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Kind_Party7329

What did they think was going to happen???


[deleted]

[удалено]


TheCivilRanger

Mission accomplished! Fuck that bridge


208GregWhiskey

Bridges are taken down like this every day in this country and that scale of failure doesn't happen.


PracticableSolution

Task failed successfully. Where was this?


mr_usher

Israel, a few days ago


numb_mind

This was today


mr_usher

Sorry, it's been a long day for me... this felt like 2 days ago. Thanks for the correction


SurveySean

They apparently don’t have explosive charges over there.


Lomarandil

Lots of good reasons to not use explosives for ordinary bridge demo with good access. Especially concrete bridges, which take a lot of beating. Fun fact, "explosive" demo for steel bridges is really more about remote thermite cutting than a conventional explosive.


mr_express_1k

They do… they just prefer to use them on innocent people instead of demos…


appalachianengineer

OSH-it.


CivilMaze19

I’m not a bridge guy so can someone explain the correct way of demoing a concrete bridge? The steel girder bridges I’ve seen removed all involved the machines on the bridge demoing the concrete deck, followed by a crane to remove the girders afterwards.


peachyenginerd

Concrete beam bridges are designed with different connection types where the superstructure (think concrete beams) and the substructure (columns and bent caps the beams sit on) connect. Bridges have fixed or expansion designs at these connections. A fixed connection has the ability to resist forces in two direction and moments. An expansion joint allows for the movement in the structure to be absorbed in the longitudinal direction of the bridge, so in the same direction the cars are moving. My assumptions from this video are that the end bent, or abutment, is not a fixed connection and the intermediate bent does have a fixed connection. When the middle span was demolished, two things happened. First, the stability of the structure was disrupted due to type of connections and the support removal. This new structural configuration should have been checked for stability during the demolition plan. Second, the force of gravity,with the elevation difference from the higher span, was applied to the structure and there was no longer support resisting that force. The beam connection at the end bent is most likely a rubber or reinforced bearing pad that the beams sits on and are not locked into. When the span was removed, the beams simply slid off the bearing pad at the end and stay connected to the fixed intermediate bent. Let me know if that was clear or if a further breakdown would be helpful. Source: female bridge guy in Georgia (I have no bad feelings or ill will toward the term bridge guy! I legitimately introduce myself as a bridge guy at conferences as that is how most refer to bridge engineers in our industry lol) Edit: spelling


be_easy_1602

Lolol female bridge guy, that’s great


Gandalfthebrown7

You have a knack for explaining things. Thanks for the info.


Earthdog6

Would my elementary analysis as an engineering student be somewhat accurate? A pin connection at the column and a roller connection at the end. Since the pin connection can pull horizontally, it does just that when the middle section goes down and the whole bridge between column and end shifts. The roller connection at the end has no horizontal force to resist this motion so bridge just moves horizontally until everything is out of whack and down goes everything (and everybody)? Not sure if this is what you were saying or not because your terminology is different than what I've learned in statics class.


peachyenginerd

Yes, exactly! If you’re wondering how that affects the design of the bridge, the fixed connection at the intermediate bent requires what we call ‘negative moment steel’ in the top of the deck that provides the required moment resistance. Here’s why: If you’ve taken statics and have seen shear moment diagrams of simply supported beams, that’s essentially what’s going on here. When the beam is locked in place with a fixed connection, modeled as a pin, it generates a negative moment at that support. Edited to add: Here’s a shear moment diagram depicting what I said above https://imgur.io/a/zuqjVSI


Earthdog6

Excellent, thanks for your reply. I've always felt pretty good about Sheer Moment diagrams but it's interesting to see them as a part of a bigger physical product like this. I found statics to be interesting and I'm in Structural Analysis now.


benabart

What's the difference between a male and a female bridge?


peachyenginerd

I can’t tell over the internet if this question is serious or a joke so I’ll answer it seriously. The male or female identity refers to the term ‘bridge guy’. A ‘bridge guy’ is a common reference for a bridge engineer. The term guys is used as gender neutral in today’s society (at least here in the US), so a bridge guy can be a woman or man. I am a woman, so I specify that I am a female bridge guy because it makes me giggle.


benabart

Oh thanks! And yes, this was a serious question as male/female is often used to describe how things plugs into each other and I assumed that it was the same for bridge design. Have a nice day.


