Footbridge collapse in New Delhi 1

[hokie66]

Not a good look. The concrete deck was being placed, and down she came. This and other issues are making some countries and athletes reluctant to go to the Commonwealth Games.

http://news.ninemsn.com.au/glance/7978694/drama-as-bridge-collapses-in-delhi

 

[MikeHalloran]

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



Mike Halloran
Pembroke Pines, FL, USA

 

[JStephen]

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.

 

[hokie66]

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?

 

[jenofstructures]

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

 

[msquared48]

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

 

[engineertipsman]

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

 

[JStephen]

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.)

 

[graybeach]

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.

 

[bones206]

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.

 

[dhengr]

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.

 

[msquared48]

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

 

[MikeHalloran]

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

 

[a2mfk]

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...

 

[mrlc]

@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

 

[MikeHalloran]

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

 

[hokie66]

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.

 

[scode99]

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.

 

[hokie66]

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.

 

[scode99]

@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