Condo wreckage hints at less steel in columns than design drawings
nytimes.com
nytimes.com
Personally, I have a feeling it might have been rusted rebar in the basement that caused the accident?
Rebar can completely rust through, even encased in concrete if continually exposed to water. This happens only a very small percentage of the time though. It takes more years than this building was up though?
I know of ferro cement boats that have hollow spaces where the rebar used to be because the owner didn't know about electrolytic, and galvanic action.
(I would love to hear from an engineer, or a trades person on this. Have you ever seen rusted rebar in such a young building?)
I would not have ever thought rebar could rust that quick over pool water, or rain water though in those columns. I originally though the standing water in the basement was salt water, which might make the rusting process easier.
I am no expert. I'm not an engineer. I just know rebar can rust through in concrete. It is very rare though. I have seen one column where rust got to the rebar, and the rust went through the concrete. It was like a rust highway, and the rebar was the road. Rusted right into all the rebar encased in the concrete.
I do want to stress I have never seen a collapse like this, even when building codes were not as strict as they are now. Building codes have been very strict for probally 70 years.
I hope they don't revise building codes again unless they find the exact reason this building failed. The building codes in high rises/apartments/homes you guys live in are in many cases overkill.
It is presumed that all foundation bolts are shot after about 50 years on any foundation in terms of their seismic performance. If you pull out an old foundation from say the 1950s, the bolts are almost invariably either totally corroded through or just a thread in the middle.
For a building basically sitting in saltwater, I would expect there to be widespread reinforcing steel failure at that age without proof to the contrary. Which is certainly one of the big reasons why they require recertification, although obviously the 40 year recertification schedule has proven to be woefully inadequate.
This will probably not wind up being more interesting than a failure to have rigorous enough inspection schedules and people dragging their feet to do what obviously had to happen. Those items appear far more important that the somewhat reduced amount of reinforcing steel compared to drawings at this point. It seems like relatively pedestrian negligence.
This prompted a review of many building across UK, and lo and behold, thousand or so buildings in UK have massive structural and fire safety defficiencies. Remediation works go anywhere from 25%-75% of original property cost.
The best part is, the builders are not on the hook, the building owner is not on the hook, the management company is not liable, but a leaseholder that bought 25% of the apartment is responsible for 100% of the bill to put things right. Those properties are unsellable, and have become a toxic asset.
That's pretty wild. I thought city halls had copies of all building plans from when they were submitted for permit approval.
https://www.itv.com/news/london/2020-09-14/grenfell-files-lo...
No it isn't quite the same. I recently had a look at the docs about Grenfell. That's here: https://www.gov.uk/guidance/aluminium-composite-material-cla...
I haven't quite got to the bottom of whether the standards relating to fire was broken or whether the guidance for builders had a hole in it that allowed for what we now know as sub standard cladding.
https://www.insidehousing.co.uk/news/news/grenfell-contracto...
You mention that the fire safety cert. was forged, they missed out firebreaks and there was a lack of escape routes. Also inadequate alarms and several other failings.
That is "just" crass negligence (dangerous and as it turns out massively fatal, negligence)
My point is that there also seems to be a possible systemic failure. There seem to be a few document releases since the disaster, of updates to standards. That implies that the standards themselves were inadequate and that is also a problem.
Not insurers? Or the owners aren’t required to carry insurance?
The other question that obviously follows from this is, were those columns to fail, why did the failure of the columns on one edge of the building cause the entire section of building to collapse catastrophically? At 1:08 of the simulation, you can see the rest of the columns are still standing under the building.
The rebar would have different load bearing capacities in different directions, particularly if it was rusting (i.e. most likely the corrosion was principally on the top face).
A bit counter intuitive.
But that’s building by the sea. Salt can be deposited by mist and chloride ions are the nemesis of reinforced concrete.
Looks almost like punch-through of all floors simultaneously due to shock, almost as if it was a planned demolition where stuctural supports are compromised with precision to assure orderly collapse.
