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.<p>Personally, I have a feeling it might have been rusted rebar in the basement that caused the accident?<p>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?<p>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.<p>(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?)<p>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.<p>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.<p>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.<p>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.
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.<p>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.<p>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.
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:<p><a href="https://www.youtube.com/watch?v=hynHiWE818c" rel="nofollow">https://www.youtube.com/watch?v=hynHiWE818c</a>
> <i>Mr. Kilsheimer cautioned that it is common in construction for the final product to differ from drawn designs.</i><p>Yes, and there's also a decent history of structural failure, or nearly so, from that particular habit.<p>The Hyatt walkway collapse (<a href="https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse#Investigation" rel="nofollow">https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse...</a>) 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.<p>The I-35 bridge collapse was another case of "various safety factors were eliminated until the safety factor was less than one." <a href="https://en.wikipedia.org/wiki/I-35W_Mississippi_River_bridge#Collapse" rel="nofollow">https://en.wikipedia.org/wiki/I-35W_Mississippi_River_bridge...</a><p>> <i>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]</i><p>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.<p>It's going to be an interesting report to read, whatever the causes.
Where I work an old building had massive plumbing problems for years-- flooded floors.<p>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.<p>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.
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.
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?<p>This isn't something I've thought about until now, are all buildings' drawings available at some... Central authority, an archive?
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.
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:
<a href="https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ" rel="nofollow">https://www.youtube.com/channel/UC9xpl8LyFRsKXASGHBBj_xQ</a>
The most important section though is buried in a late paragraph:<p>>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.<p>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?"
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.
The building collapsed because there was less steel due to corrosion than in the design drawings…less concrete too due to spalling.<p>But mainly it collapsed because the-building-is-falling-apart issues were not addressed despite being obvious even to lay people.<p>More steel might have delayed the collapse. It would not have avoided it altogether.
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.
As I predicted, shoddy concrete work will be the root cause of this.<p><a href="https://news.ycombinator.com/item?id=27636224" rel="nofollow">https://news.ycombinator.com/item?id=27636224</a>
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.
> less steel reinforcement in certain areas than would have been expected from the 1979 design drawings<p>They address this later, so it's a clickbait implication.<p>Who cares if it's different to the design, is it not enough? How does it compare to normal.<p>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.<p>If the implication is, this might mean other things are wrong. It goes to how normal is this in industry?<p>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.<p>> Engineers said it seemed unlikely that having less rebar would trigger a collapse in and of itself