9 ms·

Are we underestimating the vulnerability of bridges?

92 points by smb06 9y ago

dpeck 9y ago
Atlanta checking in (https://en.wikipedia.org/wiki/Interstate_85_bridge_collapse https://en.wikipedia.org/wiki/Interstate_85_bridge_collapse), yes.
- jameskilton 9y ago
  I'm not sure if that situation is strictly relevant. We don't normally design bridges to withstand heat directly on the supporting structure of potentially a thousand degrees or more.
  - freehunter 9y ago
    I don't think it's that bridges need to be able to withstand that much heat, but that no one should ever be able to apply that much heat to it. If a pipeline runs under it and is able to be accessed by anyone, that inherently means the infrastructure is strongly vulnerable to attack and it just takes one person mere seconds to destroy everything. I'm not blaming the designers of the freeway though. My house has a giant plate glass window right next to my deadlocked front door. Our entire society is built around trusting that most people don't want to destroy the nice things we've collectively built. But if someone smashed my window and stole my TV, I'd probably make sure that window was a little more secure. Incremental improvements.
    - quadrangle 9y ago
      At least you aren't being stupid and weighing the window/door risks backwards leading to installing a double-keyed knob or deadbolt. That's the insanity that happens from poor risk analysis.
- delinka 9y ago
  Not really the kind of vulnerability the article discusses. Most every aspect of our infrastructure is vulnerable to maliciousness.
  - deleted 9y ago
    [deleted]
- Shivetya 9y ago
  Most Georgia bridges have fifty years before rebuild or replacement. We had our 1000 year flood not to long ago and some were replaced quicker. It is not uncommon to be traveling country roads and come across a recently rebuilt or new bridge. Now this I85 debacle is purely in the camp of mismanagement and vandalism. The vandalism of course being that a person set a fire sufficient to ignite supposed non flammable building materials that should never have been stored under a bridge. Doubtful anyone in the State will suffer consequences due to sovereign immunity. What many of us who watched all this unfold is to find out exactly what was stored there and in what quantity. While not flammable doesn't mean it won't burn it should not have been this simple to ignite. Credit the contractors rebuilding the bridges, damn they are fast when they need to be. Of course another contractor managed to buckle the I20 interstate by filling pipes improperly
  - BatFastard 9y ago
    As some one who lives very close to the bridge in Atlanta, it is hard to believe how disruptive it has been. While I thought traffic in the past was bad, it recently took me an hour to go 1.5 miles. A trip that usually takes 10 minutes at most. People don't go to restaurants or out at all, anytime close to rush hour. I use to pop up to corner to grab a pizza, now it takes me 20 minutes just to get to the end of my street! Glad I can bike places.
  - dsfyu404ed 9y ago
    >damn they are fast when they need to be They are fast when the situation is dire enough that the politicians don't care what it costs and the NIMBYs and nit-pickers shut their mouths.
  - Symbiote 9y ago
    The UK had a similar fire, though the viaduct didn't collapse. I think the result was a reduction in what was permitted to be stored under bridges and viaducts, in common with a similar restriction that was already implemented on major railways. I can't find a source for that. http://www.bbc.com/news/uk-16425491 http://www.bbc.com/news/uk-16425491
- deelowe 9y ago
  Totally irrelevant unless you're going to argue the Oklahoma City building was also under engineered.
Spooky23 9y ago
That's the beauty of facts and engineering. We may overestimate or underestimate. Nobody has built the vast network of bridges that we have before to the same standards, so operating experience should result in changes in our understanding of what and how we assess them! If we look at the bridges that have survived 100, 150 or more years, they are mostly massively overbuilt due to limitations of the era they were built in. Perhaps some of the more modern spans are less overbuilt and are thus more vulnerable to environmental or other changes?
- hollander 9y ago
  When the budget is small, you don't build for situations that you cannot imagine. You get what you pay for. Now climate is changing, these situations are suddenly reality.
- knz 9y ago
  The biggest threat is politicians (and voters) who don't understand that "structurally deficient" means we need to invest in inspections, repairs, and replacement. The I-35W collapse was near my house at the time and the fact that Governor Pawlenty had long pushed for reduced government spending (inspections in particular) was not lost on many people. His replacement, Governor Dayton, was partly elected due to promises to rebuild/repair even if taxes had to be raised to fund it (what a radical theory!).
  - afpx 9y ago
    If I build a big tower, and it falls down and injures or damages, I'm liable, right? If government-owned infrastructure falls down (because of lack of funding) and injures or damages, is anyone liable? Not a rhetorical question
    - knz 9y ago
      IIRC for 35W there were lawsuits against the engineering company and department of transportation. http://www.mprnews.org/story/2012/11/14/law/i35w-bridge-settlement-jacobs-engineering http://www.mprnews.org/story/2012/11/14/law/i35w-bridge-sett... "After the structure fell into the Mississippi River during rush hour Aug. 1, 2007, killing 13 people and injuring 145 more, Minnesota lawmakers set up a compensation fund for victims. As part of that legislation, they nullified a statute of limitations that would have prevented the state from seeking damages. In May, the nation's highest court declined to hear Jacobs' challenge to that law, and the company had little recourse. State Sen, Ron Latz sponsored the legislation that set up the compensation fund. While the state recovered from Jacobs and another firm less than half of the nearly $37 million paid out in compensation to victims, Latz said it was the right thing to do, not just for the victims and their families but also for Minnesota taxpayers."
niftich 9y ago