Only this part of the building fell precisely without any carefuly placed dynamite.
But when buildings are stronger, sometimes intentional demolition projects do not complete the job so thoroughly on the first attempt.
Yes, and there's also a decent history of structural failure, or nearly so, from that particular habit.
The Hyatt walkway collapse (https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse...) is one of the better known - designed one way, built another so it would be easier and cheaper to build, and nobody thought through the changes in terms of how it impacted loading. Result? 114 dead.
The I-35 bridge collapse was another case of "various safety factors were eliminated until the safety factor was less than one." https://en.wikipedia.org/wiki/I-35W_Mississippi_River_bridge...
> On November 13, 2008, the NTSB released the findings of its investigation. The primary cause of the collapse was the undersized gusset plates, at 0.5 inches (13 mm) thick. Contributing to that design or construction error was the fact that 2 inches (51 mm) of concrete had been added to the road surface over the years, increasing the static load by 20%. Another factor was the extraordinary weight of construction equipment and material resting on the bridge just above its weakest point at the time of the collapse. That load was estimated at 578,000 pounds (262 tonnes), consisting of sand, water and vehicles. The NTSB determined that corrosion was not a significant contributor, but that inspectors did not routinely check that safety features were functional.[126]
There's a lot of redundancy built into modern construction, but if you remove some of it because it's cheaper to build, and other degrades over time from wear, well... at some point, there's nothing left.
It's going to be an interesting report to read, whatever the causes.
https://www.reddit.com/r/talesfromtechsupport/comments/5s9mr...
Obviously their "solution" was lethal. But the original presumably safe design seems impractical at best.
> Analysis of these two details revealed that the original design of the rod hanger connection would have supported 90 kN, only 60% of the 151 kN required by the Kansas City building code. Even if the details had not been modified the rod hanger connection would have violated building standards. As-built, however, the connection only supported 30% of the minimum load which explains why the walkways collapsed well below maximum load (Feld and Carper, 1997).
(my emphasis)
http://anengineersaspect.blogspot.com/2009/07/the-28th-anniv...
I worked in a gear shop for 5 years, yes, threads that long can be done. I suspect it might have been cheaper to get a rolled thread in that length, rather than a cut thread. Rolled thread is likely to be stronger, as it is formed, and not cut.
For I-35, the NTSB report indicates that the design itself was undersized.
Designs need to be be accommodate for imperfect (and sometimes somewhat negligent) manufacturing, but these two examples aren't the best given the relative impact of flawed design, or design/change control process.
I suspect you if you really go through (https://www.osha.gov/construction/engineering) you'll find some good examples of construction time problems. By it's nature, the vast majority of these are going to be "during construction time", so it'll be biased. They're also typically smaller scale operations... but that's also reflective of reality. Most construction is not the scale of 100+ unit condo buildings.
From my skimming through it there's a pretty even mix of:
a) Designer dominant (note there are a significant number of so called "design-build" entities present as well).
b) Construction/contractor supervisor/company dominant
c) Construction/contractor crew on the ground dominant
The NTSB also has a set of building related investigations to read through. Unfortunately, I seem to be having problems figuring out their search.
https://en.wikipedia.org/wiki/Normalization_of_deviance
See Charles Perrow's Normal Accidents and The Next Disaster.
Knowing the extant nomenclature is useful in researching ideas / literature further. I'm often stymied because I don't know what things are called in certain domains. Psychology seems to be especially prone to this for me.
The Hyatt walkway collapse was at a big dance party with a fair few people watching from above. Perhaps dancing?
I-35 bridge collapse was rush hour.
What's the peak here? Why 1am?
