23 ms·

Condo wreckage hints at less steel in columns than design drawings

114 points by bigpumpkin 5y ago

adamrezich 5y ago
the news told me it was climate change tho
leetrout 5y ago
https://archive.is/pdNGl https://archive.is/pdNGl
politelemon 5y ago
The design drawings being referenced. Are they public documents, or I suppose I'm asking, how did those engineers get a hold of it? Can I, a public person get it? This isn't something I've thought about until now, are all buildings' drawings available at some... Central authority, an archive?
- l1tany11 5y ago
  Typically approved, permitted plans are public record on file at the local authority (city or county usually). If you have an address you can request access to the plans.
- lbotos 5y ago
  At least for NYC, it's not easy to get, but in theory NYC has records of all buildings and renovations (that were legally done) as they have to sign off on the drawings to issue permits. I wish it was public, but I haven't be able to find drawings but you can find permit info.
- gumby 5y ago
  In the USA most approved plans are public documents, and approval requires code compliance. 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.
- Someone 5y ago
  In theory, it seems you can. https://www.buildingrecords.us/blog/how-to-find-blueprints-of-a-building https://www.buildingrecords.us/blog/how-to-find-blueprints-o...: “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-plans https://www.buildingrecords.us/construction-data/building-pl...
- josh3736 5y ago
  The answer is "it depends" on the particular city, county, and/or state. 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-clerk/champlain-towers-public-records-documents 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 https://sfdbi.org/DOP) But generally, yes, all buildings' plans are maintained by (usually) the county-level office that issues permits.
  - politelemon 5y ago
    Thanks so much. That was useful to learn.
- brudgers 5y ago
  In Florida, with very limited exceptions, documents related to building permits are public records. Florida has a very aggressive “sunshine law.” Almost all public records fall under it and nearly any time two or more elected officials meet requires public notice and public access (again with limited exceptions).
- jeffbee 5y ago
  I can't find them now because the Google search results for the topic are too noisy but I remember immediately after the condo collapse I downloaded the detailed plans of the building from the city's website. These are not the original drawings, but those submitted for the structural work that was to happen. https://www.townofsurfsidefl.gov/docs/default-source/default-document-library/town-clerk-documents/champlain-towers-south-public-records/8777-collins-avenue---preliminary-review-plans-for-40-year-re-certification.pdf?sfvrsn=9e2a1194_2 https://www.townofsurfsidefl.gov/docs/default-source/default...
- ggcdn 5y ago
  In this case the city proactively made all its files available for the building. 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.
Syonyk 5y ago
> Mr. Kilsheimer cautioned that it is common in construction for the final product to differ from drawn designs. 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#Investigation 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#Collapse 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.
- MattGaiser 5y ago
  Reminded me of this /r/tfts post. https://www.reddit.com/r/talesfromtechsupport/comments/5s9mrr/it_was_useless_so_i_removed_it/ https://www.reddit.com/r/talesfromtechsupport/comments/5s9mr...
- slipframe 5y ago
  If the Hyatt walkway had been built as it was designed, I'm sure it would have worked fine. But was it realistic to build it as designed? The design called for something like 12 meters (12m is my estimate from it needing to span the 2nd to 4th floor) of continuously threaded rod. Is cutting 12 meters of continuous thread on one rod a realistic design? This is a real question, I don't know the answer but this seems suspect to me. Wikipedia says the reason the construction company changed the design is because they would have to screw the bolts past several meters of thread per rod and they thought such long sections of threading would be subject to damage during construction. Obviously their "solution" was lethal. But the original presumably safe design seems impractical at best.
brandon272 5y ago
Saw a video today of a simulated collapse that suggests a possible failure mode given the likely parking garage collapse that occurred before primary collapse: https://www.youtube.com/watch?v=hynHiWE818c https://www.youtube.com/watch?v=hynHiWE818c
- secabeen 5y ago
  That's an interesting theory that I hadn't seen before. It would require the horizontal rebar in the pool deck to be strong enough that it could pull over the columns, which contrasts with that rebar also being weak enough to collapse. Likewise, in this scenario, would there still be punch-through columns in the parking deck area, instead of those columns falling over too? 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.
  - XorNot 5y ago
    Steel is strongest in extension, and a horizontal pulling moment is going through the cross section of the rebar rather then perpendicular to it. 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).
