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It’s also worth noting that geotechnical engineering is a high risk and low tech field. Most of their design relations involve pounding a stick into the ground and counting how many hits it took to sink a unit depth (that’s a little bit jest, but also not far from the truth)

Imagine being tasked with identifying a famous painting, But you aren’t allowed to see the painting. You are provided with the five predominant colours in the painting, the type of paint used, and a 10mm x 10mm sample of the painting.

Now, please tell me the name of that painting?

This is something that the profession has done a terrible job in communicating with the public.

But if you think about the nature of earthquakes, it starts to make a little more sense. There is basically a probabilistic distribution of earthquake frequency and energy. The more powerful the quake, the less frequently it occurs, and there is a long tail to this distribution. So we need to draw a line in the sand somewhere and say “we will design for X, and detail the structure to avoid collapse if X is exceeded.” There is no such thing as an earthquake proof building, because there is always a bigger earthquake than the one considered for design. All we can do is play with probabilities.

In the US the life safety objective corresponds to earthquake hazard of 10% probability of exceedance in 50yrs. The industry has long accepted this as a good X point that balances construction cost and longevity. But more recently, with ballooning recovery costs in recent earthquakes, some are starting to see its not enough. For instance, in the Canterbury NZ earthquake many structures performed “well” and met their design intents, but around 70% of the downtown ended up being demolished. Insurance deemed them too costly and risky to repair.

Now industry is starting to use “performance based design” more often for seismic design of tall buildings (including the Millennium tower). It allows you to pick multiple hazards and set different objectives for them. For instance, we might say no damage allowed at 30% in 50yr hazard, cracking and light damage at 10%/50yr, and no collapse at 2%/50yr hazards. Then we do a bunch more sophisticated modelling to demonstrate the design meets the objectives. I wrote a little bit more about performance based design here :

https://kinson.io/post/what-is-performance-based-design/

Unfortunately it didn’t help the millennium tower with this geotechnical issue. Which I suppose says something about design being only as good as the input assumptions.

I’ve spent a cumulative 6 months there (3 separate trips) including 3 months with a 1 and 3yo, and never was there a point where I felt unsafe. I am a tall white guy and stand out. Met lots of curious, friendly, amused locals that wanted to take pictures with me, especially if they were from the less globalized regions. There is a strong police/security presence everywhere. Even my apartment block had its own 8 person security team.

We’ve been misled for so long into thinking this is a consumer problem that needs downstream solutions. Actually I think it’s a regulatory problem that needs upstream regulation

Not sure, it’s not been proposed on our projects before. Most likely, that means it’s not cheaper than geofoam or fill.

We use this a lot to support landscaping in the sky (rooftop terraces and such on high rises) which is an architectural trend that really needs to go away. There is nothing green or sustainable about the extra concrete needed to support it.

But the alternative to geofoam is usually clean fill, like sand, which weighs about 110 lb/cf. contractors ask to substitute it because it’s cheaper, but it almost always results in thicker structure and more rebar to support it.

In this case the city proactively made all its files available for the building.

In general, that doesn’t happen (perhaps in Florida it does, I have no experience there). But most cities will only release their record drawings if you have permission of the owner.

which regions and industry do you see them used? In west coast buildings, its uncommon.

Not sure why you're being downvoted, because you're right, atleast on the west coast of north america. My firm hasn't use epoxied rebar since like 1990, and we removed all references to it on our drawings long ago.

The coatings were super fragile, and often damaged while being placed in the field. Then someone had to come along with magic paint and touch up all the cracks. But of coarse they would never find 100% of them...

One of the big reasons is ductility. We want structures to show signs of distress before failing catastrophically. With ductile reinforcing (steel), the deformation at which failure occurs is easily 5 times larger than the deformation where yielding occurs. Large cracks will open up, it hopefully gets noticed, and there is a chance to intervene.

With GF or CF reinforcing, failure is sudden and catastrophic.

One thing I noticed in Chinese cities is that they often had a cleaner assigned to each block. They would have a blue jumpsuit, broom, shovel, and wheelie bin.

In the big cities, streets were very clean.

I haven’t heard of NEET before, so I looked it up.

NEET, an acronym for "Not in Education, Employment, or Training", refers to a person who is unemployed and not receiving an education or vocational training

Very good point. Most building projects actually use admixtures to get as rapid strength increase as possible, even if it means less strength increase long term, because the early strength determines when you can strip formwork and start building the next floor. Builders want concrete reaching ~18MPA in like <2 days.

Welding rebar is almost never used in North American building construction, and is actually forbidden in high seismic zones.

