Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Millennium Tower is tilting, sinking

sf.curbed.com

Post reply on HN
Print view View original

171–180 of 187 posts

Re: Millennium Tower is tilting, sinking

#171

Post by amatix »

mikekchar wrote: post #138
flukus wrote: post #132

Earlier quoted context omitted.

Has there been a comparable earthquake yet?

Here's a list of large earthquakes in Japan: https://en.wikipedia.org/wiki/List_of_earthquakes_in_Japan There have been several large M7+ earthquakes in populated areas since the Hanshin (Kobe) earthquake. Tohoku was obviously the biggest. Several of the Tohoku aftershocks were over M7. This spring there was a M7 earthquake in Kumamoto, which I think is the largest earthquake in a very populated area since 2011. Japa…

https://www.geonet.org.nz/quakes/felt is the same for New Zealand... there's a moderate or strong quake every couple of weeks, and little ones all the time

Re: Millennium Tower is tilting, sinking

#172

Post by discardorama »

irq11 wrote: post #163
fennecfoxen wrote: post #136

Earlier quoted context omitted.

The fact that they're not able to pass 100% of the cost of whatever capital improvements they feel like on to their renters is part of a massive wealth transfer from landlords to long-established tenants. In other circumstances I'd accuse that of deterring investment and being a contributor to the terrible housing situation in the Bay Area in general, but honestly, the zoning / planning-permit situation is the first…

Instead of "massive wealth transfer", I think you meant to write "slight dent in disgustingly fat profit margins", because - just based on aggregate metrics - most landlords are making a stone-cold killing in this market. Indeed, let's all shed a tear for the SF landlord. I don't know how those poor folks can stay in business when property taxes are capped and median rent rises at ten times the rate of inflation!

Clearly, you have not heard of "rent control". I know people paying $1200/month for a 2BR in the heart of the City. I even met a guy who was paying $350 for a 1BR in Nob Hill, not far from Grace Cathedral.

About 72% of SF's units are under rent control. So not all landlords are making "fat profit margins".

Re: Millennium Tower is tilting, sinking

#173

Post by huuu »

SagelyGuru wrote: post #154

Surely, the tilting is the biggest worry. Anybody care to estimate how many more inches can this tall building tilt before the lateral stresses lead to its collapse?

I think you would be amazed how far it could tilt before it collapses.

For example the Tower of Pisa (55m height) is leaning much worse: almost 4 meters.

https://en.wikipedia.org/wiki/List_of_leaning_towers

Re: Millennium Tower is tilting, sinking

#174

Post by trey-jones »

astrodust wrote: post #143
WalterBright wrote: post #23

Earlier quoted context omitted.

I did a lot of things to reduce risk. None were expensive. I watch other houses go up in the neighborhood, and they do none of them. My most expensive mistake was not having a geothermal heading system installed when the yard was all dug up anyway. I could have had it essentially for free, and save 30% on the heating bill.

What type of system were you evaluating? I'm not sure why this isn't a common feature in homes, as I've only seen it done on more industrial scales (e.g. mid-sized condos).

I just bought two of these: http://www.bosch-climate.us/products-bosch-thermotechnology/...

I have only installed one, and I can't comment on how effective it is at reducing cooling costs as it's a new home (though I lived there for a couple of weeks before I got the heat pump units). But I can comment on the "why not".

Generally it's very expensive to install because it requires several thousand feet of underground pipe to normalize the temperature of the water going through the system. Many homes don't really have enough land to support this horizontally. You can install the loop vertically (like a drilled well), which is again, pretty expensive up front. Few take the long view.

I happen to have plenty of land and a backhoe so I just dug a ditch.

Re: Millennium Tower is tilting, sinking

#175

Post by dsfyu404ed »

FWIW building on sand isn't all that bad if you design the building expecting it to be on sand. The Nazis build AA defenses on sand because a concrete building that's sandwiched between the recoil of small artillery and bedrock won't be around very long. The sand acts like a damper. It's harder to break a cinder block with a hammer if the block is sitting on a pile of sand than if it's on a paved surface and you can apply the same principal at scale if you've got the resources to do all the prerequisite work.

It's not that exotic of a design when you consider that the ground under California tends to move around. Too bad it doesn't look like this building was meant to support itself atop a less than solid underlayment. Too bad for the developers.\s If they have to take corrective action they only get a crazy profit margin instead of an insane one. Should have done it right the first time.

Re: Millennium Tower is tilting, sinking

#176

Post by dmux »

jghn wrote: post #99
Finnucane wrote: post #31

Earlier quoted context omitted.

Most of our big coastal cities are like that. Boston is about twice as big as it was in colonial times; all of the Back Bay is landfill. A lot of Cambridge is landfill. And yes, most of the taller buildings cluster around the more solid bedrock areas closer to downtown. But the engineering principles needed here aren't unknown--cities like Las Vegas and New Orleans have modern buildings that are much taller than were…

As a kid I always wondered why so many of the taller buildings clustered up near DTX and then down that little strip down Boylston. As I got a bit earlier and learned what Boston originally looked like, it all made sense.

Part of the clustering is planned: https://en.wikipedia.org/wiki/High_Spine

Re: Millennium Tower is tilting, sinking

#177

Post by andyidsinga »

WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I couldn't resist looking up the monty python bit :) https://www.youtube.com/watch?v=aNaXdLWt17A

fwiw: the whole dialog between the father and the guards that follows is awesome -- reminds be of requirements discussions.

Re: Millennium Tower is tilting, sinking

#178

Post by astrodust »

Gibbon1 wrote: post #155
astrodust wrote: post #144

Earlier quoted context omitted.

Clay can be a total pain in the ass to work with, it's more stubborn than concrete to remove, but you'd be hard pressed to find a material more solid to build on than rock. What's your beef with clay? The kind of glacial packed clay mentioned in this article is the sort of stuff even a power shovel has trouble with. It looks like light coloured slate, dry, brittle, and dense. I'm not sure what your preference for san…

Not sure but my understanding is high clay soils expand and contract seasonally due to moisture changes.

In a location with a variable water table this could be trouble, but I'm not sure it's going to be much better in the same situation with sand.

I wonder what kind of foundation these homes are built on. Do they include a full basement?

Re: Millennium Tower is tilting, sinking

#179

Post by superuser2 »

webXL wrote: post #168
_Codemonkeyism wrote: post #161

Earlier quoted context omitted.

Same here in Germany, people build in "big blue sections" because the nature is nice and the land is cheap, then they get flooded.

And don't forget to throw in some insurance , aka moral hazard.

Insurance ought to just price people out of areas that are too risky.

Why doesn't it?

Re: Millennium Tower is tilting, sinking

#180

Post by clock_tower »

clock_tower wrote: post #9
erdevs wrote: post #5

Earlier quoted context omitted.

Probably not good. According to this and other articles, the building's concrete slab foundation sits roughly 80 ft below street level upon sand, while bedrock lies 200 ft down. That means there is 120 ft of sand, possibly susceptible to liquefaction, between the buildings foundation and solid bedrock. That sounds bad enough. But now imagine the building is tipping over slightly. The already potentially worrisome pro…

How much would it have cost to dig down to bedrock, and pour a concrete foundation from the bedrock up to surface level? Between the amount of sand to be moved and the amount of concrete to be poured, it sounds like an enormous fortune; I guess that the relevant questions are whether the market could bear it and whether it would be cheaper than the rapidly-developing lawsuits. It may be that the building didn't make…

Update: I hadn't known that the usual practice was to build a foundation down to normal depth for a foundation, then set up (large numbers of) pilings from the foundation down to bedrock. That makes sense.
Post reply on HN