As of writing, this links to university news release. The actual paper is doi:10.1061/(ASCE)IS.1943-555X.0000354 [1]. Abstract Predictions of the risk to built infrastructure posed by climate and land-use change have suggested that bridge collapses may increase due to more frequent or intense flooding. Assessments of the United States often assume that bridges may collapse when the 100-year flood (i.e., a flood with 1% annual frequency of exceedance) occurs, but this assumption has not been fully tested because of a lack of comprehensive collapse records. Thirty-five bridges for which a stream gauge on or near the bridge recorded the flow during total or partial collapse were identified and used to test this assumption. Flood frequency analyses, other statistical analyses, and structural reliability methods were used to quantify the return periods of collapse-inducing flows, identify trends linked to event and site characteristics, and evaluate the potential importance of collapse return period variability in assessing the impact of climate and land-use change on hydraulic collapse risk. The results indicate that the collapse-inducing flow return periods varied considerably (range: 1 to >1,000 years) and were frequently lower than values considered in many climate impact assessments: 23 of the 35 bridges were estimated to have collapsed during flows with return periods of lower than 100 years. Annual failure probabilities computed using the full distribution of return periods of the collapse-inducing flows, as opposed to central values (e.g., means), were more sensitive to an assumed increase or decrease in the underlying frequency of flooding. These results suggest that linking bridge collapse to only the 100-year flow does not capture significant variability associated with collapse return periods, potentially reducing sensitivity to flood frequency changes and reducing the robustness of assessments of the impact of climate, land-use, and streamflow-regulation change on hydraulic bridge collapse risk. [1] http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IS.1943-555X.0000354 http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IS.1943-555...
VLM 9y ago
Lured in for a spanning tree protocol CVE, left with an equally important civil engineering discussion. It would be interesting to see an evolution of the concept of 100-year event over the few decades that its existed. Given the crazy rate of change compared to more stable engineering challenges like the national bureau of standards definition of the second or length standard, the endlessly changing definition of 100 year events look barely more scientific than rolling DnD dice.
peterwwillis 9y ago
The thing is, we've been underestimating bridge failure potential for decades. At least with reinforced concrete bridges, corrosion is deadly and silent, and some substances took decades to slowly corrode the steel. It took unexpected catastrophic failure for us to understand how to build them better.
- jacquesm 9y ago
  The real killer here is salt on the concrete in winter. It slowly leaches through the top level of the concrete and starts eating away at the steel. Very effective, totally invisible. Also lots of balconies at risk because of this.
  - yborg 9y ago
    I thought everybody uses epoxy-coated rebar on bridges now.
    - InclinedPlane 9y ago
      "Now". Not all bridges in use now were built now. In fact, most are quite old, which is the problem.
  - ggcdn 9y ago
    Do people salt their balconies? I've never seen nor heard of this.
    - jacquesm 9y ago
      Balconies and galleries in apartment buildings to avoid falls in winter. There's a huge flap around that theme here in NL right now with 1000's of apartment buildings having to be inspected before mid-june because a building shed it's balconies. https://www.nrc.nl/nieuws/2015/12/22/ministerie-laat-vloeren-van-alle-flats-van-voor-1975-onderzoeken-a1410616 https://www.nrc.nl/nieuws/2015/12/22/ministerie-laat-vloeren... (Dutch, sorry, no English source)
dockd 9y ago
What exactly are "modern design standards" required by bridges? When did the modern era start? Is there really a major moment in bridge design where the standards changed? Is there even broad agreement on what these standards are? (Side note: the bridge pictured in the article is the Bridge of the Gods, just upstream of Bonneville Dam on the Columbia River. There's going to be more than bridge problems if the flow of the river takes out that bridge.)
- wiredfool 9y ago
  Yes. There are standards, they're the Building Codes. There are several versions of them that have come out over time, and they've been evolving with the advances in the science and engineering. When I was in Engineering school, we were generally taught off of a newer code than was in common use in the wild, but that transition was occurring in the couple of years that I was actually doing bridges. In the case of bridges, you're going to get the basic Steel or Concrete code, maybe some federal guidelines if it's an interstate, definitely state DOT standards. As for modern vs not -- There are definitely classes of bridges that I'd not consider modern. Anything with rivets, or sections that are built up by lots of little pieces (like the old style riveted trusses). Those aren't done anymore for several reasons: onsite labor is more expensive than shop labor, rivets are inconsistent and weak compared to bolts or welds, and the ongoing painting to control corrosion is a nightmare. In places like the West Coast, the older bridges are not built to current seismic standards, which have been evolving as quickly as the rest of the codes (e.g. tiedowns, base isolation, column jacketing). A lot of the older bridges also have details that aren't terribly good for fatigue performance. There was definitely an inflection point, probably in the 80's where precast prestressed concrete started being the go-to design for more than just a plain old girder bridge over the interstate.
- WatchDog 9y ago
  As a layman, the difference I notice between "modern" and older bridges is, less exposed steel and more concrete.
  - kevin_thibedeau 9y ago
elihu 9y ago
How many bridge collapses are caused by floods versus other kinds of failure? In the Northwest, we're pretty worried about the next big earthquake, whenever it happens. I also assume that bridges sometimes just fall down on their own due to corrosion, metal fatigue, low quality materials, improper construction, or uneven thermal expansion of various materials.