But then again so is stainless steel rebar and carbon fibre rebar and most of these other types of products because they lack ductility

I think many commentators, including yourself, have an erroneous assumption about structural design which is roughly summarized as: the inputs are known with certainty. This is really not the case especially when considering natural hazards like wind and earthquake. What happens to your 500 year lifespan design when we discover new information about earthquakes at the site. This is happening regularly with every building code update. Our design loads change To reflect the latest research on things like seismicity. When you factor in this consideration, it may actually make a lot of sense to only design for shorter lifespans.

Plain concrete is simply not allowed by code for many applications. So even if you could theoretically justify the design, you couldn’t get the permit to build it.

Physics, economics, and bureaucratics is a good summary of structural engineering. The last one can’t be ignored.

In many parts of North America, testing and upgrades are only triggered with a change of use, or if required by buyers during sale of a building. The state does not maintain any kind of testing program of private buildings.

One exception is the mandatory retrofit programs implemented by some cities like San Francisco and Los Angeles.

Good! It’s long irked me that the responsibility for dealing with plastic waste lands on the individual and municipalities, when they have little to no say in its production and regulation.

Current residential recycling is more about feeling like you’re doing good, rather than actually making any impact. I can dump cardboard, all types of plastic, and metals into my magic blue bin and believe it’s getting sorted and dealt with appropriately, when in reality the plastic portion is just landfilled or shipped to a poorer country.

Fun fact, because of that earthquake, there is a 160ft height restriction on certain types of construction in US building codes even to this day!

Not op but our mortgage lender offers a “total home warranty” for like $8/month which covers appliances and systems (hvac, boiler, etc). It’s basically appliance insurance. And at that price it’s a pretty good deal when buying a used house.

Wow incredible story. Do you happen to have any photos online of the mill and/or the flood

But the Supreme Court doesn’t make the rules, it just interprets them. The rules are made by elected representatives.

Many earthquake engineers and researchers are all too familiar with Tcl, because for years the preeminent structural analysis tool OpenSees [1] required Tcl scripts to use/run. Just in the last few years was it forked to python.

https://opensees.berkeley.edu/OpenSees/home/about.php

> An unforgivably naive market of architects and contractors then began merrily specifying it for a wide range of uses well beyond its original test.

Architects are architects, Contractors are contractors, and neither are fire engineers. No one can be an expert on everything. This is why we have building codes, product certification, and engineering assurance process. The problem here appeared to be dishonest players. If certified independent labs were required to test products, and licensed engineers were required to approve the assembly and submit their letters of insurance for the permit, it seems like there would be a net benefit to the public (this is how it works in Canada). If there was a stronger regulatory system, the investigators would be able to look up the letters of assurance for this permit, obtain the project documentation from the responsible engineer, investigate and possible charge him with negligence if he failed to spec a certified fire assembly. It appears that in the UK, there is no clear hierarchy of responsibility. When everyone is responsible, no one is responsible.

As an aside, Fire rating generally involves more than just a single product - it requires an 'assembly'. That assembly must be recreated every time the product is used to achieve the fire rating. If the testing assembly required 1/2" non-combustible cement backing board, the installation also requires it. It sounds like the fire rated assemblies were not being followed in this case.

Perhaps I misunderstood your description of subfloor, but I don’t think it’s common anywhere to insulate between interior floors or walls.

I liked “A guide to the good life” by William Irving, which covers the history, techniques, and advice from the big names of Stoicism.

I wouldn’t call myself a Stoic, but I have a lot of anxiety from my job and life and found this book helpful in changing the way I think and feel about situations in life.

Frequently rode greyhounds from Vancouver up through northern BC when I was young. About 1/5 rides would have some memorable event. A drunk yelling slurs at no one in particular, a mother screaming at her kids to the point the driver is threatening to call child services if she doesn’t calm down. Police pulling the bus over in the middle of nowhere and arresting someone. These kind of things.

Generally it was only the poorest people who would be riding Greyhounds up north, or those unfortunate enough not able to drive themselves.

Good points, it makes you wonder how many day to day things could have vastly improved user experience if government efforts were targeted at underlying problems instead of symptoms (borrowing your definitions of those two things).

But plastics recycling comes to mind as a bit of a counter example, where all the effort has been put on dealing with the end problem, when perhaps they should be targeting the symptom (regulating unnecessary plastics and packaging, and taxing the producers instead of the consumers). Currently plastic producers have incentive to generate more plastics, and consumers are left trying to deal with the waste.

weird, I was looking for this exact concept (except for Javascript code) literally right before checking whats new on HN.

This looks great. Its super useful for when you need to perform calculations and also keep a saved record of it (like structural engineering calcs)

Its a great catchy book, and it was interesting to learn more about the origins of it. Both my 3yo and I can recite it from memory.