Incidentally, that chill is also why the 'low battery' alarms on smoke detectors tend to vexingly wake you up in the middle of the night, rather than conveniently running out in the 16 hours a day you're awake, which you might expect to happen twice as often. No, it's not just a bias that causes you to remember waking up to smoke alarm low battery chirps but not hearing them in the daytime, the electrochemical reaction in the batteries happens more readily at higher temperatures. It's a different chemistry, but the same reason a lead acid car battery has a hard time turning a starter in the dead of winter. The sensors in the smoke alarm always draw the same few microamps of current, but when it's coldest in the middle of the night, the battery is less able to meet the demand, and wakes you from your sleep.
I wondered this too. Maybe contraction or rate of contraction?
Sun has gone down, outdoor temperature is dropping, max heat radiation out if the sky is clear, and everybody is home so A/C is on in all units.
Max rate of change of temperature is sunset and sunrise. Rate of contraction I'd expect similar?
I'm not sure AC would change the thermal mass of a building much. One cubic meter of air weights 1.2kg. Changing the concrete walls would be hard.
A drunk hitting a pole at speed in the carpark would fit perhaps. Drunkenness to an empty carpark would be high.
The building (and deck surface) will continue to radiate heat throughout the night on a clear night, especially with few obstructions like a waterfront building has. That's how crops can frost with airtemp > freezing, and why the guidance is to cover your plants. It's not to insulate them against convection.
Counterintuitively in this scenario, this effect is greatest when the wind is calm.
https://en.wikipedia.org/wiki/Radiative_cooling#Architecture
For me a good story is when a friend built a house the design didn't fit the actual plot, so it was changed by the builders.
One of the final problems was an overhang on the upper roof went over the sky light.
Lessons -
Contrary to common beliefs land plots are not well known.
Engineers/Designers work off incomplete information.
Problems cascade to strange places.
https://www.cbc.ca/news/canada/toronto/radiohead-stage-colla...
> Due to material changes during construction, the building as initially completed was structurally unsound.
After it happened a few times someone went back to the original plans to see if it might reveal the cause. They were shocked to discover it specified & contracted to have copper pipes. The building had PVC instead. And engineering firm was brought in to make an assessment and determined that the PVC used wasn't even rated for the type of plumbing application necessary.
No one knew how it happened, how inspections could have signed off on the discrepancy. Everyone from that time was gone, and the construction company was a ghost. It's unclear if it was incompetent oversight that allowed the contracter to cut corners or something more "inside job" in nature.
So yes an inside job as inside as inside can be.
I can also easily imagine that the cost overruns we're overstated and the contractor pocketed the extra profit.
Anyway, the Owner's underlings are the Owner if they have the authority to approve changes.
And if you saw the Owner pissed off, then it is not unlikely that they are the sort of person who blames others for their errors.
As for the distribution of the money, everyone probably got some except the Design team...it's the sort of change that the Owner and Contractor collaborate on despite the professional opinions of the Design team. And so the Design team can wash its hands of responsibility since they did not get paid for the extra work of changing the design (which is why the design documents differ from the asbuilts).
Or to put it another way, with any substantial size building everyone was sitting around the table when the option was discussed and the Design team walked the site prior to approving the Contractor's pay requests for plumbing labor and materials.
There are lots and lots of checks and balances in even below average construction projects. Swapping PVC for copper throughout is not the sort of thing that goes under the radar.
We have the original plans, which were somehow never registered with the city (which has been part of the permitting process for buildings of this size since long before it was built). The codes to the fire alarms were never registered with the fire department (also a requirement). A lot of extremely visible features, like stairways, are not up to code. Every time we fix, rebuild or renovate anything, we find the builders didn't just ignore the plans here and there: they may as well be plans for a different buildings. Nothing matches except the floor plan and the amount of units/stories.
Yet the permits are on file and were all signed on. Somehow when we try to get permits for anything, the processes are INCREDIBLY strict, stricter than in any other city I've lived by an order of magnitude. But somehow, for this building, there's very nearly more violations than there are things done kosher.
It's not an isolated incident either...that shit happens everywhere. Inspectors get paid, turn a blind eye, profit.