GoldenMegaStaff

First thing you do (after the proper structural analysis that wasn't done) is not put three hammers on it and blow and go. Contractor is just out of control.


filthymousepad

I only work in design but I’ve spoke with a contractor about something very similar to this. What might have happened here is that the abutments were wanting to move but the deck was actually acting as shoring to keep them from moving. Once the deck lost the capacity to push back the abutments, the abutments started to slide and then that’s the collapse. The contractor I worked with said they pin the abutments with essentially soil nails before they begin demolition, and they’ve had great results.


AlphSaber

>soil nails Now I want to see a giant nail gun attachment for a Cat 345 excavator.


chicken_flavored_poo

[the soil nail launcher](https://www.geostabilization.com/lp/g-soil-nailing/?utm_source=google-ads&utm_medium=cpc&utm_campaign=18336450843&utm_agid=141662954615&utm_term=supernails&utm_creative=621825962385&utm_device=m&utm_placement=&gclid=Cj0KCQiAz9ieBhCIARIsACB0oGJbmIzhk64wVyieV7iQPolEVHZ-bDcPbzdI3pHRPoPKbgop_c8rsjIaArk_EALw_wcB) Ask and you shall receive


adamdj96

I was thinking that too but going frame-by-frame, it seems like way too much lateral movement just prior to total collapse to be attributed just to internal energies being released from the abutment. This is most apparent if you look almost all the way to the right at the guardrail just next to the vertical light post (?), the structure remains almost perfectly level, but slides left *several feet*, before the progressive collapse at the pier. My guess is it’s not a *push* from the release of the abutment’s stored energy, but a *pull* from the free fall of the main span. Again my *guess* is the structure from the piers back to the abutment would have been stable if free standing on its own (they may have even analyzed this), but they did not account for un-cut rebar still connecting to the main span yanking the standing structure to the left as the main span fell.


EnderWillEndUs

Yeah that's what I was thinking too. Uncut rebar pull the first section away from the abutnent. That's what it looks like it the video too - when the middle section drops, it only drops a small amount and stops until the rebar pulls the rest of the bridge down.


DaveTheRocketGuy

Put the excavators ON the bridge???? WTF did they think was going to happen??? What crack smoking PM/engineer approved this procedure?


Pronounced_Sherbert

This is very common. It is quite safe with proper planning. Clearly didn’t go per plan here. Some DOTs require PE approved demo plans and others do not.


xion_gg

I worked on the planning for bridge removal. It requires a lot of work and the use of specialized software to know the reactions and stresses. It seems that these guys were just cutting corners.


ChineseEntrepreneur

Could you name some software? I'm not sure why it requires specialized software, and I'm curious what features they have that something like SAP2000 doesn't have.


Lomarandil

I work in major bridge demo.. the most sophisticated software we use is for staged non-linear analysis. And that's only on 10-15% of projects. Usually, basic FEA and a lot of hand calcs.


ChineseEntrepreneur

Sorry, I was trying to get a name. SAP2000 does staged non-linear analysis.


ChineseEntrepreneur

Here's an example of that https://www.aisc.org/education/continuingeducation/education-archives/staged-construction-analysis---simple-to-advanced-r2/


Lomarandil

I know, and I know ;-) Lots of ways to skin the cat, I don't feel that any of the current offerings have a notable advantage over the other.


xion_gg

We use Midas. I heard some people using AASHTOWare Bridge for some projects, but I never used it before.


ChineseEntrepreneur

> Midas I know of their software offerings. Never considered them to be specialized. Cool!


