5 ms·

There's a similar story happening with our rail lines. The story seems to be that the materials we used in the UK are not stressed to deal with 40 degree heat.

by LightG 4y ago

There's a similar story happening with our rail lines. The story seems to be that the materials we used in the UK are not stressed to deal with 40 degree heat. They never thought it would be an issue in the UK. Whereas many European railway lines were made to deal with 40-45 degree heat. I'm guessing it's the same for runway tarmac or whatever it is ... Climate change is here ...

mhandley 4y ago
It's not so much the materials - modern rail, especially for high speed trains is laid in long continuously welded sections. The track is pre-tensioned so that at cold temperatures as it tries to shrink it is under significant tension and as it warms it becomes less tensioned. The question is what temperature to tension it to - at some temperature it is no longer under tension and above that it becomes in compression and then you have risk of the rails buckling. If I recall correctly, in England the track is tensioned for 27C (a typical hot summers day temperatures). They could tension for a higher temperature, but then you risk rails cracking in very cold weather. So in the end it's a compromise, but one that was made without expecting the current 40C temperatures.
- jaclaz 4y ago
  The relevant HN thread, a few days ago: https://news.ycombinator.com/item?id=32118818 https://news.ycombinator.com/item?id=32118818
- iggldiggl 4y ago
  > at some temperature it is no longer under tension and above that it becomes in compression and then you have risk of the rails buckling. If I recall correctly, in England the track is tensioned for 27C (a typical hot summers day temperatures) While the basic gist is correct, a certain amount of compression is fine, too, because the trackbed can resist a certain amount of sideways buckling force, especially once the track has settled in a bit. It's only when the buckling forces caused by the temperature expansion and resultant compression exceed the sideways resistance of the trackbed that you get buckling. Besides, rail temperatures on a hot summer day in the sun will definitively be higher than 27 °C – that value just happens to be the neutral temperature between maximum allowable compression and maximum allowable tension, whatever those temperatures exactly are.
  - mhandley 4y ago
    Yes, exactly. And once it's in compression even at higher temperatures it will often be fine if left alone. This is why railway companies impose speed restrictions when it gets hot - they don't want the dynamic load of a passing train to exceed the ability of the track bed to resist buckling. Running at low speeds helps in this respect.
  - Someone 4y ago
    https://www.networkrail.co.uk/stories/why-rails-buckle-in-britain/ https://www.networkrail.co.uk/stories/why-rails-buckle-in-br... says “rail can actually be up to 20 degrees higher.” and “For some of our track, such high temperatures are more than our track is designed to cope with”, so it depends on the track, but can be around 50°C. A rail that’s in the shade for most of the day will get less hot, so I expect location also influences at what air temperature track will buckle.
smcl 4y ago
> There's a similar story happening with our rail lines No, there's a similar story happening with everyone's rail lines. There's a curious thing bout Britain where the British press love a hysterical "here's an example of Broken Britain!" headline, and Europe and America quite enjoy seeing the UK getting any sort of comeuppance (and normally I wouldn't begrudge them this, there have been a lot of insane goings on in the UK of late). But the only instance I've seen of this - not announcements of restricted services or reduced speeds as a precaution or due to reduce damage in overhead lines, actual buckling - today has been in Spain: - https://twitter.com/rail_arri/status/1549039421525458945 https://twitter.com/rail_arri/status/1549039421525458945 - https://twitter.com/rail_arri/status/1549034924010655745 https://twitter.com/rail_arri/status/1549034924010655745 edit: and just minutes after I post this, I spot an instance in England from the weekend! https://twitter.com/networkrail/status/1548760985246261249/photo/3 https://twitter.com/networkrail/status/1548760985246261249/p...
- LightG 4y ago
  Britain is broken. This isn't the place to debate it, but we're currently a rudderless, borderline second world country. It's going to take a generation to recover (let alone thrive) from what the last decade of flagshagging idiots have done to this once great country.
  - dragonwriter 4y ago
    > This isn't the place to debate it, but we're currently a rudderless, borderline second world country. You are teetering on the brink of alliance with the Soviet Union? (The first/second/third world thing originally referred to cold war alignment: first and second were US and Soviet spheres, third non-aligned; later first- and third-world got adopted as synonyms for “developed“ and “less developed”, but second-world is never used in that economic sense.)
    - LightG 4y ago
      Well, I'm using it in an economic and social sense. Glad I could clarify. Edit: and now my annoyance has settled down, I accept your correction. Thank you. Second division is more appropriate.

