one boat. The word overcrowding feels little Infront of that. Bhet Dwarka is also a temple and it is considered inauspicious to return back if you are heading towards a temple. Still, I strongly resisted the idea of getting on board on those boats and wanted to return back. However, my parents and wife didn't share the same concern and insisted on doing it without me. I prayed to all the Gods and it still remains one of the most horrifying travels of my life. Add to it the fact that I can barely swim to save myself, lest anyone else.

[GJ01]

Originally Posted by Mr.Ogre

I think catastrophes like this are waiting to happen in every nook and corner of our country. Has anyone been to Bhet Dwarka - apologies if I spelt it incorrectly.

Grown up very close to Beyt Dwarka at the Tata Chemicals factory 10 KM ahead of Okha, after Dwarka. What you say is completely true, however - they are now building a bridge over the strait between Okha and Beyt Dwarka to allow vehicles to drive to the island. I was born and grew up there - lived for 20 years, in all that time, I don't recall incidents of boats sinking. Yes there were many accidents of people loosing limbs, falling tripping while navigating from the jetty on or off the boats. But there can always be a first time - many places of worship are getting way more pilgrims than what they are designed, infrastructure wise, to handle.

[aim120]

If 500 people where there on the bridge thats like 25 hatchback cars on the bridge ment for pedestrians. Add to that the idiots swaying the bridge, the already stretched cables and connecting points would have had the final blow. You can't beat laws of physics.

The idiots who swayed the bridge are the same kind of people who will start pushing or start crushing people in queue.

[vishnurp99]

Originally Posted by VKumar

People were doing mischief on the bridge?
Personally called a friend who is a contractor with setu nigam (Bridge Corporation), he said that suspension bridge cables are supposed to have a safety factor of 3.0 minimum and that is way beyond what we have seen in videos. This is a case of improper job done, which resulted in catastrophe.

My condolences to the victims of this tragedy and their families. One can't even imagine the plight of families who are impacted.

@VKumar - Wanted to request for a more detailed explanation here since you are from this field.

If there were around 500 people on the bridge, we are talking about 500 * 80 say 40 tons on the bridge. How does that tie back to safety factor of 3.0 minimum?

[deetee]

Originally Posted by vishnurp99

If there were around 500 people on the bridge, we are talking about 500 * 80 say 40 tons on the bridge. How does that tie back to safety factor of 3.0 minimum?

This 500 figure is higher approximation. It was reported that about 600 tickets were sold on Sunday. This figure got twisted and interpreted as 500 people got onto the bridge at time of incident.
Since there were about 140 dead, these being in middle section, we may assume about 300 are present on bridge. Among 140 dead, 45 are children. So,we can assume there maybe 80 children among the 300 present on bridge. So, the payload comes to like 220 * 80= 17600kg , 80*30= 2400kg , for a total of 20T.

[fhdowntheline]

With regard to people swaying the ropes, isnt this kind of behavior a familiar sight? Here are similar examples:
1) Driving on the footpath to circumvent a traffic jam
2) driving on the wrong side for quick convenience
3) triple seat riding
4) Hum do, hamare do on a 2 wheeler.
5) Hanging out on train doors
6) standing or sitting with legs dangling at the edge of a cliff
7) Breaking out into a dance in drunken state in the middle of a road, especially in monsoon
8) loudspeakers with ear splitting obnoxious music during cultural or religious festivals.
Somewhere it is ingrained in our genes to cause public nuisance.

[mygodbole]

My condolences to the grieving families.

-------------------
MODS, please remove all of the following if not adhering to Team-BHP guideline
-------------------

I am guilty of being part of a 130+ crore part of humanity that is essentially law-fearing, not law-abiding. Ingrained in my personal DNA after at least two generations before me that (d?)evolved from law-abiding citizens to danda-fearing citizens.

Call me dumb, but all those pre-Independence protests, that gained my nation its freedom from foreign rule, was subverted by all those 'masters' of the colonial-era divide-and-rule, better known as political leaders of post-1947 India.

Call it trickle-down effect, but this sense of "who will dare challenge me" has percolated down from the top to the bottom. Not just the so-called 'leaders' in political, financial, social and moral domains, but also all those that follow.

Someone, say, like me. I will repeat others and myself: "Sense of entitlement".

I personally, and as part of a larger collective called the "citizen of India", bear full responsibility for this, all past and all future tragedies.

I need to change. I hope my collective changes with me.

I thank everyone for their condolences on behalf of the victims of the next tragedy.

[GutsyGibbon]

Originally Posted by rkv_2401

This is like saying I crashed my car because my child in the back seat kicked the door!
What a tragic and completely, 100% avoidable, incident. This bridge was standing for 100+ years and it collapsed 4 days after the renovation was complete. I see only one party responsible for this mass death event.

In some of the older pictures (from TripAdvisor) shared by Ninjatalli the floor of the bridge seem to appear dodgy. What are the chances that they replaced the floor with some fancy metal fabrication, or tiles without taking into account the weight of this new flooring? In the new video the floor does appear better, they certainly seemed to have done some flooring work. In such a case the refurbishing itself would cause additional weight, plus the new visitors. 100% avoidable, if structural engineers were to be involved in the refurb.

