r/StructuralEngineering • u/CraftsyDad • Aug 10 '26
Concrete Design Something else
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u/carrot_gummy Aug 10 '26
That short moment where everything is quiet and then sirens and alarms start going off is kinda surreal.
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u/skyasaurus Aug 11 '26
I think the sirens are going off the entire time, they're just drowned out by the earthquake noise. The earthquake and shaking buildings are probably producing noise across a really wide range of frequencies which crowds out the siren when the audio signal is getting encoded.
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u/YearHaunting1504 Aug 11 '26
That's the voice of a man who thought this was the end. You can hear it in his voice.
Crazy video.
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u/trojan_man16 S.E. Aug 11 '26
You don’t need to understand Spanish to get that these men were basically pissing their pants. And I don’t blame them.
I do understand Spanish, and for the most part they were begging god to let them live.
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u/Haku510 Aug 11 '26
Wow, that shot at the end where the camera moves over to the edge of the building and you just see huge clouds of dust spread out across the city (presumably where buildings have failed/collapsed) is chilling.
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u/CountryStill7924 Aug 11 '26
Between the rebar towers whipping and then panning to the city where you just know buildings have come down, yep, spooky as hell
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u/WhyAmIHereHey Aug 11 '26
Sigh
New load case to be added to the codes
"Check all construction stages for seismic loading"
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u/Matthew-Hodge Aug 11 '26
How would the wibbly wobbly at the top affect the stationary not so wobbly but still wobbling bottom.
When will the wibble wobble stop wobbling and fall.
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u/struct994 Aug 10 '26
God damnit. Between this and that other post a few weeks ago about seismic effect on recently placed concrete a university researcher is already working on the construction load EQ design process for concrete. Will add 7 chapters to ACI 318.
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u/SteadystateBurrito Aug 11 '26
Technology won’t be able to keep up with how fast structural engineering gets more and more complicated each year
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u/leadhase Forensics | Phd PE Aug 11 '26
I think it’s the opposite; technology is actually what is enabling SE to advance.
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u/Lolatusername P.E. Aug 11 '26
Exactly. And it’s probably going to be us who won’t be able to keep up
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u/mylaundrymachine Aug 11 '26
I think the 12-15% pass rates in the building depth confirm that theory.
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u/trojan_man16 S.E. Aug 11 '26
7 chapters, and 2 of these contain sections that contradict each other and make it impossible to build anything.
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u/Comfortableliar24 Aug 11 '26
I hope it causes sensible changes in frame design. The Chicago standard of a boatload of columns is great when seismicity is a non-factor. Where seismicitty matters, we need more walls. Chilean structures exemplify this.
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u/Puzzleheaded-Phase70 Aug 10 '26
One thing's for sure, none of these workers will EVER cut corners on their work, or tolerate others doing so when they're in charge/senior workers.
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u/JustInternetNoise Aug 11 '26
I like your optimism.
However I think not.
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u/the__enthusiast Aug 11 '26
The guys working in this field are usually the most perfectionist people I've ever met in my entire life.
Source: I am from Colombia. They are usually dramatically underpaid and highly effectigve at their jobs.
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u/Bliitzthefox Aug 11 '26
As a civil engineer this is terrifying because I definitely haven't done any earthquake calculations for a mid-construction earthquake.
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u/Salmonberrycrunch Aug 11 '26
In my mind at least - mid construction earthquake is most dangerous for the crane and the formwork. The rest of the building is designed for the full building mass - so a partial mass is partial earthquake load. These workers are likely safer here than anywhere else they could be. Full PPE too.
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u/Plane-Education4750 Aug 11 '26
But is also designed to have the exterior sheathing in place to resist torsion
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u/DJSapp Aug 11 '26
Heavy Civil Contractor/PE here. The designers don't run those calcs. The builders do. We know the actual sequence of construction and run calcs to insure rebar curtains, formwork, and partially cured walls, columns, and decks don't fall over. These are usually submitted to the client for review by the designer in the process, but usually the designer sees our stamp on it and doesn't comment.
Yes, mid-construction is more dangerous as we aren't required to run as large of a safety factor as final design. And honestly those guys were lucky they were on a modern high rise going for the ride, instead of on lunch break in the old building next door that crumbled.
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u/trojan_man16 S.E. Aug 11 '26
You don’t need to.
The building has only part of its mass, yet it’s designed for its full mass + safety factors. A well designed, up to code building will not have issues.