by LightG 4y ago

mhandley 4y ago

It's not so much the materials - modern rail, especially for high speed trains is laid in long continuously welded sections. The track is pre-tensioned so that at cold temperatures as it tries to shrink it is under significant tension and as it warms it becomes less tensioned. The question is what temperature to tension it to - at some temperature it is no longer under tension and above that it becomes in compression and then you have risk of the rails buckling. If I recall correctly, in England the track is tensioned for 27C (a typical hot summers day temperatures). They could tension for a higher temperature, but then you risk rails cracking in very cold weather. So in the end it's a compromise, but one that was made without expecting the current 40C temperatures.

jaclaz 4y ago
The relevant HN thread, a few days ago: https://news.ycombinator.com/item?id=32118818 https://news.ycombinator.com/item?id=32118818
iggldiggl 4y ago
> at some temperature it is no longer under tension and above that it becomes in compression and then you have risk of the rails buckling. If I recall correctly, in England the track is tensioned for 27C (a typical hot summers day temperatures) While the basic gist is correct, a certain amount of compression is fine, too, because the trackbed can resist a certain amount of sideways buckling force, especially once the track has settled in a bit. It's only when the buckling forces caused by the temperature expansion and resultant compression exceed the sideways resistance of the trackbed that you get buckling. Besides, rail temperatures on a hot summer day in the sun will definitively be higher than 27 °C – that value just happens to be the neutral temperature between maximum allowable compression and maximum allowable tension, whatever those temperatures exactly are.
- mhandley 4y ago
  Yes, exactly. And once it's in compression even at higher temperatures it will often be fine if left alone. This is why railway companies impose speed restrictions when it gets hot - they don't want the dynamic load of a passing train to exceed the ability of the track bed to resist buckling. Running at low speeds helps in this respect.
- Someone 4y ago
  https://www.networkrail.co.uk/stories/why-rails-buckle-in-britain/ https://www.networkrail.co.uk/stories/why-rails-buckle-in-br... says “rail can actually be up to 20 degrees higher.” and “For some of our track, such high temperatures are more than our track is designed to cope with”, so it depends on the track, but can be around 50°C. A rail that’s in the shade for most of the day will get less hot, so I expect location also influences at what air temperature track will buckle.

smcl 4y ago

> There's a similar story happening with our rail lines No, there's a similar story happening with everyone's rail lines. There's a curious thing bout Britain where the British press love a hysterical "here's an example of Broken Britain!" headline, and Europe and America quite enjoy seeing the UK getting any sort of comeuppance (and normally I wouldn't begrudge them this, there have been a lot of insane goings on in the UK of late). But the only instance I've seen of this - not announcements of restricted services or reduced speeds as a precaution or due to reduce damage in overhead lines, actual buckling - today has been in Spain: - https://twitter.com/rail_arri/status/1549039421525458945 https://twitter.com/rail_arri/status/1549039421525458945 - https://twitter.com/rail_arri/status/1549034924010655745 https://twitter.com/rail_arri/status/1549034924010655745 edit: and just minutes after I post this, I spot an instance in England from the weekend! https://twitter.com/networkrail/status/1548760985246261249/photo/3 https://twitter.com/networkrail/status/1548760985246261249/p...

LightG 4y ago
Britain is broken. This isn't the place to debate it, but we're currently a rudderless, borderline second world country. It's going to take a generation to recover (let alone thrive) from what the last decade of flagshagging idiots have done to this once great country.
- dragonwriter 4y ago
  > This isn't the place to debate it, but we're currently a rudderless, borderline second world country. You are teetering on the brink of alliance with the Soviet Union? (The first/second/third world thing originally referred to cold war alignment: first and second were US and Soviet spheres, third non-aligned; later first- and third-world got adopted as synonyms for “developed“ and “less developed”, but second-world is never used in that economic sense.)
  - LightG 4y ago
    Well, I'm using it in an economic and social sense. Glad I could clarify. Edit: and now my annoyance has settled down, I accept your correction. Thank you. Second division is more appropriate.