from the low-standards-and-dramatic-photos dept.
David Petley blogs at the American Geophysical Union
The collapse of the Weiguan Jinlong apartment complex [in the February 6 Taiwan earthquake] should not have occurred--a building of this type should have been able to withstand the peak ground accelerations associated with an earthquake of this magnitude, even allowing for the potential for some amplification from the sediments under the foundation. The collapse is quite odd in many ways--the building has clearly toppled over. But, over the last day or so, images have emerged of the state of the key columns that supported the building and the images are shocking:
The apparent replacement of structural concrete with empty cooking oil cans may have critically weakened the building and, if these are load-bearing, may have played a role in the failure. The cans provide almost no structural strength and of course mean that the amount of rebar within the concrete is also reduced. Interestingly, there is surprisingly little rebar in the section of the column that does have concrete.
[Continues.]
NPR (formerly National Public Radio) reports
Taiwanese President-elect Tsai Ing-wen [who will take office in May] is promising extensive safety checks of old buildings two days after [a magnitude 6.4] earthquake killed at least 38 people, according to local media. New questions emerged after stacks of cans were found in the walls of a 17-story building that was the scene of all but two of those deaths.
Those cans are blue cooking oil containers, reports Central News Agency; other media outlets call them old paint cans. Structural engineer Tai Yun-fa tells the state-run agency that in structures built before 1999, oil cans were used to fill out pillars and make them look larger. The Golden Dragon apartment building in the city of Tainan was reportedly completed in 1994.
From the CNA:
The use of cooking oil cans for such purposes in construction was not illegal prior to September 1999 but, since then, styrofoam and formwork boards have been used instead he said.
It is preposterous to think that cooking oil cans would be used in a pillar for support purposes Tai said.
[...] A team of prosecutors [is] now at the site to look for any signs of wrongdoing, the newspaper adds.
[...] Dozens of people were still missing--but some survivors were still being pulled from rubble some 60 hours after the quake. Two people who were trapped inside the large apartment building that has been at the heart of rescue operations were brought to safety Monday--an 8-year-old girl and a woman from Vietnam.
(Score: 2) by takyon on Tuesday February 09 2016, @02:03PM
Developers, developers, developers!
http://www.npr.org/sections/thetwo-way/2016/02/09/466120298/developers-arrested-over-building-that-collapsed-in-taiwan-s-earthquake [npr.org]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 4, Insightful) by Dunbal on Tuesday February 09 2016, @02:31PM
Hopefully someone will be smart enough to seriously inspect anything else these guys might have built.
(Score: 5, Informative) by Runaway1956 on Tuesday February 09 2016, @02:36PM
I believe that someone may hang for this. I've built a lot of pillars, in my time. There's a hospital in Texarkana, where half of the pillars are my handiwork. One does NOT screw around when building supporting pillars. If you're going to cut corners ANYWHERE, you do it elsewhere. My - uhhhh - "competition" - who was an "expert" with pillars had to tear a bunch of his down, and do them again, because he couldn't slip anything past the inspectors. Just a little bit of honeycombing was enough to have him jackhammer the pillar down, and start all over again.
And, believe me, if anyone was filling pillars with empty cans, styrofoam, or anything else, then a lot of other people were involved. That isn't something that one or two guys can do in secrecy. Every individual who worked that job site needs to be investigated, from the lowest helper up to the superintendants and the owners.
(Score: 3, Insightful) by Dunbal on Tuesday February 09 2016, @02:43PM
I'm sure an extra $20 or so takes care of a lot. The answers you'll get from the workers will range from "I didn't see anything" to "we were told this was a new, approved technique".
(Score: 3, Funny) by deadstick on Tuesday February 09 2016, @03:16PM
One of the celebrated casino demolitions in Vegas -- I'm trying to remember which one -- almost failed to come down for the opposite reason: it was built too well. Seems that when it was being built, there had been some controversy over shoddy construction. So a representative pointed out to the contractor that "Mr. Gambino and Mr.Giancana are eager to know they're getting good value" -- whereupon it was hard to buy rebar in the region for a while.
(Score: 2) by Runaway1956 on Tuesday February 09 2016, @03:32PM
That's kinda humorous. I know that Texas sent some contractors and inspectors to prison for use a four bag mix where a five bag mix was specified. I wonder what would happen if a contractor used an extra bag instead of cheating a bag? Texas, being Texas, would probably prosecute them. I like Texas, but it does have it peculiarities.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @05:44PM
wonder what would happen if a contractor used an extra bag instead of cheating a bag?
