Kinophile
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Posts posted by Kinophile
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1 hour ago, Ultradave said:
Part of this is suffering what we used to call a "beyond design basis accident" A structure is designed to accommodate the weight of anything attached to it, moving across it, the vibrations associated with those (no resonance), and likely, or even very unlikely shock effects, and of course it's own weight.
Take an earthquake for example. An earthquake will impact a structure in known ways and directions. So the decision is how much intensity you design it to take. If a beyond design basis event hits it, all bets are off. The Kerch bridge would not have been designed for a 8.0 earthquake. There is no evidence of that kind of earthquake being a reasonably possible event there, compared to say, Japan. If, let's say, a missile warhead explodes at the top of a pier, well, no bridge is designed for that. Bad things are going to happen. Truck bomb - probably a small one is within the envelope of earthquake shock. A big one is going to be a problem. It's a different forcing function. High frequency short duration as opposed to low frequency longer duration of an earthquake. And it's at a specific location, rather than affecting the structure as a whole, where it can flex together.
Submarine structures that I worked with of course, are designed to withstand massive shock in multiple directions. But even we have what we would term "beyond design basis" There is a point, where it's not practical to strengthen things any more - the sub still has to operate. That's about all I can say about that subject.
I wouldn't necessarily fault the Russian engineers and designers. If you did the same thing to the brand new shiny Tappan Zee bridge on the Hudson, the same thing would happen, I'd imagine.
DaveIan Bank's "Outside Context Problem", but for structures
As you state, the design decisions are various points are the key. Find the trade offs and you'll find the failure.
The Kerch bridge was a massively corrupt project but its still reasonable that the engineers were left relatively alone. The whole assembly is quite sensible, no visually bad structural design decisions (the bridge clearance is a bit low, but not unsound). Very little original imagination in the design that isn't imposed by the site conditions.
No matter the corruption, the damn thing still had to stay up, even just politically, (because Putin). I'm going to lean towards the quality is enough for the basic job of being a bridge in tricky ground and environmental but with very little margin for OCPs.
A 500lb high explosive airburst is absolutely a structural OCP (as is a truck bomb but those videos make me dismiss that, personally).
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Before I moved into film I was an architect. One early lesson in structure in Uni for me was that the basic physical mechanics you see in a simple tabletop scale model of wood,, glue & card are very similar to the actual structural reactions in RL.
In First year We modeled various structures, incl bridges and subjected them to various dynamic forces and loads. The earthquake tests were really fun, Esp on tall structures. We did tests where we deliberately failed parts of lollipop stick towers at upper levels,, then watched multiple floors pancake down, accelerating as they went. No fire, no explosions, just simple sheer for e cutting through the structural connections, piling impact on impact, overwhelming the lower structure.
Then A few days into my second year, I'm in the Student hall watching the Twin Towers pancake down in the exact same manner. I heard many people around me being shocked why the flattening of the towers was happening so fast, but I intuitively understood, even then in the middle of that horror. Nothing special about me, just that those early modelling classes were critical learning moments in understanding why certain visuals of catastrophic failure look the way they do, and can be misconstrued from simple lack of exposure to physical realities.
Relevant to the bridge here, another a-ha moment for me was learning that a massive, hundred+ ton steel&concrete span can literally bounce meters vertically - just like a wood plank across two supports will flex and bounce off those supports. The physics doesn't change, just the scale.
Something for me still doesn't ring true about a truck bomb. @chrisls note about the span probably bouncing/rippling and flexing enough to sheer/pop off its pins to the supports does make sense and correlates with my learning and prior experience.
To go back to Steve's note about missing information that will clarify, Quality of construction and the inherent trade offs in any design are critical to understanding structural failure, and why the bridge failed in the manner it has, exposed to the forces that it was.
We have a lot of info, but there's something still missing.
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4 minutes ago, chrisl said:
Nice. The long beam mounting doesn't really match what it looks like in the pics, but I imagine whoever did it had to guess and wasn't really building a model to analyze its collapse.
Exactly, it stops being accurate a few hundred meters past the bridge heads. Definitely pre construction. The roads were brought lower, I wonder why. Cost reduction, possibly. The railway stays level because, well, trains.
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https://sketchfab.com/3d-models/crimean-bridge-3d-1977dbf64436435e9836713dccaa5006
Not quite the section hit but gives a good sense of the overall structural approach.
