Cross-Laminated Timber

Re:Cross-Laminated Timber by peterwwillis on Monday October 07, 2019 @05:27PM (#21186147)

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.

[ Parent | on HN ]

Re:Cross-Laminated Timber by ethbro on Monday October 07, 2019 @07:42PM (#21187198)

"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+.

[ Parent | on HN ]

Re:Cross-Laminated Timber by youngtaff on Tuesday October 08, 2019 @03:53AM (#21189812)

But yet elsewhere in the world they can build multi-storey CLT buildings

https://www.theb1m.com/video/top-5-the-world-s-tallest-timbe...

[ Parent | on HN ]

Re:Cross-Laminated Timber by ethbro on Tuesday October 08, 2019 @03:00PM (#21195812)

- completed in 2012

- completed in 2015

- completed in 2017

- completed in 2015

- completed in 2017

Mmhmm.

[ Parent | on HN ]

Re:Cross-Laminated Timber by rumanator on Tuesday October 08, 2019 @12:21AM (#21188739)

> 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".

[ Parent | on HN ]

Re:Cross-Laminated Timber by peterwwillis on Tuesday October 08, 2019 @11:21AM (#21193244)

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_fai... 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.

[ Parent | on HN ]

Re:Cross-Laminated Timber by floatingatoll on Tuesday October 08, 2019 @10:36AM (#21192771)

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.

[ Parent | on HN ]