- ajsnigrutin 5y ago
  This is an interesting theory... one would wonder, how come it collapsed at the place, where it only held one slab, and not somewhere under more weight... but i'm not a civil engineer, so yeah... time (and analysis) will tell.
  - Tarball10 5y ago
    That area, the pool deck, was exposed to the elements. Rainwater was allowed to pool on top and seep into the concrete because it was not constructed correctly. It should have been slanted to allow water to drain off. The slabs and pillars under the actual building may have been in better condition since they were mostly protected from the weather.
LatteLazy 5y ago
One of the worst things about these disasters is that we will get months of daily reports of things being "hinted at". All the noise means that when the final cause is found, no one will care anymore or remember or they'll remember wrong and swear it was all to do with sinkholes or whatever. We need some quite and some rapid inspection of other buildings. Not hints and opinions.
- VortexDream 5y ago
  I'm just waiting for somebody to blame 5G.
  - LatteLazy 5y ago
    Mole people!
  - ajsnigrutin 5y ago
    Just count the number of vaccinated! That much 5G injected into people must be the cause! /s ... just in case
- slipframe 5y ago
  > "one of the worst things" 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.
  - deleted 5y ago
    [deleted]
- dehrmann 5y ago
  I'm mostly ignoring all the theories until something definitive comes out. All this speculation is just so media outlets can sell ads.
99_00 5y ago
This is a single observation of a discrepancy from a small area in a multi-month long investigation. It's hardly worth commenting on, never mind speculating and extrapolating from.
brudgers 5y ago
The building collapsed because there was less steel due to corrosion than in the design drawings…less concrete too due to spalling. 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.
- secabeen 5y ago
  Do you have a source for these claims? Concrete has great compressive strength, and that strength increases as it ages: > https://www.hunker.com/12003167/tension-vs-compression-of-concrete 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.
  - brudgers 5y ago
    Was in AEC in Florida for nearly twenty years. Started in a precast plant. During my MArch studied under one of the top forensic architects in Florida, Chuck Goldsmith, after grad school I worked as a Licensed Plans Examiner, got my Florida Architect License in 2007 - though it is currently inactive since I don’t practice there. 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.
aaron695 5y ago
> less steel reinforcement in certain areas than would have been expected from the 1979 design drawings 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
- slipframe 5y ago
  > 20 years of pumping concrete is enough to know if it's significantly wrong. 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.
  - aaron695 5y ago
    Sorry, I mean a high school educated concrete pumper with 20 years experience will rote learn what the standards are. So the workers should see it's less than standard. 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.
    - throwawayboise 5y ago
      It was 1979. The height of Mafia control over large building projects especially anything using cement. I would be totally unsurprised if corners were cut to reduce costs and pad the pockets of some capo who was running the union on that job.
ineedasername 5y ago
Where I work an old building had massive plumbing problems for years-- flooded floors. 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.
- brudgers 5y ago
  My William of Occam hat says most likely the Owner approved the change. Shaving money from the materials budget saved money. So yes an inside job as inside as inside can be.
  - ineedasername 5y ago
    Hard to say-- the owner was pretty damn pissed off about things too. Given what I saw if that, I could more easily imagine an underling dealing with cost overruns & agreeing to let the contractor go the cheap route. I can also easily imagine that the cost overruns we're overstated and the contractor pocketed the extra profit.
    - brudgers 5y ago
      It's not uncommon for Owners to be pissed off by their own cheaper-now decisions. The Owner and the Contractor spend all day on site talking about how stupid the Designers were...which is easy because all their mistakes are right there on paper. 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.
secabeen 5y ago
The most important section though is buried in a late paragraph: >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?"
- 8note 5y ago
  I am partial to the climate change theory. Rising sea level means higher soil expanding/shrinking with the tides, leading to fatigue
  - secabeen 5y ago
    Possible. I wonder if there was some unexpected external force; a car crashed into the critical pillar at moderate-to-high speed (as high as you can get in a parking lot) or something like that.
  - dehrmann 5y ago
    But we're talking 4 inches over the life of the building. I'm not sure if buildings are positioned that precisely (if I had to guess, I'd guess it's right around there), the tidal range around Miami looks like it's around 16 inches, and hurricanes and tropical storms will do much more than sea level rise. 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.
