Condo wreckage hints at less steel in columns than design drawings • Hacker News Board

Re: Condo wreckage hints at less steel in columns than design drawings

#91

Post by aaron695 » Mon, Jul 05, 2021, 6:28 AM UTC

s5300 wrote: post #70

aaron695 wrote: post #51

Earlier quoted context omitted.

I'm not a fan of the "Hyatt walkway collapse" as a teaching tool. The mathematics is extra interesting. Not sure it's good for the design failure which people reference. More people die from bad insulation design each year, it's the boring stuff that matters. 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…

The 1978 Citigroup Center engineering crisis is a good teaching tool. The chair of my Uni's Mechanical Engineering department has gotten a good amount of engineering colleges (mainly Mechanical and Civil) to use it as an example/study for students first semester.

What did you learn from the Citigroup Center story?

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.

Re: Condo wreckage hints at less steel in columns than design drawings

#92

Post by Czarcasm » Mon, Jul 05, 2021, 7:16 AM UTC

sjg007 wrote: post #84

sandworm101 wrote: post #66

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.

Are you suggesting it’s ok for the contractor to not follow the plans?

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.

Re: Condo wreckage hints at less steel in columns than design drawings

#93

Post by sofixa » Mon, Jul 05, 2021, 7:37 AM UTC

shados wrote: post #80

ineedasername wrote: post #69

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 t…

This is unfortunately very common. The building I live in is not that old (about 15 years. I moved in 10 years ago). 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 v…

> 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?

Re: Condo wreckage hints at less steel in columns than design drawings

#94

Post by himinlomax » Mon, Jul 05, 2021, 7:51 AM UTC

slipframe wrote: post #22

Syonyk wrote: post #9

> 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... ) is one of the better known - designed one way, built another so it would be easier and cheaper to build, and…

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 su…

Screw threads are incredibly strong. From memory, small (M3) standard screws with common materials are rated for several kN of load.

Re: Condo wreckage hints at less steel in columns than design drawings

#95

Post by MertsA » Mon, Jul 05, 2021, 7:52 AM UTC

brudgers wrote: post #57

secabeen wrote: post #44

Earlier quoted context omitted.

> 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. 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.…

See all that fairly fresh paint? 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 engineer…

Yeah that's some pretty widespread spalling on the garage deck. Regardless of what went wrong, I'd be surprised if rust jacking or just plain section loss of the rebar wasn't a principle factor behind the collapse. All of that rebar has just been rusting for an additional 3 years since those photos were taken and it looks like the corrosion was already pretty spread out at the time and no one did anything to address it.

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.

https://www.youtube.com/watch?v=mOCJFCaXN0s

Re: Condo wreckage hints at less steel in columns than design drawings

#96

Post by cmcginty » Mon, Jul 05, 2021, 8:41 AM UTC

Syonyk wrote: post #9

> 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... ) is one of the better known - designed one way, built another so it would be easier and cheaper to build, and…

Also interesting is the Citigroup Center building in NYC that almost suffered a catastrophic failure after construction completed in 1977.

> Due to material changes during construction, the building as initially completed was structurally unsound.

Re: Condo wreckage hints at less steel in columns than design drawings

#97

Post by [deleted] » Mon, Jul 05, 2021, 10:27 AM UTC

slipframe wrote: post #25

LatteLazy wrote: post #12

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.

> "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]

Re: Condo wreckage hints at less steel in columns than design drawings

#98

Post by sdflhasjd » Mon, Jul 05, 2021, 11:10 AM UTC

brandon272 wrote: post #11

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

Fwiw: there's a video circulating social media showing what appears to be rubble in the parking garage, claimed to be taken a few minutes before the tower collapse.

Re: Condo wreckage hints at less steel in columns than design drawings

#99

Post by secabeen » Mon, Jul 05, 2021, 12:15 PM UTC

MertsA wrote: post #95

brudgers wrote: post #57

Earlier quoted context omitted.

See all that fairly fresh paint? 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 engineer…

Yeah that's some pretty widespread spalling on the garage deck. Regardless of what went wrong, I'd be surprised if rust jacking or just plain section loss of the rebar wasn't a principle factor behind the collapse. All of that rebar has just been rusting for an additional 3 years since those photos were taken and it looks like the corrosion was already pretty spread out at the time and no one did anything to address…

Thanks to both of you; this is better analysis than I've seen in other forums.

Re: Condo wreckage hints at less steel in columns than design drawings

#100

Post by dredmorbius » Mon, Jul 05, 2021, 12:58 PM UTC

cratermoon wrote: post #49

Syonyk wrote: post #9

> 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... ) is one of the better known - designed one way, built another so it would be easier and cheaper to build, and…

Don't forget the Challenger SRB failure. Flown outside of design criteria with known flaws. But each time the shuttle flew with and SRBs had burn through, it was taken to mean not that there was a problem, but that the behavior was "safe".

Normalisation of Deviance.

https://en.wikipedia.org/wiki/Normalization_of_deviance

See Charles Perrow's Normal Accidents and The Next Disaster.

https://en.wikipedia.org/wiki/Charles_Perrow