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sitigeltfel
16th Mar 2018, 11:22
The design drawing shows the bridge was to be supported by cables.
Did the builders/designers gamble on the structure being strong enough to support itself before the cable supports were attached?

Prior to the collapse

http://www.miamiherald.com/news/local/community/miami-dade/4n5qdu/picture205431999/alternates/FREE_1140/116FIUBridge11%20NEW%20PPP

Design drawing

http://news.fiu.edu/wp-content/uploads/TYLIN_UniversityCity_1_980x487.jpg

treadigraph
16th Mar 2018, 11:28
Those look to be entirely different designs to me? :confused:

Yep, the design looks different, but certainly cable-stayed... I will probably be drinking with structural engineering friends tonight/tomorrow so will doubtless get a view from them.

https://cdn.vox-cdn.com/thumbor/7OoYGcXmjX-jbBuSDIFEsHkSfq4=/0x0:3514x2492/920x613/filters:focal(1476x965:2038x1527):format(webp)/cdn.vox-cdn.com/uploads/chorus_image/image/56203955/University_Bridge_Residences.0.jpg

TWT
16th Mar 2018, 11:48
The truth will eventually surface.

There'll be a lot of finger pointing in the mean time. I wonder if the 'stress test' they were allegedly doing at the time of the collapse was a factor ?

Stress tests may have contributed to FIU bridge collapse | Miami Herald (http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html)

Pontius Navigator
16th Mar 2018, 11:55
TWT, if that collapse was caused by a stress test over an OPEN highway that was criminal

TWT
16th Mar 2018, 12:19
It's early days in the investigation.

The NTSB are there, I wonder if they do preliminary reports on transport infrastructure incidents as they do in aviation related incidents ?

ORAC
16th Mar 2018, 12:37
TWT. Looking at the reports linked through the page below there don’t appear to be any preliminary reports, and the reports themselves seem to take between 12-18 months.

https://www.ntsb.gov/about/organization/HS/Pages/office_hs.aspx

“The Office of Highway Safety investigates significant crashes likely to impact the public's confidence in highway transportation safety, generate high public interest, or highlight national safety issues. Investigators examine accidents involving issues with wide-ranging safety significance, such as collapses of highway bridge structures......”

RedhillPhil
16th Mar 2018, 13:31
Terrible irony in that the bridge was erected for safety reasons to keep pedestrians off the highway.
R.I.P. for those killed.

FLCH
16th Mar 2018, 13:33
Ban bridges ! They are dangerous

RAT 5
16th Mar 2018, 14:07
But what is the answer about the different photos? Otherwise i have the obvious answer. They've put the wrong bridge in the wrong place and so it was not fit for purpose and collapsed. QED.

G-CPTN
16th Mar 2018, 14:21
I cannot believe that a bridge designed as a cable-stayed structure would be viable without the cable support - unless it was grossly over-specified - which it clearly was not.

chuks
16th Mar 2018, 14:39
There are mentions of the tensioning of cables in the reporting about the collapse, but where were these cables meant to attach?

Usually you have pillars above a bridge, with support cables descending to the bridge, but I don't see any pillars, nor do I see a place where cables are meant to attach. It's baffling.

The other thing is having traffic passing under an unfinished bridge still being tested. Tested for safety, I assume? Well, they got their test result.

You can see from the post-collapse images that one end of the bridge seems to have slipped off the support, to land flat on the road. People in cars under that part probably did not have a chance of survival.

Bee Rexit
16th Mar 2018, 15:03
There is a video of the collapse, it fails exactly where they appear to be working.

There does appear to be areas where the cables were to join if you look at the first photo. These match the image supplied by tredigraph.
This looks like the first half that sits over the road with another section to be added nearer the building both supported by cable and tower.

