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Someone is having a bad day...
Someone is having a bad day...
- Thread starter K'Tesh
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DAllen
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As a construction tech...I have many questions.
There is a fine line between bravery and stupidity. Standing under all that without any extra support is on the edge....
It looks like he doesn't want to be there, but his hand is stuck
It's ok. He's wearing his hard hat! 
That's why it's called RE-bar.
Nyuk nyuk.
Nyuk nyuk.
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That can be fixed with duct tape and zip ties. No problem!
ljwilley
I’m pretty sure it will work…
maybe a little super glue
boatgeek
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Nothing on the edge about that one. The company Health and Safety department has already run screaming from the scene.
That looks very suspicious to me. I'm not understanding what would cause that kind of damage and only that exact amount of damage.
One of the most common is compression failure, which occurs when the axial load applied to a column exceeds its compressive strength capacity. This failure can be a consequence of a design that does not consider the expected loads, or that determines insufficient dimensions for the cross-section, or occur due to low concrete strength or lack of adequate reinforcement.
I was intrigued and had to go find out….
The above from…
https://amusementlogic.com/company-news/failures-in-reinforced-concrete-columns/
When you go to that website what do you find? It appears to be a made-up site by someone who collected images from other places. Do a google search on the 2 images posted above in this thread and most of the hits are "click-bait" posters on facebook and youtube. There should be something available on the internet that would describe what the photo is actually showing, if it is a real photo. On the webpage linked above there were other photos that are more realistic for concrete column failures.
The first photo published by the OP could depict a compression failure. I find it unusual that a compression element of that size doesn't contain normal column ties, a lot of them, but none are visible in the photo. Also the shapes depict something that dropped quite a bit during the failure. Once it failed that much, it should all be on the ground. Similarly with the second photo in post #12- the shape of the reinforcing indicates that the floor would have dropped quite a bit but there is no deflection obvious in any of the surroundings and again why didn't it deflect farther. At this stage the column is not supporting any vertical load.
I am querying earthquake failure. I remember seeing an article years ago after a big LA earthquake that there were roadways that had collapsed because the columns didn't have any tension members around the outside. They buckled in the middle, blew out the sides and collapsed. Since then there is usually a layer of steel around the outside to prevent that mode of failure.
I think the earthquake motion alternately puts the outside edges of the column in tension, thus the sides blow out.
I think the earthquake motion alternately puts the outside edges of the column in tension, thus the sides blow out.
I was in China during an earthquake and it wasn’t my sides that threatened to blow out.
Seismic zones do put additional requirements on the ties- quantity and spacing. One thing that makes that first photo appear bogus is that there are no ties shown. Designed for earthquake or not, something of that size would have ties in it. (When you see buildings with holes in them, pieces missing, etc. in movies the first thin you notice is that there is no reinforcing steel shown. A piece doesn't just break out of a building like breaking a potato chip, it has to fracture the reinforcing steel and you see at lease some remnants of that.) Earthquakes go back and forth and the goal of the structural design is to go along with the motion which usually means failing one direction, then reversing and failing the other direction, numerous times, but also to stay mostly in one piece while doing that. You can find photos of earthquake damage where columns have been broken into chunks but there are enough ties to keep the chunks together and still carrying load. And BTW one of the areas doing a lot of earthquake design is very close to you- New Zealand.
Engineers learn from each new earthquake what works and what doesn't. A lot of testing is done in between earthquakes, and revisions make it into the codes, but a new earthquake will point out things that were not known before or maybe things that worked in testing but didn't work in a real earthquake. There aren't enough earthquakes to provide a lot of data. We could build everything to resist earthquakes and go on with it but there are 2 obstacles- cost is one and the desire of architects to be innovate is another. A building designed with earthquake resistance in mind would be plain looking and expensive. In the central part of the US we are now designing certain buildings such as parts of schools to have tornado shelters. These are designed for 250 mph wind plus debris load and flying debris load. Architects have a real problem with these because they pretty much have to be a box with no windows, no parapets, no roof overhangs, no sloping roofs, etc.
My first thought when I saw that photo was that all the rebar was on the outside and there were no supporting elements of any kind, other than concrete, in the interior of the pier. I am an electrical and not a mechanical engineer, but my suspicion was that the contractor just got caught skimming money by failing to purchase and install important (hidden) structural elements.
boatgeek
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So here's some writeup on this, largely based on structural design classes in college 25+ years ago, plus looking in at reinforced concrete columns being installed in our local seismic zone. The state of the art has no doubt improved somewhat since...