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12 minutes ago, chrisl said:
Very tiny ones.
Curiouser and curiouser!
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4 minutes ago, chrisl said:
Just a 2kx2k camera, and the data are optically encoded.
Ah. You're 360 scanning rooms/spaces right?
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19 minutes ago, chrisl said:
That road is probably pretty floppy when you're driving it with the kind of energy a point explosion of a truck bomb (or bigass missile, for Steve) would put in. It's going to both ripple longitudinally and have twisting modes. It could walk/bounce itself off to the side a little and then tumble to get the amount of offset that's there. It also looks like the longitudinal beams sit on small pier blocks on top of the big piers, so it would be tipping off those to one side and could have had enough momentum to tumble as much as it did.
Very true. Those piers, and the pinning designs (which seem pretty routine) are inadequate for anything dynamic, like what you've described.
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19 minutes ago, Vet 0369 said:
I thought that the Russian Charter or Constitution, or whatever it’s called, doesn’t allow conscripts to be used outside the country. Perhaps that’s why Putin illegally annexed the territories in Ukraine, to keep his mobilization “legal?”
That's exactly why.
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25 minutes ago, chrisl said:
It's 3D data compressed to 2D as a physical part of the data acquisition process, so it's already compressed by the time it hits the detector and lossless compression doesn't reduce the size. You can do lossy compression, but then you can't get the 3D data back.
Very interesting. What's the recording device?
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53 minutes ago, chrisl said:
It's got to have a lot of compression to do that - I take a lot of incompressible video data at 2kx2kx8 bit x 15 fps and that uses half of a GigE pipe for one monochrome camera and spinning drives can't generally keep up with sustained recording - we have to use SSDs to avoid losing frames.
The video looking along the bridge very well could be higher than 10 fps frame rate - the frame to frame motion is pretty small for the vehicles, and the resolution is pretty chunky.
Very true. I can't imagine HDDs keeping up with modern data throughputs of 2k, even at 15ps, for a usefully reliable timeframe.
I'm curious what you mean by "incompressible" video. All digital video is fundamentally compressible so are you operating according to external, end user delivery requirements/parameters?
Don't want to come across as snarky, just genuinely interested.
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45 minutes ago, akd said:
You can see part of it here:
The other breaks are clean and at joints, not from separate explosions. All evidence points to a single explosion happening on the road surface in the middle of this span. Airburst of a warhead would just diminish the damage done.
Hmmm.
A single explosion at the road surface, in the middle of a span? That shouldnt push the whole span sidewayss, off its pinning. It should just rip a lot of steel apart and fracture/break the rebar support beams.
To push the whole span sideways requires an enormous amount of force, and needs to come from a direction non-perpendicular to the surface.
A blast favouring one side of the span (eg above one lane as you mention) might do it. But it's a big ask...
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13 minutes ago, chrisl said:
Yes. The original shows the bottom ~20% of the lines in the frame saturated when the explosion starts. It's entirely possible for the truck to be intact in the first half of the frame scan (and show that way in the frame) while it's turned into very small parts as the last 20% of the frame is read out.
The frame rate and shutter speed aren't terrible for a night-video - the motion is pretty smooth and objects aren't rippled from the line scan. It could be as high as 15 fps - we could work it out backward if someone knows the speed limit on the bridge and the road dashed line marking standards. If we call it 10 fps then there's at least ~120 ms (maybe 220 ms?) where the camera is totally saturated in the original video before the fireball diminishes. And it's complicated by aliasing with the frame rate and compression of the phone used to record the video from the computer monitor.
I've done shoots where we used CCTV footage as part of the narrative. We manually adjust the camera's framerate to visually match CCTV, so we go to 15 fps (very choppy, gas station/pawn shop type) or 20fps (smooth, but still less than the classic 24fps of film).
But proper modern, high grade CCTV can now be 36-48fps. It just comes down to storage capacity and priorities. I do know that some large scale national infrastructure in Europe has some good CCTV quality.
I don't view that video mentioned above as fake. .
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RAILWAY. X Airburst
||. X or Airburst (more likely)
||. ROAD 1. ROAD 2.
|| ||. ||
~~||~~~~~~~~||~~~~~~~||~~~~ water
1. Railway is still in place
2. Road 1 still in place
3. Road 2 broken AND PUSHED OFF
So,
- Railway not directly impacted. Light guard rails are blown off but a shockwave from exploding railway tank explains that.