The section where they were working was furthest away from the building.

dastocks
16th Mar 2018, 15:16
It's quite possible that the bridge deck was supposed to be installed first and the cable stays added later but (obviously) before any live loads were added to the structure. This is how the Millau Viaduct - probably the largest cable stayed bridge in the world - was built.

pattern_is_full
16th Mar 2018, 15:29
I would say the middle drawing (beige bridge) is an extremely early "conceptual" design. It is not even on the same side of the road intersection as the later drawing or the actual bridge, and lacks the awning as well as numerous other changes.

That concrete decking (first photo) looks damn thin to carry the reported 950 tons of weight across 172 ft/52m free span with nothing but a dozen post-tensioning cables inside to reinforce concrete's notoriously poor performance under tension. (The post-tensioning cables are the "black nuts" on the end of the deck - not to be confused with the overhead suspension cables that were never in place).

I think the "canal" end slipping off its support was secondary - a result of the deck falling and dragging the tip off the upright.

Bee Rexit
16th Mar 2018, 15:38
Recently there was a collapse of another suspension bridge under construction in Colombia!

www.bbc.co.uk/news/world-latin-america-42701262

Difficult things to get right or some fundamental issue.

lomapaseo
16th Mar 2018, 16:26
Yes ORAC, I'm aware of their role in this case, I was just enquiring as to whether the NTSB might be in the habit of releasing a preliminary report after 30 days or so as is the case in aviation related investigations.That's all.

Think of it this way

for whose benefit?

charliegolf
16th Mar 2018, 16:28
Think of it this way

for whose benefit?

IF this one proved botched, then maybe to allow concurrent projects to go ahead- like lifting a grounding?

CG

meadowrun
16th Mar 2018, 16:35
Yes, the construction process is not likely to be confined to Florida alone.

tdracer
16th Mar 2018, 19:21
Yes, the construction process is not likely to be confined to Florida alone.
Apparently using a new concept:
https://amp.local10.com/news/florida/miami-dade/florida-international-university-installs-first-of-its-kind-pedestrian-bridge

The $14.2 million bridge at Southwest Eighth Street and Southwest 109th Avenue is being built using Accelerated Bridge Construction methods, which have been advanced at FIU. The university said the modular construction method reduces potential risks to workers, commuters and pedestrians and minimizes traffic interruptions.

Whoops :eek:

Redredrobin
16th Mar 2018, 19:51
There is a more believable rendering of the final structure at:

https://miami-grid.com/2018/03/15/fiu-fallen-bridge/

It is:

rotornut
17th Mar 2018, 00:32
I wouldn't want to be the engineer responsible for the design and construction of the bridge... reminds me of the Quebec Bridge disaster: Quebec Bridge Disaster - The Canadian Encyclopedia (http://www.thecanadianencyclopedia.ca/en/article/quebec-bridge-disaster-feature/)

evansb
17th Mar 2018, 01:14
In 1958, the Second Narrows Bridge in the Burrard Inlet of Vancouver, B.C. also collapsed during contruction, killing 19 men.

Second Narrows Bridge Collapse - The Canadian Encyclopedia (http://www.thecanadianencyclopedia.ca/en/article/second-narrows-bridge-collapse/)

Hempy
17th Mar 2018, 02:54
Engineer left voicemail about cracks 2 days before bridge fell - Associated Press (https://apnews.com/eecd6fdb2d804751b47bc3ee08fd59a7/State:-Voicemail-about-cracks-2-days-before-bridge-fell)

vapilot2004
17th Mar 2018, 11:18
That's a real shame and particularly difficult for the university team of engineering students and staff. It would have been bad enough failing, but to kill 4 people in the process...

Just when you think we've come a long ways from the days of the Brooklyn Bridge project, where at least 27 men met their makers in the construction of the iconic masonry and steel span.

SpringHeeledJack
17th Mar 2018, 11:38
I wonder why they didn't design/construct the bridge primarily out of steel ? Not as pleasant as concrete perhaps, but cheaper and sturdier I'd have imagined. How horrible for all concerned....