[kovilkalai]

I think most of us would like to take the government's word as fact. Recent experiences in Bangalore strongly suggest that their responses are generally self-serving and not necessarily entirely true.

During the recent floods in Bangalore, the Karnataka government and BBMP blamed storm water drain encroachments for all the flooding. My apartment complex was one of those that was accused of encroaching. The BBMP used bulldozers to knock down our back wall to make some space for widening the storm water drain. Despite this, in the past couple of months, we have seen multiple instances of flooding even with less than heavy rainfall - something that we had never seen in the 15 years that my apartment has been around.

I, for one, will not take the government's claim that "someone opened the bridge without telling us" seriously.

[destinykid]

Originally Posted by GutsyGibbon

In some of the older pictures (from TripAdvisor) shared by Ninjatalli the floor of the bridge seem to appear dodgy. What are the chances that they replaced the floor with some fancy metal fabrication, or tiles without taking into account the weight of this new flooring? In the new video the floor does appear better, they certainly seemed to have done some flooring work. In such a case the refurbishing itself would cause additional weight, plus the new visitors. 100% avoidable, if structural engineers were to be involved in the refurb.

Generally, the flooring weight is way too less in these cases. Even if they changed the flooring with new steel plates, the dead weight of those plates would be around 50 kg/sq.m. Whereas, the live load for design of these bridges would be not less than 500 kg/sq.m. Therefore, flooring load wouldn't have had any impact on the bridge failure.

Prima facie the failure is overloading of the bridge and shaking that creating a situation where the suspenders couldn't handle the additional loads imposed. Nevertheless, we need to wait for the technical forensic report which may point out deficiencies in suspender connections or other things that may have been carried out during the refurbishment.

On a side note, theoretically, as per Indian Standards, this pedestrian bridge should have been designed for 500(load in kg/sq.m) x1.2m (width of bridge) x 230m (length of bridge) = 138000 kg or 138 tons in addition to self weight of the bridge which includes the flooring. So, assuming that there were 500 people with an average weight of 80 kg per person, the weight on the bridge should have been around 40 tons only. Having said that it's not that straight forward calculation. The individual suspender capacity needs to be calculated to accommodate partial or uneven loading which creates secondary loads in these suspenders. Considering the spacing of each suspender as say 4m. load on one suspender should be about 0.5x1.2x4x500 = 1.2 tons.

Now, hypothetically, say that 20 people were standing under one suspender zone of 4m spacing and are creating a sway. The load on each suspender is 20x70 kg (average weight of person) / 2 (two suspenders one on each side) = 700 kg or 0.7 tons. This load is still less than what the suspender should have been designed for. And then due to sway one side suspender buckles or doesn't take load in tension then the other suspender has to take 2x0.7 = 1.4 tons and the sudden impact and unbalance load creates an additional load of say 50% - This makes it to 1.4x1.5 = 2.1 tons. This load is 1.75 times more than the design load of the suspender. In engineering practice, we do keep factor of safety as 3 for these kinds of structures. So, a properly designed suspender should've taken this load.

These numbers or factor of safety calculated here can change significantly as how many people are coming under each suspender. The main cable and pylons (towers) would definitely take the full load as they have been designed for. But this failure may have happened because of one weak link. A suspender with a bad connection to the main cable is enough to lead a catastrophe we've seen in the videos. The moment the first suspender snaps off, it leads to cascading effects of increased forces on other suspenders making them fail till the remaining structure finds a load it can handle. Here so many people on the bridge didn't help this cause leading to complete failure. There was no redundant path for the load.

A comprehensive report by a competent authority alone can point out the reason for failure. It may be due to defective engineering or material or workmanship. We need to wait and see.

[amitoj]

Compare this with how the Millenium bridge in UK was saved from similar collapse more than 20 years ago and you can only lament the lack of value of life.

[extreme_torque]

Originally Posted by extreme_torque

Given the loss of life, one would assume atleast now the hospital and authorities would be prioritising tending to the victim and their families but apparently they are preparing the hospital for an impending VIP visit.

https://www.ndtv.com/india-news/guja...ndtv_topscroll

I am sure the media channels will only show those parts of the hospital to create an image, carefully choreographed so as to put that in the subconscious.

And as I predicted, a carefully choreographed event for the optics - new beds and linen, selected injured patients moved to newly deep cleaned newly painted rooms, new water coolers with no connection to water and a show of care and sympathy and cases against minions to save the big one's. Why do we the public take ourselves for so granted?

https://www.ndtv.com/india-news/morb...dtv_topstories

To put this tragedy in context, almost the same amount of people have been killed as in one of the biggest terrorist attack on Indian soil and by far the most number of people killed in a bridge collapse in the last few decades atleast.

[dailydriver]

It is at times like these that the eternal pragmatist in me starts doubting the very future of humanity.

High time we start treating willful negligence as a punishable, cognizable offence.

https://youtu.be/xcatxsxx07c

(Just in case something happens to this video, it shows a Maruti 800 being forced to drive back from a hanging bridge. The bridge is clearly not made/fit for driving a four wheeler. Yet the car seems to have been driven there, endangering both people and property)

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