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Nearly completed high-rise collapses in Shanghai
4

Nearly completed high-rise collapses in Shanghai

Nearly completed high-rise collapses in Shanghai

(OP)
HONG KONG (Reuters) – A 13-storey residential building under construction in Shanghai collapsed Saturday, killing one worker and highlighting the dangers of shoddy building in fast-urbanising China.

The building, in the outskirts of the city, collapsed at around 6 a.m. (6 p.m. ET) with one construction worker killed, the official Xinhua news agency reported.

The block of high-rise residential flats was shown toppled onto its side in a muddy construction site, in footage from Hong Kong's Cable Television. Exposed pilings stood in the remains of the building's foundations.

It appeared to be almost complete with fitted windows and a finished, tiled facade. Other similar-looking blocks in the same property development were still standing nearby.

Shoddy construction and the use of sub-standard materials is a concern in China's construction sector as the country scrambles to build out cities and finish massive infrastructure projects to keep pace with fast economic growth.

Construction-related accidents last year included the collapse of a steel arch on a new railway bridge, which killed at least seven and a crane which fell on a kindergarten killing five.

The collapse of dozens of schools during last year's Sichuan earthquake, sometimes when buildings around them withstood the tremor, also led to a wave of public outrage about corrupt officials and construction firms.

Source: http://news.yahoo.com/s/nm/20090627/wl_nm/us_china_building

Pictures:

http://img2.cache.netease.com/cnews/2009/6/27/2009062713100745a4b.jpg

http://img4.cache.netease.com/photo/0001/2009-06-27/5CQIQQA700AN0001.jpg

http://img2.cache.netease.com/photo/0001/2009-06-27/5CQLNCTL00AN0001.jpg

http://img2.cache.netease.com/photo/0001/2009-06-27/5CQLNCTL00AN0001.jpg

http://laiba.tianya.cn/laiba/images/10243577/12460615620825065124/A/1/m.jpg

http://hk.apple.nextmedia.com/images/e-paper/20090627/large/RTR_P_N0752.jpg

 

Clansman

If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

RE: Nearly completed high-rise collapses in Shanghai

One worker was killed, several managers will disappear.

RE: Nearly completed high-rise collapses in Shanghai

Seems like a negligent lack of geotech investigations.
Have any engineering details been published?

RE: Nearly completed high-rise collapses in Shanghai

3
I think that the nearby constructing underground park   and rainstorm cause the foundation collapse,then the piles of the building were sheared to destroy and the building was overturned.
Besides I think the construction isnot shoddy.   

RE: Nearly completed high-rise collapses in Shanghai

Those piles appear to be unreinforced, I would expect some reinforcement in piles for a building of this size to take wind/seismic forces.

The rest of the building looks fine, how many buildings are capable of falling over and remaining in one piece?

PSlem,

It is unlikely that the building was pushed to failure by the soil as the soil is only very low and the weight of the building will be many times this. I would expect that the soil you see is from a circular rotation failure of the soil resulting from the building toppling over.

As always, these things are never clear cut. It would be interesting to see the results of the investigation.

RE: Nearly completed high-rise collapses in Shanghai

Agree with csd72 on probable failure mode.  Not slope push.

Anything we have is purely speculation, but would look at bearing failure on leading edge.

Piles look short...obviously didn't have enough tension capacity for overturning moment.

RE: Nearly completed high-rise collapses in Shanghai

The slope failure of the pile beside the building probably occurred when the building hit the ground from the resulting mini earthquake.   

RE: Nearly completed high-rise collapses in Shanghai

The good thing is there was enough space between this and the next building so that it didn't start a domino action.

BA

RE: Nearly completed high-rise collapses in Shanghai

I wouldn't have much confidence in the other buildings.

RE: Nearly completed high-rise collapses in Shanghai

No rebar in the broken concrete piles.   

No "slab" or floor structure in the lowest building basement: The building entry floor appears to be resting directly on the mud itself.

RE: Nearly completed high-rise collapses in Shanghai

I guess they make their buildings like they do their pipe!

RE: Nearly completed high-rise collapses in Shanghai

They were going to use the buildings to assemble Chinese toys to ship over here.

This is the Chinese version of "rollovers".

It looks like there was no basement - the grade beams appear to have been at grade.  Consequently, the building CG was much higher, amplifying any settlements and associated OTM due to gravity loads that never should have occurred.

Mike McCann
MMC Engineering

RE: Nearly completed high-rise collapses in Shanghai

On what seen in the photos above it seems excessive settlement from one side caused tilt and breakup of the unreinforced piles. That the building wouldn't sreak whilst falling says it is better than its foundation. And without seeing more, for such vast settlement one would think as maybe short piles and ... maybe excavation on the far side? It would have been wedge failure.