DaveTheRocketGuy

I don't care how common this is and I really don't care if a PE analysis was required. This is negligence that endangered the lives of everyone involved. I will bet this is someone trying to cut corners or speed up the operation and that individual ought to go to jail for a long time. Sorry if I seem a little wound up about this but...I work in road construction for a DOT and we have more than enough hazards to deal with on the daily and we definitely do not need more hazards because someone was lazy or whatever...


getefix

The negligence was that the planners didn't understand the structure sufficiently that they could say excavators could work on top of it. They will need to remove the deck before removing the piers, and it's safer to remove the deck from above than it is from below. It's perfectly understandable to be upset about people getting hurt / dying on job sites. It's not helpful to claim the cause unless you're done the investigation, especially if you're an engineer.


GoldenMegaStaff

Yes but putting four of them all at the same time gives you no chance to stop and recover if and when something doesn't go per plan.


ProfessionalEmu7319

You can put an excavator on the bridge but two on the same span is a different story


EnginerdOnABike

Nah 2 excavators sitting near the support like that are unlikely to be an issue for the girders. I'd be more concerned if they were both in the same lane traveling near midspan. I probably would make them enter and leave the bridge one at a time but it's not much of a concern that they are sitting there. The excavator tracks will do a significantly better job of distributing the load than the point load axles we design for. If you watch the video the entire superstructure slides downhill once horizontal restraint has been removed. Someone forgot to pin the uphill span to the abutment before they removed the downhill span. Source: I design bridges and load rate crazy beat up structures daily.


Lomarandil

Bridge demo engineer here.. This guy knows.


EnginerdOnABike

I do have some questions about what happened though. Like it looks like the cap sheared off from the columns? Not that the super fell off a bearing or something. Also normal gravity loads from a single span should have easily been resisted by a pier and an abutment. So did the middle span unexpectedly collapse and pull the other spans with it? Or was the design just straight fucked up from the get go? Something definitely went wrong, but it's not the placement of the excavators.


Lomarandil

I agree that the uphill abutment bearing was likely not fixed longitudinally. When the center span was made discontinuous, the resulting shear and moment at the integral pier cap seems to have created an unbalanced punching shear failure in that cap to column connection. Hard to tell whether it was driven by shear (bridge longitudinal forces) or moment (unbalanced gravity loading).


jb122894

This is common. Usually it consists of sawcutting the bridge and demolishing section by section while the excavator sits over the the beams


plentongreddit

The risks i took are calculated, but man, am i bad at math.


in_for_cheap_thrills

I think the uphill span should have been removed first. It looks to have simply slid downhill once the lateral support from the adjacent span was removed.


construction_eng

Good eye


garyoakriginal

Who agreed to the demo plan on this one?


tgrrdr

I worked on a project years ago where we had to remove an old bridge, similar to this one. The demolition contractor had removed the concrete deck and they started removing the exterior girder when the bridge collapsed. Luckily my coworker, who had been parked under the bridge, left about 15 minutes before it happened. I was probably 50-100 feet away when it came down. It was at night and there was a huge cloud of dust - took a while to be able to see that the entire bridge had collapsed.


Illustrious_Draw_571

Got-r-done.


supremePE

Well, that is one way to accelerate a demo phase


OGWhizzleDizzle

That demolition process was obscured on a level that defies description. That whole demolition crew was staffed with idiots from the project manager to the equipment operators.


FartsicleToes

That's one way to do it


construction_eng

Im guessing here, but you dont remove your vertical components and then get on the now unsupported horizontals.


Electrical_Stress_71

Did the operators survive?


Great_Tackle1418

No deaths thankfully.


bdiff

Boss we're done!


cantbuymechristmas

hopefully nobody died but yeah definitely not the best situation and setup


undeniably_confused

Get in there what are you doing just sitting around


babaroga73

So, if I'm thinking correctly , they started from sides, possibly not while on the bridge, then realized it was not coming down and got on top? So they should've started from the middle sections , from the top, than move down and from (relatively) safe spot demolish the side parts? Would that be safer way?


CrazyTranslator5

Remove asphalt, deck, sidewalk and barriers from above. Leave the beams. Then you can start working on demolishing the connections from below and or cutting each beam while it is attached to a crane. This is the most logical to me. I know that you can also have excavators on top doing this but it doesn't sound very logical to me.