92 points by smb06 9y ago

Atlanta checking in (https://en.wikipedia.org/wiki/Interstate_85_bridge_collapse https://en.wikipedia.org/wiki/Interstate_85_bridge_collapse), yes.

jameskilton 9y ago
I'm not sure if that situation is strictly relevant. We don't normally design bridges to withstand heat directly on the supporting structure of potentially a thousand degrees or more.
- freehunter 9y ago
  I don't think it's that bridges need to be able to withstand that much heat, but that no one should ever be able to apply that much heat to it. If a pipeline runs under it and is able to be accessed by anyone, that inherently means the infrastructure is strongly vulnerable to attack and it just takes one person mere seconds to destroy everything. I'm not blaming the designers of the freeway though. My house has a giant plate glass window right next to my deadlocked front door. Our entire society is built around trusting that most people don't want to destroy the nice things we've collectively built. But if someone smashed my window and stole my TV, I'd probably make sure that window was a little more secure. Incremental improvements.
  - quadrangle 9y ago
    At least you aren't being stupid and weighing the window/door risks backwards leading to installing a double-keyed knob or deadbolt. That's the insanity that happens from poor risk analysis.
delinka 9y ago
Not really the kind of vulnerability the article discusses. Most every aspect of our infrastructure is vulnerable to maliciousness.
- deleted 9y ago
  [deleted]
Shivetya 9y ago
Most Georgia bridges have fifty years before rebuild or replacement. We had our 1000 year flood not to long ago and some were replaced quicker. It is not uncommon to be traveling country roads and come across a recently rebuilt or new bridge. Now this I85 debacle is purely in the camp of mismanagement and vandalism. The vandalism of course being that a person set a fire sufficient to ignite supposed non flammable building materials that should never have been stored under a bridge. Doubtful anyone in the State will suffer consequences due to sovereign immunity. What many of us who watched all this unfold is to find out exactly what was stored there and in what quantity. While not flammable doesn't mean it won't burn it should not have been this simple to ignite. Credit the contractors rebuilding the bridges, damn they are fast when they need to be. Of course another contractor managed to buckle the I20 interstate by filling pipes improperly
- BatFastard 9y ago
  As some one who lives very close to the bridge in Atlanta, it is hard to believe how disruptive it has been. While I thought traffic in the past was bad, it recently took me an hour to go 1.5 miles. A trip that usually takes 10 minutes at most. People don't go to restaurants or out at all, anytime close to rush hour. I use to pop up to corner to grab a pizza, now it takes me 20 minutes just to get to the end of my street! Glad I can bike places.
- dsfyu404ed 9y ago
  >damn they are fast when they need to be They are fast when the situation is dire enough that the politicians don't care what it costs and the NIMBYs and nit-pickers shut their mouths.
- Symbiote 9y ago
  The UK had a similar fire, though the viaduct didn't collapse. I think the result was a reduction in what was permitted to be stored under bridges and viaducts, in common with a similar restriction that was already implemented on major railways. I can't find a source for that. http://www.bbc.com/news/uk-16425491 http://www.bbc.com/news/uk-16425491
deelowe 9y ago
Totally irrelevant unless you're going to argue the Oklahoma City building was also under engineered.