RE: Nearly completed high-rise collapses in Shanghai

How much trouble are they going to have putting people in those other three buildings?

RE: Nearly completed high-rise collapses in Shanghai

All,
The pile adopt the high-strength prestressed pipe pile.
attached for you information

RE: Nearly completed high-rise collapses in Shanghai

All works togeter. Surely the entire suppression or collapse of the farside of piles was not an hypothesis. Hence no surprise failing under forces much higher than those envisaged.

RE: Nearly completed high-rise collapses in Shanghai

for whatever reason, maybe this is a case of "just-in-time" collapse ? (before anyone got hurt)

RE: Nearly completed high-rise collapses in Shanghai

The wet dirt "uphill" from the failed building is still sliding "downhill" with a classic "half-moon" scarf near the road.

They were lucky it fell into an empty lot with no people, and not backwards into the roadway.

RE: Nearly completed high-rise collapses in Shanghai

I can't see any prestressed reinforcement from the broken cross section of the broken pile. Can anybody verify this?

RE: Nearly completed high-rise collapses in Shanghai

The piles appear to have WWF reinforcement only.

RE: Nearly completed high-rise collapses in Shanghai

Possibly spun piles?  Not so great in lateral shear I hear.

RE: Nearly completed high-rise collapses in Shanghai

Ltdog:  No, I disagree.  True, your pile drawing shows that the individual piles are supposed to be reinforced with both ring and linear reinforcing steel.   (Whether that steel would be strong enough to withstand the intended loads, or the incidental loads, or the actual oads that happened when the garage was excavated AND the nearby river overflowed into the muddy ground can't be determined by me.)  

But the photo's are clear enough, are in close enough detail, and absolutely confirm that no steel was ever inserted in the concrete pile before the concrete was poured.   Any steel - no matter how "small" would be pulled and twisted at the break, would be pulled out and be linkning the twp pile sections.  I can state absolutely that in that particular photograph of that particular pile at that particular break point, there is no reinforcing steel.

RE: Nearly completed high-rise collapses in Shanghai

Agree with racookpe1978.

At least there is no reinforcement in that broken pile in that photo.

RE: Nearly completed high-rise collapses in Shanghai

I can see WWF reinforcement in the close up photo of the broken pile. It's hard to see but it's there.

 

RE: Nearly completed high-rise collapses in Shanghai

itdog's sketch tells all here for the lateral forces seen.  A definite construction sequencing problem/booboo/CYA condition here.  This should have been one of the lateral design conditions, obviously ignored.

Mike McCann
MMC Engineering

RE: Nearly completed high-rise collapses in Shanghai

ltdog,

Thanks for the explanation.  Is that your sketch or did it come from an investigation?

RE: Nearly completed high-rise collapses in Shanghai

I was sent some more photos, see attached.

The piles are reinforced as shown on Itdog's drawing.

I don't think that the collapsed riverwall as shown in the first photo coincides with the collapse.
It does, however, show the extent of the development (and the extent of the demolition that may be required).

RE: Nearly completed high-rise collapses in Shanghai

hOkie66,
The sketch comes from I discuss with chinese structural egineers in the internet http://okok.org/forum/viewthread.php?tid=217111&extra=page%3D1&page=5


Jack1977 and racookpe1978,
From the below photo, we can see the thin prestressed reforcement.
The dia 500 pipe pile compression capacity is 2000kn
but the shear capacity only 30kn.

RE: Nearly completed high-rise collapses in Shanghai

racookpe1978,

I believe that the is reinforcement but I believe it is far less that what we would use in the western world.

With a small amount of reinforcement, the concrete tensile stress is dominant. So when the concrete cracks the small reinforcement is subject to high local strains at the crack resulting in it snapping off with very little of it exposed.

In the western world, with minimum reinforcement rules, this type of failure does not usually occur and it is usually a bond failure as well as a tensile failure.

We must be careful about being too opinionated on this one.

RE: Nearly completed high-rise collapses in Shanghai

I see one - very, very thin - linear wire in the pile photo, and that wire might 3/16" (not even 1/4") in diameter: the drawing shows ten vertical rebars (not wire!) are required, each of which should be somewhere between 1/2 to 3/4 in dia.    

The wrapped "spool" radial wire shown in the drawing is not clear (also only coat-hanger-wire thin) - if it is present at all.  (I would think they would have specified two radial wires, one clockwise, one counterclockwise.)   Wire dia?  Again, about 1/2 diameter, maybe 7/16.

Further, that spool wire should be spanning the gap between the two broken pile pieces, clearly pulled and distorted out the two ends of the concrete.    None (no remnants) is visible in any of the other piles that have separated.