Highway1
17th Mar 2018, 13:11
I wonder why they didn't design/construct the bridge primarily out of steel ? Not as pleasant as concrete perhaps, but cheaper and sturdier I'd have imagined. How horrible for all concerned....

I wondered that as well. It seemed somewhat over engineered for a simple pedestrian bridge.

Carbon Bootprint
17th Mar 2018, 14:38
That's a real shame and particularly difficult for the university team of engineering students and staff. It would have been bad enough failing, but to kill 4 people in the process...
If you're speaking of the FIU collapse and not the others mentioned, it's my understanding that the university was not involved in the bridge, although they do offer specialized courses in this particular construction method. And six people were killed, RIP.

I wonder why they didn't design/construct the bridge primarily out of steel ? Not as pleasant as concrete perhaps, but cheaper and sturdier I'd have imagined. How horrible for all concerned....The design firm is known for "signature" bridges that are as much about form as function. I think that was a factor here. Indeed, it was a beautiful design and I'm sure would have been a wonderful structure if things hadn't gone horribly wrong.

zac21
17th Mar 2018, 23:26
https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjI37f8svTZAhVEv5QKHQeLAO4QFggpMAE&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FWest_Gate_Bridge&usg=AOvVaw369j_evvz6Ngg2aTL0tdVU

meadowrun
18th Mar 2018, 00:04
And with some aviation content there is the classic Tacoma Narrows. Vortex shedding and Torsional flutter stuff. Remarkable footage given there is not one smartphone in sight.
I think they knew something was going on.
http://www.youtube.com/watch?v=j-zczJXSxnw

G-CPTN
18th Mar 2018, 01:19
Meeting over crack held hours before collapse (http://www.bbc.co.uk/news/world-us-canada-43440501).

b1lanc
18th Mar 2018, 02:03
And with some aviation content there is the classic Tacoma Narrows. Vortex shedding and Torsional flutter stuff. Remarkable footage given there is not one smartphone in sight.
I think they knew something was going on.
http://www.youtube.com/watch?v=j-zczJXSxnw
The construction crew knew - it was nicknamed Galloping Gertie. And do I remember that. The Bronx Whitestone basic design was similar and there was significant concern that it might suffer the same fate. Well do I remember being stuck in traffic on the center span of that bridge and having it sway to and fro in the wind - decades after structural improvements were added to mitigate the original design flaw.

PastTense
18th Mar 2018, 03:24
Here is a dash cam of the collapse:
https://youtu.be/Ucflj-MsJBI

The Florida Department of Transportation says it was not their project, that FIU was in charge:
Blame game between state, FIU escalates in Miami bridge collapse | Miami Herald (http://www.miamiherald.com/news/local/community/miami-dade/article205704039.html)

Here is a plausible explanation of what happened:
https://www.youtube.com/watch?v=KtiTm2dKLgU

Ogre
18th Mar 2018, 07:12
Here is a dash cam of the collapse:
https://youtu.be/Ucflj-MsJBI

Is it me or were the three lanes of traffic to the right stationary at the time? It appears that only the left hand lane of traffic was moving, so was there something further down the road that had stopped the traffic?

Also the break in the bridge appeared to be in line with, or at least in the vicinity of, the gib of the crane or rather where the gib of the crane would be connected to the bridge by a cable. Was there an attempt to lift the bridge at the time?

treadigraph
18th Mar 2018, 08:32
Is it me or were the three lanes of traffic to the right stationary at the time? It appears that only the left hand lane of traffic was moving, so was there something further down the road that had stopped the traffic?

Traffic lights! Left hand turn lanes both ways were green, straight on red.

Street view (https://www.google.co.uk/maps/@25.7610631,-80.3731475,3a,75y,95.44h,86.8t/data=!3m6!1e1!3m4!1sHGefxgQ6iMPTj74vpfaDRA!2e0!7i13312!8i665 6?hl=en).

vapilot2004
18th Mar 2018, 09:20
Thank you for the correction CB.

underfire
18th Mar 2018, 14:24
Past tense..