Spooky23 9y ago

That's the beauty of facts and engineering. We may overestimate or underestimate. Nobody has built the vast network of bridges that we have before to the same standards, so operating experience should result in changes in our understanding of what and how we assess them! If we look at the bridges that have survived 100, 150 or more years, they are mostly massively overbuilt due to limitations of the era they were built in. Perhaps some of the more modern spans are less overbuilt and are thus more vulnerable to environmental or other changes?

hollander 9y ago
When the budget is small, you don't build for situations that you cannot imagine. You get what you pay for. Now climate is changing, these situations are suddenly reality.
knz 9y ago
The biggest threat is politicians (and voters) who don't understand that "structurally deficient" means we need to invest in inspections, repairs, and replacement. The I-35W collapse was near my house at the time and the fact that Governor Pawlenty had long pushed for reduced government spending (inspections in particular) was not lost on many people. His replacement, Governor Dayton, was partly elected due to promises to rebuild/repair even if taxes had to be raised to fund it (what a radical theory!).
- afpx 9y ago
  If I build a big tower, and it falls down and injures or damages, I'm liable, right? If government-owned infrastructure falls down (because of lack of funding) and injures or damages, is anyone liable? Not a rhetorical question
  - knz 9y ago
    IIRC for 35W there were lawsuits against the engineering company and department of transportation. http://www.mprnews.org/story/2012/11/14/law/i35w-bridge-settlement-jacobs-engineering http://www.mprnews.org/story/2012/11/14/law/i35w-bridge-sett... "After the structure fell into the Mississippi River during rush hour Aug. 1, 2007, killing 13 people and injuring 145 more, Minnesota lawmakers set up a compensation fund for victims. As part of that legislation, they nullified a statute of limitations that would have prevented the state from seeking damages. In May, the nation's highest court declined to hear Jacobs' challenge to that law, and the company had little recourse. State Sen, Ron Latz sponsored the legislation that set up the compensation fund. While the state recovered from Jacobs and another firm less than half of the nearly $37 million paid out in compensation to victims, Latz said it was the right thing to do, not just for the victims and their families but also for Minnesota taxpayers."

niftich 9y ago

As of writing, this links to university news release. The actual paper is doi:10.1061/(ASCE)IS.1943-555X.0000354 [1]. Abstract Predictions of the risk to built infrastructure posed by climate and land-use change have suggested that bridge collapses may increase due to more frequent or intense flooding. Assessments of the United States often assume that bridges may collapse when the 100-year flood (i.e., a flood with 1% annual frequency of exceedance) occurs, but this assumption has not been fully tested because of a lack of comprehensive collapse records. Thirty-five bridges for which a stream gauge on or near the bridge recorded the flow during total or partial collapse were identified and used to test this assumption. Flood frequency analyses, other statistical analyses, and structural reliability methods were used to quantify the return periods of collapse-inducing flows, identify trends linked to event and site characteristics, and evaluate the potential importance of collapse return period variability in assessing the impact of climate and land-use change on hydraulic collapse risk. The results indicate that the collapse-inducing flow return periods varied considerably (range: 1 to >1,000 years) and were frequently lower than values considered in many climate impact assessments: 23 of the 35 bridges were estimated to have collapsed during flows with return periods of lower than 100 years. Annual failure probabilities computed using the full distribution of return periods of the collapse-inducing flows, as opposed to central values (e.g., means), were more sensitive to an assumed increase or decrease in the underlying frequency of flooding. These results suggest that linking bridge collapse to only the 100-year flow does not capture significant variability associated with collapse return periods, potentially reducing sensitivity to flood frequency changes and reducing the robustness of assessments of the impact of climate, land-use, and streamflow-regulation change on hydraulic bridge collapse risk. [1] http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IS.1943-555X.0000354 http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29IS.1943-555...