Texas, being Texas, would probably prosecute them.
Yeah, Texas has a really bad rep for over-regulation.
(Score: 2) by AudioGuy on Tuesday February 09 2016, @06:16PM
"I wonder what would happen if a contractor used an extra bag instead of cheating a bag? Texas, being Texas, would probably prosecute them."
Actually Texas would be right to prosecute them. Both too little OR too much will weaken the concrete. The cement just provides 'glue' between the strength elements, so too much would be replacing those with the weaker glue.
(Score: 2) by Runaway1956 on Wednesday February 10 2016, @02:16AM
It might be more accurate to say "changes the properties of the finished product", than to say to much cement will "weaken" it. Up to some point, more cement both increases the crush and the shear strength of concrete. I've never researched or experimented to find out where the point of diminishing returns might be. Very roughly speaking, a two bag mix gives you a 2000 pound strength, 3 bag mix around 3500 pound, 4 bag 5000 pound or a little more, and a 5 bag mix is supposed to be 10,000 pounds. A 10,000 pound mix is typical for highway construction in Texas, and 5000 pound mix is typical for most industrial construction. I associate lesser mixes with consumer-grade housing projects, like floor slabs and driveways.
It doesn't take any special qualifications to state that stronger mixes are more brittle. That is, I can destroy a 10,000 pound mix with a sledgehammer more easily than I can wreck a 3,000 pound mix.
It all depends on what specific properties the architect was looking for, whether more cement in the mix is going to hurt the end product.
Of course, the addition of flyash is far more probable than adding extra cement. Flyash is relatively cheap.
(Score: 2) by CirclesInSand on Tuesday February 09 2016, @04:51PM
In Chinese Metroid, collapses cause bosses to die.
(Score: 2) by frojack on Tuesday February 09 2016, @07:21PM
Better picture here:
https://metrouk2.files.wordpress.com/2016/02/ad_195714964.jpg [wordpress.com]
These look to me like sound deadening voids on an interior wall (or floor) between apartments, rather than on a pillar supporting the building.
The outer surface, clearly a finished interior wall or floor, is very thin, 2 to 3 inches. Behind (or is it below) the cans, you see a foot thick re-rod enforced structure, which failed at the joint.
Otoh, there are far rustier and more damaged cans in the nearby walls.
http://tinyurl.com/j9go2js [tinyurl.com]
No, you are mistaken. I've always had this sig.
(Score: 2) by compro01 on Wednesday February 10 2016, @02:12AM
I believe that someone may hang for this
Taiwan doesn't hang people. They shoot them.
(Score: 2, Informative) by Anonymous Coward on Tuesday February 09 2016, @03:28PM
Today, prosecutors ordered the arrest of the former chairman of the now-defunct Weiguan company and two other executives, on charges of professional negligence.
Too late, people are already dead.
Seems like China's model is more along the lines of the libertarian model, don't worry so much about regulation and enforcement, just ratchet up the consequences for malfeasance to 11. That seems to be the pattern from mainland china, at least, where they occasionally execute a public official for corruption. Taiwan's a democracy but until recently it was more of a fake democracy (like south korea was until the 1980s) so they've probably still got a lot of the mainland mindset lingering.
(Score: 1) by redneckmother on Tuesday February 09 2016, @06:11PM
You're right, it's too late for the victims. Still, perhaps those responsible should be placed in cans, then buried in concrete?
Mas cerveza por favor.
(Score: 1, Informative) by Anonymous Coward on Wednesday February 10 2016, @01:42AM
One could put it differently. There is a mainland China where there is law in place and there is Taiwan - an island occupied by the US with a US style democracy that kills innocent people as it is expected to.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @02:12PM
Another story says the cans were used to widen the pillars for cosmetic reasons. The core pillar did not have the cans in them, only the extention around them.
(Score: 4, Informative) by Dunbal on Tuesday February 09 2016, @02:26PM
Oh I read that other story. It's bullshit. Anyone with any sort of construction background can see it for what it is. Why do you need to "decorate" THE INSIDE [newsblaze.com] of a wall [turner.com]? This is criminal. Also anyone with any sort of construction background can also immediately see the "quality" of the concrete is obviously deficient for the type of building. The color is off, and the amount of aggregate is wrong. This stuff was made using mostly sand and a tiny little bit of cement. The owners, the construction company and the engineers who signed off on this project need jail time. "Pour encourager les autres".
(Score: 2, Interesting) by Anonymous Coward on Tuesday February 09 2016, @02:30PM
> Why do you need to "decorate" THE INSIDE of a wall?
