China Fireworks Explosion - Possible Shoddy Construction? - Page 1
Forum section: electronics / general

author: SgtRock
author_rank: Unknown
timestamp: February 02, 2013, 03:06:36 am
content: Greetings EEVBees:--I realize this subject is off topic. But, I know that some of you are Mechanical Engineers, so I would like your opinion on the recent Highway Overpass Collapse in China. See below link, and attached picture.http://apnews.myway.com/article/20130201/DA45RNFO1.htmlI have done a lot of layout work on Concrete High Rise Buildings. I was called an Engineer, but I preferred to be called the Layout Man. I was responsible for all critical layout measurements and leveling of concrete forms, using a Transit Theodolite and an Engineers Level. I was also responsible for taking concrete samples and Slump Testing. The reason I mention this is I am very familiar with the use of 3000 and 5000 PSI concrete and usage of re-bar. The buildings, up to 20 floors, I was working on had way better looking concrete and lots more re-bar, and they were for people and cars, not trucks. But this picture looks to me like very poor concrete and almost no re-bar. I hate to think what an earthquake could do.--1)Does this Overpass section look to be properly constructed? 2) Is it credible that a semi-load of fireworks did this kind of damage? 3) Corruption?"Hymn of Breaking StrainThe careful text-books measure Let all who build beware!)The load, the shock, the pressure Material can bear.So, when the buckled girder Lets down the grinding span,'The blame of loss, or murder, Is laid upon the man.Not on the Stuff - the Man!Rudyard Kipling 1865 -1936Best RegardsClear Ether

author: SeanB
author_rank: Super Contributor
timestamp: February 02, 2013, 05:59:18 am
content: Definitely they did not have enough steel there, and the concrete looks poor as well. Even if you detonated 20 tons of low explosive ( more than you would have in a truck anyway) the bridge should have survived, probably with severe surface damage and possibly minor through holes in the roadbed under the truck such that it was now unsafe. This one was so close to collapse that this failed it. It would likely have collapsed sooner or later, probably when fully loaded with trucks standing in a traffic jam.Locally the police confiscated 120 tons of fireworks from 2 wholesalers, who had illegal stock and more than they were licensed to carry. Those will be going up in smoke sometime soon.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: February 02, 2013, 07:57:40 am
content: Quote from: SgtRock on February 02, 2013, 03:06:36 amI agree that this is off topic, but structural failure is endlessly fascinating. I know just enough about concrete and have done just a few pours to be dangerously mis-informed so I won't address your first question, however to my eyes it does look inadequate in both rebar and that the total distance spanned by an I beam deck seems too large.2. semi load of fireworks? Yes certainly with caveats. I remember semi load of ANFO just mixed and being transported to mine in northern ontario. Similar energetics left an awesome crater bigger than a house, a whole section of two lane hiway gone. A rental truck with a smaller amount of ANFO pretty much levelled the federal building in Oklahoma, although in that case the blast wave was somewhat focused with a shaped charge technique and it lifted the floors before dropping them. Concrete decks are really weak when subjected to certain types of displacement. That bridge looks extremely bad at being able to resist any seismic event. It has very large span and the column supports don't have spall jackets. The tops of the columns would spall just under where they support the deck load in an earthquake.3. corruption in china ?It is guaranteed! On some web-site, I think it might have been ChinaSmack , there are photos of a bridge in tibet or neighbouring mountain province were the caissons which should have been poured concrete simply had gravel substituted in a wire form. The semi illiterate sub contractor just wanted to pocket the savings! This happens through the whole construction food chain. No engineer sign-off or oversight and inventive economizing substitutions.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 02, 2013, 12:55:37 pm
content: To be fair, most of the loadbearing in concrete bridge spans is provided by post-tensioned steel cables in channels within the span. One of my hobbies is urban exploration, so I've been inside a few large concrete bridges. The tensioning cable ends stick out inside the span structure walls near the ends - where they sit on the supports.The individual spans are not actually connected to each other, just the road deck on top is. The rebar you're seeing sticking out is just the road deck stuff. Yeah, looks light. But it wasn't that which initially failed.I'd like to know how a truckload of fireworks detonates with enough of single shockwave, to blow a section of the sidewall off the adjacent roadway. Wait,twotruckloads.You know it's conceivable it was deliberate. Plenty of very disgruntled people in China.

author: Hypernova
author_rank: Unknown
timestamp: February 02, 2013, 01:59:01 pm
content: Quote from: TerraHertz on February 02, 2013, 12:55:37 pmUnless it was some miss configured detonator there no point in blowing up some highway.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 02, 2013, 02:45:23 pm
content: True. Mainly I'm just mystified how a truckload of fireworks could possibly have some large portion of the fireworks detonate all at once. Doesn't seem likely.Something else - was there anyone of particular importance in the other vehicles? Just saying - if it was deliberate, maybe the target wasn't the highway. We'd never know.

