Would it help to have a higher rust/concrete ratio?
Condo wreckage hints at less steel in columns than design drawings
31–40 of 114 posts
Re: Condo wreckage hints at less steel in columns than design drawings
#32> 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…
The Hyatt walkway collapse could be interpreted as you said, but I think the specific phrasing ("built another so it would be easier and cheaper to build") shifts the blame onto suppliers and manufacturers a bit too much. The wiki article states that the architectural/engineering firm signed off on the suggestion of their supplier/manufacturer. While yes, it's easy to point the finger at cost cutting, we should also remember the point of engineering. It's to problem solve under constraints, and saving cost is absolutely a valid constraint. It's also worth noting that the original, unmodified design was already under-strength (relative to code).
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.
Re: Condo wreckage hints at less steel in columns than design drawings
#33The 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…
> 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.
Re: Condo wreckage hints at less steel in columns than design drawings
#34Earlier quoted context omitted.
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…
Excellent information, I never heard this before. Thank you.
Re: Condo wreckage hints at less steel in columns than design drawings
#35Saw 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
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.
Re: Condo wreckage hints at less steel in columns than design drawings
#36Saw 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
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.
Re: Condo wreckage hints at less steel in columns than design drawings
#37Similar 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.
Re: Condo wreckage hints at less steel in columns than design drawings
#38The 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…
> why now, after 40 years
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.
Re: Condo wreckage hints at less steel in columns than design drawings
#39Similar 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 claddi…
> 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.
Re: Condo wreckage hints at less steel in columns than design drawings
#40The 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 mi…
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.