4 ms·

TLDR is that there is no obvious cause yet. The report says that there were no failures in the fracture critical components. There is no information: on state,

by olliej 5y ago

TLDR is that there is no obvious cause yet. The report says that there were no failures in the fracture critical components. There is no information: on state, maintenance, geologic activity, or initial failure point. While interesting any claim of cause is at absolute best an “educated guess”.

ehnto 5y ago
I wonder if maintenance schedule and state information should be gathered in a public database. I know US has thousands of entities of infrastructure but some manpower and some tablets is all you would need.
- Someone 5y ago
  You mean like the National Bridge Inventory (https://www.fhwa.dot.gov/bridge/nbi.cfm https://www.fhwa.dot.gov/bridge/nbi.cfm)?
- engineer_22 5y ago
  Money is the limiting factor. Tax dollars are already stretched thin. In many areas of the country infrastructure maintenance is at unsustainable levels with no easy solution. You cant squeeze blood from a stone.
  - mrguyorama 5y ago
    Except the stone in this case is absolutely dripping with blood being slurped up by fat scavengers and building aircraft carriers (because we NEED 12 of them of course) while some asshole wags their finger at us and tells us this pinch of sand is all we can afford.
    - engineer_22 5y ago
      I take your point in good spirit, but there may be an argument to be made that military power is a net asset. But it's beside the point of my original comment. Local infrastructure budgets are not equipped to keep up with the demands.
codesnik 5y ago
Interesting. I guess that spar wasn't critical https://www.post-gazette.com/local/city/2022/01/28/pittsburgh-bridge-collapse-2018-photo-point-breeze-frick-park/stories/202201280107 https://www.post-gazette.com/local/city/2022/01/28/pittsburg...
- olliej 5y ago
  My vague recollection from my first year engineering course, that I dropped before failing, almost 20 years ago (caveat train! Choo choo!) is a failure critical component is a component that if failing would trigger a complete structure failure. There are parts of bridges where any failure would be expected to cause complete collapse, like the cracked beam on the Hernando de Soto bridge (happily that span turned out to not actually be critical). But as the Hernando de Soto bridge showed you can have a complete failure of a major structural element without a collapse (in this case we’re lucky that accidentally happened). So if the report says that none of the instant fail section were responsible I’m going to trust that.
43920 5y ago
The NTSB (almost?) never determines a cause in the preliminary report, even when the cause is obvious. Example: https://www.ntsb.gov/investigations/Pages/HWY22FH001.aspx https://www.ntsb.gov/investigations/Pages/HWY22FH001.aspx
- olliej 5y ago
  my comment was mostly because there was already one thread with people making statements about cause of the failure based on this report :D
Animats 5y ago
Yes, it's too early to tell.
shadowgovt 5y ago
It will be interesting if the result of this study is that the NTSB has to update their concept of fracture-critical components.
- olliej 5y ago
  A "fracture critical" component is by definition a component that will cause a structure to collapse should it fail :D We know what that "fracture critical" components of a structure through analysis of the design. So what the NTSB is saying here is that none of the components of this bridge that were identified as being fracture critical are the cause of failure. Of course that doesn't mean there wasn't a single component failure, it is possible that there was an error in the analysis and a fracture critical component was not identified. Alternatively an error in construction could result in weaknesses in the structure leading to more fracture critical components. It's also possible there were existing failures in non-fracture critical components that had not been detected, in which case you are getting closer and closer to every component being critical.
deleted 5y ago
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by olliej 5y ago

ehnto 5y ago

I wonder if maintenance schedule and state information should be gathered in a public database. I know US has thousands of entities of infrastructure but some manpower and some tablets is all you would need.

Someone 5y ago
You mean like the National Bridge Inventory (https://www.fhwa.dot.gov/bridge/nbi.cfm https://www.fhwa.dot.gov/bridge/nbi.cfm)?
engineer_22 5y ago
Money is the limiting factor. Tax dollars are already stretched thin. In many areas of the country infrastructure maintenance is at unsustainable levels with no easy solution. You cant squeeze blood from a stone.
- mrguyorama 5y ago
  Except the stone in this case is absolutely dripping with blood being slurped up by fat scavengers and building aircraft carriers (because we NEED 12 of them of course) while some asshole wags their finger at us and tells us this pinch of sand is all we can afford.
  - engineer_22 5y ago
    I take your point in good spirit, but there may be an argument to be made that military power is a net asset. But it's beside the point of my original comment. Local infrastructure budgets are not equipped to keep up with the demands.

codesnik 5y ago

Interesting. I guess that spar wasn't critical https://www.post-gazette.com/local/city/2022/01/28/pittsburgh-bridge-collapse-2018-photo-point-breeze-frick-park/stories/202201280107 https://www.post-gazette.com/local/city/2022/01/28/pittsburg...

olliej 5y ago
My vague recollection from my first year engineering course, that I dropped before failing, almost 20 years ago (caveat train! Choo choo!) is a failure critical component is a component that if failing would trigger a complete structure failure. There are parts of bridges where any failure would be expected to cause complete collapse, like the cracked beam on the Hernando de Soto bridge (happily that span turned out to not actually be critical). But as the Hernando de Soto bridge showed you can have a complete failure of a major structural element without a collapse (in this case we’re lucky that accidentally happened). So if the report says that none of the instant fail section were responsible I’m going to trust that.

43920 5y ago

The NTSB (almost?) never determines a cause in the preliminary report, even when the cause is obvious. Example: https://www.ntsb.gov/investigations/Pages/HWY22FH001.aspx https://www.ntsb.gov/investigations/Pages/HWY22FH001.aspx

olliej 5y ago
my comment was mostly because there was already one thread with people making statements about cause of the failure based on this report :D

Animats 5y ago

Yes, it's too early to tell.

shadowgovt 5y ago

It will be interesting if the result of this study is that the NTSB has to update their concept of fracture-critical components.

olliej 5y ago
A "fracture critical" component is by definition a component that will cause a structure to collapse should it fail :D We know what that "fracture critical" components of a structure through analysis of the design. So what the NTSB is saying here is that none of the components of this bridge that were identified as being fracture critical are the cause of failure. Of course that doesn't mean there wasn't a single component failure, it is possible that there was an error in the analysis and a fracture critical component was not identified. Alternatively an error in construction could result in weaknesses in the structure leading to more fracture critical components. It's also possible there were existing failures in non-fracture critical components that had not been detected, in which case you are getting closer and closer to every component being critical.

deleted 5y ago

[deleted]