Yes, that was ONE of the causes of the failure. With that tower structure, this should have been braced until those supports were in place.

Looking at that stress head (the device used to tension the rods) they were tensioning it and it broke. This is NOT a stress test as reported in the press, but stressing the rod which had been reported to be loose.

Engineering failure in only having one tension rod. (Also, I never use rod, only strand) Strand is much stronger and wont fail at the threads. We are talking 50ksi for rod vs 250 ksi for strand.

That rod was the main one on the truss that went to the bearing condition. That break caused an immediate shear failure.

Poor design, poor implementation, and many other issues in the videos of the construction that show out of compliance and safe practice.

RAT 5
18th Mar 2018, 14:54
Considering some people, possibly even some engineers, do not walk under a ladder for superstitious reasons, the thought that authorities could allow traffic to flow under this on-going engineering project is astonishing. The lawyers will have a field day. A simple risk assessment of the possibilities would surely have said NO.

artschool
18th Mar 2018, 15:18
Past tense..

Yes, that was ONE of the causes of the failure. With that tower structure, this should have been braced until those supports were in place.

Looking at that stress head (the device used to tension the rods) they were tensioning it and it broke. This is NOT a stress test as reported in the press, but stressing the rod which had been reported to be loose.

Engineering failure in only having one tension rod. (Also, I never use rod, only strand) Strand is much stronger and wont fail at the threads. We are talking 50ksi for rod vs 250 ksi for strand.

That rod was the main one on the truss that went to the bearing condition. That break caused an immediate shear failure.

Poor design, poor implementation, and many other issues in the videos of the construction that show out of compliance and safe practice.

from what I can tell the tower and "cables" were for aesthetic reasons only?

RAT 5
18th Mar 2018, 16:07
from what I can tell the tower and "cables" were for aesthetic reasons only?

I may be wrong, but was it not said that this new construction method was for simplicity, speed, cost saving etc. If so, why would you increase the time & cost significantly for aesthetic reasons? Of course it is nice to have structures looking more attractive, but would that be the case here?

I'm still curious about the artist's drawing and the initial structure. The latter has a roof the former does not. What was intended and stressed for? The latter has considerably increased weight.

RatherBeFlying
18th Mar 2018, 17:32
Did the bridge come off the pillar?

or

Did the lower deck fold where it met the beam from the top deck?

Once it fails at one point, it will fail at the other point.

Possibly the loads were equal at both points and failure was simultaneous, but we are talking subsecond intervals.

Carbon Bootprint
18th Mar 2018, 20:49
Did the lower deck fold where it met the beam from the top deck?
There was only one deck. It did have a roof that was to have not only provided shade and shelter from rain but also would have included ceiling fans and wifi. It was a grand design that was intended to be a "space" and not just a bridge. The roof was also made of heavy concrete; whether it played a factor remains to be seen. It appears to have only been anchored to the main deck of the bridge.

artschool
18th Mar 2018, 20:53
I thought it had been designed as a huge truss?

treadigraph
18th Mar 2018, 21:24
I don't think you'd build a concrete truss bridge of that span without a mid span pier.

aerobelly
18th Mar 2018, 21:35
I thought it had been designed as a huge truss?

Looks like a half-way compromise between truss and cable-stayed to me. Note how the truss legs follow the lines of the cables due to be installed later. Those cables, if at any tension, are going to change the loads in the trusses and possibly put them in tension, which concrete cannot take without reinforcement. The analysis video above makes the point that the support positions used during movement between the fabrication site and installation are not as originally planned and that some temporary reinforcement was missing too. So the original damage was probably done while it was not supported either in the final way nor in the planned movement position.

However, to be adjusting the internal reinforcement of the truss legs with live traffic going under is unbelievable and unforgivable.


