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Footbridge collapse in New Delhi

Footbridge collapse in New Delhi

RE: Footbridge collapse in New Delhi

Photo 3 shows the lower suspension cable terminations appear to be bent.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Footbridge collapse in New Delhi

The problem I see is that what is basically a construction accident gets written up like it's a structural failure- they don't seem to realize the difference.

RE: Footbridge collapse in New Delhi

(OP)
Well, it was a structural failure which occurred while under construction.  What's the difference?  Do you mean it is better for the workers to be injured than the public?

RE: Footbridge collapse in New Delhi

so why she fell?is it the bridge itself too heavy?
 

Poems are made by fools like me, but only God can make a tree. engineers creates wonderful buildings, but only God can creates wonderful minds

RE: Footbridge collapse in New Delhi

This does not look like that complicated of a structure.  The report will be verrrry interesting.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Footbridge collapse in New Delhi

If there is a report, looks like they are already cutting it up and removing

RE: Footbridge collapse in New Delhi

Hokie, I just glanced at it, and after looking again, I take back what I said.  I assumed this was a typical hoisting/shoring/bracing issue, but it looks like the bridge was more or less structurally complete at the time of failure.  (The distinction would have been, that an otherwise sound structure can fail during erection due to poor erection practices, while if if fails afterwards, it makes you wonder about the safety of every other similar structure.)

RE: Footbridge collapse in New Delhi

It's interesting how the weldments protruding from the deck bent up, as shown in Photo 2.  Looks as if they did not have a good moment connection to the deck.

RE: Footbridge collapse in New Delhi

It looks like the cables were attached to the short cantilever beams along the side of the bridge. Some of the pictures show the beams deflected upwards, which might explain the bent cable terminators.

RE: Footbridge collapse in New Delhi

Given the way the steel framing under the conc. deck would work, as a continuous beam frame structure on many spring supports (the hanger cables and arches), and possibly even torsionally if loaded too much on one side; it is not hard to imagine that they overloaded a coupe neighboring cables, or their terminal hardware, and the whole thing just unzipped then.  A fairly simple structural concept as MikeM said, but fraught with danger during erection and conc. pouring.  Improper construction loading could draw unexpected additional DL's to a couple cables.
 

RE: Footbridge collapse in New Delhi

Ftom checking out the first photo further, I wonder if all the vertical cables were in place, looking at the horizontal bracing locations between the arches, and assuming, I did say assuming, one cable at each intersection point at each arch.  If all were not in place - boom!

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Footbridge collapse in New Delhi

I'm curious that the arch end to baseplate gussets were apparently field-installed, and there are indications of application of heat adjacent to the end plates of all the arch-to-arch spacers.  Or maybe they just touch up with burnt black primer..

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Footbridge collapse in New Delhi

The article said it collapsed "as workers were paving it", but that is just non-technical journalism speak for "as concrete was being placed on the bridge deck", as can be seen on Photo 4.

According to CNN's version of the article, "The bridge near Jawarharlal Nehru Stadium came down while workers were laying a concrete slab, said Rakesh Mishra, engineer-in-chief for New Delhi's Public Works Department." Not jumping to any conclusions, but being a student of forensic engineering, most collapses during construction of structures, especially while concrete is being placed, involve a lack of shoring or improper sequencing. But we will have to wait and see...

And with all due respect to Hokie66, there is a HUGE difference between an error in the structural engineering design, and a construction error that is related to sequencing, shoring, general means and methods... Not just important to those who may have fingers pointed at them, but for preventing it in the future, and for advancing the state of the art. IE, if it was a unique failure and something can be learned from it.

As a practicing SE I sure do not take responsibility, nor does any other engineer, for how our designs get built...

 

RE: Footbridge collapse in New Delhi

@a2mfk: If a structure requires a specific order or method of construction, and knowledge of this is conditioned by insights into statics and structural knowledge - is it not then the responsibility of a structural engineer to pass these insights on and take at least some responsibility for how his designs get built?

/mrlc, the metric system, Denmark

RE: Footbridge collapse in New Delhi

I'm wondering how big a paving machine they had to pull out of the wreckage before notifying anyone....

Mike Halloran
Pembroke Pines, FL, USA

RE: Footbridge collapse in New Delhi

(OP)
a2mfk,
mrlc has asked the question, and the answer is a resounding yes.  If a structure requires a certain sequence of construction, it is the responsibility of the engineer to not only define that sequence, but to take all steps available to him to assure that the required methods are followed.  I don't know if careful sequencing was required here or not...I simply stated that it was a structural failure which occurred during construction, which seems obvious.

RE: Footbridge collapse in New Delhi

Sure the design engineer can pass insights of the construction sequencing based on their design assumpions but in practice this may not be followed on site by the contractor who will execute the work according to their own programming and resourcing considerations.