- sellyme 5y ago
  > An inherent safety factor built into most projects would mean that a slight reduction in steel content would not necessarily lead to disaster. On the other hand, it can lead to disaster, which is why that safety factor exists. We're not doing that just for fun.
  - 5y ago
sporkologist 5y ago
Would it help to have a higher rust/concrete ratio?
- dane-pgp 5y ago
  Classic HN response: "Should have built it in Rust."
  - brudgers 5y ago
    Show HN: All your are belong to Rust.
ClumsyPilot 5y ago
Similar to the Grenfell Tower fire in Uk, where over 70 people burned alive. The residents warned that the building was unsafe, fire inspector warned it was unsafe, yet nothong was done. Now investigation is 4 years in and it has been an endless processions of code violations, cost cutting, lost building plans (the company told the court that intern deleted them) and outright fraud by the company that produced cladding to mark it as firesafe when it wasn't. 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.
- jagger27 5y ago
  > lost building plans That's pretty wild. I thought city halls had copies of all building plans from when they were submitted for permit approval.
  - cnorthwood 5y ago
    In the UK the local council (town hall) only holds the plans relevant to making planning decisions, not the detailed construction plans. Private companies can sign off the building safety (known as building control) usually as part of providing a new build warranty on the development (but then one of the biggest providers, Zurich, offloaded their portfolio to a shell company than then went bankrupt under the liabilities due to incorrectly signing off buildings. The whole situation is a major scandal in the UK at that moment)
  - ClumsyPilot 5y ago
    I thought so too https://www.itv.com/news/london/2020-09-14/grenfell-files-lost-forever-after-laptop-wiped-inquiry-hears https://www.itv.com/news/london/2020-09-14/grenfell-files-lo...
- gerdesj 5y ago
sandworm101 5y ago
Rip open any building short of a nuclear reactor complex and you will find such differences. Nothing, ever, gets built exactly as planned. We have only a few photos, blurry ones at that. Hold off on the conclusions until reasonable evidence emerges.
- sjg007 5y ago
  Are you suggesting it’s ok for the contractor to not follow the plans?
  - Czarcasm 5y ago
    Of course it’s not ideal, but in the real world the designs are often impossible or impractical to build. If work halted every time construction workers came across a design that didn’t work, instead of tweaking the design onsite and keeping going, nothing would get built. Source: multi-generational heavy construction family business.
    - sjg007 5y ago
      So in the case of a tructural support columns or foundations, How does the contractor insure they are still safe and capable of performing?
- PeterisP 5y ago
  Sure, changes often are required when plans come to a practical implementation, but they (should?) have to be documented and re-verified by the engineers/architects at least for structural components, and the plans should get updated to match the on-site modifications.
hansthehorse 5y ago
If you are interested in the Surfside collapse investigation here is the best channel I've found by a guy who does this for a living: https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ
xrd 5y ago
There are lots of comments on HN over the years lamenting the cost of building infrastructure in the US, compared to China or elsewhere. I'm genuinely curious if this kind of corruption described in this article would be more or less common in China, or if this practice is rampant whenever you have construction projects anywhere in the world.
- analog31 5y ago
  It doesn't seem to be all that uncommon to read about a building collapse, or fire, somewhere in the world. Invariably one learns about some kind of corruption in the process. 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.
- x0x0 5y ago
  Is there a reason to jump to this was corruption, rather than a fuckup? When you look at the price of rebar per linear foot, this doesn't seem like the first place I'd look to cut costs. A fuckup aggravated by what seems like not particularly aggressive maintenance of the structure generally.
hellbannedguy 5y ago
As a former Contractor, and union electrician, who has worked on condos, pretty much just like this building in San Francisco for years; I can honestly say this is Very unusual. 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.
- sgc 5y ago
  It's not that rare, I see it several times a year. 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.
mikewarot 5y ago
Looking at the photo of the column, I see 3 of the 4 rods in one direction (the side labeled 72) 2 sticking out of the column, can't see the 3rd one presumably sheared off, and the 4th obviously slid down the column, and is the loop sticking up, and 4 of 4 in the other, labeled 73.
throwawayboise 5y ago
As I predicted, shoddy concrete work will be the root cause of this. https://news.ycombinator.com/item?id=27636224 https://news.ycombinator.com/item?id=27636224
sunstone 5y ago
I guess that would be a false economy then.