'a

aerobelly
18th Mar 2018, 21:49
I don't think you'd build a concrete truss bridge of that span without a mid span pier.

Perhaps the philosophy that led to the students crossing an eight lane highway at grade to get between school and residential accommodation had something to do with it?

Must not inconvenience the automobile traffic.


I have never designed for concrete, but steel no problem. It would be cheaper and lighter if there was a central support, but there is no space for one without changing the highway layout, which would mean getting Florida DoT to agree to it.


'a

tdracer
18th Mar 2018, 22:25
It's certainly not uncommon for a structure to be 'understrength' during construction - but to not use some sort of temporary reinforcement to help take the load until there is enough structure to insure it's integrity is just plain dumb, and possibly criminal.

artschool
19th Mar 2018, 01:16
Looks like a half-way compromise between truss and cable-stayed to me. Note how the truss legs follow the lines of the cables due to be installed later. Those cables, if at any tension, are going to change the loads in the trusses and possibly put them in tension, which concrete cannot take without reinforcement. The analysis video above makes the point that the support positions used during movement between the fabrication site and installation are not as originally planned and that some temporary reinforcement was missing too. So the original damage was probably done while it was not supported either in the final way nor in the planned movement position.

However, to be adjusting the internal reinforcement of the truss legs with live traffic going under is unbelievable and unforgivable.


'a

I had a look at the drawings. they didn't seem to be planning on installing cables. steel tubes were to be installed for aesthetic reasons.

flash8
19th Mar 2018, 01:34
Sorry if this sounds a truly amateur question.

Is this likely the fault of the initial Engineers (the guys that do the heavy math) or the Construction guys here (who I presume choose the materials to some sort of minimum allowable spec).

Is there a large separation between the two?

meadowrun
19th Mar 2018, 01:48
I believe they are supposed to work together like a well-oiled machine with agreement on critical issues - like materials and methods.

evansb
19th Mar 2018, 04:32
It now comes to light that there were acknowledged pre-exististing cracks...

Pinky the pilot
19th Mar 2018, 11:28
It now comes to light that there were acknowledged pre-exististing cracks...

I think I hear the sounds of Lawyers salivating!:hmm:

radeng
19th Mar 2018, 11:41
I think I hear the sounds of Lawyers salivating!

Also, insurance company lawyers looking for 'get out' clauses!

treadigraph
19th Mar 2018, 12:14
I had a look at the drawings. they didn't seem to be planning on installing cables. steel tubes were to be installed for aesthetic reasons.

Can you share those drawings please?

RAT 5
19th Mar 2018, 12:18
And also the local council officials who gave the OK to keep the road open. They will need some very hard hats. IMHO therein lies the root cause of the crushed cars and associated deaths. For any onsite construction workers' death/injuries the root cause lies in design/construction failings. In the council someone's risk assessment was too weak.

RatherBeFlying
19th Mar 2018, 17:23
The bridge was a truss entirely done in reinforced cement. The failure happened where workers were adjusting tension (perhaps for camber) on the roof. Amazingly those workers survived.

With steel trusses there's flexibility - much less so with concrete.

https://youtu.be/GxQJj8D_FE0

artschool
19th Mar 2018, 19:42
Can you share those drawings please?

they were on an image board. the thread has gone.

if I find them I will post.

treadigraph
19th Mar 2018, 20:04
Thanks artschool, it would be interesting to see them.

Bazzo
19th Mar 2018, 20:23
like these

funfly
19th Mar 2018, 23:31
RBF
very interesting video, thanks.

treadigraph
19th Mar 2018, 23:53
Thanks RBF, hadn't managed to watch vid earlier - passed it on to my structural friends.

Artschool, don't worry about the drawings, ta.

tescoapp
21st Mar 2018, 17:41
They are now reporting there was a design change last year to move the central support 3meters towards the canal to allow for the possibility of another carriageway.