You don't. And no one said you did. Please re-read the GP.
(Score: 2) by Dunbal on Tuesday February 09 2016, @02:41PM
It's much easier, cheaper and less labor intensive to make a "wide" column by pouring an empty space in the middle instead of doing what they did. You can re-use the forms if you set them up properly. You can't re-use the tin cans when you bury them in the wall.
(Score: 1, Informative) by Anonymous Coward on Tuesday February 09 2016, @03:19PM
Its like you are being deliberately obtuse.
You can't widen a column buying pouring it hollow after its already been poured.
You don't need to re-use the tin cans because they are cheap-ass tin cans.
(Score: 4, Interesting) by Dunbal on Tuesday February 09 2016, @06:03PM
I'd say you're being obtuse, insisting that columns on a COLLAPSED BUILDING must have been wide for "decorative" purposes. There are a million ways to make a column "look" bigger - probably the easiest being putting studs and fake chip/particle board panelling around the outside of it and covering that with plaster, paint, or whatever. Or you can pour two walls or 4 walls instead. But shoving it full of empty tin cans is not a "decorative" method. It's an "I'm going to cheat and bill people for cubic meters of concrete I didn't actually use" method. Although I hear that there are people willing to defend the devil himself.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @06:51PM
> I'd say you're being obtuse, insisting that columns on a COLLAPSED BUILDING must have been wide for "decorative" purposes.
Jesus fycking christ you are an idiot!
The FACADES, not the columns.
> There are a million ways to make a column "look" bigger - probably the easiest being putting studs and fake chip/particle board panelling around the outside of it and covering that with plaster, paint,
Would you be screaming bloody murder if the rubble had a bunch of hardieboard in it instead? No you wouldn't. Just because cement was used in the facade does not make it load bearing.
(Score: 2) by Dunbal on Wednesday February 10 2016, @12:39AM
The FACADES, not the columns.
Just because cement was used in the facade does not make it load bearing.
Yeah, the building collapsed because the load bearing structures were 100% sound and up to code. 6.4 is NOTHING where earthquakes are concerned - modern buildings are designed to withstand much more than this. You are disconnected from reality. Reality is that load bearing structures were compromised and the building collapsed in a moderate earthquake - was the ONLY building to collapse in this earthquake, and the builders have been arrested and will be tried. That is reality. But you cling to this fantasy that someone mentioned somewhere that maybe the obviously compromised and collapsed building collapsed due to some other act of god because the OBVIOUS and highly visible answer couldn't possibly be right.
(Score: 2) by Runaway1956 on Tuesday February 09 2016, @03:41PM
The only hollow columns I've ever seen were elevator shafts. Something similar were "tunnel forms" used to build prison cells. Hollow columns just aren't in great demand in any of the work I've ever done. Far more common, is a 24" x 36" column with cantilevers at the top, which might spread out another 2, 4, or even 6 feet. I don't like building them very much, because they are difficult to plumb and brace. But if you want to support a large area, but don't expect it to carry a lot of weight, that's the way it's done.
(Score: 2) by Dunbal on Tuesday February 09 2016, @06:07PM
Slip forms. You can build lots of neat things [google.com] with slip forms :) But this is 100% not what was being attempted.
(Score: 5, Interesting) by Phoenix666 on Tuesday February 09 2016, @03:34PM
When I was a student at Capital Normal University in Beijing they were putting a dozen highrise residential towers up around the campus. You could gouge the bearing columns with your finger nail for the same reason. The Chinese students would tell me every time there was a rumor of an impending earthquake people would light out for the countryside; I said that was a damn good idea.
Washington DC delenda est.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @03:53PM
Also where it was done once it probably was done elsewhere. I predict many 'reconstruction' and 'abandoned' buildings in the future.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @05:15PM
FTA:
They weren't decorating the inside of anything, they wanted to make the pillar bigger than what was needed for mere support purposes (IOW, make it bigger for aesthetic purposes) and used the cans for filler between the load-bearing core of the pillar and its outer facade.
(Score: 0) by Anonymous Coward on Tuesday February 09 2016, @03:24PM
COMMENCE WILD SPECULATION!!1111
(Score: 2) by Dunbal on Wednesday February 10 2016, @12:44AM
To be fair, all evidence points to them not being load bearing - they certainly didn't bear the load.
(Score: 1) by CHK6 on Tuesday February 09 2016, @03:27PM
If the stories are true, there are some cement buildings where some ill-repute individuals might have been last seen near cement trucks.