If something goes wrong, isn't the inspector who signed off liable? Maybe not for damages, but they'd certainly lose their credentials and job. Do they just hope it never happens while they're still at it?
Fortunately the cases I know about haven't been life threatening, but there have been road construction projects in my town in the US, that had to be torn up and re-done at the contractor's expense because they missed some crucial specification such as the required thickness of the materials, and the roads started to crumble and buckle.
A fuckup aggravated by what seems like not particularly aggressive maintenance of the structure generally.
This isn't something I've thought about until now, are all buildings' drawings available at some... Central authority, an archive?
I wish it was public, but I haven't be able to find drawings but you can find permit info.
Some buildings, like banks or certain public buildings (jails?) don't have publicly available plans.
Some buildings' usage (such as chemical storage or compressed gasses) will require additional detail.
“Once the blueprints have been filed by the contractor with the municipality building department, these building plans are public records and technically attainable by anyone wanting to view them.”
That page links to https://www.buildingrecords.us/construction-data/building-pl...
Florida is a little unusual in that state law makes a very wide range of information public and easy to get. In this case, the town has actually posted all the relevant documents on their website (https://www.townofsurfsidefl.gov/departments-services/town-c...), so you can just click that link to get the plans.
Other places have varying levels of access to building documents. In SF, for example, DBI maintains plans and other documents, but state law prohibits reproduction without the property owner's consent. A member of the public can, however, make an appointment to view the plans in the DBI office. (https://sfdbi.org/DOP)
But generally, yes, all buildings' plans are maintained by (usually) the county-level office that issues permits.
https://www.townofsurfsidefl.gov/docs/default-source/default...
In general, that doesn’t happen (perhaps in Florida it does, I have no experience there). But most cities will only release their record drawings if you have permission of the owner.
Source: multi-generational heavy construction family business.
>Engineers said it seemed unlikely that having less rebar would trigger a collapse in and of itself, even factoring in significant deterioration over many years. An inherent safety factor built into most projects would mean that a slight reduction in steel content would not necessarily lead to disaster.
This certainly suggests that there may have been some shortcuts taken during building, but this is not a smoking gun, and doesn't even start to answer the questions of "why now, after 40 years?"
Rising sea level means higher soil expanding/shrinking with the tides, leading to fatigue
I could be wrong, it just seems like there are bigger factors at play, and I'd be surprised that it was build so close to safety margins.
On the other hand, it can lead to disaster, which is why that safety factor exists. We're not doing that just for fun.
If this is a case of wear leading to total failure, isn't this like asking why we take the turkey out of the oven on Thanksgiving after 3 hours? Because that’s how long it takes.
Even then, most buildings are not really designed for much more than 60 or 70 years. Of course, most buildings are also supposed to be designed in such a way that even if it fails, it does not result in a cascading failure. The fact that this particular kind of disaster (apparently spontaneous collapse) is so rare is what makes it newsworthy.
Huh? Cyclic fatigue yo. Incredibly simple and well known killer.
Less whatever type of supports than spec'd to distribute the fatigue across, earlier things fall apart or break from it.
/s ... just in case
The set of "worst things about these disasters" includes a pile of corpses. Non-engineering members of the general public continuing to be non-engineers is not even remotely as bad as a pile of corpses. It isn't in this set.
But mainly it collapsed because the-building-is-falling-apart issues were not addressed despite being obvious even to lay people.
More steel might have delayed the collapse. It would not have avoided it altogether.
> https://www.hunker.com/12003167/tension-vs-compression-of-co...
I haven't seen any claims by qualified engineers that the spalling and corrosion described in the documents or personal reports were to a level that would risk building collapse. I've seen suggestions that the pool and parking deck might collapse, but not ones that would threaten the 40-year old columns holding up the building.
So yeah I do know someone with an informed opinion.
Concrete beams fail in tension. Likewise so do concrete moment connections where said beams join columns.
On the other hand columns fail by buckling when they become too slender…which is effectively what happens when a column loses steel and concrete due to corrosion and spalling.