The project was also late and way way over budget.

aerobelly
21st Mar 2018, 20:39
They are now reporting there was a design change last year to move the central support 3meters towards the canal to allow for the possibility of another carriageway.

BEWARE: supposition follows

And that change moved the junction where the struts met the deck further out too.

That then meant that the junction would be over the grass bank, which would be unlikely take the 200 tonnes of the temporary installation supports which originally would have been on the roadway.

So that meant the support for the movement from fabrication to final location was not in its planned position, in order to keep it on the road surface.

So the tension in the outer struts was wound up to compensate.

Once it was over the permanent pillars the temporary supports were removed to re-open the highway.

So the loads in the structure changed again as it was now supported at a different point, and it sat like that for 4 (?) days.


I wonder how many times the words "Don't worry, it'll be OK" were said?



There are a number of other concerns about the strut junctions which, basically, should not have been done in concrete (assuming the drawings so far published represent the actual construction).


Now the lawyers are operating at 200% (fees) we are unlikely to learn much more for a couple of years.


'a

tescoapp
22nd Mar 2018, 09:08
I suspect there are heap of materials stuff going on as well.

Concrete takes months to come up to full strength. Its a exothermic reaction and the speed it cures at plays a big part in its final strength. They were late and nobody has said the time interval between pouring and them putting it in place.

They use 12 cables along the bottom to take the tension load. I haven't seen anything about how they transfer the load to those cables from the upper compression roof. (it seems to have 6 cables) but should be in compression all the time). Load spreading plate or just letting the concrete base material do it.

Also to me the drawings show it being flat based bridge with a slight slope. The dash cam to me shows it not flat and significantly higher at one end but this could be due to dashcam through a windscreen optical effect.

CYTN
22nd Mar 2018, 14:57
That video , whilst presenting good detail of design is not good as the presentation is flawed . He is basically saying the truss / bracing arrangement of the 2 outer sections of the fail section is handed ( mirrored ) it is clearly not . Also he keeps refering to brace member 22 , it is actually 11 . Easy mistake to make but if you put something like that together you should sanity check before you present . The cheapest way to do engineering - is to do it right in the first place .

RatherBeFlying
23rd Mar 2018, 07:38
TWT has rightly pointed out same video on Pg 2 Post 33

Apologies

tescoapp
23rd Mar 2018, 08:58
I wouldn't agree with that statement.

The rod was loose because the member wasn't under the expected load.

Because concrete is so poor under tension they pre tension load it so that it never gets under tensile load.

If the rod was pre loaded and then became loose alarm bells should have started ringing that the member it was pre loading was under significantly more compressive load than expected. If you then apply more load to it with the rod tension rod then that again increases the compression loading.

I suspect the rod didn't break the interface where its load is applied to the concrete flange is what failed. How that connection was meant to work I haven't seen. If its like the top then its just a metal plate embedded in the concrete with no metal connection to the bottom flange tension cables. Personally I would want something that would spread the load over the full set of cables or half of them either side depending on the loading they were carrying.

The tension along the bottom flange is taken by the 12 cables they take the load but also keep the concrete flange under compression so it doesn't crack. Cables can only do load along the current axis, if the concrete goes then they bend.

If instead of compressing the whole of the flange with the cables and left the ends floating. Had they tethered the two ends then the cables could have continued to take load and the concrete would have broken and the cables moved to redistribute the load but the span wouldn't have folded and collapsed. Its back would have been broken but it wouldn't have dropped the tethered cables would have turned it into a huge rope bridge.

chuks
23rd Mar 2018, 14:28
It's interesting that the bridge was supported closer to its middle on both ends than originally planned for its being moved into place. That was to do with obstructions at the sides of the road. It looks as if both ends were left dangling as it was being moved.

The initial failure appears to have happened about where one end went past the support used to move it into place, which gives rise to a notion that the bridge ended up bending there under its own weight more than it was designed for, as it was being moved into place. Kind of the way you snap a cracker, is what I was thinking of ....

