Nearly completed high-rise collapses in Shanghai 4

[GalileoG]

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.

 

[oldestguy]

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.

 

[petertor]

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!

 

[dgillette]

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.

 

[petertor]

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.

 

[dgillette]

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.

 

[oldestguy]

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.

 

[dik]

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.

 

[BAretired]

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