Let's start with this column posted later in the thread. If it was really intended for seismic loads, it would (a) be a little bigger and (b) would have a crap-ton of cross ties (see below). Like instead of having cross ties at ~12" spacing, they'd be at 2" spacing. The point of all of those cross ties is to hold the concrete in the middle of the column inside the rebar cage. The concrete can be busted up into gravel, but if it can't get out of the rebar cage, the building will stay standing. In this case, the main bars and cross ties held the concrete inside OK, but the remaining column wasn't big enough to keep from buckling under the load. You'll sometimes see retrofits where they put a steel or composite shell around the column for much the same reason--it keeps the concrete gravel in place during an earthquake.
So now back to the picture that started this thread. Like several other people have said, there's pretty minimal evidence of cross ties in the structure, though there's a few (see arrows below). The rebar takes a pretty substantial amount of load, and I'm guessing that the bars buckled outwards and blew the ~2" of concrete covering them off. If the internal structure wasn't well reinforced, the buckling vertical rebar might have pulled the body of the column out. It's entirely possible that the failure mode was that the few cross ties there were are inside of the vertical rebar instead of outside like it should have been. It's also possible that the horizontal rebar that should have been cross ties just run along the long face of the column instead of wrapping all the way around.
To me, this doesn't look like a seismic failure--I think the column would be more broken up than it is, and likely lying in a heap of rubble on the ground. Another underappreciated aspect of seismic design is that a structural engineer's definition of "success" in a major earthquake is that everyone gets out of the building. Even if the building has to be demolished afterwards, you're happy if it's still standing after an 8+ quake.
Let's start with this column posted later in the thread. If it was really intended for seismic loads, it would (a) be a little bigger and (b) would have a crap-ton of cross ties (see below). Like instead of having cross ties at ~12" spacing, they'd be at 2" spacing. The point of all of those cross ties is to hold the concrete in the middle of the column inside the rebar cage. The concrete can be busted up into gravel, but if it can't get out of the rebar cage, the building will stay standing. In this case, the main bars and cross ties held the concrete inside OK, but the remaining column wasn't big enough to keep from buckling under the load. You'll sometimes see retrofits where they put a steel or composite shell around the column for much the same reason--it keeps the concrete gravel in place during an earthquake.
So now back to the picture that started this thread. Like several other people have said, there's pretty minimal evidence of cross ties in the structure, though there's a few (see arrows below). The rebar takes a pretty substantial amount of load, and I'm guessing that the bars buckled outwards and blew the ~2" of concrete covering them off. If the internal structure wasn't well reinforced, the buckling vertical rebar might have pulled the body of the column out. It's entirely possible that the failure mode was that the few cross ties there were are inside of the vertical rebar instead of outside like it should have been. It's also possible that the horizontal rebar that should have been cross ties just run along the long face of the column instead of wrapping all the way around.
To me, this doesn't look like a seismic failure--I think the column would be more broken up than it is, and likely lying in a heap of rubble on the ground. Another underappreciated aspect of seismic design is that a structural engineer's definition of "success" in a major earthquake is that everyone gets out of the building. Even if the building has to be demolished afterwards, you're happy if it's still standing after an 8+ quake.
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It's easy enough to imagine corners being cut in a corrupt place. "The way we do things here" is not always a good framework or baseline assumption for figuring out what happened elsewhere.
Reinforced concrete elements typically have the majority of the reinforcing around the perimeter, at least with respect to longitudinal reinforcing bars. The nature of prestress and post tensioning reinforcing is that it is located more towards the center of the concrete. There are situations where a concrete column might have a heavy wide flange beam in the center of it, and I've built heavily reinforced columns where all of the reinforcing would not fit in the perimeter so we had a second layer of bars just inside of that. That was a 6' diameter column designed for 15 million pounds.
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"Just one more tap should do it."
Dr. Banner: "Sorry".
bobby_hamill
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I hope the photographer was using a telephoto lens as I would not want to be standing
any where near that mess !!!
any where near that mess !!!
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Very interesting comments. Thank you.
It reminds me of my first job (paper machinery design engineer) where we had a good amount of Civil Engineers on staff, as well as the expected Mechanical Engineers. The Civil guys were very good at overall structural analysis and often handled the framework but were bummed out they had to use only steel and not throw in a little concrete. The mechanical guys typically did the rest of the fiddly/moving bits and relied on the structure to do its job.
My current job used to only have mechanical guys doing it all. I bet a few good civil engineers would have helped over the years.
In this particuar case, though, my expert opinion is that the bumper/barrier was too short. Obviously the failure stopped there, so it should have been a few feet taller. I blame the contractor.