114 points by bigpumpkin 5y ago

adamrezich 5y ago

the news told me it was climate change tho

leetrout 5y ago

https://archive.is/pdNGl https://archive.is/pdNGl

politelemon 5y ago

The design drawings being referenced. Are they public documents, or I suppose I'm asking, how did those engineers get a hold of it? Can I, a public person get it? This isn't something I've thought about until now, are all buildings' drawings available at some... Central authority, an archive?

l1tany11 5y ago
Typically approved, permitted plans are public record on file at the local authority (city or county usually). If you have an address you can request access to the plans.
lbotos 5y ago
At least for NYC, it's not easy to get, but in theory NYC has records of all buildings and renovations (that were legally done) as they have to sign off on the drawings to issue permits. I wish it was public, but I haven't be able to find drawings but you can find permit info.
gumby 5y ago
In the USA most approved plans are public documents, and approval requires code compliance. 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.
Someone 5y ago
In theory, it seems you can. https://www.buildingrecords.us/blog/how-to-find-blueprints-of-a-building https://www.buildingrecords.us/blog/how-to-find-blueprints-o...: “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-plans https://www.buildingrecords.us/construction-data/building-pl...
josh3736 5y ago
The answer is "it depends" on the particular city, county, and/or state. 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-clerk/champlain-towers-public-records-documents 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 https://sfdbi.org/DOP) But generally, yes, all buildings' plans are maintained by (usually) the county-level office that issues permits.
- politelemon 5y ago
  Thanks so much. That was useful to learn.
brudgers 5y ago
In Florida, with very limited exceptions, documents related to building permits are public records. Florida has a very aggressive “sunshine law.” Almost all public records fall under it and nearly any time two or more elected officials meet requires public notice and public access (again with limited exceptions).
jeffbee 5y ago
I can't find them now because the Google search results for the topic are too noisy but I remember immediately after the condo collapse I downloaded the detailed plans of the building from the city's website. These are not the original drawings, but those submitted for the structural work that was to happen. https://www.townofsurfsidefl.gov/docs/default-source/default-document-library/town-clerk-documents/champlain-towers-south-public-records/8777-collins-avenue---preliminary-review-plans-for-40-year-re-certification.pdf?sfvrsn=9e2a1194_2 https://www.townofsurfsidefl.gov/docs/default-source/default...
ggcdn 5y ago
In this case the city proactively made all its files available for the building. 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.

Syonyk 5y ago

> Mr. Kilsheimer cautioned that it is common in construction for the final product to differ from drawn designs. 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#Investigation 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#Collapse 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.

MattGaiser 5y ago
Reminded me of this /r/tfts post. https://www.reddit.com/r/talesfromtechsupport/comments/5s9mrr/it_was_useless_so_i_removed_it/ https://www.reddit.com/r/talesfromtechsupport/comments/5s9mr...
slipframe 5y ago
If the Hyatt walkway had been built as it was designed, I'm sure it would have worked fine. But was it realistic to build it as designed? The design called for something like 12 meters (12m is my estimate from it needing to span the 2nd to 4th floor) of continuously threaded rod. Is cutting 12 meters of continuous thread on one rod a realistic design? This is a real question, I don't know the answer but this seems suspect to me. Wikipedia says the reason the construction company changed the design is because they would have to screw the bolts past several meters of thread per rod and they thought such long sections of threading would be subject to damage during construction. Obviously their "solution" was lethal. But the original presumably safe design seems impractical at best.

brandon272 5y ago

Saw a video today of a simulated collapse that suggests a possible failure mode given the likely parking garage collapse that occurred before primary collapse: https://www.youtube.com/watch?v=hynHiWE818c https://www.youtube.com/watch?v=hynHiWE818c

secabeen 5y ago
That's an interesting theory that I hadn't seen before. It would require the horizontal rebar in the pool deck to be strong enough that it could pull over the columns, which contrasts with that rebar also being weak enough to collapse. Likewise, in this scenario, would there still be punch-through columns in the parking deck area, instead of those columns falling over too? 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.
- XorNot 5y ago
  Steel is strongest in extension, and a horizontal pulling moment is going through the cross section of the rebar rather then perpendicular to it. 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).
ajsnigrutin 5y ago
This is an interesting theory... one would wonder, how come it collapsed at the place, where it only held one slab, and not somewhere under more weight... but i'm not a civil engineer, so yeah... time (and analysis) will tell.
- Tarball10 5y ago
  That area, the pool deck, was exposed to the elements. Rainwater was allowed to pool on top and seep into the concrete because it was not constructed correctly. It should have been slanted to allow water to drain off. The slabs and pillars under the actual building may have been in better condition since they were mostly protected from the weather.