Unless allowed for in the procurement brief such as a Design & build contract it would be unfair to expect an independent design engineer to take responsibilty for the temporary shoring works and sequencing. The contractor would have their own suitably competent and qualified specialists to interpret the design and sequence the construction.

RE: Footbridge collapse in New Delhi

(OP)
Making the assumption that a competent contractor will build your project is a bad mistake.  I am not advocating making the engineer responsible for the contractor's work, but if anything special is required, then the contractor has to be appropriately warned.  

RE: Footbridge collapse in New Delhi

@hokie66..
I am in full agreement that the contractor should be warned of any special requirements etc. but experience shows that even when issued with a full detailed specification and method statement this likely to be ignored/overlooked by contractors opting to use alternative sequencincing and programming to suit their own way of doing things and chasing targets

RE: Footbridge collapse in New Delhi

Fine.  

Then place a statement on the drawings/specs that if the construction sequencing/staging stipulated by the engineer of record ion these drawings/specs is either needed or desired to be deviated from, then the contractor must contact the engineer of record in writing for additional instructions, and receive those instructions prior to proceeding according to such instructions.  To do otherwise relieves the engineer of record from any and all liability from any documented or undocumented damage, present or future, resulting from such action.

Are you confused now?  I am.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Footbridge collapse in New Delhi

Hokie would be aware of the article in the engineers Australia this month about a similar bridge failure in Australia.

http://www.abc.net.au/news/stories/2010/08/24/2992277.htm?site=canberra&section=audio

It is very difficult in my mind to decide who gets the blame from an engineering stand point. In the review of the failure of the bridge above, 4 or so different engineering firms were involved in the project.  The different bodies are: GHD superintendent, AECOM design of the highway, sellick consultant designer of temporary works, Aurecon design of temp foundations. Then there are the contractors all experienced in the construction of bridges, Reynders Constructions, IFS scaffolding, Abergeldie contactors, Roads ACT.

Smec is the consulting engineers reviewing the failure event and have indicated the failure is due: "Lateral bracing of the girders was absent which affected their stability and bending capacity when subject to both horizontal and vertical loads. Web stiffeners were not installed at critical locations near concentrated loads being transferred from the girders to the cross heads and the cross heads to the props. Props were not fixed to the foundations to prevent uplift in the case where there was deflection and rotation of the main girders. "  

From this you can see that a lot had to go wrong for a collapse and every member of the team can be implicated.
 

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Footbridge collapse in New Delhi

(OP)
RE,
I hadn't read about that.  That failure sounds like a failure of the temporary works, while the Delhi collapse appears to be a failure of the permanent works, albeit while still under construction.

RE: Footbridge collapse in New Delhi

Is it possible that the design included the concrete slab to be a structural member, which of course it was not during construction?

RE: Footbridge collapse in New Delhi

(OP)
Yes, that is possible.  If so, the builder missed the requirement to shore the structure.  We may or may not find out the cause at some stage.

RE: Footbridge collapse in New Delhi

To me it looks like the deck did not fail, nor the concreting sequence. I cannot see how concreting in any or other way might overstress the hanger to the deck connections, which, for me, is the failure point.

There was a new's bit saying that not all the hangers were connected, that would overstress the closest one, make it fail and creating a zipper effect.

Other options would be design flaw, connection overstress.

But one thing that suprises and bothers me is that in the photos I have seen, the socket forks, although some of them bent, appear to be intact, while pins cannot be seen anywhere. Those socket assemblies are designed to be stronger than the hanger, so if overstress failure occurs, it does so on the bar/hanger and not on the socket/pin assembly. What about putting wrong pin size or material? That would cause failure and an inexperienced contractor might miss it.

In any case, I do not think we will ever know for sure.

 

RE: Footbridge collapse in New Delhi

(OP)
Different bridge collapse in Delhi, BA.  This one on the Metro construction.

RE: Footbridge collapse in New Delhi

(OP)
The one you posted was in July 2009.  Another one in October 2008.  A dangerous place for bridge workers.

RE: Footbridge collapse in New Delhi

Wow!  I'll say.

BA

RE: Footbridge collapse in New Delhi

Hi,

Some of the cable connections are not destroyed, I think they contractor neglected to connect it, thus the steel frame was subjected to longer spans while casting the concrete, obviously will lead to failure.........it not designed for that spans,

If you need a special method to construct a whatever structure, the engineer should advise the contractor on the method – or it's sending a guy into a dog fight without telling him the dogs have rabies ?!?
 

RE: Footbridge collapse in New Delhi

Nice metaphor, STATICPH, and welcome to the forum.

BA

RE: Footbridge collapse in New Delhi

The stiffness of a reinforced concrete structure comes after the mass.

For the post which RE put up, the first two points sound like issues which should of been picked up by the engineer. When I'm onsite and see that lateral bracing has not been installed, I make note to the builder that bracing needs to be installed. Likewise the absense of web stiffeners should of been picked up by the engineer during the review of shop drawings.

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