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

#21

Post by aaron695 » Sun, Jul 04, 2021, 11:23 PM UTC

> 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

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

#22

Post by slipframe » Sun, Jul 04, 2021, 11:32 PM 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…

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.

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

#23

Post by slipframe » Sun, Jul 04, 2021, 11:40 PM UTC

aaron695 wrote: post #21

> 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 imp…

> 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.

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

#24

Post by secabeen » Sun, Jul 04, 2021, 11:47 PM UTC

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?"

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

#25

Post by slipframe » Sun, Jul 04, 2021, 11:48 PM UTC

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.

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

#26

Post by 8note » Sun, Jul 04, 2021, 11:51 PM UTC

secabeen wrote: post #24

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 s…

I am partial to the climate change theory.

Rising sea level means higher soil expanding/shrinking with the tides, leading to fatigue

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

#27

Post by secabeen » Sun, Jul 04, 2021, 11:52 PM UTC

brudgers wrote: post #19

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.

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-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.

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

#28

Post by nemetroid » Sun, Jul 04, 2021, 11:57 PM 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…

The original design was bad in several ways.

> 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...

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

#29

Post by secabeen » Sun, Jul 04, 2021, 11:58 PM UTC

8note wrote: post #26

secabeen wrote: post #24

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 s…

I am partial to the climate change theory. Rising sea level means higher soil expanding/shrinking with the tides, leading to fatigue

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.

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

#30

Post by ajsnigrutin » Sun, Jul 04, 2021, 11:59 PM UTC

VortexDream wrote: post #14

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.

I'm just waiting for somebody to blame 5G.

Just count the number of vaccinated! That much 5G injected into people must be the cause!

/s ... just in case