VLM 9y ago

Lured in for a spanning tree protocol CVE, left with an equally important civil engineering discussion. It would be interesting to see an evolution of the concept of 100-year event over the few decades that its existed. Given the crazy rate of change compared to more stable engineering challenges like the national bureau of standards definition of the second or length standard, the endlessly changing definition of 100 year events look barely more scientific than rolling DnD dice.

peterwwillis 9y ago

The thing is, we've been underestimating bridge failure potential for decades. At least with reinforced concrete bridges, corrosion is deadly and silent, and some substances took decades to slowly corrode the steel. It took unexpected catastrophic failure for us to understand how to build them better.

jacquesm 9y ago
The real killer here is salt on the concrete in winter. It slowly leaches through the top level of the concrete and starts eating away at the steel. Very effective, totally invisible. Also lots of balconies at risk because of this.
- yborg 9y ago
  I thought everybody uses epoxy-coated rebar on bridges now.
  - InclinedPlane 9y ago
    "Now". Not all bridges in use now were built now. In fact, most are quite old, which is the problem.
- ggcdn 9y ago
  Do people salt their balconies? I've never seen nor heard of this.
  - jacquesm 9y ago
    Balconies and galleries in apartment buildings to avoid falls in winter. There's a huge flap around that theme here in NL right now with 1000's of apartment buildings having to be inspected before mid-june because a building shed it's balconies. https://www.nrc.nl/nieuws/2015/12/22/ministerie-laat-vloeren-van-alle-flats-van-voor-1975-onderzoeken-a1410616 https://www.nrc.nl/nieuws/2015/12/22/ministerie-laat-vloeren... (Dutch, sorry, no English source)

dockd 9y ago

What exactly are "modern design standards" required by bridges? When did the modern era start? Is there really a major moment in bridge design where the standards changed? Is there even broad agreement on what these standards are? (Side note: the bridge pictured in the article is the Bridge of the Gods, just upstream of Bonneville Dam on the Columbia River. There's going to be more than bridge problems if the flow of the river takes out that bridge.)

wiredfool 9y ago
Yes. There are standards, they're the Building Codes. There are several versions of them that have come out over time, and they've been evolving with the advances in the science and engineering. When I was in Engineering school, we were generally taught off of a newer code than was in common use in the wild, but that transition was occurring in the couple of years that I was actually doing bridges. In the case of bridges, you're going to get the basic Steel or Concrete code, maybe some federal guidelines if it's an interstate, definitely state DOT standards. As for modern vs not -- There are definitely classes of bridges that I'd not consider modern. Anything with rivets, or sections that are built up by lots of little pieces (like the old style riveted trusses). Those aren't done anymore for several reasons: onsite labor is more expensive than shop labor, rivets are inconsistent and weak compared to bolts or welds, and the ongoing painting to control corrosion is a nightmare. In places like the West Coast, the older bridges are not built to current seismic standards, which have been evolving as quickly as the rest of the codes (e.g. tiedowns, base isolation, column jacketing). A lot of the older bridges also have details that aren't terribly good for fatigue performance. There was definitely an inflection point, probably in the 80's where precast prestressed concrete started being the go-to design for more than just a plain old girder bridge over the interstate.
WatchDog 9y ago
As a layman, the difference I notice between "modern" and older bridges is, less exposed steel and more concrete.
- kevin_thibedeau 9y ago

elihu 9y ago

How many bridge collapses are caused by floods versus other kinds of failure? In the Northwest, we're pretty worried about the next big earthquake, whenever it happens. I also assume that bridges sometimes just fall down on their own due to corrosion, metal fatigue, low quality materials, improper construction, or uneven thermal expansion of various materials.