5 ms·

This comment on the article is more interesting than the article itself IMHO http://disq.us/p/24slwwt http://disq.us/p/24slwwt

by kitcar 7y ago

floatingatoll 7y ago
Unshortened: https://avc.com/2019/10/cross-laminated-timber/#comment-4643481053 https://avc.com/2019/10/cross-laminated-timber/#comment-4643...
- mooreds 7y ago
  JLM and his comments are a treasure. Check out his blog at https://themusingsofthebigredcar.com/ https://themusingsofthebigredcar.com/
- peterwwillis 7y ago
  That commenter is doing a lot of gymnastics to avoid talking about reinforced concrete's hidden failures. It's difficult to determine reinforced concrete failures before it gets bad, and repairing it is very expensive. Concrete can get really complex depending on how you make and apply it, and what it's exposed to. I agree with the author that water is now a bigger deal than fire for wood construction, and we need way more testing for taller construction, perhaps even designs tailored to the material.
  - ethbro 7y ago
    "The issue with CLT as a building system is exactly that -- its behavior as a whole when subjected to differing forces as statistically magnified by the great number of joints. There are a ton of connections in a CLT building. Thousands of them. One connection failure can create a cascade of failure that may destroy the building. Each connection has the fingerprints of a single worker. One bonehead can wreck a connection." That's a non-negligible practical problem and a perfectly valid point. And it's difficult to take the residential approach of "just over-spec" when you're building mid-rise+.
    - deleted 7y ago
      [deleted]
    - youngtaff 7y ago
      But yet elsewhere in the world they can build multi-storey CLT buildings https://www.theb1m.com/video/top-5-the-world-s-tallest-timber-buildings https://www.theb1m.com/video/top-5-the-world-s-tallest-timbe...
      - ethbro 7y ago
        - completed in 2012 - completed in 2015 - completed in 2017 - completed in 2015 - completed in 2017 Mmhmm.
  - rumanator 7y ago
    > That commenter is doing a lot of gymnastics to avoid talking about reinforced concrete's hidden failures. It's difficult to determine reinforced concrete failures before it gets bad, and repairing it is very expensive. Care to elaborate? Concrete has already been extensively studied and has enjoyed widespread use, including under seismic loads. I don't understand how in this day and age where rc structures have been used for over a century there is any mention of "hidden failures".
    - peterwwillis 7y ago
      Concrete in general can fail from simply being mixed poorly, which the slump and strength tests used on each batch are meant to address. But also additives can sometimes be added to concrete, which in some cases react with surfaces/chemicals over time and cause all sorts of problems. For reinforced concrete failures, see here: https://en.wikipedia.org/wiki/Reinforced_concrete#Common_failure_modes_of_steel_reinforced_concrete https://en.wikipedia.org/wiki/Reinforced_concrete#Common_fai... https://www.usbr.gov/ssle/damsafety/risk/BestPractices/Chapters/V-1-20150422.pdf https://www.usbr.gov/ssle/damsafety/risk/BestPractices/Chapt... By the time there's spalling the reinforcement is already rusted and breaking up the concrete. Of course you can say "Oh but we know all that now, so just design it right and you're good!" Sure. Unless you make a mistake, in which case you won't know it until the structure is crumbling. And remember, "it's a monolith", so good luck with those repairs. I'm not saying CLT is better - but let's not kid ourselves, reinforced concrete isn't perfect. It's just cheap, strong, and easy to install.
  - floatingatoll 7y ago
    I felt the same way. They said a lot of plausible things, but their motivation seemed more to be “don’t disrupt my life by pursuing alternatives to concrete” than “here is a reasoned and well-structured argument against CLT”. It read like a series of talking points. Glad it’s not just me.
- aitchnyu 7y ago
  Now I want to know how it will recover after fires. I read it will burn/collapse well after occupants have escaped. But will a building with some burnt CLT members be a total loss?
notJim 7y ago
Really? It seems like a lot of words to say "unfamiliar material bad." Surely the people advocating CLT have thought of some of these obvious downsides, and have ideas for how they're addressing them. If those are inadequate, then talk about that. Instead we get "In my professional judgment it is driven by a certain "gee whiz, isn't this cool" environmental state of mind." Excuse me if I want facts and not someone's un-sourced, un-backed-up "professional judgment".
- hermitdev 7y ago
  > "unfamiliar material bad." I think its more "unfamiliar material" has different properties than we're used to, and there will need to be some adjustment.
- rumanator 7y ago
  > Really? It seems like a lot of words to say "unfamiliar material bad." Your reading comprehension skills are a bit lacking. If anything, they're a lot of words to say "unfamiliar material behaves in an unfamiliar way" which, as you might agree, is in itself a huge problem if you are tasked with designing a structure intended to be perfectly safe by design for well over 50 years. And then there's the fact that some of those words are there to point out the fact that the material in question, and the technology that's used to put it to use, suffer from shortcomings that jeopardize the safety and longevity of a structure.
- rkachowski 7y ago
  The comment repeatedly states that CLT is neither new nor unfamiliar, one main issue is that CLT requires many joints with individual properties (many points of failure with manufacturing errors specific to the people that worked there) whilst concrete behaves / accepts load as a singular structure. Admittedly, this isn't an argument against CLT but instead against anything that doesn't behave as a single structure under load - but it does point out that CLT isn't a suitable replacement for all building materials everywhere. High rise buildings need the safety of reenforced concrete, with it's load handling and simplified calculations (due to lack of joints), and until something can perform in a similar manner it's not likely to be replaced.
rmason 7y ago
JLM's comments some days are better than Fred's. The guy has been a high ranking army officer, built a lot of the newer skyscrapers in Austin and now is retired from CEO of a Fortune 500 company.

