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.

 

[Jack1977]

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

 

[Robertmet]

Strangely Xinhua has not mentioned this story.

http://news.xinhuanet.com/english/2009-06/29/content_11621577.htm

But they have others to work with !

 

[PSlem]

The piles appear to have WWF reinforcement only.

 

[BigH]

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

 

[Ltdog]

all,
the prestressed reinforcements is too smaller to see.
i draw a figure for you all information

 

[racookpe1978]

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.

 

[Jack1977]

Agree with racookpe1978.

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

 

[bones206]

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

 

[msquared48]

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

 

[hokie66]

ltdog,

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

 

[apsix]

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).

 

[Ltdog]

hOkie66,
The sketch comes from I discuss with chinese structural egineers in the internet

http://okok.org/forum/viewthread.php?tid=217111&extra=page=1&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.

 

[csd72]

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.

 

[racookpe1978]

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.

 

[bridgebuster]

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.

 

[CTW]

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

Really??

http://dcnonl.com/article/id34398

 

[PSlem]

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.

 

[dgillette]

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).

 

[westheimer1234]

see attached ms word

 

[dgillette]

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.