Doubt whether it is there?  Get close and look.  But that is what the defense/offense lawyers and a good investigating team should be doing now.  

Not a observer (me!) off site speculating and scaling from web pictures.

RE: Nearly completed high-rise collapses in Shanghai

Might not be a prestressed pile. The Chinese have developed a pile for use in soft soil known as Cast-in-place tubular pile.

It consists of driving a steel casing within a casing. Both are driven simultaneously. Theres a donut shape shoe that's used on the casing. The soil between the casings is forced out during driving; then the space is filled with concrete; then the casings are vibrated out. Light reinforcement is sometimes used. It's supposed to be a quick, economical method of pile installation.

RE: Nearly completed high-rise collapses in Shanghai

Initial investigation reveals that it fell over due to a "tall pile of dirt next to the building."  

Really??

http://dcnonl.com/article/id34398

RE: Nearly completed high-rise collapses in Shanghai

I'll agree with that.  I think the failure plane ran through the piles at the break point.  The scarcity of reinforcement allowed the piles to shear and displace.  If it was the only force, though, the building would have fell towards the river, like rapidly pushing a refrigerator near the bottom would topple it on you.  But with the displacement of pile sections, there was then a bearing failure which toppled it towards the garage excavation, IMO.

RE: Nearly completed high-rise collapses in Shanghai

I think the photo at http://img2.cache.netease.com/photo/0001/2009-06-27/5CQLNCTL00AN0001.jpg tells a big part of the story, but seems to me any number of things could have happened to start the chain of events.  If the piles on the "low side" buckled (not impossible if there was no lateral support from the apparently weak soil around them) or had a bearing capacity failure, that would be all it needed to start the tilt.  Once that started, the piles on the high side didn't need to pull out, since they apparently had little tensile strength.

The intact structure reminds me of the Kawagishi-Cho apartment building that fell over in the 1964(?) Niigata EQ when the foundation liquefied and lost most of its strength.  Structural designer did fine; foundation designer didn't (although in the latter's defense, liquefaction wasn't really part of standard practice then).
 

RE: Nearly completed high-rise collapses in Shanghai

Thanks, westheimer1234.

Seems quite possible that the excavation and softening of ground on that side removed lateral support allowing the piles to buckle simply due to compression force.  In the picture with the firefighters, the piles appear to have fairly small diameter, therefore small EI.  It is far from certain that the dirt pile was the triggering cause.

Photo here is the aforementioned apartment building in Niigata, Japan.

RE: Nearly completed high-rise collapses in Shanghai

Hey guys:  Ldog and Pslem got it right.  In one picture you even see the soil shear failure scarp of the rear part of the slip near that river.

Then, look at the breaks of those piles.  They all are typical of a diagonal shear failure, upper part moving toward the excavation near the building.   No evidence of compression failures.  Better reinforcing might have helped, but unlikely would have saved things.  

Is vertical reinforcing designed for shear resistance?  I doubt it.

Sequence of failure would indicate the piles near the excavation failed first.

This would show the "down-hill" part of the slip moved first towards the open hole there.

RE: Nearly completed high-rise collapses in Shanghai

racookpe1978 (Nuclear) - Roger that. Pencil rod pipe piles, and bribed piling contractor and building inspector who would have had to see that in chew back and splice of the pipe pile tendons to the foundation steel in the "foundation" slab pour that it wasn't prestressed tendons. Look at the piles in the background. Where are the steel tendons tangling out? Nada. Those other two towers are now rendered uninhabitable. Tough!
Hey, at least tower held together even after the impact! Wow!

RE: Nearly completed high-rise collapses in Shanghai

Which picture shows the scarp?  In one of them I can see what looks like an area that was heaved up on the north side as the building rotated.

Also, are we able to see the southernmost row of piles exposed?  They would be the ones I would check for buckling.  I'm under the impression that they are buried and out of sight, and that what we can see are the ones that failed primarily in tension or pulled out.

RE: Nearly completed high-rise collapses in Shanghai

Note, in classic circular slope failure terms, the building would have fallen *backwards*, if in fact differential soil pressure caused them to shear off in a rotation slip plane.

Instead it's likely the excavation was inadequately shored and the front row of piles buckled or were hit, especially considering how under-reinforced they are for a building of this A.R. in a potentially seismic area and that clay soil.

The building should've been able to remain standing even if 20 feet of soil sloughed from under it into the excavation, but the report, done by the architect (conflict of interest)
is so flawed it would make Terzaghi roll over in his grave.

RE: Nearly completed high-rise collapses in Shanghai

I don't think I would look for a circular failure surface here (so I wouldn't read too much into the fact that it fell southward toward the exc).  I would expect (without having done any analysis or seeing drill logs, test data, or anything at all but the pictures) that it would be more like an active wedge pushing a block that translates more or less horizontally toward the exc.  In that case, the building would probably fall toward whichever side had the piles buckle/shear/fail in bending first.