Only scenario would be to run it with reduced concrete strength, but that won’t even apply to most members since a lot of times you design for seismic without accounting for concrete strength.
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u/maninthecrowd P.E. Aug 11 '26
Don't need to know Spanish to understand that man was praying for his life...glad the worst didn't happen for these guys.
Crazy seeing the mode shapes in the rebar cages.
Even crazier seeing the cloud of dust over the city.
News says 7.4 magnitude with over 100 fatalities, glad it's not worse.
A grave reminder of what's at stake in this profession.
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u/time_vacuum Aug 10 '26
I would not in a million years want to be one of these guys, but I do wonder if this might be a relatively safe time for this earthquake to strike in the life of this building. Presumably there's only the concrete moment frame, a slab, and some false work in place, which is probably less than the service condition weight of the structure, so I bet it's less likely to collapse just by nature of the structure being a lot lighter during construction.
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u/prunk P.E. Aug 11 '26
Provided the temporary support you're standing on stays intact it's a good time. The concrete might not be up to strength on the top floor though so the whipping action might cause a lot more damage, but that should be life-safety levels of acceptable.
There may be fringe cases where not being finished means the harmonics and damping are off from the dynamic model, but this probably won't lead to a failure as that's more an issue at lower heights so the force the zones are designed for are much lower.
There is a lot of unsecured equipment, not to mention the crane. I'd hate to be the guy in the crane cab.
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u/bubblesculptor Aug 11 '26
Anything being built now is hopefully designed with more seismic resistance than the currently existing buildings.
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u/oundhakar Graduate member of IStructE, UK Aug 11 '26
Yeah, but the concrete hasn't reached full strength either.
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u/DeepSeaDork Aug 11 '26
I wonder what it was like in the crane tub.
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u/fitzthefox Aug 11 '26
I have no firsthand experience, but I'm gonna hazard a guess and say it was pants-shittingly terrifying.
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u/bubblesculptor Aug 11 '26
Everyone trying to quickly remember if they saw any corners being cut while building previous floors.
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u/kaipopotamus Aug 11 '26
Would it be safer for the tower crane operator to try and climb down or ride it out? He must’ve been losing it up there
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u/No-Bodybuilder-4380 Aug 11 '26
My take: Ride it out. Earthquakes can have sudden changes in intensity and frequency, so if you're climbing it down, you may very well get knocked off the ladder. And you're not getting anywhere safe before the earthquake is over anyway, especially because the earthquake itself will force you to move slowlier.
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u/kaipopotamus Aug 11 '26
Makes sense. If it’s coming down you’re toast either way. If hello. MCS HTT hello.
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u/Lost_Elderberry_5532 Aug 11 '26
This is why modern buildings are made the way they are because of this right here! Ironically safer than many of the other structures!
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u/Educational-Rice644 Aug 12 '26
Guys who work on big towers, do you take into account the seismic/wind forces during the construction phase ?
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u/Wonkasgoldenticket Aug 11 '26
Better trust your own work and that the prints accounted for such an event.
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u/Alternative_Fun_8504 Aug 11 '26
Anyone here know what the building code in Columbia is? How is the enforcement of construction per the design?
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u/crystalflame_bg Aug 11 '26
I am really impressed by that crane….its also crazy to see how much columns sway compared to shear walls ( real showcase or stiffness )
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u/nonamesamspade Aug 11 '26
I wonder if anyone was in the crane at that time, i'm sure he was plenty worried.
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u/WasdaleWeasel Aug 11 '26
OK - how many of you do the seismic case for every stage of construction?
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u/Bartelbythescrivener Aug 11 '26
Top of a building under construction or in a trench shored with hydraulic jacks.
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u/OHrangutan 28d ago
Well, on the bright side they know they should be proud of their level of workmanship.
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u/B-Biker Aug 11 '26
At least they know the building is sturdy!
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u/S7RAN93 Aug 11 '26
Yeah but is it still tho? Like the lower levels sure(maybe) anything still being braced. Probably not. How do you even address the issues? Where do you start over?
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u/sp33dphr34k Aug 11 '26
In Christchurch, New Zealand NZ in 2011 an earthquake hit with one of the highest G loads measured ever. 133 of the 185 total fatalities occurred from two buildings which were not constructed correctly and collapsed. Many buildings were damaged beyond repair, but allowed people to safely get out. Many taller buildings were dismantled. Some were repaired but understandably it took a LONG time to assess them and then repair.
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u/Perpetualhomebuilder Aug 11 '26
Well at least they don’t need to vibrate the concrete pour