(Score: 2) by bob_super on Tuesday February 09 2016, @07:14PM
Actually, I'd take the corpses-reinforced building over the tin-can one, given that hair and bones will provide extra tensile strength for a few centuries.
(Score: 5, Informative) by VLM on Tuesday February 09 2016, @04:13PM
To a crude first approximation you can assume cement tensile strength is zero. It isn't, of course, but "first approximation" and all that. Its a weird material in that most bulk "stuff" has economically useful levels of all three stresses but unreinforced concrete in tension is roughly economically useless.
Interestingly, there is surprisingly little rebar in the section of the column that does have concrete.
So reducing the cross section of a column by 10% by replacing the center 10% of the volume with tin cans will roughly drop the shear strength by 10%. It'll have darn near zero impact on bending loads if the cans aren't near the surface. I'd theorize that was not the problem. Well yeah its a problem that someone paid for 100% of shear load and was provided only 90% but thats not why this building out of all of them collapsed.
The killer this time is the lack of rebar. So as the earthquake rocks and rolls like waves on the sea, you find a weird point (resonance or whatever) where the concrete compression momentarily drops to zero, tries to put un-reinforced cement under tensile load, see first line to a crude approximation the tensile strength of cement is zero, the column fails and once its under compression again it buckles out or completely shears.
I bet there's buildings all over Taiwan with tin cans in the center of the column, and if surrounded by rebar they aren't and didn't fail.
The popular media if focusing on the tin cans which don't really matter. The real killer was no, or improper, rebar.
Paradoxically its easier to break concrete pillars if they're not under load. Concrete is very strong in compression so if you put a heavy as hell thing on top, there's nothing you can do with explosives or earthquakes or whatever to take it out of compression. But lightly enough loaded and you can more easily reach a tensile load. And concrete being about as strong in tensile stress as water, you can guess where this is going. I know you can't crack an interstate overpass bridge column by crashing into it with anything that can drive on the interstate, but I bet during construction an unloaded overpass column could be cracked and tipped over by the usual heavy construction machinery.
(Score: 1, Interesting) by Anonymous Coward on Tuesday February 09 2016, @05:37PM
>> first line to a crude approximation the tensile strength of cement is zero, the column fails
>> and once its under compression again it buckles out or completely shears.
In the context of resisting an earthquake, this statement is nonsense.
The problem in earthquake is not so much the strength when first loaded but the integrity under repeated loads during the shaking that follows. Rebar has to be placed so that it contains the concrete once it starts cracking. That means that the rebar forms a cage around the crumbling concrete, maintaining some strength. Take away that cage and the concrete falls out and the structure is reduced to a bunch of flimsy rebar. In real terms, regardless of the amount or spacing of longitudinal rebar (along the length of a beam or height of a column), it is the shear rebar that wraps the beam/column that contains the concrete as it cracks. This type or rebar has to continue through the joints between beams and column (these joints are the most likely points of failure in an earthquake).
If you want an idea of the kind of strength that crumbled concrete contained in a cage can achieve, take a look at gabions. These are wire cages that are filled with rock - no cement or mortar. They are frequently used to make retaining walls or shore up embankments. They look pretty flimsy (at least the small amount of what seems to be heavy-duty chicken wire) but hold up a lot.
(Score: 1, Funny) by Anonymous Coward on Tuesday February 09 2016, @05:10PM
Reminds me of this: https://i.eprci.net/image/chinese-capacitors [eprci.net]
(Score: 2, Informative) by Anonymous Coward on Tuesday February 09 2016, @05:42PM
There was a bridge built in Shanghai in 2009 in which "Styrofoam, bags of garbage, scrap wood and plastic waste" were used in a similar way, reportedly filling load-bearing piers. Fortunately no one died when the bridge fell apart.
http://www.chinadaily.com.cn/china/2009-12/30/content_9244857.htm [chinadaily.com.cn]
http://www.weirdasianews.com/2010/02/05/shanghai-wonderbridge-trash-collapses/ [weirdasianews.com]
(Score: 2) by Phoenix666 on Tuesday February 09 2016, @06:37PM
That's the thing that Old China Hands know that the rest of the world doesn't realize when they see stuff like the Beijing Olympics--it's all built half-assed. There is shoddy construction all over the world, but in many places there are reasonably serious attempts to inspect the work to make sure it's up to snuff. In China, why bother? If you lose 1000 peasants in a construction disaster there are always another 1000 peasants to occupy in rebuilding it. Eventually it'll remain standing long enough to call it done.
Washington DC delenda est.