LatteLazy 5y ago

One of the worst things about these disasters is that we will get months of daily reports of things being "hinted at". All the noise means that when the final cause is found, no one will care anymore or remember or they'll remember wrong and swear it was all to do with sinkholes or whatever. We need some quite and some rapid inspection of other buildings. Not hints and opinions.

VortexDream 5y ago
I'm just waiting for somebody to blame 5G.
- LatteLazy 5y ago
  Mole people!
- ajsnigrutin 5y ago
  Just count the number of vaccinated! That much 5G injected into people must be the cause! /s ... just in case
slipframe 5y ago
> "one of the worst things" 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.
- deleted 5y ago
  [deleted]
dehrmann 5y ago
I'm mostly ignoring all the theories until something definitive comes out. All this speculation is just so media outlets can sell ads.

99_00 5y ago

This is a single observation of a discrepancy from a small area in a multi-month long investigation. It's hardly worth commenting on, never mind speculating and extrapolating from.

brudgers 5y ago

The building collapsed because there was less steel due to corrosion than in the design drawings…less concrete too due to spalling. 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.

secabeen 5y ago
Do you have a source for these claims? Concrete has great compressive strength, and that strength increases as it ages: > https://www.hunker.com/12003167/tension-vs-compression-of-concrete 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.
- brudgers 5y ago
  Was in AEC in Florida for nearly twenty years. Started in a precast plant. During my MArch studied under one of the top forensic architects in Florida, Chuck Goldsmith, after grad school I worked as a Licensed Plans Examiner, got my Florida Architect License in 2007 - though it is currently inactive since I don’t practice there. 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.

aaron695 5y ago

> less steel reinforcement in certain areas than would have been expected from the 1979 design drawings 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

slipframe 5y ago
> 20 years of pumping concrete is enough to know if it's significantly wrong. 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.
- aaron695 5y ago
  Sorry, I mean a high school educated concrete pumper with 20 years experience will rote learn what the standards are. So the workers should see it's less than standard. 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.
  - throwawayboise 5y ago
    It was 1979. The height of Mafia control over large building projects especially anything using cement. I would be totally unsurprised if corners were cut to reduce costs and pad the pockets of some capo who was running the union on that job.

ineedasername 5y ago

Where I work an old building had massive plumbing problems for years-- flooded floors. 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.

brudgers 5y ago
My William of Occam hat says most likely the Owner approved the change. Shaving money from the materials budget saved money. So yes an inside job as inside as inside can be.
- ineedasername 5y ago
  Hard to say-- the owner was pretty damn pissed off about things too. Given what I saw if that, I could more easily imagine an underling dealing with cost overruns & agreeing to let the contractor go the cheap route. I can also easily imagine that the cost overruns we're overstated and the contractor pocketed the extra profit.
  - brudgers 5y ago
    It's not uncommon for Owners to be pissed off by their own cheaper-now decisions. The Owner and the Contractor spend all day on site talking about how stupid the Designers were...which is easy because all their mistakes are right there on paper. 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.

secabeen 5y ago

The most important section though is buried in a late paragraph: >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?"

8note 5y ago
I am partial to the climate change theory. Rising sea level means higher soil expanding/shrinking with the tides, leading to fatigue
- secabeen 5y ago
  Possible. I wonder if there was some unexpected external force; a car crashed into the critical pillar at moderate-to-high speed (as high as you can get in a parking lot) or something like that.
- dehrmann 5y ago
  But we're talking 4 inches over the life of the building. I'm not sure if buildings are positioned that precisely (if I had to guess, I'd guess it's right around there), the tidal range around Miami looks like it's around 16 inches, and hurricanes and tropical storms will do much more than sea level rise. 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.
sellyme 5y ago
> An inherent safety factor built into most projects would mean that a slight reduction in steel content would not necessarily lead to disaster. On the other hand, it can lead to disaster, which is why that safety factor exists. We're not doing that just for fun.
- 5y ago

sporkologist 5y ago

Would it help to have a higher rust/concrete ratio?

dane-pgp 5y ago
Classic HN response: "Should have built it in Rust."
- brudgers 5y ago
  Show HN: All your are belong to Rust.