From a personal standpoint I take the shit seriously because people might die if I get it wrong. I have been personally liable for buildings subject to salty conditions and dealt with the kind of people who would rather spend money on crown moldings than stainless steel structural components.
There is a lot of incentive to find rationales for saying the collapse is a one off.
The only unusual aspect is that it is the first. But Florida has buildings with similar issues down one side, up the other, and around the Big Bend all the way to Alabama.
I wasn’t surprised when I saw the building fell. I wasn’t surprised when I read that the first reports went back to the 1990’s. Wasn’t surprised to see the pictures from under the pool.
That’s what happens to concrete in salt air and how people ignore bad news about buildings falling apart.
The real price of fixing the problems with that building would have been comparable to building it new…hundreds of dollars per square foot not the few thousand per unit that the board was willing to spend.
No board is.
Okay, great. So you're clearly more qualified than I. The above fits with my understanding too. I haven't seen reports that the columns in question were losing dangerous amounts of steel or concrete. Here is the picture from the 2018 report. Is this collapse-level amounts of spalling?
https://static01.nyt.com/images/2021/06/27/world/27miami-mys...
These are 2018 pictures, it could have certainly gotten worse. Enough to threaten the building in 3 years?
There were contractors and engineers bidding on the work for the upcoming 40-year maintenance. Would damage sufficient to threaten the building be obvious at a glance, or would that need testing and detailed analysis?
> The only unusual aspect is that it is the first. But Florida has buildings with similar issues down one side, up the other, and around the Big Bend all the way to Alabama.
This doesn't surprise me, unfortunately.
In the first picture they painted over failed concrete. The pictures are said to be “typical.”
The reasons it wasn’t evacuated at the time were business and politics not comprehensive structural investigation.
You see if the client isn’t paying to find problems below the surface, then they won’t be found. And it is common for clients to not want to find such problems. And for engineers to limit their analysis accordingly.
I know what my professional opinion would have been based on those pictures. It would not have been good for my business given the client profile.
Or to put it another way, those pictures show that what happened had a real chance of happening. That’s not hindsight. It would have caused me grave concerns.
Tyler Ley has dozens of videos on the topic, I know I've seen a great overview of concrete deterioration but he's got so many videos I can't find it. Here's a intro to concrete corrosion though that explains some of it.
As I have said elsewhere, the only thing I suspect is unique is that this was the first building to spectacularly fail.
It failed with people in it because there are tremendous disincentives toward saying the sky is falling even when the sky is falling. It's bad for business and it's bad politics.
Or to put it another way, suppose it was bad design or bad soil. Do you think that the same engineers, owners, contractors, and government agents did everything right on every other building? Think of how hard it is to keep salt off of rebar during construction next to the ocean. Now do so when there is every incentive to save money and no incentive to predict catastrophe.
Show HN: All your are belong to Rust.They address this later, so it's a clickbait implication.
Who cares if it's different to the design, is it not enough? How does it compare to normal.
Given it's a cookie cutter design the workers would notice if it wasn't enough. 20 years of pumping concrete is enough to know if it's significantly wrong.
If the implication is, this might mean other things are wrong. It goes to how normal is this in industry?
When you look at China and their bad concrete, it goes to pushing things to the extreme, like how will they go in an earthquake.
> Engineers said it seemed unlikely that having less rebar would trigger a collapse in and of itself
No, that doesn't make sense to me. Concrete buildings are expected to last longer than 20 years, though not expected to last forever. If the shortcuts they take were cutting the expected lifetime of the structure in half, 20 years of experience would not be enough time to see those failures start to happen.
For something to be really off standard, it has to be complex or using illegal immigrant workers or something that is hard to see, like a bad concrete mix being brought in.
It also needs a reason. The cost benefit has to be more than risk. The builders won't risk a $xx million building by saving on re-bar. A contractor might, but they'd have to get away with it.