India's infrastructure

As we had often come back to discussing economic benefits/impact of sports I thought it was about time for an economic discussion forum.
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prasen9
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Re: India's infrastructure

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The electrical company Oreva/Ajantha is being blamed for opening the bridge before inspection. Reopening a bridge is a big thing. They even held a function to open the bridge. And, we are to believe that the local authorities did not know about this? Why? Why did not anyone check if the bridge was inspected before reopening it? Either way, the local government owns this and should be brought to task. That is, the officials in the government who should have known should be prosecuted for criminal negligence leading to manslaughter. What are the regulatory failures that led to this? Are we going to fix those and build a system that works?

I lived in Doha for two years and in those two years I have seen many fires break out in the highrise buildings often including once in our building when we had to go out and wait for 2-3 hours with a young baby at 2am in the morning. I have never seen that many fires in highrise buildings in the U.S. at that regularity. It was obvious that the difference was the regulatory regime and the system set up in the U.S. after the devastating fires in the early 1900s and the care taken to inspect buildings in meaningful ways before they are approved for habitation. In Doha, corrupt constructors cut corners. Appliances were not tested/checked and bad materials were used in the wiring, with shoddy, underpaid workers doing the job. There was inspection but not up to the mark obviously. Hence the situation.

This is a failure in multiple fronts. The development of India perhaps depends upon one thing. Enforcement. First, we need to enforce the laws we have. And, second fix the laws to set up a system that protects people. Will this happen? Soon enough?

People are saying that the bridge was overloaded and someone started shaking the bridge. Guess what that happens and will happen. I am not a civil engineer but the only class I took, we were designing things with 10x the normal load or something like that. Bridges must have huge safety factors and be built kowing that people will do all sorts of crazy things. If you really have a low limit, then the government needed to put in a gate and regulate the number of people entering the bridge. Why was this not done? The local government says that they had said a limit of 20 people on the bridge. Really? If you do not enforce it, how do you expect people to follow this? Were there at least signs? Stupidity!

We have a very renowned civil engineer among us. If I have said anything wrong, please correct. :-)


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Re: India's infrastructure

Post by jayakris »

As I may be the only civil engineer here, I think you are referring to me. Thank you for saying I am renowned. Certainly. In this forum, that is! :)

The safety factor for designs are never more than 50% over the maximum expected load (that is, failure shouldnt' happen till then). The 10 times you say is probably the safety over the normal expected load, not maximum. Here, it seems about 400 or so people on the bridge (about 2 or so per square meter) may have been the maximum expected. If so, perhaps 200 people's load on one suspension cable, and 200 on the other, for maximum case - to put it in simplistic terms (it is not exactly that).

That means each cable would have been designed to fail only at 50% more load. That is 300 or so people's load per cable (so 600 total) as the failure load. These are approximate numbers I am guesstimating. But a normal load would be as little as 50 people on the bridge (so your 10 times is an acceptable mutliplier from "normal load" - but designs are always for maximum load, with 50% factor of safety). If I were running the bridge operation, I would certainly not let more than 200 or so on the bridge, if even that. More like 100 max.

I went frame by frame over the best videos from the deck that I could find of the few seconds before the failure. It seems like some sort of wind (even mild breeze enough) was causing the bridge to sway. In fact this bridge is known for the sway and people apparently walk on it just for that experience. A friend of mine (an IITM civil engrg classmate) just told me that he found earlier pictures which seem to show that they may have changed the safety net on either side to one with less perforation recently during maintenance. If so, the wind may have caused even more swaying of the bridge than in the past. The side-to-side sway will naturally cause the deck to twist a bit - ie, up and down on either side. From what I see in the video, it seems like at one point a lot of people were going to the right side net, just before the right cable snapped. Basically a much higher unbalanced load on the right side main suspension cable. My wild guess is some 75% of the people load (that is probably over 350 people's load, out of the 500 on the bridge -- over the cables maximum design load, as my guesstimate). Not sure if those main cables were ever replaced in 140 years. If not, they may no longer have the 50% extra safety capacity anymore, due to corrosion, metal fatigue etc. Probably ready to fail if 250 people's load and the deck-weight went to it. Disaster.

I think the problem here was that they gave a maintenance contract and allowed that company to collect tolls. I don't think replacing the main suspension cables was part of their contract. That is an extremely elaborate process that this company is certainly not equipped to handle. Plus it would need a year or two for this bridge, and typically people would consider building a new bridge instead! The key issue was the toll collection. It appears that there wasn't a strict maximum number they were allowed to let in on the bridge, in the contract. That is stupidity at it worst. Of course, the company was going to just let in as many people as would pay for it (Rs. 17 each, I believe) to make money. They did just that, at unfortunately a time with good wind swaying. That and the netting issue above caused an unbalanced load transfer to one cable, which may be 30% weaker after a century, and we have 150+ dead. This is where my thinking is. We will see what the forensic team finds out later.

Rather than blame the maintenance company, and act like they didn't do maintenance right, the people who gave them the contract to collect money without maximum stipulations should be jailed.


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Re: India's infrastructure

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The idiots at the local government said that the bridge capacity was 20 people and not more than that should have been let in. If so, who was enforcing that this was being observed? If you let a company collect tolls, you need to check to see that they are not being too greedy and violating the rules and packing as many people as possible.

The bridge's maximum load should be the number of people that can be packed onto the bridge. Or else, there needs to be a system where the number of people were being restricted. It seems like they never restricted the number of people. The company should have known this and the local government should have enforced this.

Yes, I was talking about 10 times the "normal" or average load. When we calculate the maximum load, we need to calculate the really really maximum load possible. Now, of course 120 years ago or whatever they may not have expected that many people to come all at once, but really the maximum load should be maximum possible. If you do not have the money or do not want to spend that much to make it that strong, then you have to limite the number of people going in.

Both should be criminally prosecuted.