It's a bit odd to design something out of concrete that's going to be stressed in tension due to being supported at both ends, thus making it sag under the force of gravity. I understand how prestressing the concrete should have made it strong enough to serve its purpose, but there you are faced with an intrinsic weakness in the material. It's sort of like choosing to make your tea pot out of chocolate because it will look nice.

The possible cause could be something we have seen before: one team doing a design according to certain conditions, but a different team with a different goal then doing something to change those conditions, without being aware of possible consequences. In other words, the team moving the bridge into place supported it in a different way than it had been designed for.

Anyway, just like an air accident, we will have to wait for the NTSB report to find out the exact failure mechanism.

The strangest thing was to design this bridge to look as if it were using cable supports, when what looked like cable supports were nothing of the sort. I suppose the bridge was designed that way in the first place so that it could be built as self-supporting, able to be built and installed without having to close that major road for very long.

tescoapp
23rd Mar 2018, 18:00
Does anyone know anything about

Punching Shear Strength of concrete slabs?

Have been reading,

Punching Shear Strength of Reinforced Concrete Slabs without Transverse Reinforcement
by Aurelio Muttoni

Also the Harbour Cay Condominiums collapse and Skyline Plaza at Bailey's Crossroads collapse.

Must admit I worked mainly with metal.

Per say the moving inwards of the supports while moving will lower the max stress until you go past the quarter way in point. So I could see how an onsite engineer would give the ok after a brief think about it.

aerobelly
23rd Mar 2018, 20:21
Does anyone know anything about

Punching Shear Strength of concrete slabs?

There is what appears to be a pretty well-informed discussion here:
Miami Pedestrian Bridge, Part I - Engineering Failures & Disasters - Eng-Tips (http://www.eng-tips.com/viewthread.cfm?qid=436595)

Now approaching 800 posts with lots of photos.



Must admit I worked mainly with metal.


Me too.


'a

Ogre
24th Mar 2018, 00:08
BEWARE: supposition follows
I wonder how many times the words "Don't worry, it'll be OK" were said?

Aerobelly, I am more concerned with the potential number of people who concluded it was "Someone else's problem". Not to drift in the the Meldrew Moments thread, there seems to be a ground swell recently of everyone thinking that the responsiblity for thinking about things lies with everyone else, and that if you raise your voice to say "hang on, has anyone thought about...." you are automatically questioned as to a) whether you are qualified to ask that question or b) don't you know that someone else is looking after that.

Yet when you try and track down who has thought of that, most people would assume ti was someone else, and then you find out that no-one has thought of it.

aerobelly
24th Mar 2018, 01:35
Aerobelly, I am more concerned with the potential number of people who concluded it was "Someone else's problem".

I first worked in steel, by actual hand and then on the drawing board with the help of slide-rule and log tables. Then with bits, bytes and pixels. I have seen things I have designed explode in a shower of small pieces of cast iron on the test bench, I have seen wonderful concepts explode in a shower of realism. I do not think I have come across that attitude except in jest.

When it gets to things that can hurt other people engineers worry a lot.


My two penn'th.

'a

tescoapp
24th Mar 2018, 07:09
Unfortunately I have but never from the engineering side of things more the project management side.

Must admit very early on I was told by a mentor if your going to get involved with concrete and civil engineers you have to know everything they do. You can't just pick and choose which bits your going to be involved with. Concrete is a none linear material and most of the structures are none linear geometry but they like to treat everything as linear.

That punching shear strength stuff was interesting and fitted in with my knowledge about critical crack intensity's. Small angles make a huge difference in the failure mode.

That link to the engineering forum is very interesting.

Usual focus on only the loads with no thought to materials.

Seems that someone heard a major fast fracture of a tensioned item a couple of hours before the collapse.

The NTSB have issue a progress report which doesn't say much apart from various bits of equipment have been taken for testing and samples of materials and certain sections of the bridge.