This comment on the article is more interesting than the article itself IMHO http://disq.us/p/24slwwt http://disq.us/p/24slwwt

by kitcar 7y ago

This comment on the article is more interesting than the article itself IMHO http://disq.us/p/24slwwt http://disq.us/p/24slwwt

floatingatoll 7y ago

Unshortened: https://avc.com/2019/10/cross-laminated-timber/#comment-4643481053 https://avc.com/2019/10/cross-laminated-timber/#comment-4643...

mooreds 7y ago
JLM and his comments are a treasure. Check out his blog at https://themusingsofthebigredcar.com/ https://themusingsofthebigredcar.com/
peterwwillis 7y ago
That commenter is doing a lot of gymnastics to avoid talking about reinforced concrete's hidden failures. It's difficult to determine reinforced concrete failures before it gets bad, and repairing it is very expensive. Concrete can get really complex depending on how you make and apply it, and what it's exposed to. I agree with the author that water is now a bigger deal than fire for wood construction, and we need way more testing for taller construction, perhaps even designs tailored to the material.
- ethbro 7y ago
  "The issue with CLT as a building system is exactly that -- its behavior as a whole when subjected to differing forces as statistically magnified by the great number of joints. There are a ton of connections in a CLT building. Thousands of them. One connection failure can create a cascade of failure that may destroy the building. Each connection has the fingerprints of a single worker. One bonehead can wreck a connection." That's a non-negligible practical problem and a perfectly valid point. And it's difficult to take the residential approach of "just over-spec" when you're building mid-rise+.
  - deleted 7y ago
    [deleted]
  - youngtaff 7y ago
    But yet elsewhere in the world they can build multi-storey CLT buildings https://www.theb1m.com/video/top-5-the-world-s-tallest-timber-buildings https://www.theb1m.com/video/top-5-the-world-s-tallest-timbe...
    - ethbro 7y ago
      - completed in 2012 - completed in 2015 - completed in 2017 - completed in 2015 - completed in 2017 Mmhmm.
- rumanator 7y ago
  > That commenter is doing a lot of gymnastics to avoid talking about reinforced concrete's hidden failures. It's difficult to determine reinforced concrete failures before it gets bad, and repairing it is very expensive. Care to elaborate? Concrete has already been extensively studied and has enjoyed widespread use, including under seismic loads. I don't understand how in this day and age where rc structures have been used for over a century there is any mention of "hidden failures".
  - peterwwillis 7y ago
    Concrete in general can fail from simply being mixed poorly, which the slump and strength tests used on each batch are meant to address. But also additives can sometimes be added to concrete, which in some cases react with surfaces/chemicals over time and cause all sorts of problems. For reinforced concrete failures, see here: https://en.wikipedia.org/wiki/Reinforced_concrete#Common_failure_modes_of_steel_reinforced_concrete https://en.wikipedia.org/wiki/Reinforced_concrete#Common_fai... https://www.usbr.gov/ssle/damsafety/risk/BestPractices/Chapters/V-1-20150422.pdf https://www.usbr.gov/ssle/damsafety/risk/BestPractices/Chapt... By the time there's spalling the reinforcement is already rusted and breaking up the concrete. Of course you can say "Oh but we know all that now, so just design it right and you're good!" Sure. Unless you make a mistake, in which case you won't know it until the structure is crumbling. And remember, "it's a monolith", so good luck with those repairs. I'm not saying CLT is better - but let's not kid ourselves, reinforced concrete isn't perfect. It's just cheap, strong, and easy to install.
- floatingatoll 7y ago
  I felt the same way. They said a lot of plausible things, but their motivation seemed more to be “don’t disrupt my life by pursuing alternatives to concrete” than “here is a reasoned and well-structured argument against CLT”. It read like a series of talking points. Glad it’s not just me.
aitchnyu 7y ago
Now I want to know how it will recover after fires. I read it will burn/collapse well after occupants have escaped. But will a building with some burnt CLT members be a total loss?

notJim 7y ago

Really? It seems like a lot of words to say "unfamiliar material bad." Surely the people advocating CLT have thought of some of these obvious downsides, and have ideas for how they're addressing them. If those are inadequate, then talk about that. Instead we get "In my professional judgment it is driven by a certain "gee whiz, isn't this cool" environmental state of mind." Excuse me if I want facts and not someone's un-sourced, un-backed-up "professional judgment".

hermitdev 7y ago
> "unfamiliar material bad." I think its more "unfamiliar material" has different properties than we're used to, and there will need to be some adjustment.
rumanator 7y ago
> Really? It seems like a lot of words to say "unfamiliar material bad." Your reading comprehension skills are a bit lacking. If anything, they're a lot of words to say "unfamiliar material behaves in an unfamiliar way" which, as you might agree, is in itself a huge problem if you are tasked with designing a structure intended to be perfectly safe by design for well over 50 years. And then there's the fact that some of those words are there to point out the fact that the material in question, and the technology that's used to put it to use, suffer from shortcomings that jeopardize the safety and longevity of a structure.
rkachowski 7y ago
The comment repeatedly states that CLT is neither new nor unfamiliar, one main issue is that CLT requires many joints with individual properties (many points of failure with manufacturing errors specific to the people that worked there) whilst concrete behaves / accepts load as a singular structure. Admittedly, this isn't an argument against CLT but instead against anything that doesn't behave as a single structure under load - but it does point out that CLT isn't a suitable replacement for all building materials everywhere. High rise buildings need the safety of reenforced concrete, with it's load handling and simplified calculations (due to lack of joints), and until something can perform in a similar manner it's not likely to be replaced.

rmason 7y ago

JLM's comments some days are better than Fred's. The guy has been a high ranking army officer, built a lot of the newer skyscrapers in Austin and now is retired from CEO of a Fortune 500 company.