author: G7PSK
author_rank: Super Contributor
timestamp: February 02, 2013, 05:33:32 pm
content: As it has given way at an expansion joint it is very difficult to say much about the quantity of rebar exposed one would not really expect to see much on a joint. Some of the bearing plates appear to be still extant. It would be far more interesting to see the remains of the beams and to know at what point in the road way the truck exploded or if it was underneath the bridge at the time and the blast lifted the bridge up and sideways. Bloody big firecrackers though to do that much damage more like military pyrotechnics.

author: ftransform
author_rank: Frequent Contributor
timestamp: February 02, 2013, 06:11:20 pm
content: Quote from: chickenHeadKnob on February 02, 2013, 07:57:40 amWhat? There was a shaped charge "effect"? How do you mean, how did he possibly shape charge a explosive like anfo? Did he weld together a monster steel cone? Did he utilize a simple wooden cone? Why was there not a clean hole blown in the building given the behavior of shaped charges?I think you are under some misconception because what you said seems too interesting to be true but I can be wrong.

author: saturation
author_rank: Super Contributor
timestamp: February 02, 2013, 07:23:12 pm
content: You can find a lot of this under 'epic fail' as a search term. Here's one in a engineer oriented forum:http://forum.skyscraperpage.com/showthread.php?t=183620

author: BravoV
author_rank: Super Contributor
timestamp: February 02, 2013, 07:43:04 pm
content: At least they have an excuse that tons of fireworks caused it.Now look at this one below, no fireworks nor earthquake what so ever.Source ->Bridge 9340As a Layout Man, whats your opinion about this one Sarge ?

author: SgtRock
author_rank: Unknown
timestamp: February 02, 2013, 08:58:37 pm
content: Dear BravoV:--The proximate cause would appear to be the engineering. The joints in and around the critical support node (picture attached below) appear to be so many and their relationships so complex that they outwitted the engineers from Sverdup & Parcel, now Jacobs Engineering who designed them. Quite possibly there is more wrong with the design than just the thickness and total area of the gusset plates. The second cause is of course the inspectors who took the pictures of the bowed gusset plates and took no notice.--The part of the commissions report about the extra 2 inches of concrete and construction load from the ongoing repair is bull. This bridge was supposed to be designed to tolerate a 2.5 time design load. The shear number of rivets in the gusset plate make me suspect the engineer was "swaging" it. This one reminds me of the Hyatt Walkway Collapse (see link below), where the engineers were guilty of criminally negligent lack of attention to detail. I think probably the case against Jacobs will probably end up the same way, when the State of Minnesota show that computer analysis easily proves the design is failure prone.http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse--I have also worked as a Roof Truss Designer, and so I know just enough to be dangerous. And that is why I was always glad to have the Bona Fide Engineers putting their seals on the designs, but I still used to wake up at night worrying, that I might have failed to include some loading or a point load on a particular girder or beam. All structural engineering, buildings, bridges, ships, aircraft, etc. can be a very scary business."I wear suspenders and a belt. I am a security man all the way"Justin Wilson (The Cajun Cook) 1914 - 2001Best RegardsClear Ether

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: February 02, 2013, 09:38:33 pm
content: Quote from: ftransform on February 02, 2013, 06:11:20 pmTimothy Mcveigh packed Ammonium nitrate prills (you have to grind and dry them) with oil and Nitro-methane. The later making the composition like commercial two part explosive astrolite-G a very powerful high order explosive -as far as I know. He put it into multiple rows of plastic barrels stacked with a horizontal gap facing the building. Dude knew what he was doing. You don't need a metal liner to achieve the munroe effect, just a concave surface as that is what focuses the blast wave in that direction.As far as fireworks go, I also think that usually a stockpile would just deflagrate, however explosion in firework factories have happened. The lift charges are black powder which under some conditions can go high-order. I was once told by a pyro/chemist that blackpowder decomposition is actually extremely complicated. The chlorates/perchlorates in the color effects are sensitized by sulfur contamination or static electricity could set off either one. The official story sounds fishy but not completely implausible.

author: G7PSK
author_rank: Super Contributor
timestamp: February 02, 2013, 10:40:32 pm
content: The Romans built bridges that are still standing today and in many cases carrying modern traffic which is a lot heavier than the odd pack horse or cart, I cannot see many modern bridges lasting 200 years let alone 2000.