We'll probably never know the exact mechanism of initial failure of the piles, for reasons both technical and human.

RE: Nearly completed high-rise collapses in Shanghai

Picture showing scarp also shows the river on the right.  Scarp shows near the river. Not sure where I saw it among the many posted.

Right about the shear plane not necessarily a circle.  Could have been a horizontal weak plane in a weak sediment.

Question comes up about which part of a slippage plane moves first.

I see many slips where an excavation started it and the stuff up-hill them progressively slips.

 Here the excavation probably triggered it causing buckling or loss of lateral pile support on the excavation side.

RE: Nearly completed high-rise collapses in Shanghai

Corporate Record
 NO

012]  Building Collapsed In Shanghai (06/27/2009)  (Daqi)
At around 5:30am on June 27, an unoccupied building still under construction at Lianhuanan Road in the Minhang district of Shanghai city toppled over.  One worker was killed.  According to information, a 70 meter section of the flood prevention wall in nearby Dianpu River and that may have something to do with this building collapse.

But the high-resolution photos are really amazing.

(China Daily)   

Improper construction methods are believed to be the reason of last Saturday's building collapse in Shanghai, according to a report from the investigation team. The investigation team's report said that workers dug an underground garage on one side of the building while on the other side earth was heaped up to 10 meters high, which was apparently an error in construction, according to a report on eastday.com, Shanghai's official news website. "Any construction company with common sense would not make such a mistake," said an expert from the investigation team.

Earlier this week, there were also reports saying that cracks on the flood-prevention wall near the building, as well as the special geological condition in the water bank area, may be part of the reason for the collapse. "These factors are not the basic reason of this accident," said the expert.

Nine people linked to the building collapse, including the real estate developer, contractor and the supervisor for the project, have been put "under appropriate control", said the official Xinhua News Agency Sunday evening.

(SCMP)  Firm's ignorance led to toppling of Shanghai building, report says  By Will Clem and Lillian Zhang.  July 4, 2009.

An official investigation into the collapse of an unfinished building in Shanghai has said that the accident was due to the construction company's "ignorance", rather than flaws in the design or building materials. However, the report stopped short of apportioning blame, and has been criticised for failing to address key issues.

The report said the collapse was caused by earth, excavated to make a 4.6-metre deep pit for an underground car park alongside the building, being piled to depths of up to 10 metres on the other side of the structure. The weight of the pile created a "pressure differential" which led to a shift in the soil structure, eventually weakening the foundations and causing them to fail. This situation "may" have been aggravated by several days of heavy rain leading up to the collapse, but investigators would not say whether this was a crucial factor. The report said the construction company - Shanghai Zhongxin Construction - "did not consider clearly" that the earth pile could have such a devastating effect.

Investigators stopped short of saying whether the company's errors were negligent or easily avoidable. However, they stressed that the building's foundations and construction materials all complied with the city's building regulations.

Huang Rong , director of the Shanghai Urban Construction and Communications Council, said inspections had shown that none of the remaining 10 apartment blocks was in immediate danger. "The surrounding buildings are now stable," he said. "The safety inspection of these homes will be the second phase of our professional team's work."

Jiang Huancheng , an architect and a lead investigator for the report, said it had been an "enormous shock" to see the site for the first time. "In my 46 years in the industry, I have never seen or heard of this," he said. "To put it simply this was ignorance leading to rashness. We need to take this accident as an important lesson ... and ensure that it does not happen again."

Several days before the release of the report, Wu Hang , Mr Jiang's assistant, accused the construction company of incompetence and lacking "common sense". Mr Wu said the investigation had found there had been no structures to support the walls of the car park pit, and this had been a key factor contributing to the accident.


(1) An underground garage was being dug on the south side, to a depth of 4.6 meters
(2) The excavated dirt was being piled up on the north side, to a height of 10 meters
(3) The building experienced uneven lateral pressure from south and north
(4) This resulted in a lateral pressure of 3,000 tonnes, which was greater than why the pilings could tolerate.  Thus the building toppled over in the southerly direction.

(Sina.com)

First, the apartment building was constructed. Then the plan called for an underground garage to be dug out. The excavated soil was piled up on the other side of the building. Heavy rains resulted in water seeping into the ground. The building began to shift and the concrete pilings were snapped due to the uneven lateral pressures.

The building began to tilt.

And thus came the eighth wonder of the world.
 

RE: Nearly completed high-rise collapses in Shanghai

Excavating earth on the south side of the building and stockpiling it on the north side seems like a strange strategy, particularly when there was plenty of room on the south side to stockpile.  Any ideas why this was done?

BA

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