- Road 1 not directly impacted. It's scorched but surface is still intact. Structure took a downward hit but is structurally configured to absorb downward force. Blast centerpoint was far enough away (ie high enough) and possibly enough off the road axis that significant blast missed the road span itself.
- Road 2 possibly directly impacted BUT: (A) it's broken in two similar positions and lies in similar arrangement, (B) it's pushed off its piers, the spans are not structured to survive that type of twisting deformation (from direct force and sudden change in dead load configuration). So Road 2 took downward angled force, that shoved it laterally away, sheering the connection to its purr. Not the steel pinning themselves - they still stand up, so probably the concrete /steel of the span was ripped through by the pins as it moved sideways, away from the blast center. Once off the pier centers the span folded and broke from its own weight (not impacts) and also the current catching it and shoving it back against its own piers.
This was no truck bomb, is my thinking.
A missile (maybe two, if they blew perfectly simultaneously).
I think the missing piece of info that will explain/refute various ideas will be when we see the Road 2 spans that are currently submerged, Esp the part adjacent to the large scorch mark on Road 1.
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2 hours ago, sburke said:
The entire goddamn Black Sea Fleet.
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Where the hell us everyone? Y' know, everyone who would respond to a major, structurally destructive fire (with large booster amounts in fuel still adjacent) on a critical piece of national infrastructure, that's also vital to an ongoing invasion?
What Emergency Services doin'?
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This feels very apropos for the current moment....
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7 hours ago, sburke said:
good lord enough of the socks and boots already. There should be a thread limit of 6 responses on any grognard discussions.ol
LOL guilty
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7 hours ago, Artkin said:
Even with the moisture barrier inside the socks? Extreme mountaineers consistently use moisture barriers. Without it, their socks and then feet would freeze.
Jeepers. No. Then your feet just turn slippery and wet. Uggvgh.
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5 minutes ago, Grigb said:
Watched quicky new Prigozhin movie. What is interesting is that they try to portray UKR troops not as Evil Nazis but sort of equals. Given recent Putin words about how RU respect UKR it might mean Kremlin is planning to tone down RU propaganda, cut RU military fever to manageable level and return to Minsk 3 deal.
In this context recent escalation might be nothing more than leverage to force UKR/West back to negotiation table.
Classic bullies. Try to browbeat someone smaller then give them "grudging respect", as a "worthy adversary". Still just a fascist bunch of rapist looter a$$holes. Keep their "respect" and shove it where the sun doesn't shine.
Scum.
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7 hours ago, Vet 0369 said:
Have to disagree. The plastic will retain the moisture from your sweat and will saturate your socks and make things much worse. You want materials that are permeable and let moisture escape. That include changing your socks. When we were in freezing conditions, I’d have my men remove their boots during a rest stop so I could inspect their feet for condition. Of course, that would mostly go by the wayside in combat situations. I seriously doubt many Russian NCOs have any interest in trying to take care of the men though.
100% agree. Trapping moisture just leads to enormously stinky feet - ie the start of trench rot.
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Oh I get the purpose but nope nopity nope no.
Until the first shell lands near this armchair warrior, I'm sure...
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1 hour ago, JonS said:
Aside from saving your life, trenches and pits are actually pretty cosy places to hang out. Total PITA to dig, but once you've done the mahi they're gold.
Edit: but yeah, I do get the instinctive "nope!" when looking from the outside in
The trench I'm fine, totally. But no ****ing way am I going under earth that dense and heavy with only a tiny mousehole to escape. Also, that hole is at floor level, so first heavy rain that cozy little death trap is gonna flood.
How Hot is Ukraine Gonna Get?
in Combat Mission Black Sea
Posted
@poesel is 100% correct re the heat ****ing the beams internal structure. You could drive a train, slowly, maybe. But every wagon passing over will strain those beams like crazy.
It's quite realistic that if the RUS do go "full retard" and restart heavy loaded trains then the railway span will start to warp and twist. Keep doing it and theyll have an unplanned rapid dissembly event. And it would be easily as destructive as another missile strike. Winter weather will make things even worse.
Ivan being Ivan, UKR could quite conceivably leave the bridge alone, interdict any attempted repairs, let trains pass and watch the bridge eventually rip itself apart.