ClumsyPilot 5y ago

Similar to the Grenfell Tower fire in Uk, where over 70 people burned alive. The residents warned that the building was unsafe, fire inspector warned it was unsafe, yet nothong was done. Now investigation is 4 years in and it has been an endless processions of code violations, cost cutting, lost building plans (the company told the court that intern deleted them) and outright fraud by the company that produced cladding to mark it as firesafe when it wasn't. 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.

jagger27 5y ago
> lost building plans That's pretty wild. I thought city halls had copies of all building plans from when they were submitted for permit approval.
- cnorthwood 5y ago
  In the UK the local council (town hall) only holds the plans relevant to making planning decisions, not the detailed construction plans. Private companies can sign off the building safety (known as building control) usually as part of providing a new build warranty on the development (but then one of the biggest providers, Zurich, offloaded their portfolio to a shell company than then went bankrupt under the liabilities due to incorrectly signing off buildings. The whole situation is a major scandal in the UK at that moment)
- ClumsyPilot 5y ago
  I thought so too https://www.itv.com/news/london/2020-09-14/grenfell-files-lost-forever-after-laptop-wiped-inquiry-hears https://www.itv.com/news/london/2020-09-14/grenfell-files-lo...
gerdesj 5y ago

sandworm101 5y ago

Rip open any building short of a nuclear reactor complex and you will find such differences. Nothing, ever, gets built exactly as planned. We have only a few photos, blurry ones at that. Hold off on the conclusions until reasonable evidence emerges.

sjg007 5y ago
Are you suggesting it’s ok for the contractor to not follow the plans?
- Czarcasm 5y ago
  Of course it’s not ideal, but in the real world the designs are often impossible or impractical to build. If work halted every time construction workers came across a design that didn’t work, instead of tweaking the design onsite and keeping going, nothing would get built. Source: multi-generational heavy construction family business.
  - sjg007 5y ago
    So in the case of a tructural support columns or foundations, How does the contractor insure they are still safe and capable of performing?
PeterisP 5y ago
Sure, changes often are required when plans come to a practical implementation, but they (should?) have to be documented and re-verified by the engineers/architects at least for structural components, and the plans should get updated to match the on-site modifications.

hansthehorse 5y ago

If you are interested in the Surfside collapse investigation here is the best channel I've found by a guy who does this for a living: https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ

xrd 5y ago

There are lots of comments on HN over the years lamenting the cost of building infrastructure in the US, compared to China or elsewhere. I'm genuinely curious if this kind of corruption described in this article would be more or less common in China, or if this practice is rampant whenever you have construction projects anywhere in the world.

analog31 5y ago
It doesn't seem to be all that uncommon to read about a building collapse, or fire, somewhere in the world. Invariably one learns about some kind of corruption in the process. 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.
x0x0 5y ago
Is there a reason to jump to this was corruption, rather than a fuckup? When you look at the price of rebar per linear foot, this doesn't seem like the first place I'd look to cut costs. A fuckup aggravated by what seems like not particularly aggressive maintenance of the structure generally.

hellbannedguy 5y ago

As a former Contractor, and union electrician, who has worked on condos, pretty much just like this building in San Francisco for years; I can honestly say this is Very unusual. 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.

sgc 5y ago
It's not that rare, I see it several times a year. 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.

mikewarot 5y ago

Looking at the photo of the column, I see 3 of the 4 rods in one direction (the side labeled 72) 2 sticking out of the column, can't see the 3rd one presumably sheared off, and the 4th obviously slid down the column, and is the loop sticking up, and 4 of 4 in the other, labeled 73.

throwawayboise 5y ago

As I predicted, shoddy concrete work will be the root cause of this. https://news.ycombinator.com/item?id=27636224 https://news.ycombinator.com/item?id=27636224

sunstone 5y ago

I guess that would be a false economy then.